From 148ede7f0f42f0ccb1620b13d91f35d0c7d04c2f Mon Sep 17 00:00:00 2001
From: Titus Wormer <tituswormer@gmail.com>
Date: Fri, 29 Jul 2022 10:49:07 +0200
Subject: Refactor to work on bytes (`u8`)

---
 src/compiler.rs                                |  45 +++++----
 src/construct/attention.rs                     |  66 ++++++++-----
 src/construct/autolink.rs                      |  40 ++++----
 src/construct/blank_line.rs                    |   2 +-
 src/construct/block_quote.rs                   |   6 +-
 src/construct/character_escape.rs              |   4 +-
 src/construct/character_reference.rs           |  27 ++---
 src/construct/code_fenced.rs                   |  56 +++++------
 src/construct/code_indented.rs                 |   8 +-
 src/construct/code_text.rs                     |  14 +--
 src/construct/definition.rs                    |   8 +-
 src/construct/hard_break_escape.rs             |   4 +-
 src/construct/heading_atx.rs                   |  16 +--
 src/construct/heading_setext.rs                |  30 +++---
 src/construct/html_flow.rs                     | 131 ++++++++++++-------------
 src/construct/html_text.rs                     | 108 ++++++++++----------
 src/construct/label_end.rs                     |  24 ++---
 src/construct/label_start_image.rs             |   4 +-
 src/construct/label_start_link.rs              |   2 +-
 src/construct/list.rs                          |  45 ++++-----
 src/construct/mod.rs                           |   1 +
 src/construct/paragraph.rs                     |   4 +-
 src/construct/partial_bom.rs                   |  54 ++++++++++
 src/construct/partial_data.rs                  |  16 +--
 src/construct/partial_destination.rs           |  28 +++---
 src/construct/partial_label.rs                 |  22 ++---
 src/construct/partial_non_lazy_continuation.rs |   2 +-
 src/construct/partial_space_or_tab.rs          |  12 +--
 src/construct/partial_title.rs                 |  44 ++++-----
 src/construct/partial_whitespace.rs            |  22 ++---
 src/construct/thematic_break.rs                |  36 +++----
 src/content/document.rs                        |  17 +---
 src/content/flow.rs                            |   4 +-
 src/content/string.rs                          |   2 +-
 src/content/text.rs                            |  20 ++--
 src/lib.rs                                     |   2 +-
 src/parser.rs                                  |   8 +-
 src/tokenizer.rs                               | 126 ++++++++++++------------
 src/util/slice.rs                              |  44 ++++-----
 39 files changed, 576 insertions(+), 528 deletions(-)
 create mode 100644 src/construct/partial_bom.rs

diff --git a/src/compiler.rs b/src/compiler.rs
index f5673b4..de76142 100644
--- a/src/compiler.rs
+++ b/src/compiler.rs
@@ -60,7 +60,7 @@ struct Definition {
 struct CompileContext<'a> {
     /// Static info.
     pub events: &'a [Event],
-    pub chars: &'a [char],
+    pub bytes: &'a [u8],
     /// Fields used by handlers to track the things they need to track to
     /// compile markdown.
     pub atx_opening_sequence_size: Option<usize>,
@@ -92,13 +92,13 @@ impl<'a> CompileContext<'a> {
     /// Create a new compile context.
     pub fn new(
         events: &'a [Event],
-        chars: &'a [char],
+        bytes: &'a [u8],
         options: &Options,
         line_ending: LineEnding,
     ) -> CompileContext<'a> {
         CompileContext {
             events,
-            chars,
+            bytes,
             atx_opening_sequence_size: None,
             heading_setext_buffer: None,
             code_flow_seen_data: None,
@@ -177,6 +177,7 @@ impl<'a> CompileContext<'a> {
 
     /// Add a line ending if needed (as in, there’s no eol/eof already).
     pub fn line_ending_if_needed(&mut self) {
+        // To do: fix to use bytes.
         let last_char = self.buf_tail().chars().last();
         let mut add = true;
 
@@ -196,7 +197,7 @@ impl<'a> CompileContext<'a> {
 
 /// Turn events and codes into a string of HTML.
 #[allow(clippy::too_many_lines)]
-pub fn compile(events: &[Event], chars: &[char], options: &Options) -> String {
+pub fn compile(events: &[Event], bytes: &[u8], options: &Options) -> String {
     let mut index = 0;
     let mut line_ending_inferred = None;
 
@@ -209,7 +210,7 @@ pub fn compile(events: &[Event], chars: &[char], options: &Options) -> String {
             && (event.token_type == Token::BlankLineEnding || event.token_type == Token::LineEnding)
         {
             line_ending_inferred = Some(LineEnding::from_str(
-                &Slice::from_position(chars, &Position::from_exit_event(events, index)).serialize(),
+                &Slice::from_position(bytes, &Position::from_exit_event(events, index)).serialize(),
             ));
             break;
         }
@@ -237,7 +238,7 @@ pub fn compile(events: &[Event], chars: &[char], options: &Options) -> String {
         }
     };
 
-    let mut context = CompileContext::new(events, chars, options, line_ending_default);
+    let mut context = CompileContext::new(events, bytes, options, line_ending_default);
     let mut definition_indices = vec![];
     let mut index = 0;
     let mut definition_inside = false;
@@ -604,7 +605,7 @@ fn on_enter_strong(context: &mut CompileContext) {
 /// Handle [`Exit`][EventType::Exit]:[`AutolinkEmail`][Token::AutolinkEmail].
 fn on_exit_autolink_email(context: &mut CompileContext) {
     let value = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .serialize();
@@ -623,7 +624,7 @@ fn on_exit_autolink_email(context: &mut CompileContext) {
 /// Handle [`Exit`][EventType::Exit]:[`AutolinkProtocol`][Token::AutolinkProtocol].
 fn on_exit_autolink_protocol(context: &mut CompileContext) {
     let value = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .serialize();
@@ -678,7 +679,7 @@ fn on_exit_character_reference_value(context: &mut CompileContext) {
         .take()
         .expect("expected `character_reference_kind` to be set");
     let reference = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .serialize();
@@ -696,7 +697,7 @@ fn on_exit_character_reference_value(context: &mut CompileContext) {
 /// Handle [`Exit`][EventType::Exit]:[`CodeFlowChunk`][Token::CodeFlowChunk].
 fn on_exit_code_flow_chunk(context: &mut CompileContext) {
     let value = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .serialize();
@@ -765,6 +766,7 @@ fn on_exit_code_flow(context: &mut CompileContext) {
 /// Handle [`Exit`][EventType::Exit]:[`CodeText`][Token::CodeText].
 fn on_exit_code_text(context: &mut CompileContext) {
     let result = context.resume();
+    // To do: use bytes.
     let mut chars = result.chars();
     let mut trim = false;
 
@@ -797,7 +799,7 @@ fn on_exit_drop(context: &mut CompileContext) {
 /// Handle [`Exit`][EventType::Exit]:{[`CodeTextData`][Token::CodeTextData],[`Data`][Token::Data],[`CharacterEscapeValue`][Token::CharacterEscapeValue]}.
 fn on_exit_data(context: &mut CompileContext) {
     let value = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .serialize();
@@ -841,7 +843,7 @@ fn on_exit_definition_destination_string(context: &mut CompileContext) {
 /// Handle [`Exit`][EventType::Exit]:[`DefinitionLabelString`][Token::DefinitionLabelString].
 fn on_exit_definition_label_string(context: &mut CompileContext) {
     let value = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .serialize();
@@ -879,7 +881,7 @@ fn on_exit_heading_atx_sequence(context: &mut CompileContext) {
     // First fence we see.
     if context.atx_opening_sequence_size.is_none() {
         let rank = Slice::from_position(
-            context.chars,
+            context.bytes,
             &Position::from_exit_event(context.events, context.index),
         )
         .size();
@@ -909,11 +911,11 @@ fn on_exit_heading_setext_underline(context: &mut CompileContext) {
         .take()
         .expect("`atx_opening_sequence_size` must be set in headings");
     let head = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .head();
-    let level = if head == Some('-') { 2 } else { 1 };
+    let level = if head == Some(b'-') { 2 } else { 1 };
 
     context.line_ending_if_needed();
     context.tag(&*format!("<h{}>", level));
@@ -929,7 +931,7 @@ fn on_exit_html(context: &mut CompileContext) {
 /// Handle [`Exit`][EventType::Exit]:{[`HtmlFlowData`][Token::HtmlFlowData],[`HtmlTextData`][Token::HtmlTextData]}.
 fn on_exit_html_data(context: &mut CompileContext) {
     let value = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .serialize();
@@ -947,7 +949,7 @@ fn on_exit_label(context: &mut CompileContext) {
 /// Handle [`Exit`][EventType::Exit]:[`LabelText`][Token::LabelText].
 fn on_exit_label_text(context: &mut CompileContext) {
     let value = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .serialize();
@@ -964,7 +966,7 @@ fn on_exit_line_ending(context: &mut CompileContext) {
         context.slurp_one_line_ending = false;
     } else {
         let value = Slice::from_position(
-            context.chars,
+            context.bytes,
             &Position::from_exit_event(context.events, context.index),
         )
         .serialize();
@@ -1017,7 +1019,7 @@ fn on_exit_list_item_value(context: &mut CompileContext) {
 
     if expect_first_item {
         let value = Slice::from_position(
-            context.chars,
+            context.bytes,
             &Position::from_exit_event(context.events, context.index),
         )
         .serialize();
@@ -1037,7 +1039,8 @@ fn on_exit_media(context: &mut CompileContext) {
     let mut index = 0;
 
     // Skip current.
-    while index < (context.media_stack.len() - 1) {
+    let end = context.media_stack.len() - 1;
+    while index < end {
         if context.media_stack[index].image {
             is_in_image = true;
             break;
@@ -1123,7 +1126,7 @@ fn on_exit_paragraph(context: &mut CompileContext) {
 /// Handle [`Exit`][EventType::Exit]:[`ReferenceString`][Token::ReferenceString].
 fn on_exit_reference_string(context: &mut CompileContext) {
     let value = Slice::from_position(
-        context.chars,
+        context.bytes,
         &Position::from_exit_event(context.events, context.index),
     )
     .serialize();
diff --git a/src/construct/attention.rs b/src/construct/attention.rs
index 65c2f6f..b042645 100644
--- a/src/construct/attention.rs
+++ b/src/construct/attention.rs
@@ -110,23 +110,23 @@ enum MarkerKind {
 }
 
 impl MarkerKind {
-    /// Turn the kind into a [char].
-    fn as_char(&self) -> char {
+    /// Turn the kind into a byte ([u8]).
+    fn as_byte(&self) -> u8 {
         match self {
-            MarkerKind::Asterisk => '*',
-            MarkerKind::Underscore => '_',
+            MarkerKind::Asterisk => b'*',
+            MarkerKind::Underscore => b'_',
         }
     }
-    /// Turn [char] into a kind.
+    /// Turn a byte ([u8]) into a kind.
     ///
     /// ## Panics
     ///
-    /// Panics if `char` is not `*` or `_`.
-    fn from_char(char: char) -> MarkerKind {
-        match char {
-            '*' => MarkerKind::Asterisk,
-            '_' => MarkerKind::Underscore,
-            _ => unreachable!("invalid char"),
+    /// Panics if `byte` is not `*` or `_`.
+    fn from_byte(byte: u8) -> MarkerKind {
+        match byte {
+            b'*' => MarkerKind::Asterisk,
+            b'_' => MarkerKind::Underscore,
+            _ => unreachable!("invalid byte"),
         }
     }
 }
@@ -160,9 +160,9 @@ struct Sequence {
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(char) if tokenizer.parse_state.constructs.attention && matches!(char, '*' | '_') => {
+        Some(byte) if tokenizer.parse_state.constructs.attention && matches!(byte, b'*' | b'_') => {
             tokenizer.enter(Token::AttentionSequence);
-            inside(tokenizer, MarkerKind::from_char(char))
+            inside(tokenizer, MarkerKind::from_byte(byte))
         }
         _ => State::Nok,
     }
@@ -175,7 +175,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 ///     ^^
 /// ```
 fn inside(tokenizer: &mut Tokenizer, marker: MarkerKind) -> State {
-    if tokenizer.current == Some(marker.as_char()) {
+    if tokenizer.current == Some(marker.as_byte()) {
         tokenizer.consume();
         State::Fn(Box::new(move |t| inside(t, marker)))
     } else {
@@ -188,7 +188,6 @@ fn inside(tokenizer: &mut Tokenizer, marker: MarkerKind) -> State {
 /// Resolve attention sequences.
 #[allow(clippy::too_many_lines)]
 fn resolve_attention(tokenizer: &mut Tokenizer) {
-    let chars = &tokenizer.parse_state.chars;
     let mut start = 0;
     let mut balance = 0;
     let mut sequences = vec![];
@@ -203,21 +202,34 @@ fn resolve_attention(tokenizer: &mut Tokenizer) {
             if enter.token_type == Token::AttentionSequence {
                 let end = start + 1;
                 let exit = &tokenizer.events[end];
-                let marker =
-                    MarkerKind::from_char(Slice::from_point(chars, &enter.point).head().unwrap());
+
+                let before_end = enter.point.index;
+                let before_start = if before_end < 4 { 0 } else { before_end - 4 };
+                let string_before =
+                    String::from_utf8_lossy(&tokenizer.parse_state.bytes[before_start..before_end]);
+                let char_before = string_before.chars().last();
+
+                let after_start = exit.point.index;
+                let after_end = if after_start + 4 > tokenizer.parse_state.bytes.len() {
+                    tokenizer.parse_state.bytes.len()
+                } else {
+                    after_start + 4
+                };
+                let string_after =
+                    String::from_utf8_lossy(&tokenizer.parse_state.bytes[after_start..after_end]);
+                let char_after = string_after.chars().next();
+
+                let marker = MarkerKind::from_byte(
+                    Slice::from_point(tokenizer.parse_state.bytes, &enter.point)
+                        .head()
+                        .unwrap(),
+                );
                 let before = classify_character(if enter.point.index > 0 {
-                    Slice::from_point(
-                        chars,
-                        &Point {
-                            index: enter.point.index - 1,
-                            ..enter.point
-                        },
-                    )
-                    .tail()
+                    char_before
                 } else {
                     None
                 });
-                let after = classify_character(Slice::from_point(chars, &exit.point).tail());
+                let after = classify_character(char_after);
                 let open = after == GroupKind::Other
                     || (after == GroupKind::Punctuation && before != GroupKind::Other);
                 // To do: GFM strikethrough?
@@ -490,7 +502,7 @@ fn resolve_attention(tokenizer: &mut Tokenizer) {
 /// *   [`micromark-util-classify-character` in `micromark`](https://github.com/micromark/micromark/blob/main/packages/micromark-util-classify-character/dev/index.js)
 fn classify_character(char: Option<char>) -> GroupKind {
     match char {
-        // Custom characters.
+        // EOF.
         None => GroupKind::Whitespace,
         // Unicode whitespace.
         Some(char) if char.is_whitespace() => GroupKind::Whitespace,
diff --git a/src/construct/autolink.rs b/src/construct/autolink.rs
index 399570b..b843af8 100644
--- a/src/construct/autolink.rs
+++ b/src/construct/autolink.rs
@@ -115,7 +115,7 @@ use crate::tokenizer::{State, Tokenizer};
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('<') if tokenizer.parse_state.constructs.autolink => {
+        Some(b'<') if tokenizer.parse_state.constructs.autolink => {
             tokenizer.enter(Token::Autolink);
             tokenizer.enter(Token::AutolinkMarker);
             tokenizer.consume();
@@ -137,16 +137,16 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn open(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(char) if char.is_ascii_alphabetic() => {
+        Some(byte) if byte.is_ascii_alphabetic() => {
             tokenizer.consume();
             State::Fn(Box::new(scheme_or_email_atext))
         }
-        Some(char) if is_ascii_atext(char) => email_atext(tokenizer),
+        Some(byte) if is_ascii_atext(byte) => email_atext(tokenizer),
         _ => State::Nok,
     }
 }
 
-/// After the first character of the protocol or email name.
+/// After the first byte of the protocol or email name.
 ///
 /// ```markdown
 /// > | a<https://example.com>b
@@ -156,7 +156,7 @@ fn open(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn scheme_or_email_atext(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('+' | '-' | '.' | '0'..='9' | 'A'..='Z' | 'a'..='z') => {
+        Some(b'+' | b'-' | b'.' | b'0'..=b'9' | b'A'..=b'Z' | b'a'..=b'z') => {
             scheme_inside_or_email_atext(tokenizer, 1)
         }
         _ => email_atext(tokenizer),
@@ -173,11 +173,11 @@ fn scheme_or_email_atext(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn scheme_inside_or_email_atext(tokenizer: &mut Tokenizer, size: usize) -> State {
     match tokenizer.current {
-        Some(':') => {
+        Some(b':') => {
             tokenizer.consume();
             State::Fn(Box::new(url_inside))
         }
-        Some('+' | '-' | '.' | '0'..='9' | 'A'..='Z' | 'a'..='z')
+        Some(b'+' | b'-' | b'.' | b'0'..=b'9' | b'A'..=b'Z' | b'a'..=b'z')
             if size < AUTOLINK_SCHEME_SIZE_MAX =>
         {
             tokenizer.consume();
@@ -195,12 +195,12 @@ fn scheme_inside_or_email_atext(tokenizer: &mut Tokenizer, size: usize) -> State
 /// ```
 fn url_inside(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             tokenizer.exit(Token::AutolinkProtocol);
             end(tokenizer)
         }
-        Some(char) if char.is_ascii_control() => State::Nok,
-        None | Some(' ') => State::Nok,
+        Some(byte) if byte.is_ascii_control() => State::Nok,
+        None | Some(b' ') => State::Nok,
         Some(_) => {
             tokenizer.consume();
             State::Fn(Box::new(url_inside))
@@ -216,11 +216,11 @@ fn url_inside(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn email_atext(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('@') => {
+        Some(b'@') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| email_at_sign_or_dot(t, 0)))
         }
-        Some(char) if is_ascii_atext(char) => {
+        Some(byte) if is_ascii_atext(byte) => {
             tokenizer.consume();
             State::Fn(Box::new(email_atext))
         }
@@ -236,7 +236,7 @@ fn email_atext(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn email_at_sign_or_dot(tokenizer: &mut Tokenizer, size: usize) -> State {
     match tokenizer.current {
-        Some(char) if char.is_ascii_alphanumeric() => email_value(tokenizer, size),
+        Some(byte) if byte.is_ascii_alphanumeric() => email_value(tokenizer, size),
         _ => State::Nok,
     }
 }
@@ -249,11 +249,11 @@ fn email_at_sign_or_dot(tokenizer: &mut Tokenizer, size: usize) -> State {
 /// ```
 fn email_label(tokenizer: &mut Tokenizer, size: usize) -> State {
     match tokenizer.current {
-        Some('.') => {
+        Some(b'.') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| email_at_sign_or_dot(t, 0)))
         }
-        Some('>') => {
+        Some(b'>') => {
             let index = tokenizer.events.len();
             tokenizer.exit(Token::AutolinkProtocol);
             // Change the token type.
@@ -275,11 +275,11 @@ fn email_label(tokenizer: &mut Tokenizer, size: usize) -> State {
 /// ```
 fn email_value(tokenizer: &mut Tokenizer, size: usize) -> State {
     match tokenizer.current {
-        Some('-') if size < AUTOLINK_DOMAIN_SIZE_MAX => {
+        Some(b'-') if size < AUTOLINK_DOMAIN_SIZE_MAX => {
             tokenizer.consume();
             State::Fn(Box::new(move |t| email_value(t, size + 1)))
         }
-        Some(char) if char.is_ascii_alphanumeric() && size < AUTOLINK_DOMAIN_SIZE_MAX => {
+        Some(byte) if byte.is_ascii_alphanumeric() && size < AUTOLINK_DOMAIN_SIZE_MAX => {
             tokenizer.consume();
             State::Fn(Box::new(move |t| email_label(t, size + 1)))
         }
@@ -297,7 +297,7 @@ fn email_value(tokenizer: &mut Tokenizer, size: usize) -> State {
 /// ```
 fn end(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             tokenizer.enter(Token::AutolinkMarker);
             tokenizer.consume();
             tokenizer.exit(Token::AutolinkMarker);
@@ -324,6 +324,6 @@ fn end(tokenizer: &mut Tokenizer) -> State {
 /// IETF.
 ///
 /// [`is_ascii_alphanumeric`]: char::is_ascii_alphanumeric
-fn is_ascii_atext(x: char) -> bool {
-    matches!(x, '#'..='\'' | '*' | '+' | '-'..='9' | '=' | '?' | 'A'..='Z' | '^'..='~')
+fn is_ascii_atext(byte: u8) -> bool {
+    matches!(byte, b'#'..=b'\'' | b'*' | b'+' | b'-'..=b'9' | b'=' | b'?' | b'A'..=b'Z' | b'^'..=b'~')
 }
diff --git a/src/construct/blank_line.rs b/src/construct/blank_line.rs
index 6780f40..f397a48 100644
--- a/src/construct/blank_line.rs
+++ b/src/construct/blank_line.rs
@@ -59,7 +59,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn after(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('\n') => State::Ok,
+        None | Some(b'\n') => State::Ok,
         _ => State::Nok,
     }
 }
diff --git a/src/construct/block_quote.rs b/src/construct/block_quote.rs
index 49a0ea0..7e4753d 100644
--- a/src/construct/block_quote.rs
+++ b/src/construct/block_quote.rs
@@ -65,7 +65,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn before(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             tokenizer.enter(Token::BlockQuote);
             cont_before(tokenizer)
         }
@@ -98,7 +98,7 @@ pub fn cont(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn cont_before(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             tokenizer.enter(Token::BlockQuotePrefix);
             tokenizer.enter(Token::BlockQuoteMarker);
             tokenizer.consume();
@@ -118,7 +118,7 @@ fn cont_before(tokenizer: &mut Tokenizer) -> State {
 ///      ^
 /// ```
 fn cont_after(tokenizer: &mut Tokenizer) -> State {
-    if let Some('\t' | ' ') = tokenizer.current {
+    if let Some(b'\t' | b' ') = tokenizer.current {
         tokenizer.enter(Token::SpaceOrTab);
         tokenizer.consume();
         tokenizer.exit(Token::SpaceOrTab);
diff --git a/src/construct/character_escape.rs b/src/construct/character_escape.rs
index e9263af..02e8b62 100644
--- a/src/construct/character_escape.rs
+++ b/src/construct/character_escape.rs
@@ -44,7 +44,7 @@ use crate::tokenizer::{State, Tokenizer};
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\\') if tokenizer.parse_state.constructs.character_escape => {
+        Some(b'\\') if tokenizer.parse_state.constructs.character_escape => {
             tokenizer.enter(Token::CharacterEscape);
             tokenizer.enter(Token::CharacterEscapeMarker);
             tokenizer.consume();
@@ -63,7 +63,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn inside(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(char) if char.is_ascii_punctuation() => {
+        Some(byte) if byte.is_ascii_punctuation() => {
             tokenizer.enter(Token::CharacterEscapeValue);
             tokenizer.consume();
             tokenizer.exit(Token::CharacterEscapeValue);
diff --git a/src/construct/character_reference.rs b/src/construct/character_reference.rs
index 59043d1..90763c1 100644
--- a/src/construct/character_reference.rs
+++ b/src/construct/character_reference.rs
@@ -106,15 +106,15 @@ impl Kind {
         }
     }
 
-    /// Check if a char is allowed.
-    fn allowed(&self, char: char) -> bool {
+    /// Check if a byte ([`u8`]) is allowed.
+    fn allowed(&self, byte: u8) -> bool {
         let check = match self {
-            Kind::Hexadecimal => char::is_ascii_hexdigit,
-            Kind::Decimal => char::is_ascii_digit,
-            Kind::Named => char::is_ascii_alphanumeric,
+            Kind::Hexadecimal => u8::is_ascii_hexdigit,
+            Kind::Decimal => u8::is_ascii_digit,
+            Kind::Named => u8::is_ascii_alphanumeric,
         };
 
-        check(&char)
+        check(&byte)
     }
 }
 
@@ -141,7 +141,7 @@ struct Info {
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('&') if tokenizer.parse_state.constructs.character_reference => {
+        Some(b'&') if tokenizer.parse_state.constructs.character_reference => {
             tokenizer.enter(Token::CharacterReference);
             tokenizer.enter(Token::CharacterReferenceMarker);
             tokenizer.consume();
@@ -164,7 +164,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 ///       ^
 /// ```
 fn open(tokenizer: &mut Tokenizer) -> State {
-    if let Some('#') = tokenizer.current {
+    if let Some(b'#') = tokenizer.current {
         tokenizer.enter(Token::CharacterReferenceMarkerNumeric);
         tokenizer.consume();
         tokenizer.exit(Token::CharacterReferenceMarkerNumeric);
@@ -192,7 +192,7 @@ fn open(tokenizer: &mut Tokenizer) -> State {
 ///        ^
 /// ```
 fn numeric(tokenizer: &mut Tokenizer) -> State {
-    if let Some('x' | 'X') = tokenizer.current {
+    if let Some(b'x' | b'X') = tokenizer.current {
         tokenizer.enter(Token::CharacterReferenceMarkerHexadecimal);
         tokenizer.consume();
         tokenizer.exit(Token::CharacterReferenceMarkerHexadecimal);
@@ -229,10 +229,11 @@ fn numeric(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn value(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some(';') if info.size > 0 => {
+        Some(b';') if info.size > 0 => {
             if Kind::Named == info.kind {
+                // To do: fix slice.
                 let value = Slice::from_position(
-                    &tokenizer.parse_state.chars,
+                    tokenizer.parse_state.bytes,
                     &Position {
                         start: &info.start,
                         end: &tokenizer.point,
@@ -252,8 +253,8 @@ fn value(tokenizer: &mut Tokenizer, mut info: Info) -> State {
             tokenizer.exit(Token::CharacterReference);
             State::Ok
         }
-        Some(char) => {
-            if info.size < info.kind.max() && info.kind.allowed(char) {
+        Some(byte) => {
+            if info.size < info.kind.max() && info.kind.allowed(byte) {
                 info.size += 1;
                 tokenizer.consume();
                 State::Fn(Box::new(|t| value(t, info)))
diff --git a/src/construct/code_fenced.rs b/src/construct/code_fenced.rs
index 98fa54f..21e9259 100644
--- a/src/construct/code_fenced.rs
+++ b/src/construct/code_fenced.rs
@@ -136,23 +136,23 @@ pub enum Kind {
 }
 
 impl Kind {
-    /// Turn the kind into a [char].
-    fn as_char(&self) -> char {
+    /// Turn the kind into a byte ([u8]).
+    fn as_byte(&self) -> u8 {
         match self {
-            Kind::GraveAccent => '`',
-            Kind::Tilde => '~',
+            Kind::GraveAccent => b'`',
+            Kind::Tilde => b'~',
         }
     }
-    /// Turn a [char] into a kind.
+    /// Turn a byte ([u8]) into a kind.
     ///
     /// ## Panics
     ///
-    /// Panics if `char` is not `~` or `` ` ``.
-    fn from_char(char: char) -> Kind {
-        match char {
-            '`' => Kind::GraveAccent,
-            '~' => Kind::Tilde,
-            _ => unreachable!("invalid char"),
+    /// Panics if `byte` is not `~` or `` ` ``.
+    fn from_byte(byte: u8) -> Kind {
+        match byte {
+            b'`' => Kind::GraveAccent,
+            b'~' => Kind::Tilde,
+            _ => unreachable!("invalid byte"),
         }
     }
 }
@@ -207,7 +207,7 @@ fn before_sequence_open(tokenizer: &mut Tokenizer) -> State {
     if let Some(event) = tail {
         if event.token_type == Token::SpaceOrTab {
             prefix = Slice::from_position(
-                &tokenizer.parse_state.chars,
+                tokenizer.parse_state.bytes,
                 &Position::from_exit_event(&tokenizer.events, tokenizer.events.len() - 1),
             )
             .size();
@@ -215,14 +215,14 @@ fn before_sequence_open(tokenizer: &mut Tokenizer) -> State {
     }
 
     match tokenizer.current {
-        Some(char) if matches!(char, '`' | '~') => {
+        Some(byte) if matches!(byte, b'`' | b'~') => {
             tokenizer.enter(Token::CodeFencedFenceSequence);
             sequence_open(
                 tokenizer,
                 Info {
                     prefix,
                     size: 0,
-                    kind: Kind::from_char(char),
+                    kind: Kind::from_byte(byte),
                 },
             )
         }
@@ -240,7 +240,7 @@ fn before_sequence_open(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn sequence_open(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some(char) if char == info.kind.as_char() => {
+        Some(byte) if byte == info.kind.as_byte() => {
             tokenizer.consume();
             State::Fn(Box::new(|t| {
                 info.size += 1;
@@ -265,7 +265,7 @@ fn sequence_open(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn info_before(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::CodeFencedFence);
             // Do not form containers.
             tokenizer.concrete = true;
@@ -289,7 +289,7 @@ fn info_before(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn info_inside(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::Data);
             tokenizer.exit(Token::CodeFencedFenceInfo);
             tokenizer.exit(Token::CodeFencedFence);
@@ -297,12 +297,12 @@ fn info_inside(tokenizer: &mut Tokenizer, info: Info) -> State {
             tokenizer.concrete = true;
             at_break(tokenizer, info)
         }
-        Some('\t' | ' ') => {
+        Some(b'\t' | b' ') => {
             tokenizer.exit(Token::Data);
             tokenizer.exit(Token::CodeFencedFenceInfo);
             tokenizer.attempt_opt(space_or_tab(), |t| meta_before(t, info))(tokenizer)
         }
-        Some('`') if info.kind == Kind::GraveAccent => State::Nok,
+        Some(b'`') if info.kind == Kind::GraveAccent => State::Nok,
         Some(_) => {
             tokenizer.consume();
             State::Fn(Box::new(|t| info_inside(t, info)))
@@ -320,7 +320,7 @@ fn info_inside(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn meta_before(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::CodeFencedFence);
             // Do not form containers.
             tokenizer.concrete = true;
@@ -344,7 +344,7 @@ fn meta_before(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn meta(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::Data);
             tokenizer.exit(Token::CodeFencedFenceMeta);
             tokenizer.exit(Token::CodeFencedFence);
@@ -352,7 +352,7 @@ fn meta(tokenizer: &mut Tokenizer, info: Info) -> State {
             tokenizer.concrete = true;
             at_break(tokenizer, info)
         }
-        Some('`') if info.kind == Kind::GraveAccent => State::Nok,
+        Some(b'`') if info.kind == Kind::GraveAccent => State::Nok,
         _ => {
             tokenizer.consume();
             State::Fn(Box::new(|t| meta(t, info)))
@@ -413,7 +413,7 @@ fn at_non_lazy_break(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn close_begin(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.enter(Token::LineEnding);
             tokenizer.consume();
             tokenizer.exit(Token::LineEnding);
@@ -452,7 +452,7 @@ fn close_start(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn close_before(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some(char) if char == info.kind.as_char() => {
+        Some(byte) if byte == info.kind.as_byte() => {
             tokenizer.enter(Token::CodeFencedFenceSequence);
             close_sequence(tokenizer, info, 0)
         }
@@ -470,7 +470,7 @@ fn close_before(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn close_sequence(tokenizer: &mut Tokenizer, info: Info, size: usize) -> State {
     match tokenizer.current {
-        Some(char) if char == info.kind.as_char() => {
+        Some(byte) if byte == info.kind.as_byte() => {
             tokenizer.consume();
             State::Fn(Box::new(move |t| close_sequence(t, info, size + 1)))
         }
@@ -492,7 +492,7 @@ fn close_sequence(tokenizer: &mut Tokenizer, info: Info, size: usize) -> State {
 /// ```
 fn close_sequence_after(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::CodeFencedFence);
             State::Ok
         }
@@ -538,7 +538,7 @@ fn content_start(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn content_begin(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => at_break(tokenizer, info),
+        None | Some(b'\n') => at_break(tokenizer, info),
         _ => {
             tokenizer.enter(Token::CodeFlowChunk);
             content_continue(tokenizer, info)
@@ -556,7 +556,7 @@ fn content_begin(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn content_continue(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::CodeFlowChunk);
             at_break(tokenizer, info)
         }
diff --git a/src/construct/code_indented.rs b/src/construct/code_indented.rs
index bb1615c..4a3a9f6 100644
--- a/src/construct/code_indented.rs
+++ b/src/construct/code_indented.rs
@@ -79,7 +79,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 fn at_break(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
         None => after(tokenizer),
-        Some('\n') => tokenizer.attempt(further_start, |ok| {
+        Some(b'\n') => tokenizer.attempt(further_start, |ok| {
             Box::new(if ok { at_break } else { after })
         })(tokenizer),
         _ => {
@@ -97,7 +97,7 @@ fn at_break(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn content(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::CodeFlowChunk);
             at_break(tokenizer)
         }
@@ -133,7 +133,7 @@ fn further_start(tokenizer: &mut Tokenizer) -> State {
         State::Nok
     } else {
         match tokenizer.current {
-            Some('\n') => {
+            Some(b'\n') => {
                 tokenizer.enter(Token::LineEnding);
                 tokenizer.consume();
                 tokenizer.exit(Token::LineEnding);
@@ -177,7 +177,7 @@ fn further_begin(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn further_after(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\n') => further_start(tokenizer),
+        Some(b'\n') => further_start(tokenizer),
         _ => State::Nok,
     }
 }
diff --git a/src/construct/code_text.rs b/src/construct/code_text.rs
index 150f63b..b36a208 100644
--- a/src/construct/code_text.rs
+++ b/src/construct/code_text.rs
@@ -98,9 +98,9 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
     let len = tokenizer.events.len();
 
     match tokenizer.current {
-        Some('`')
+        Some(b'`')
             if tokenizer.parse_state.constructs.code_text
-                && (tokenizer.previous != Some('`')
+                && (tokenizer.previous != Some(b'`')
                     || (len > 0
                         && tokenizer.events[len - 1].token_type == Token::CharacterEscape)) =>
         {
@@ -119,7 +119,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 ///     ^
 /// ```
 fn sequence_open(tokenizer: &mut Tokenizer, size: usize) -> State {
-    if let Some('`') = tokenizer.current {
+    if let Some(b'`') = tokenizer.current {
         tokenizer.consume();
         State::Fn(Box::new(move |t| sequence_open(t, size + 1)))
     } else {
@@ -137,13 +137,13 @@ fn sequence_open(tokenizer: &mut Tokenizer, size: usize) -> State {
 fn between(tokenizer: &mut Tokenizer, size_open: usize) -> State {
     match tokenizer.current {
         None => State::Nok,
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.enter(Token::LineEnding);
             tokenizer.consume();
             tokenizer.exit(Token::LineEnding);
             State::Fn(Box::new(move |t| between(t, size_open)))
         }
-        Some('`') => {
+        Some(b'`') => {
             tokenizer.enter(Token::CodeTextSequence);
             sequence_close(tokenizer, size_open, 0)
         }
@@ -162,7 +162,7 @@ fn between(tokenizer: &mut Tokenizer, size_open: usize) -> State {
 /// ```
 fn data(tokenizer: &mut Tokenizer, size_open: usize) -> State {
     match tokenizer.current {
-        None | Some('\n' | '`') => {
+        None | Some(b'\n' | b'`') => {
             tokenizer.exit(Token::CodeTextData);
             between(tokenizer, size_open)
         }
@@ -181,7 +181,7 @@ fn data(tokenizer: &mut Tokenizer, size_open: usize) -> State {
 /// ```
 fn sequence_close(tokenizer: &mut Tokenizer, size_open: usize, size: usize) -> State {
     match tokenizer.current {
-        Some('`') => {
+        Some(b'`') => {
             tokenizer.consume();
             State::Fn(Box::new(move |t| sequence_close(t, size_open, size + 1)))
         }
diff --git a/src/construct/definition.rs b/src/construct/definition.rs
index f2b5ae0..14755c9 100644
--- a/src/construct/definition.rs
+++ b/src/construct/definition.rs
@@ -137,7 +137,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn before(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('[') => tokenizer.go(
+        Some(b'[') => tokenizer.go(
             |t| {
                 label(
                     t,
@@ -162,7 +162,7 @@ fn before(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn label_after(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(':') => {
+        Some(b':') => {
             tokenizer.enter(Token::DefinitionMarker);
             tokenizer.consume();
             tokenizer.exit(Token::DefinitionMarker);
@@ -231,7 +231,7 @@ fn after(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn after_whitespace(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::Definition);
             // You’d be interrupting.
             tokenizer.interrupt = true;
@@ -294,7 +294,7 @@ fn title_after(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn title_after_after_optional_whitespace(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('\n') => State::Ok,
+        None | Some(b'\n') => State::Ok,
         _ => State::Nok,
     }
 }
diff --git a/src/construct/hard_break_escape.rs b/src/construct/hard_break_escape.rs
index 0585c4c..cdbc192 100644
--- a/src/construct/hard_break_escape.rs
+++ b/src/construct/hard_break_escape.rs
@@ -51,7 +51,7 @@ use crate::tokenizer::{State, Tokenizer};
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\\') if tokenizer.parse_state.constructs.hard_break_escape => {
+        Some(b'\\') if tokenizer.parse_state.constructs.hard_break_escape => {
             tokenizer.enter(Token::HardBreakEscape);
             tokenizer.consume();
             State::Fn(Box::new(inside))
@@ -69,7 +69,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn inside(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.exit(Token::HardBreakEscape);
             State::Ok
         }
diff --git a/src/construct/heading_atx.rs b/src/construct/heading_atx.rs
index 7a7cf2e..9a73b77 100644
--- a/src/construct/heading_atx.rs
+++ b/src/construct/heading_atx.rs
@@ -87,7 +87,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 ///     ^
 /// ```
 fn before(tokenizer: &mut Tokenizer) -> State {
-    if Some('#') == tokenizer.current {
+    if Some(b'#') == tokenizer.current {
         tokenizer.enter(Token::HeadingAtxSequence);
         sequence_open(tokenizer, 0)
     } else {
@@ -103,11 +103,11 @@ fn before(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn sequence_open(tokenizer: &mut Tokenizer, rank: usize) -> State {
     match tokenizer.current {
-        None | Some('\n') if rank > 0 => {
+        None | Some(b'\n') if rank > 0 => {
             tokenizer.exit(Token::HeadingAtxSequence);
             at_break(tokenizer)
         }
-        Some('#') if rank < HEADING_ATX_OPENING_FENCE_SIZE_MAX => {
+        Some(b'#') if rank < HEADING_ATX_OPENING_FENCE_SIZE_MAX => {
             tokenizer.consume();
             State::Fn(Box::new(move |tokenizer| {
                 sequence_open(tokenizer, rank + 1)
@@ -129,15 +129,15 @@ fn sequence_open(tokenizer: &mut Tokenizer, rank: usize) -> State {
 /// ```
 fn at_break(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::HeadingAtx);
             tokenizer.register_resolver("heading_atx".to_string(), Box::new(resolve));
             // Feel free to interrupt.
             tokenizer.interrupt = false;
             State::Ok
         }
-        Some('\t' | ' ') => tokenizer.go(space_or_tab(), at_break)(tokenizer),
-        Some('#') => {
+        Some(b'\t' | b' ') => tokenizer.go(space_or_tab(), at_break)(tokenizer),
+        Some(b'#') => {
             tokenizer.enter(Token::HeadingAtxSequence);
             further_sequence(tokenizer)
         }
@@ -157,7 +157,7 @@ fn at_break(tokenizer: &mut Tokenizer) -> State {
 ///           ^
 /// ```
 fn further_sequence(tokenizer: &mut Tokenizer) -> State {
-    if let Some('#') = tokenizer.current {
+    if let Some(b'#') = tokenizer.current {
         tokenizer.consume();
         State::Fn(Box::new(further_sequence))
     } else {
@@ -175,7 +175,7 @@ fn further_sequence(tokenizer: &mut Tokenizer) -> State {
 fn data(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
         // Note: `#` for closing sequence must be preceded by whitespace, otherwise it’s just text.
-        None | Some('\t' | '\n' | ' ') => {
+        None | Some(b'\t' | b'\n' | b' ') => {
             tokenizer.exit(Token::Data);
             at_break(tokenizer)
         }
diff --git a/src/construct/heading_setext.rs b/src/construct/heading_setext.rs
index f9dd3f7..2a4adbf 100644
--- a/src/construct/heading_setext.rs
+++ b/src/construct/heading_setext.rs
@@ -88,23 +88,23 @@ pub enum Kind {
 }
 
 impl Kind {
-    /// Turn the kind into a [char].
-    fn as_char(&self) -> char {
+    /// Turn the kind into a byte ([u8]).
+    fn as_byte(&self) -> u8 {
         match self {
-            Kind::Dash => '-',
-            Kind::EqualsTo => '=',
+            Kind::Dash => b'-',
+            Kind::EqualsTo => b'=',
         }
     }
-    /// Turn a [char] into a kind.
+    /// Turn a byte ([u8]) into a kind.
     ///
     /// ## Panics
     ///
-    /// Panics if `char` is not `-` or `=`.
-    fn from_char(char: char) -> Kind {
-        match char {
-            '-' => Kind::Dash,
-            '=' => Kind::EqualsTo,
-            _ => unreachable!("invalid char"),
+    /// Panics if `byte` is not `-` or `=`.
+    fn from_byte(byte: u8) -> Kind {
+        match byte {
+            b'-' => Kind::Dash,
+            b'=' => Kind::EqualsTo,
+            _ => unreachable!("invalid byte"),
         }
     }
 }
@@ -148,9 +148,9 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn before(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(char) if matches!(char, '-' | '=') => {
+        Some(byte) if matches!(byte, b'-' | b'=') => {
             tokenizer.enter(Token::HeadingSetextUnderline);
-            inside(tokenizer, Kind::from_char(char))
+            inside(tokenizer, Kind::from_byte(byte))
         }
         _ => State::Nok,
     }
@@ -165,7 +165,7 @@ fn before(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn inside(tokenizer: &mut Tokenizer, kind: Kind) -> State {
     match tokenizer.current {
-        Some(char) if char == kind.as_char() => {
+        Some(byte) if byte == kind.as_byte() => {
             tokenizer.consume();
             State::Fn(Box::new(move |t| inside(t, kind)))
         }
@@ -185,7 +185,7 @@ fn inside(tokenizer: &mut Tokenizer, kind: Kind) -> State {
 /// ```
 fn after(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             // Feel free to interrupt.
             tokenizer.interrupt = false;
             tokenizer.register_resolver("heading_setext".to_string(), Box::new(resolve));
diff --git a/src/construct/html_flow.rs b/src/construct/html_flow.rs
index e2b66e5..5860c5d 100644
--- a/src/construct/html_flow.rs
+++ b/src/construct/html_flow.rs
@@ -108,7 +108,7 @@ use crate::token::Token;
 use crate::tokenizer::{Point, State, Tokenizer};
 use crate::util::slice::{Position, Slice};
 
-const CDATA_SEARCH: [char; 6] = ['C', 'D', 'A', 'T', 'A', '['];
+const CDATA_SEARCH: [u8; 6] = [b'C', b'D', b'A', b'T', b'A', b'['];
 
 /// Kind of HTML (flow).
 #[derive(Debug, PartialEq)]
@@ -151,23 +151,23 @@ enum QuoteKind {
 }
 
 impl QuoteKind {
-    /// Turn the kind into a [char].
-    fn as_char(&self) -> char {
+    /// Turn the kind into a byte ([u8]).
+    fn as_byte(&self) -> u8 {
         match self {
-            QuoteKind::Double => '"',
-            QuoteKind::Single => '\'',
+            QuoteKind::Double => b'"',
+            QuoteKind::Single => b'\'',
         }
     }
-    /// Turn a [char] into a kind.
+    /// Turn a byte ([u8]) into a kind.
     ///
     /// ## Panics
     ///
-    /// Panics if `char` is not `"` or `'`.
-    fn from_char(char: char) -> QuoteKind {
-        match char {
-            '"' => QuoteKind::Double,
-            '\'' => QuoteKind::Single,
-            _ => unreachable!("invalid char"),
+    /// Panics if `byte` is not `"` or `'`.
+    fn from_byte(byte: u8) -> QuoteKind {
+        match byte {
+            b'"' => QuoteKind::Double,
+            b'\'' => QuoteKind::Single,
+            _ => unreachable!("invalid byte"),
         }
     }
 }
@@ -179,8 +179,7 @@ struct Info {
     kind: Kind,
     /// Whether this is a start tag (`<` not followed by `/`).
     start_tag: bool,
-    /// Used depending on `kind` to either collect all parsed characters, or to
-    /// store expected characters.
+    /// Used depending on `kind` to collect all parsed bytes.
     start: Option<Point>,
     /// Collected index, for various reasons.
     size: usize,
@@ -225,7 +224,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 ///     ^
 /// ```
 fn before(tokenizer: &mut Tokenizer) -> State {
-    if Some('<') == tokenizer.current {
+    if Some(b'<') == tokenizer.current {
         tokenizer.enter(Token::HtmlFlowData);
         tokenizer.consume();
         State::Fn(Box::new(open))
@@ -256,16 +255,16 @@ fn open(tokenizer: &mut Tokenizer) -> State {
     };
 
     match tokenizer.current {
-        Some('!') => {
+        Some(b'!') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| declaration_open(t, info)))
         }
-        Some('/') => {
+        Some(b'/') => {
             tokenizer.consume();
             info.start = Some(tokenizer.point.clone());
             State::Fn(Box::new(|t| tag_close_start(t, info)))
         }
-        Some('?') => {
+        Some(b'?') => {
             info.kind = Kind::Instruction;
             tokenizer.consume();
             // Do not form containers.
@@ -274,7 +273,7 @@ fn open(tokenizer: &mut Tokenizer) -> State {
             // right now, so we do need to search for `>`, similar to declarations.
             State::Fn(Box::new(|t| continuation_declaration_inside(t, info)))
         }
-        Some('A'..='Z' | 'a'..='z') => {
+        Some(b'A'..=b'Z' | b'a'..=b'z') => {
             info.start_tag = true;
             info.start = Some(tokenizer.point.clone());
             tag_name(tokenizer, info)
@@ -295,18 +294,18 @@ fn open(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn declaration_open(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some('-') => {
+        Some(b'-') => {
             tokenizer.consume();
             info.kind = Kind::Comment;
             State::Fn(Box::new(|t| comment_open_inside(t, info)))
         }
-        Some('[') => {
+        Some(b'[') => {
             tokenizer.consume();
             info.kind = Kind::Cdata;
             info.size = 0;
             State::Fn(Box::new(|t| cdata_open_inside(t, info)))
         }
-        Some('A'..='Z' | 'a'..='z') => {
+        Some(b'A'..=b'Z' | b'a'..=b'z') => {
             tokenizer.consume();
             info.kind = Kind::Declaration;
             // Do not form containers.
@@ -325,7 +324,7 @@ fn declaration_open(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn comment_open_inside(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('-') => {
+        Some(b'-') => {
             tokenizer.consume();
             // Do not form containers.
             tokenizer.concrete = true;
@@ -343,7 +342,7 @@ fn comment_open_inside(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn cdata_open_inside(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some(char) if char == CDATA_SEARCH[info.size] => {
+        Some(byte) if byte == CDATA_SEARCH[info.size] => {
             info.size += 1;
             tokenizer.consume();
 
@@ -368,7 +367,7 @@ fn cdata_open_inside(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn tag_close_start(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('A'..='Z' | 'a'..='z') => {
+        Some(b'A'..=b'Z' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| tag_name(t, info)))
         }
@@ -386,11 +385,11 @@ fn tag_close_start(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn tag_name(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        None | Some('\t' | '\n' | ' ' | '/' | '>') => {
-            let slash = matches!(tokenizer.current, Some('/'));
+        None | Some(b'\t' | b'\n' | b' ' | b'/' | b'>') => {
+            let slash = matches!(tokenizer.current, Some(b'/'));
             let start = info.start.take().unwrap();
             let name = Slice::from_position(
-                &tokenizer.parse_state.chars,
+                tokenizer.parse_state.bytes,
                 &Position {
                     start: &start,
                     end: &tokenizer.point,
@@ -428,7 +427,7 @@ fn tag_name(tokenizer: &mut Tokenizer, mut info: Info) -> State {
                 }
             }
         }
-        Some('-' | '0'..='9' | 'A'..='Z' | 'a'..='z') => {
+        Some(b'-' | b'0'..=b'9' | b'A'..=b'Z' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| tag_name(t, info)))
         }
@@ -444,7 +443,7 @@ fn tag_name(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn basic_self_closing(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             tokenizer.consume();
             // Do not form containers.
             tokenizer.concrete = true;
@@ -462,7 +461,7 @@ fn basic_self_closing(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn complete_closing_tag_after(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('\t' | ' ') => {
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_closing_tag_after(t, info)))
         }
@@ -491,15 +490,15 @@ fn complete_closing_tag_after(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn complete_attribute_name_before(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('/') => {
+        Some(b'/') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_end(t, info)))
         }
-        Some('0'..='9' | ':' | 'A'..='Z' | '_' | 'a'..='z') => {
+        Some(b'0'..=b'9' | b':' | b'A'..=b'Z' | b'_' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_attribute_name(t, info)))
         }
-        Some('\t' | ' ') => {
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_attribute_name_before(t, info)))
         }
@@ -519,7 +518,7 @@ fn complete_attribute_name_before(tokenizer: &mut Tokenizer, info: Info) -> Stat
 /// ```
 fn complete_attribute_name(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('-' | '.' | '0'..='9' | ':' | 'A'..='Z' | '_' | 'a'..='z') => {
+        Some(b'-' | b'.' | b'0'..=b'9' | b':' | b'A'..=b'Z' | b'_' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_attribute_name(t, info)))
         }
@@ -538,11 +537,11 @@ fn complete_attribute_name(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn complete_attribute_name_after(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('=') => {
+        Some(b'=') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_attribute_value_before(t, info)))
         }
-        Some('\t' | ' ') => {
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_attribute_name_after(t, info)))
         }
@@ -561,13 +560,13 @@ fn complete_attribute_name_after(tokenizer: &mut Tokenizer, info: Info) -> State
 /// ```
 fn complete_attribute_value_before(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        None | Some('<' | '=' | '>' | '`') => State::Nok,
-        Some(char) if matches!(char, '"' | '\'') => {
-            info.quote = Some(QuoteKind::from_char(char));
+        None | Some(b'<' | b'=' | b'>' | b'`') => State::Nok,
+        Some(byte) if matches!(byte, b'"' | b'\'') => {
+            info.quote = Some(QuoteKind::from_byte(byte));
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_attribute_value_quoted(t, info)))
         }
-        Some('\t' | ' ') => {
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_attribute_value_before(t, info)))
         }
@@ -585,8 +584,8 @@ fn complete_attribute_value_before(tokenizer: &mut Tokenizer, mut info: Info) ->
 /// ```
 fn complete_attribute_value_quoted(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => State::Nok,
-        Some(char) if char == info.quote.as_ref().unwrap().as_char() => {
+        None | Some(b'\n') => State::Nok,
+        Some(byte) if byte == info.quote.as_ref().unwrap().as_byte() => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_attribute_value_quoted_after(t, info)))
         }
@@ -605,7 +604,7 @@ fn complete_attribute_value_quoted(tokenizer: &mut Tokenizer, info: Info) -> Sta
 /// ```
 fn complete_attribute_value_unquoted(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\t' | '\n' | ' ' | '"' | '\'' | '/' | '<' | '=' | '>' | '`') => {
+        None | Some(b'\t' | b'\n' | b' ' | b'"' | b'\'' | b'/' | b'<' | b'=' | b'>' | b'`') => {
             complete_attribute_name_after(tokenizer, info)
         }
         Some(_) => {
@@ -624,7 +623,7 @@ fn complete_attribute_value_unquoted(tokenizer: &mut Tokenizer, info: Info) -> S
 /// ```
 fn complete_attribute_value_quoted_after(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('\t' | ' ' | '/' | '>') => complete_attribute_name_before(tokenizer, info),
+        Some(b'\t' | b' ' | b'/' | b'>') => complete_attribute_name_before(tokenizer, info),
         _ => State::Nok,
     }
 }
@@ -637,7 +636,7 @@ fn complete_attribute_value_quoted_after(tokenizer: &mut Tokenizer, info: Info)
 /// ```
 fn complete_end(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_after(t, info)))
         }
@@ -653,12 +652,12 @@ fn complete_end(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn complete_after(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             // Do not form containers.
             tokenizer.concrete = true;
             continuation(tokenizer, info)
         }
-        Some('\t' | ' ') => {
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| complete_after(t, info)))
         }
@@ -674,27 +673,27 @@ fn complete_after(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn continuation(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('-') if info.kind == Kind::Comment => {
+        Some(b'-') if info.kind == Kind::Comment => {
             tokenizer.consume();
             State::Fn(Box::new(|t| continuation_comment_inside(t, info)))
         }
-        Some('<') if info.kind == Kind::Raw => {
+        Some(b'<') if info.kind == Kind::Raw => {
             tokenizer.consume();
             State::Fn(Box::new(|t| continuation_raw_tag_open(t, info)))
         }
-        Some('>') if info.kind == Kind::Declaration => {
+        Some(b'>') if info.kind == Kind::Declaration => {
             tokenizer.consume();
             State::Fn(Box::new(|t| continuation_close(t, info)))
         }
-        Some('?') if info.kind == Kind::Instruction => {
+        Some(b'?') if info.kind == Kind::Instruction => {
             tokenizer.consume();
             State::Fn(Box::new(|t| continuation_declaration_inside(t, info)))
         }
-        Some(']') if info.kind == Kind::Cdata => {
+        Some(b']') if info.kind == Kind::Cdata => {
             tokenizer.consume();
             State::Fn(Box::new(|t| continuation_character_data_inside(t, info)))
         }
-        Some('\n') if info.kind == Kind::Basic || info.kind == Kind::Complete => {
+        Some(b'\n') if info.kind == Kind::Basic || info.kind == Kind::Complete => {
             tokenizer.exit(Token::HtmlFlowData);
             tokenizer.check(blank_line_before, |ok| {
                 if ok {
@@ -704,7 +703,7 @@ fn continuation(tokenizer: &mut Tokenizer, info: Info) -> State {
                 }
             })(tokenizer)
         }
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::HtmlFlowData);
             continuation_start(tokenizer, info)
         }
@@ -741,7 +740,7 @@ fn continuation_start(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn continuation_start_non_lazy(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.enter(Token::LineEnding);
             tokenizer.consume();
             tokenizer.exit(Token::LineEnding);
@@ -760,7 +759,7 @@ fn continuation_start_non_lazy(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn continuation_before(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => continuation_start(tokenizer, info),
+        None | Some(b'\n') => continuation_start(tokenizer, info),
         _ => {
             tokenizer.enter(Token::HtmlFlowData);
             continuation(tokenizer, info)
@@ -776,7 +775,7 @@ fn continuation_before(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn continuation_comment_inside(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('-') => {
+        Some(b'-') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| continuation_declaration_inside(t, info)))
         }
@@ -792,7 +791,7 @@ fn continuation_comment_inside(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn continuation_raw_tag_open(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some('/') => {
+        Some(b'/') => {
             tokenizer.consume();
             info.start = Some(tokenizer.point.clone());
             State::Fn(Box::new(|t| continuation_raw_end_tag(t, info)))
@@ -809,12 +808,12 @@ fn continuation_raw_tag_open(tokenizer: &mut Tokenizer, mut info: Info) -> State
 /// ```
 fn continuation_raw_end_tag(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             info.size = 0;
 
             let start = info.start.take().unwrap();
             let name = Slice::from_position(
-                &tokenizer.parse_state.chars,
+                tokenizer.parse_state.bytes,
                 &Position {
                     start: &start,
                     end: &tokenizer.point,
@@ -830,7 +829,7 @@ fn continuation_raw_end_tag(tokenizer: &mut Tokenizer, mut info: Info) -> State
                 continuation(tokenizer, info)
             }
         }
-        Some('A'..='Z' | 'a'..='z') if info.size < HTML_RAW_SIZE_MAX => {
+        Some(b'A'..=b'Z' | b'a'..=b'z') if info.size < HTML_RAW_SIZE_MAX => {
             tokenizer.consume();
             info.size += 1;
             State::Fn(Box::new(|t| continuation_raw_end_tag(t, info)))
@@ -850,7 +849,7 @@ fn continuation_raw_end_tag(tokenizer: &mut Tokenizer, mut info: Info) -> State
 /// ```
 fn continuation_character_data_inside(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some(']') => {
+        Some(b']') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| continuation_declaration_inside(t, info)))
         }
@@ -874,11 +873,11 @@ fn continuation_character_data_inside(tokenizer: &mut Tokenizer, info: Info) ->
 /// ```
 fn continuation_declaration_inside(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| continuation_close(t, info)))
         }
-        Some('-') if info.kind == Kind::Comment => {
+        Some(b'-') if info.kind == Kind::Comment => {
             tokenizer.consume();
             State::Fn(Box::new(|t| continuation_declaration_inside(t, info)))
         }
@@ -894,7 +893,7 @@ fn continuation_declaration_inside(tokenizer: &mut Tokenizer, info: Info) -> Sta
 /// ```
 fn continuation_close(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::HtmlFlowData);
             continuation_after(tokenizer)
         }
diff --git a/src/construct/html_text.rs b/src/construct/html_text.rs
index b1ad113..f10a476 100644
--- a/src/construct/html_text.rs
+++ b/src/construct/html_text.rs
@@ -58,7 +58,7 @@ use crate::construct::partial_space_or_tab::space_or_tab;
 use crate::token::Token;
 use crate::tokenizer::{State, StateFn, Tokenizer};
 
-const CDATA_SEARCH: [char; 6] = ['C', 'D', 'A', 'T', 'A', '['];
+const CDATA_SEARCH: [u8; 6] = [b'C', b'D', b'A', b'T', b'A', b'['];
 
 /// Start of HTML (text)
 ///
@@ -67,7 +67,7 @@ const CDATA_SEARCH: [char; 6] = ['C', 'D', 'A', 'T', 'A', '['];
 ///       ^
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
-    if Some('<') == tokenizer.current && tokenizer.parse_state.constructs.html_text {
+    if Some(b'<') == tokenizer.current && tokenizer.parse_state.constructs.html_text {
         tokenizer.enter(Token::HtmlText);
         tokenizer.enter(Token::HtmlTextData);
         tokenizer.consume();
@@ -89,19 +89,19 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn open(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('!') => {
+        Some(b'!') => {
             tokenizer.consume();
             State::Fn(Box::new(declaration_open))
         }
-        Some('/') => {
+        Some(b'/') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_close_start))
         }
-        Some('?') => {
+        Some(b'?') => {
             tokenizer.consume();
             State::Fn(Box::new(instruction))
         }
-        Some('A'..='Z' | 'a'..='z') => {
+        Some(b'A'..=b'Z' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open))
         }
@@ -121,15 +121,15 @@ fn open(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn declaration_open(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('-') => {
+        Some(b'-') => {
             tokenizer.consume();
             State::Fn(Box::new(comment_open_inside))
         }
-        Some('[') => {
+        Some(b'[') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| cdata_open_inside(t, 0)))
         }
-        Some('A'..='Z' | 'a'..='z') => {
+        Some(b'A'..=b'Z' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(declaration))
         }
@@ -145,7 +145,7 @@ fn declaration_open(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn comment_open_inside(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('-') => {
+        Some(b'-') => {
             tokenizer.consume();
             State::Fn(Box::new(comment_start))
         }
@@ -168,8 +168,8 @@ fn comment_open_inside(tokenizer: &mut Tokenizer) -> State {
 /// [html_flow]: crate::construct::html_flow
 fn comment_start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('>') => State::Nok,
-        Some('-') => {
+        None | Some(b'>') => State::Nok,
+        Some(b'-') => {
             tokenizer.consume();
             State::Fn(Box::new(comment_start_dash))
         }
@@ -192,7 +192,7 @@ fn comment_start(tokenizer: &mut Tokenizer) -> State {
 /// [html_flow]: crate::construct::html_flow
 fn comment_start_dash(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('>') => State::Nok,
+        None | Some(b'>') => State::Nok,
         _ => comment(tokenizer),
     }
 }
@@ -206,8 +206,8 @@ fn comment_start_dash(tokenizer: &mut Tokenizer) -> State {
 fn comment(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
         None => State::Nok,
-        Some('\n') => at_line_ending(tokenizer, Box::new(comment)),
-        Some('-') => {
+        Some(b'\n') => at_line_ending(tokenizer, Box::new(comment)),
+        Some(b'-') => {
             tokenizer.consume();
             State::Fn(Box::new(comment_close))
         }
@@ -226,7 +226,7 @@ fn comment(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn comment_close(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('-') => {
+        Some(b'-') => {
             tokenizer.consume();
             State::Fn(Box::new(end))
         }
@@ -242,7 +242,7 @@ fn comment_close(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn cdata_open_inside(tokenizer: &mut Tokenizer, index: usize) -> State {
     match tokenizer.current {
-        Some(char) if char == CDATA_SEARCH[index] => {
+        Some(byte) if byte == CDATA_SEARCH[index] => {
             tokenizer.consume();
 
             if index + 1 == CDATA_SEARCH.len() {
@@ -264,8 +264,8 @@ fn cdata_open_inside(tokenizer: &mut Tokenizer, index: usize) -> State {
 fn cdata(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
         None => State::Nok,
-        Some('\n') => at_line_ending(tokenizer, Box::new(cdata)),
-        Some(']') => {
+        Some(b'\n') => at_line_ending(tokenizer, Box::new(cdata)),
+        Some(b']') => {
             tokenizer.consume();
             State::Fn(Box::new(cdata_close))
         }
@@ -284,7 +284,7 @@ fn cdata(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn cdata_close(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(']') => {
+        Some(b']') => {
             tokenizer.consume();
             State::Fn(Box::new(cdata_end))
         }
@@ -300,8 +300,8 @@ fn cdata_close(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn cdata_end(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('>') => end(tokenizer),
-        Some(']') => cdata_close(tokenizer),
+        Some(b'>') => end(tokenizer),
+        Some(b']') => cdata_close(tokenizer),
         _ => cdata(tokenizer),
     }
 }
@@ -314,8 +314,8 @@ fn cdata_end(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn declaration(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('>') => end(tokenizer),
-        Some('\n') => at_line_ending(tokenizer, Box::new(declaration)),
+        None | Some(b'>') => end(tokenizer),
+        Some(b'\n') => at_line_ending(tokenizer, Box::new(declaration)),
         _ => {
             tokenizer.consume();
             State::Fn(Box::new(declaration))
@@ -332,8 +332,8 @@ fn declaration(tokenizer: &mut Tokenizer) -> State {
 fn instruction(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
         None => State::Nok,
-        Some('\n') => at_line_ending(tokenizer, Box::new(instruction)),
-        Some('?') => {
+        Some(b'\n') => at_line_ending(tokenizer, Box::new(instruction)),
+        Some(b'?') => {
             tokenizer.consume();
             State::Fn(Box::new(instruction_close))
         }
@@ -352,7 +352,7 @@ fn instruction(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn instruction_close(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('>') => end(tokenizer),
+        Some(b'>') => end(tokenizer),
         _ => instruction(tokenizer),
     }
 }
@@ -365,7 +365,7 @@ fn instruction_close(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn tag_close_start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('A'..='Z' | 'a'..='z') => {
+        Some(b'A'..=b'Z' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_close))
         }
@@ -381,7 +381,7 @@ fn tag_close_start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn tag_close(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('-' | '0'..='9' | 'A'..='Z' | 'a'..='z') => {
+        Some(b'-' | b'0'..=b'9' | b'A'..=b'Z' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_close))
         }
@@ -397,8 +397,8 @@ fn tag_close(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn tag_close_between(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\n') => at_line_ending(tokenizer, Box::new(tag_close_between)),
-        Some('\t' | ' ') => {
+        Some(b'\n') => at_line_ending(tokenizer, Box::new(tag_close_between)),
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_close_between))
         }
@@ -414,11 +414,11 @@ fn tag_close_between(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn tag_open(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('-' | '0'..='9' | 'A'..='Z' | 'a'..='z') => {
+        Some(b'-' | b'0'..=b'9' | b'A'..=b'Z' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open))
         }
-        Some('\t' | '\n' | ' ' | '/' | '>') => tag_open_between(tokenizer),
+        Some(b'\t' | b'\n' | b' ' | b'/' | b'>') => tag_open_between(tokenizer),
         _ => State::Nok,
     }
 }
@@ -431,16 +431,16 @@ fn tag_open(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn tag_open_between(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\n') => at_line_ending(tokenizer, Box::new(tag_open_between)),
-        Some('\t' | ' ') => {
+        Some(b'\n') => at_line_ending(tokenizer, Box::new(tag_open_between)),
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open_between))
         }
-        Some('/') => {
+        Some(b'/') => {
             tokenizer.consume();
             State::Fn(Box::new(end))
         }
-        Some(':' | 'A'..='Z' | '_' | 'a'..='z') => {
+        Some(b':' | b'A'..=b'Z' | b'_' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open_attribute_name))
         }
@@ -456,7 +456,7 @@ fn tag_open_between(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn tag_open_attribute_name(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('-' | '.' | '0'..='9' | ':' | 'A'..='Z' | '_' | 'a'..='z') => {
+        Some(b'-' | b'.' | b'0'..=b'9' | b':' | b'A'..=b'Z' | b'_' | b'a'..=b'z') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open_attribute_name))
         }
@@ -473,12 +473,12 @@ fn tag_open_attribute_name(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn tag_open_attribute_name_after(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\n') => at_line_ending(tokenizer, Box::new(tag_open_attribute_name_after)),
-        Some('\t' | ' ') => {
+        Some(b'\n') => at_line_ending(tokenizer, Box::new(tag_open_attribute_name_after)),
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open_attribute_name_after))
         }
-        Some('=') => {
+        Some(b'=') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open_attribute_value_before))
         }
@@ -495,15 +495,15 @@ fn tag_open_attribute_name_after(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn tag_open_attribute_value_before(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('<' | '=' | '>' | '`') => State::Nok,
-        Some('\n') => at_line_ending(tokenizer, Box::new(tag_open_attribute_value_before)),
-        Some('\t' | ' ') => {
+        None | Some(b'<' | b'=' | b'>' | b'`') => State::Nok,
+        Some(b'\n') => at_line_ending(tokenizer, Box::new(tag_open_attribute_value_before)),
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open_attribute_value_before))
         }
-        Some(char) if char == '"' || char == '\'' => {
+        Some(byte) if byte == b'"' || byte == b'\'' => {
             tokenizer.consume();
-            State::Fn(Box::new(move |t| tag_open_attribute_value_quoted(t, char)))
+            State::Fn(Box::new(move |t| tag_open_attribute_value_quoted(t, byte)))
         }
         Some(_) => {
             tokenizer.consume();
@@ -518,14 +518,14 @@ fn tag_open_attribute_value_before(tokenizer: &mut Tokenizer) -> State {
 /// > | a <b c="d"> e
 ///             ^
 /// ```
-fn tag_open_attribute_value_quoted(tokenizer: &mut Tokenizer, marker: char) -> State {
+fn tag_open_attribute_value_quoted(tokenizer: &mut Tokenizer, marker: u8) -> State {
     match tokenizer.current {
         None => State::Nok,
-        Some('\n') => at_line_ending(
+        Some(b'\n') => at_line_ending(
             tokenizer,
             Box::new(move |t| tag_open_attribute_value_quoted(t, marker)),
         ),
-        Some(char) if char == marker => {
+        Some(byte) if byte == marker => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open_attribute_value_quoted_after))
         }
@@ -546,8 +546,8 @@ fn tag_open_attribute_value_quoted(tokenizer: &mut Tokenizer, marker: char) -> S
 /// ```
 fn tag_open_attribute_value_unquoted(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('"' | '\'' | '<' | '=' | '`') => State::Nok,
-        Some('\t' | '\n' | ' ' | '/' | '>') => tag_open_between(tokenizer),
+        None | Some(b'"' | b'\'' | b'<' | b'=' | b'`') => State::Nok,
+        Some(b'\t' | b'\n' | b' ' | b'/' | b'>') => tag_open_between(tokenizer),
         Some(_) => {
             tokenizer.consume();
             State::Fn(Box::new(tag_open_attribute_value_unquoted))
@@ -564,7 +564,7 @@ fn tag_open_attribute_value_unquoted(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn tag_open_attribute_value_quoted_after(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\t' | '\n' | ' ' | '>' | '/') => tag_open_between(tokenizer),
+        Some(b'\t' | b'\n' | b' ' | b'>' | b'/') => tag_open_between(tokenizer),
         _ => State::Nok,
     }
 }
@@ -577,7 +577,7 @@ fn tag_open_attribute_value_quoted_after(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn end(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             tokenizer.consume();
             tokenizer.exit(Token::HtmlTextData);
             tokenizer.exit(Token::HtmlText);
@@ -599,7 +599,7 @@ fn end(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn at_line_ending(tokenizer: &mut Tokenizer, return_state: Box<StateFn>) -> State {
     match tokenizer.current {
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.exit(Token::HtmlTextData);
             tokenizer.enter(Token::LineEnding);
             tokenizer.consume();
diff --git a/src/construct/label_end.rs b/src/construct/label_end.rs
index 5ea788f..6399f81 100644
--- a/src/construct/label_end.rs
+++ b/src/construct/label_end.rs
@@ -182,7 +182,7 @@ struct Info {
 /// > | [a] b
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
-    if Some(']') == tokenizer.current && tokenizer.parse_state.constructs.label_end {
+    if Some(b']') == tokenizer.current && tokenizer.parse_state.constructs.label_end {
         let mut label_start_index = None;
         let mut index = tokenizer.label_start_stack.len();
 
@@ -217,7 +217,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
                     // To do: virtual spaces not needed, create a `to_str`?
                     id: normalize_identifier(
                         &Slice::from_position(
-                            &tokenizer.parse_state.chars,
+                            tokenizer.parse_state.bytes,
                             &Position {
                                 start: &tokenizer.events[label_start.start.1].point,
                                 end: &tokenizer.events[label_end_start - 1].point,
@@ -258,7 +258,7 @@ fn after(tokenizer: &mut Tokenizer, info: Info) -> State {
 
     match tokenizer.current {
         // Resource (`[asd](fgh)`)?
-        Some('(') => tokenizer.attempt(resource, move |is_ok| {
+        Some(b'(') => tokenizer.attempt(resource, move |is_ok| {
             Box::new(move |t| {
                 // Also fine if `defined`, as then it’s a valid shortcut.
                 if is_ok || defined {
@@ -269,7 +269,7 @@ fn after(tokenizer: &mut Tokenizer, info: Info) -> State {
             })
         })(tokenizer),
         // Full (`[asd][fgh]`) or collapsed (`[asd][]`) reference?
-        Some('[') => tokenizer.attempt(full_reference, move |is_ok| {
+        Some(b'[') => tokenizer.attempt(full_reference, move |is_ok| {
             Box::new(move |t| {
                 if is_ok {
                     ok(t, info)
@@ -382,7 +382,7 @@ fn nok(tokenizer: &mut Tokenizer, label_start_index: usize) -> State {
 /// ```
 fn resource(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('(') => {
+        Some(b'(') => {
             tokenizer.enter(Token::Resource);
             tokenizer.enter(Token::ResourceMarker);
             tokenizer.consume();
@@ -411,7 +411,7 @@ fn resource_start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn resource_open(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(')') => resource_end(tokenizer),
+        Some(b')') => resource_end(tokenizer),
         _ => tokenizer.go(
             |t| {
                 destination(
@@ -451,7 +451,7 @@ fn destination_after(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn resource_between(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('"' | '\'' | '(') => tokenizer.go(
+        Some(b'"' | b'\'' | b'(') => tokenizer.go(
             |t| {
                 title(
                     t,
@@ -486,7 +486,7 @@ fn title_after(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn resource_end(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(')') => {
+        Some(b')') => {
             tokenizer.enter(Token::ResourceMarker);
             tokenizer.consume();
             tokenizer.exit(Token::ResourceMarker);
@@ -505,7 +505,7 @@ fn resource_end(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn full_reference(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('[') => tokenizer.go(
+        Some(b'[') => tokenizer.go(
             |t| {
                 label(
                     t,
@@ -537,7 +537,7 @@ fn full_reference_after(tokenizer: &mut Tokenizer) -> State {
 
     // To do: virtual spaces not needed, create a `to_str`?
     let id = Slice::from_position(
-        &tokenizer.parse_state.chars,
+        tokenizer.parse_state.bytes,
         &Position::from_exit_event(&tokenizer.events, end),
     )
     .serialize();
@@ -563,7 +563,7 @@ fn full_reference_after(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn collapsed_reference(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('[') => {
+        Some(b'[') => {
             tokenizer.enter(Token::Reference);
             tokenizer.enter(Token::ReferenceMarker);
             tokenizer.consume();
@@ -584,7 +584,7 @@ fn collapsed_reference(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn collapsed_reference_open(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(']') => {
+        Some(b']') => {
             tokenizer.enter(Token::ReferenceMarker);
             tokenizer.consume();
             tokenizer.exit(Token::ReferenceMarker);
diff --git a/src/construct/label_start_image.rs b/src/construct/label_start_image.rs
index 078026d..d30b8dd 100644
--- a/src/construct/label_start_image.rs
+++ b/src/construct/label_start_image.rs
@@ -40,7 +40,7 @@ use crate::tokenizer::{LabelStart, State, Tokenizer};
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('!') if tokenizer.parse_state.constructs.label_start_image => {
+        Some(b'!') if tokenizer.parse_state.constructs.label_start_image => {
             tokenizer.enter(Token::LabelImage);
             tokenizer.enter(Token::LabelImageMarker);
             tokenizer.consume();
@@ -59,7 +59,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 pub fn open(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('[') => {
+        Some(b'[') => {
             tokenizer.enter(Token::LabelMarker);
             tokenizer.consume();
             tokenizer.exit(Token::LabelMarker);
diff --git a/src/construct/label_start_link.rs b/src/construct/label_start_link.rs
index d7ae1d6..c47941c 100644
--- a/src/construct/label_start_link.rs
+++ b/src/construct/label_start_link.rs
@@ -39,7 +39,7 @@ use crate::tokenizer::{LabelStart, State, Tokenizer};
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('[') if tokenizer.parse_state.constructs.label_start_link => {
+        Some(b'[') if tokenizer.parse_state.constructs.label_start_link => {
             let start = tokenizer.events.len();
             tokenizer.enter(Token::LabelLink);
             tokenizer.enter(Token::LabelMarker);
diff --git a/src/construct/list.rs b/src/construct/list.rs
index 355eeee..9b59130 100644
--- a/src/construct/list.rs
+++ b/src/construct/list.rs
@@ -102,19 +102,19 @@ enum Kind {
 }
 
 impl Kind {
-    /// Turn a [char] into a kind.
+    /// Turn a byte ([u8]) into a kind.
     ///
     /// ## Panics
     ///
-    /// Panics if `char` is not `.`, `)`, `*`, `+`, or `-`.
-    fn from_char(char: char) -> Kind {
-        match char {
-            '.' => Kind::Dot,
-            ')' => Kind::Paren,
-            '*' => Kind::Asterisk,
-            '+' => Kind::Plus,
-            '-' => Kind::Dash,
-            _ => unreachable!("invalid char"),
+    /// Panics if `byte` is not `.`, `)`, `*`, `+`, or `-`.
+    fn from_byte(byte: u8) -> Kind {
+        match byte {
+            b'.' => Kind::Dot,
+            b')' => Kind::Paren,
+            b'*' => Kind::Asterisk,
+            b'+' => Kind::Plus,
+            b'-' => Kind::Dash,
+            _ => unreachable!("invalid byte"),
         }
     }
 }
@@ -149,11 +149,11 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 fn before(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
         // Unordered.
-        Some('*' | '+' | '-') => tokenizer.check(thematic_break, |ok| {
+        Some(b'*' | b'+' | b'-') => tokenizer.check(thematic_break, |ok| {
             Box::new(if ok { nok } else { before_unordered })
         })(tokenizer),
         // Ordered.
-        Some(char) if char.is_ascii_digit() && (!tokenizer.interrupt || char == '1') => {
+        Some(byte) if byte.is_ascii_digit() && (!tokenizer.interrupt || byte == b'1') => {
             tokenizer.enter(Token::ListItemPrefix);
             tokenizer.enter(Token::ListItemValue);
             inside(tokenizer, 0)
@@ -183,11 +183,11 @@ fn before_unordered(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn inside(tokenizer: &mut Tokenizer, size: usize) -> State {
     match tokenizer.current {
-        Some(char) if char.is_ascii_digit() && size + 1 < LIST_ITEM_VALUE_SIZE_MAX => {
+        Some(byte) if byte.is_ascii_digit() && size + 1 < LIST_ITEM_VALUE_SIZE_MAX => {
             tokenizer.consume();
             State::Fn(Box::new(move |t| inside(t, size + 1)))
         }
-        Some('.' | ')') if !tokenizer.interrupt || size < 2 => {
+        Some(b'.' | b')') if !tokenizer.interrupt || size < 2 => {
             tokenizer.exit(Token::ListItemValue);
             marker(tokenizer)
         }
@@ -262,7 +262,7 @@ fn whitespace(tokenizer: &mut Tokenizer) -> State {
 ///      ^
 /// ```
 fn whitespace_after(tokenizer: &mut Tokenizer) -> State {
-    if matches!(tokenizer.current, Some('\t' | ' ')) {
+    if matches!(tokenizer.current, Some(b'\t' | b' ')) {
         State::Nok
     } else {
         State::Ok
@@ -277,7 +277,7 @@ fn whitespace_after(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn prefix_other(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\t' | ' ') => {
+        Some(b'\t' | b' ') => {
             tokenizer.enter(Token::SpaceOrTab);
             tokenizer.consume();
             tokenizer.exit(Token::SpaceOrTab);
@@ -303,7 +303,7 @@ fn after(tokenizer: &mut Tokenizer, blank: bool) -> State {
             &[Token::ListItem],
         );
         let mut prefix = Slice::from_position(
-            &tokenizer.parse_state.chars,
+            tokenizer.parse_state.bytes,
             &Position {
                 start: &tokenizer.events[start].point,
                 end: &tokenizer.point,
@@ -400,13 +400,10 @@ pub fn resolve_list_item(tokenizer: &mut Tokenizer) {
             if event.event_type == EventType::Enter {
                 let end = skip::opt(&tokenizer.events, index, &[Token::ListItem]) - 1;
                 let marker = skip::to(&tokenizer.events, index, &[Token::ListItemMarker]);
-                let kind = Kind::from_char(
-                    Slice::from_point(
-                        &tokenizer.parse_state.chars,
-                        &tokenizer.events[marker].point,
-                    )
-                    .head()
-                    .unwrap(),
+                let kind = Kind::from_byte(
+                    Slice::from_point(tokenizer.parse_state.bytes, &tokenizer.events[marker].point)
+                        .head()
+                        .unwrap(),
                 );
                 let current = (kind, balance, index, end);
 
diff --git a/src/construct/mod.rs b/src/construct/mod.rs
index 569c609..7b50957 100644
--- a/src/construct/mod.rs
+++ b/src/construct/mod.rs
@@ -84,6 +84,7 @@ pub mod label_start_image;
 pub mod label_start_link;
 pub mod list;
 pub mod paragraph;
+pub mod partial_bom;
 pub mod partial_data;
 pub mod partial_destination;
 pub mod partial_label;
diff --git a/src/construct/paragraph.rs b/src/construct/paragraph.rs
index 5d230d3..146dc40 100644
--- a/src/construct/paragraph.rs
+++ b/src/construct/paragraph.rs
@@ -44,7 +44,7 @@ use crate::util::skip::opt as skip_opt;
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             unreachable!("unexpected eol/eof")
         }
         _ => {
@@ -63,7 +63,7 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn inside(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::Data);
             tokenizer.exit(Token::Paragraph);
             tokenizer.register_resolver_before("paragraph".to_string(), Box::new(resolve));
diff --git a/src/construct/partial_bom.rs b/src/construct/partial_bom.rs
new file mode 100644
index 0000000..be8d6c8
--- /dev/null
+++ b/src/construct/partial_bom.rs
@@ -0,0 +1,54 @@
+//! To do.
+
+use crate::token::Token;
+use crate::tokenizer::{State, Tokenizer};
+
+/// Before a BOM.
+///
+/// ```text
+/// > | 0xEF 0xBB 0xBF
+///     ^^^^
+/// ```
+pub fn start(tokenizer: &mut Tokenizer) -> State {
+    match tokenizer.current {
+        Some(0xEF) => {
+            tokenizer.enter(Token::ByteOrderMark);
+            tokenizer.consume();
+            State::Fn(Box::new(cont))
+        }
+        _ => State::Nok,
+    }
+}
+
+/// Second byte in BOM.
+///
+/// ```text
+/// > | 0xEF 0xBB 0xBF
+///          ^^^^
+/// ```
+fn cont(tokenizer: &mut Tokenizer) -> State {
+    match tokenizer.current {
+        Some(0xBB) => {
+            tokenizer.consume();
+            State::Fn(Box::new(end))
+        }
+        _ => State::Nok,
+    }
+}
+
+/// Last byte in BOM.
+///
+/// ```text
+/// > | 0xEF 0xBB 0xBF
+///               ^^^^
+/// ```
+fn end(tokenizer: &mut Tokenizer) -> State {
+    match tokenizer.current {
+        Some(0xBF) => {
+            tokenizer.consume();
+            tokenizer.exit(Token::ByteOrderMark);
+            State::Ok
+        }
+        _ => State::Nok,
+    }
+}
diff --git a/src/construct/partial_data.rs b/src/construct/partial_data.rs
index 0b66b09..335d7ab 100644
--- a/src/construct/partial_data.rs
+++ b/src/construct/partial_data.rs
@@ -15,9 +15,9 @@ use crate::tokenizer::{EventType, State, Tokenizer};
 /// > | abc
 ///     ^
 /// ```
-pub fn start(tokenizer: &mut Tokenizer, stop: &'static [char]) -> State {
+pub fn start(tokenizer: &mut Tokenizer, stop: &'static [u8]) -> State {
     match tokenizer.current {
-        Some(char) if stop.contains(&char) => {
+        Some(byte) if stop.contains(&byte) => {
             tokenizer.enter(Token::Data);
             tokenizer.consume();
             State::Fn(Box::new(move |t| data(t, stop)))
@@ -32,16 +32,16 @@ pub fn start(tokenizer: &mut Tokenizer, stop: &'static [char]) -> State {
 /// > | abc
 ///     ^
 /// ```
-fn at_break(tokenizer: &mut Tokenizer, stop: &'static [char]) -> State {
+fn at_break(tokenizer: &mut Tokenizer, stop: &'static [u8]) -> State {
     match tokenizer.current {
         None => State::Ok,
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.enter(Token::LineEnding);
             tokenizer.consume();
             tokenizer.exit(Token::LineEnding);
             State::Fn(Box::new(move |t| at_break(t, stop)))
         }
-        Some(char) if stop.contains(&char) => {
+        Some(byte) if stop.contains(&byte) => {
             tokenizer.register_resolver_before("data".to_string(), Box::new(resolve_data));
             State::Ok
         }
@@ -58,10 +58,10 @@ fn at_break(tokenizer: &mut Tokenizer, stop: &'static [char]) -> State {
 /// > | abc
 ///     ^^^
 /// ```
-fn data(tokenizer: &mut Tokenizer, stop: &'static [char]) -> State {
+fn data(tokenizer: &mut Tokenizer, stop: &'static [u8]) -> State {
     let done = match tokenizer.current {
-        None | Some('\n') => true,
-        Some(char) if stop.contains(&char) => true,
+        None | Some(b'\n') => true,
+        Some(byte) if stop.contains(&byte) => true,
         _ => false,
     };
 
diff --git a/src/construct/partial_destination.rs b/src/construct/partial_destination.rs
index 6447228..0a3721c 100644
--- a/src/construct/partial_destination.rs
+++ b/src/construct/partial_destination.rs
@@ -117,7 +117,7 @@ pub fn start(tokenizer: &mut Tokenizer, options: Options) -> State {
     };
 
     match tokenizer.current {
-        Some('<') => {
+        Some(b'<') => {
             tokenizer.enter(info.options.destination.clone());
             tokenizer.enter(info.options.literal.clone());
             tokenizer.enter(info.options.marker.clone());
@@ -125,8 +125,8 @@ pub fn start(tokenizer: &mut Tokenizer, options: Options) -> State {
             tokenizer.exit(info.options.marker.clone());
             State::Fn(Box::new(|t| enclosed_before(t, info)))
         }
-        None | Some(' ' | ')') => State::Nok,
-        Some(char) if char.is_ascii_control() => State::Nok,
+        None | Some(b' ' | b')') => State::Nok,
+        Some(byte) if byte != b'\0' && byte.is_ascii_control() => State::Nok,
         Some(_) => {
             tokenizer.enter(info.options.destination.clone());
             tokenizer.enter(info.options.raw.clone());
@@ -144,7 +144,7 @@ pub fn start(tokenizer: &mut Tokenizer, options: Options) -> State {
 ///      ^
 /// ```
 fn enclosed_before(tokenizer: &mut Tokenizer, info: Info) -> State {
-    if let Some('>') = tokenizer.current {
+    if let Some(b'>') = tokenizer.current {
         tokenizer.enter(info.options.marker.clone());
         tokenizer.consume();
         tokenizer.exit(info.options.marker.clone());
@@ -166,13 +166,13 @@ fn enclosed_before(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn enclosed(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('>') => {
+        Some(b'>') => {
             tokenizer.exit(Token::Data);
             tokenizer.exit(info.options.string.clone());
             enclosed_before(tokenizer, info)
         }
-        None | Some('\n' | '<') => State::Nok,
-        Some('\\') => {
+        None | Some(b'\n' | b'<') => State::Nok,
+        Some(b'\\') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| enclosed_escape(t, info)))
         }
@@ -191,7 +191,7 @@ fn enclosed(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn enclosed_escape(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('<' | '>' | '\\') => {
+        Some(b'<' | b'>' | b'\\') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| enclosed(t, info)))
         }
@@ -207,7 +207,7 @@ fn enclosed_escape(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn raw(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some('(') => {
+        Some(b'(') => {
             if info.balance >= info.options.limit {
                 State::Nok
             } else {
@@ -216,7 +216,7 @@ fn raw(tokenizer: &mut Tokenizer, mut info: Info) -> State {
                 State::Fn(Box::new(move |t| raw(t, info)))
             }
         }
-        Some(')') => {
+        Some(b')') => {
             if info.balance == 0 {
                 tokenizer.exit(Token::Data);
                 tokenizer.exit(info.options.string.clone());
@@ -229,7 +229,7 @@ fn raw(tokenizer: &mut Tokenizer, mut info: Info) -> State {
                 State::Fn(Box::new(move |t| raw(t, info)))
             }
         }
-        None | Some('\t' | '\n' | ' ') => {
+        None | Some(b'\t' | b'\n' | b' ') => {
             if info.balance > 0 {
                 State::Nok
             } else {
@@ -240,8 +240,8 @@ fn raw(tokenizer: &mut Tokenizer, mut info: Info) -> State {
                 State::Ok
             }
         }
-        Some(char) if char.is_ascii_control() => State::Nok,
-        Some('\\') => {
+        Some(byte) if byte != b'\0' && byte.is_ascii_control() => State::Nok,
+        Some(b'\\') => {
             tokenizer.consume();
             State::Fn(Box::new(move |t| raw_escape(t, info)))
         }
@@ -260,7 +260,7 @@ fn raw(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn raw_escape(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some('(' | ')' | '\\') => {
+        Some(b'(' | b')' | b'\\') => {
             tokenizer.consume();
             State::Fn(Box::new(move |t| raw(t, info)))
         }
diff --git a/src/construct/partial_label.rs b/src/construct/partial_label.rs
index ee31533..7e40a2d 100644
--- a/src/construct/partial_label.rs
+++ b/src/construct/partial_label.rs
@@ -82,9 +82,9 @@ pub struct Options {
 struct Info {
     /// Whether we’ve seen our first `ChunkString`.
     connect: bool,
-    /// Whether there are non-blank characters in the label.
+    /// Whether there are non-blank bytes in the label.
     data: bool,
-    /// Number of characters in the label.
+    /// Number of bytes in the label.
     size: usize,
     /// Configuration.
     options: Options,
@@ -98,7 +98,7 @@ struct Info {
 /// ```
 pub fn start(tokenizer: &mut Tokenizer, options: Options) -> State {
     match tokenizer.current {
-        Some('[') => {
+        Some(b'[') => {
             let info = Info {
                 connect: false,
                 data: false,
@@ -124,10 +124,10 @@ pub fn start(tokenizer: &mut Tokenizer, options: Options) -> State {
 /// ```
 fn at_break(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        None | Some('[') => State::Nok,
-        Some(']') if !info.data => State::Nok,
+        None | Some(b'[') => State::Nok,
+        Some(b']') if !info.data => State::Nok,
         _ if info.size > LINK_REFERENCE_SIZE_MAX => State::Nok,
-        Some(']') => {
+        Some(b']') => {
             tokenizer.exit(info.options.string.clone());
             tokenizer.enter(info.options.marker.clone());
             tokenizer.consume();
@@ -135,7 +135,7 @@ fn at_break(tokenizer: &mut Tokenizer, mut info: Info) -> State {
             tokenizer.exit(info.options.label);
             State::Ok
         }
-        Some('\n') => tokenizer.go(
+        Some(b'\n') => tokenizer.go(
             space_or_tab_eol_with_options(EolOptions {
                 content_type: Some(ContentType::String),
                 connect: info.connect,
@@ -168,7 +168,7 @@ fn at_break(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn label(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n' | '[' | ']') => {
+        None | Some(b'\n' | b'[' | b']') => {
             tokenizer.exit(Token::Data);
             at_break(tokenizer, info)
         }
@@ -176,12 +176,12 @@ fn label(tokenizer: &mut Tokenizer, mut info: Info) -> State {
             tokenizer.exit(Token::Data);
             at_break(tokenizer, info)
         }
-        Some('\t' | ' ') => {
+        Some(b'\t' | b' ') => {
             tokenizer.consume();
             info.size += 1;
             State::Fn(Box::new(|t| label(t, info)))
         }
-        Some('\\') => {
+        Some(b'\\') => {
             tokenizer.consume();
             info.size += 1;
             if !info.data {
@@ -208,7 +208,7 @@ fn label(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn escape(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some('[' | '\\' | ']') => {
+        Some(b'[' | b'\\' | b']') => {
             tokenizer.consume();
             info.size += 1;
             State::Fn(Box::new(|t| label(t, info)))
diff --git a/src/construct/partial_non_lazy_continuation.rs b/src/construct/partial_non_lazy_continuation.rs
index 068e30f..6005a6c 100644
--- a/src/construct/partial_non_lazy_continuation.rs
+++ b/src/construct/partial_non_lazy_continuation.rs
@@ -22,7 +22,7 @@ use crate::tokenizer::{State, Tokenizer};
 /// ```
 pub fn start(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.enter(Token::LineEnding);
             tokenizer.consume();
             tokenizer.exit(Token::LineEnding);
diff --git a/src/construct/partial_space_or_tab.rs b/src/construct/partial_space_or_tab.rs
index 6070ffe..f31cbc6 100644
--- a/src/construct/partial_space_or_tab.rs
+++ b/src/construct/partial_space_or_tab.rs
@@ -11,9 +11,9 @@ use crate::tokenizer::{ContentType, State, StateFn, Tokenizer};
 /// Options to parse `space_or_tab`.
 #[derive(Debug)]
 pub struct Options {
-    /// Minimum allowed characters (inclusive).
+    /// Minimum allowed bytes (inclusive).
     pub min: usize,
-    /// Maximum allowed characters (inclusive).
+    /// Maximum allowed bytes (inclusive).
     pub max: usize,
     /// Token type to use for whitespace events.
     pub kind: Token,
@@ -134,7 +134,7 @@ pub fn space_or_tab_eol_with_options(options: EolOptions) -> Box<StateFn> {
 /// ```
 fn start(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some('\t' | ' ') if info.options.max > 0 => {
+        Some(b'\t' | b' ') if info.options.max > 0 => {
             tokenizer
                 .enter_with_content(info.options.kind.clone(), info.options.content_type.clone());
 
@@ -165,7 +165,7 @@ fn start(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn inside(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some('\t' | ' ') if info.size < info.options.max => {
+        Some(b'\t' | b' ') if info.size < info.options.max => {
             tokenizer.consume();
             info.size += 1;
             State::Fn(Box::new(|t| inside(t, info)))
@@ -190,7 +190,7 @@ fn inside(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn after_space_or_tab(tokenizer: &mut Tokenizer, mut info: EolInfo) -> State {
     match tokenizer.current {
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.enter_with_content(Token::LineEnding, info.options.content_type.clone());
 
             if info.connect {
@@ -239,7 +239,7 @@ fn after_eol(tokenizer: &mut Tokenizer, info: EolInfo) -> State {
 /// ```
 fn after_more_space_or_tab(tokenizer: &mut Tokenizer) -> State {
     // Blank line not allowed.
-    if matches!(tokenizer.current, None | Some('\n')) {
+    if matches!(tokenizer.current, None | Some(b'\n')) {
         State::Nok
     } else {
         State::Ok
diff --git a/src/construct/partial_title.rs b/src/construct/partial_title.rs
index 15fc25e..80861af 100644
--- a/src/construct/partial_title.rs
+++ b/src/construct/partial_title.rs
@@ -78,29 +78,29 @@ enum Kind {
 }
 
 impl Kind {
-    /// Turn the kind into a [char].
+    /// Turn the kind into a byte ([u8]).
     ///
     /// > 👉 **Note**: a closing paren is used for `Kind::Paren`.
-    fn as_char(&self) -> char {
+    fn as_byte(&self) -> u8 {
         match self {
-            Kind::Paren => ')',
-            Kind::Double => '"',
-            Kind::Single => '\'',
+            Kind::Paren => b')',
+            Kind::Double => b'"',
+            Kind::Single => b'\'',
         }
     }
-    /// Turn a [char] into a kind.
+    /// Turn a byte ([u8]) into a kind.
     ///
     /// > 👉 **Note**: an opening paren must be used for `Kind::Paren`.
     ///
     /// ## Panics
     ///
-    /// Panics if `char` is not `(`, `"`, or `'`.
-    fn from_char(char: char) -> Kind {
-        match char {
-            '(' => Kind::Paren,
-            '"' => Kind::Double,
-            '\'' => Kind::Single,
-            _ => unreachable!("invalid char"),
+    /// Panics if `byte` is not `(`, `"`, or `'`.
+    fn from_byte(byte: u8) -> Kind {
+        match byte {
+            b'(' => Kind::Paren,
+            b'"' => Kind::Double,
+            b'\'' => Kind::Single,
+            _ => unreachable!("invalid byte"),
         }
     }
 }
@@ -124,10 +124,10 @@ struct Info {
 /// ```
 pub fn start(tokenizer: &mut Tokenizer, options: Options) -> State {
     match tokenizer.current {
-        Some(char) if matches!(char, '"' | '\'' | '(') => {
+        Some(byte) if matches!(byte, b'"' | b'\'' | b'(') => {
             let info = Info {
                 connect: false,
-                kind: Kind::from_char(char),
+                kind: Kind::from_byte(byte),
                 options,
             };
             tokenizer.enter(info.options.title.clone());
@@ -150,7 +150,7 @@ pub fn start(tokenizer: &mut Tokenizer, options: Options) -> State {
 /// ```
 fn begin(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some(char) if char == info.kind.as_char() => {
+        Some(byte) if byte == info.kind.as_byte() => {
             tokenizer.enter(info.options.marker.clone());
             tokenizer.consume();
             tokenizer.exit(info.options.marker.clone());
@@ -172,12 +172,12 @@ fn begin(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn at_break(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some(char) if char == info.kind.as_char() => {
+        Some(byte) if byte == info.kind.as_byte() => {
             tokenizer.exit(info.options.string.clone());
             begin(tokenizer, info)
         }
         None => State::Nok,
-        Some('\n') => tokenizer.go(
+        Some(b'\n') => tokenizer.go(
             space_or_tab_eol_with_options(EolOptions {
                 content_type: Some(ContentType::String),
                 connect: info.connect,
@@ -210,15 +210,15 @@ fn at_break(tokenizer: &mut Tokenizer, mut info: Info) -> State {
 /// ```
 fn title(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some(char) if char == info.kind.as_char() => {
+        Some(byte) if byte == info.kind.as_byte() => {
             tokenizer.exit(Token::Data);
             at_break(tokenizer, info)
         }
-        None | Some('\n') => {
+        None | Some(b'\n') => {
             tokenizer.exit(Token::Data);
             at_break(tokenizer, info)
         }
-        Some('\\') => {
+        Some(b'\\') => {
             tokenizer.consume();
             State::Fn(Box::new(|t| escape(t, info)))
         }
@@ -237,7 +237,7 @@ fn title(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn escape(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        Some(char) if char == info.kind.as_char() => {
+        Some(byte) if byte == info.kind.as_byte() => {
             tokenizer.consume();
             State::Fn(Box::new(|t| title(t, info)))
         }
diff --git a/src/construct/partial_whitespace.rs b/src/construct/partial_whitespace.rs
index 152824b..13815cb 100644
--- a/src/construct/partial_whitespace.rs
+++ b/src/construct/partial_whitespace.rs
@@ -86,25 +86,25 @@ fn trim_data(
     hard_break: bool,
 ) {
     let mut slice = Slice::from_position(
-        &tokenizer.parse_state.chars,
+        tokenizer.parse_state.bytes,
         &Position::from_exit_event(&tokenizer.events, exit_index),
     );
 
     if trim_end {
-        let mut index = slice.chars.len();
+        let mut index = slice.bytes.len();
         let vs = slice.after;
         let mut spaces_only = vs == 0;
         while index > 0 {
-            match slice.chars[index - 1] {
-                ' ' => {}
-                '\t' => spaces_only = false,
+            match slice.bytes[index - 1] {
+                b' ' => {}
+                b'\t' => spaces_only = false,
                 _ => break,
             }
 
             index -= 1;
         }
 
-        let diff = slice.chars.len() - index;
+        let diff = slice.bytes.len() - index;
         let token_type = if spaces_only
             && hard_break
             && exit_index + 1 < tokenizer.events.len()
@@ -150,16 +150,16 @@ fn trim_data(
             );
 
             tokenizer.events[exit_index].point = enter_point;
-            slice.chars = &slice.chars[..index];
+            slice.bytes = &slice.bytes[..index];
         }
     }
 
     if trim_start {
         let mut index = 0;
         let vs = slice.before;
-        while index < slice.chars.len() {
-            match slice.chars[index] {
-                ' ' | '\t' => {}
+        while index < slice.bytes.len() {
+            match slice.bytes[index] {
+                b' ' | b'\t' => {}
                 _ => break,
             }
 
@@ -168,7 +168,7 @@ fn trim_data(
 
         // The whole data is whitespace.
         // We can be very fast: we only change the token types.
-        if index == slice.chars.len() {
+        if index == slice.bytes.len() {
             tokenizer.events[exit_index - 1].token_type = Token::SpaceOrTab;
             tokenizer.events[exit_index].token_type = Token::SpaceOrTab;
             return;
diff --git a/src/construct/thematic_break.rs b/src/construct/thematic_break.rs
index bed454b..4fc4dc4 100644
--- a/src/construct/thematic_break.rs
+++ b/src/construct/thematic_break.rs
@@ -83,25 +83,25 @@ enum Kind {
 }
 
 impl Kind {
-    /// Turn the kind into a [char].
-    fn as_char(&self) -> char {
+    /// Turn the kind into a byte ([u8]).
+    fn as_byte(&self) -> u8 {
         match self {
-            Kind::Asterisk => '*',
-            Kind::Dash => '-',
-            Kind::Underscore => '_',
+            Kind::Asterisk => b'*',
+            Kind::Dash => b'-',
+            Kind::Underscore => b'_',
         }
     }
-    /// Turn a [char] into a kind.
+    /// Turn a byte ([u8]) into a kind.
     ///
     /// ## Panics
     ///
-    /// Panics if `char` is not `*`, `-`, or `_`.
-    fn from_char(char: char) -> Kind {
-        match char {
-            '*' => Kind::Asterisk,
-            '-' => Kind::Dash,
-            '_' => Kind::Underscore,
-            _ => unreachable!("invalid char"),
+    /// Panics if `byte` is not `*`, `-`, or `_`.
+    fn from_byte(byte: u8) -> Kind {
+        match byte {
+            b'*' => Kind::Asterisk,
+            b'-' => Kind::Dash,
+            b'_' => Kind::Underscore,
+            _ => unreachable!("invalid byte"),
         }
     }
 }
@@ -144,10 +144,10 @@ pub fn start(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn before(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
-        Some(char) if matches!(char, '*' | '-' | '_') => at_break(
+        Some(byte) if matches!(byte, b'*' | b'-' | b'_') => at_break(
             tokenizer,
             Info {
-                kind: Kind::from_char(char),
+                kind: Kind::from_byte(byte),
                 size: 0,
             },
         ),
@@ -163,13 +163,13 @@ fn before(tokenizer: &mut Tokenizer) -> State {
 /// ```
 fn at_break(tokenizer: &mut Tokenizer, info: Info) -> State {
     match tokenizer.current {
-        None | Some('\n' | '\r') if info.size >= THEMATIC_BREAK_MARKER_COUNT_MIN => {
+        None | Some(b'\n' | b'\r') if info.size >= THEMATIC_BREAK_MARKER_COUNT_MIN => {
             tokenizer.exit(Token::ThematicBreak);
             // Feel free to interrupt.
             tokenizer.interrupt = false;
             State::Ok
         }
-        Some(char) if char == info.kind.as_char() => {
+        Some(byte) if byte == info.kind.as_byte() => {
             tokenizer.enter(Token::ThematicBreakSequence);
             sequence(tokenizer, info)
         }
@@ -185,7 +185,7 @@ fn at_break(tokenizer: &mut Tokenizer, info: Info) -> State {
 /// ```
 fn sequence(tokenizer: &mut Tokenizer, mut info: Info) -> State {
     match tokenizer.current {
-        Some(char) if char == info.kind.as_char() => {
+        Some(byte) if byte == info.kind.as_byte() => {
             tokenizer.consume();
             info.size += 1;
             State::Fn(Box::new(|t| sequence(t, info)))
diff --git a/src/content/document.rs b/src/content/document.rs
index 935c4ef..828431d 100644
--- a/src/content/document.rs
+++ b/src/content/document.rs
@@ -11,6 +11,7 @@
 use crate::construct::{
     block_quote::{cont as block_quote_cont, start as block_quote},
     list::{cont as list_item_const, start as list_item},
+    partial_bom::start as bom,
 };
 use crate::content::flow::start as flow;
 use crate::parser::ParseState;
@@ -78,7 +79,7 @@ struct DocumentInfo {
 pub fn document(parse_state: &mut ParseState, point: Point) -> Vec<Event> {
     let mut tokenizer = Tokenizer::new(point, parse_state);
 
-    let state = tokenizer.push(0, parse_state.chars.len(), Box::new(before));
+    let state = tokenizer.push(0, parse_state.bytes.len(), Box::new(before));
     tokenizer.flush(state, true);
 
     let mut index = 0;
@@ -92,7 +93,7 @@ pub fn document(parse_state: &mut ParseState, point: Point) -> Vec<Event> {
             // don‘t need virtual spaces.
             let id = normalize_identifier(
                 &Slice::from_position(
-                    &tokenizer.parse_state.chars,
+                    tokenizer.parse_state.bytes,
                     &Position::from_exit_event(&tokenizer.events, index),
                 )
                 .serialize(),
@@ -124,15 +125,7 @@ pub fn document(parse_state: &mut ParseState, point: Point) -> Vec<Event> {
 ///     ^
 /// ```
 fn before(tokenizer: &mut Tokenizer) -> State {
-    match tokenizer.current {
-        Some('\u{FEFF}') => {
-            tokenizer.enter(Token::ByteOrderMark);
-            tokenizer.consume();
-            tokenizer.exit(Token::ByteOrderMark);
-            State::Fn(Box::new(start))
-        }
-        _ => start(tokenizer),
-    }
+    tokenizer.attempt_opt(bom, start)(tokenizer)
 }
 
 /// Before document.
@@ -358,7 +351,7 @@ fn containers_after(tokenizer: &mut Tokenizer, mut info: DocumentInfo) -> State
     // Parse flow, pausing after eols.
     tokenizer.go_until(
         state,
-        |code| matches!(code, Some('\n')),
+        |code| matches!(code, Some(b'\n')),
         move |state| Box::new(move |t| flow_end(t, info, state)),
     )(tokenizer)
 }
diff --git a/src/content/flow.rs b/src/content/flow.rs
index 09c4e2c..bf4104c 100644
--- a/src/content/flow.rs
+++ b/src/content/flow.rs
@@ -88,7 +88,7 @@ fn initial_before(tokenizer: &mut Tokenizer) -> State {
 fn blank_line_after(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
         None => State::Ok,
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.enter(Token::BlankLineEnding);
             tokenizer.consume();
             tokenizer.exit(Token::BlankLineEnding);
@@ -112,7 +112,7 @@ fn blank_line_after(tokenizer: &mut Tokenizer) -> State {
 fn after(tokenizer: &mut Tokenizer) -> State {
     match tokenizer.current {
         None => State::Ok,
-        Some('\n') => {
+        Some(b'\n') => {
             tokenizer.enter(Token::LineEnding);
             tokenizer.consume();
             tokenizer.exit(Token::LineEnding);
diff --git a/src/content/string.rs b/src/content/string.rs
index 8bc2b91..d2aec3f 100644
--- a/src/content/string.rs
+++ b/src/content/string.rs
@@ -18,7 +18,7 @@ use crate::construct::{
 };
 use crate::tokenizer::{State, Tokenizer};
 
-const MARKERS: [char; 2] = ['&', '\\'];
+const MARKERS: [u8; 2] = [b'&', b'\\'];
 
 /// Start of string.
 pub fn start(tokenizer: &mut Tokenizer) -> State {
diff --git a/src/content/text.rs b/src/content/text.rs
index ebdf888..30c98a3 100644
--- a/src/content/text.rs
+++ b/src/content/text.rs
@@ -30,16 +30,16 @@ use crate::construct::{
 };
 use crate::tokenizer::{State, Tokenizer};
 
-const MARKERS: [char; 9] = [
-    '!',  // `label_start_image`
-    '&',  // `character_reference`
-    '*',  // `attention`
-    '<',  // `autolink`, `html_text`
-    '[',  // `label_start_link`
-    '\\', // `character_escape`, `hard_break_escape`
-    ']',  // `label_end`
-    '_',  // `attention`
-    '`',  // `code_text`
+const MARKERS: [u8; 9] = [
+    b'!',  // `label_start_image`
+    b'&',  // `character_reference`
+    b'*',  // `attention`
+    b'<',  // `autolink`, `html_text`
+    b'[',  // `label_start_link`
+    b'\\', // `character_escape`, `hard_break_escape`
+    b']',  // `label_end`
+    b'_',  // `attention`
+    b'`',  // `code_text`
 ];
 
 /// Start of text.
diff --git a/src/lib.rs b/src/lib.rs
index c1b0fa0..750ca36 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -424,5 +424,5 @@ pub fn micromark(value: &str) -> String {
 #[must_use]
 pub fn micromark_with_options(value: &str, options: &Options) -> String {
     let (events, result) = parse(value, options);
-    compile(&events, &result.chars, options)
+    compile(&events, result.bytes, options)
 }
diff --git a/src/parser.rs b/src/parser.rs
index cc9c256..613b206 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -12,7 +12,7 @@ use crate::{Constructs, Options};
 pub struct ParseState<'a> {
     pub constructs: &'a Constructs,
     /// List of chars.
-    pub chars: Vec<char>,
+    pub bytes: &'a [u8],
     /// Set of defined identifiers.
     pub definitions: Vec<String>,
 }
@@ -20,11 +20,10 @@ pub struct ParseState<'a> {
 /// Turn a string of markdown into events.
 ///
 /// Passes the codes back so the compiler can access the source.
-pub fn parse<'a>(value: &str, options: &'a Options) -> (Vec<Event>, ParseState<'a>) {
+pub fn parse<'a>(value: &'a str, options: &'a Options) -> (Vec<Event>, ParseState<'a>) {
     let mut parse_state = ParseState {
         constructs: &options.constructs,
-        // To do: change to `u8`s?
-        chars: value.chars().collect::<_>(),
+        bytes: value.as_bytes(),
         definitions: vec![],
     };
 
@@ -38,5 +37,6 @@ pub fn parse<'a>(value: &str, options: &'a Options) -> (Vec<Event>, ParseState<'
         },
     );
 
+    // To do: return bytes only?
     (events, parse_state)
 }
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index 3cbad0f..9c5e9f6 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -27,8 +27,8 @@ pub enum ContentType {
 
 #[derive(Debug, PartialEq)]
 pub enum CharAction {
-    Normal(char),
-    Insert(char),
+    Normal(u8),
+    Insert(u8),
     Ignore,
 }
 
@@ -42,8 +42,8 @@ pub struct Point {
     pub line: usize,
     /// 1-indexed column number.
     /// This is increases up to a tab stop for tabs.
-    /// Some editors count tabs as 1 character, so this position is not always
-    /// the same as editors.
+    /// Some editors count tabs as 1 character, so this position is not the
+    /// same as editors.
     pub column: usize,
     /// 0-indexed position in the document.
     ///
@@ -81,7 +81,7 @@ pub struct Event {
 }
 
 /// The essence of the state machine are functions: `StateFn`.
-/// It’s responsible for dealing with the current char.
+/// It’s responsible for dealing with the current byte.
 /// It yields a [`State`][].
 pub type StateFn = dyn FnOnce(&mut Tokenizer) -> State;
 
@@ -157,9 +157,9 @@ struct InternalState {
     /// Length of the stack. It’s not allowed to decrease the stack in a check or an attempt.
     stack_len: usize,
     /// Previous code.
-    previous: Option<char>,
+    previous: Option<u8>,
     /// Current code.
-    current: Option<char>,
+    current: Option<u8>,
     /// Current relative and absolute position in the file.
     point: Point,
 }
@@ -173,17 +173,17 @@ pub struct Tokenizer<'a> {
     first_line: usize,
     /// To do.
     line_start: Point,
-    /// Track whether a character is expected to be consumed, and whether it’s
-    /// actually consumed
+    /// Track whether the current byte is already consumed (`true`) or expected
+    /// to be consumed (`false`).
     ///
     /// Tracked to make sure everything’s valid.
     consumed: bool,
     /// Track whether this tokenizer is done.
     resolved: bool,
-    /// Current character code.
-    pub current: Option<char>,
-    /// Previous character code.
-    pub previous: Option<char>,
+    /// Current byte.
+    pub current: Option<u8>,
+    /// Previous byte.
+    pub previous: Option<u8>,
     /// Current relative and absolute place in the file.
     pub point: Point,
     /// Semantic labels of one or more codes in `codes`.
@@ -297,13 +297,13 @@ impl<'a> Tokenizer<'a> {
     }
 
     /// Prepare for a next code to get consumed.
-    pub fn expect(&mut self, char: Option<char>) {
-        debug_assert!(self.consumed, "expected previous character to be consumed");
+    pub fn expect(&mut self, byte: Option<u8>) {
+        debug_assert!(self.consumed, "expected previous byte to be consumed");
         self.consumed = false;
-        self.current = char;
+        self.current = byte;
     }
 
-    /// Consume the current character.
+    /// Consume the current byte.
     /// Each [`StateFn`][] is expected to call this to signal that this code is
     /// used, or call a next `StateFn`.
     pub fn consume(&mut self) {
@@ -320,23 +320,23 @@ impl<'a> Tokenizer<'a> {
         self.consumed = true;
     }
 
-    /// Move to the next (virtual) character.
+    /// Move to the next (virtual) byte.
     pub fn move_one(&mut self) {
-        match char_action(&self.parse_state.chars, &self.point) {
+        match byte_action(self.parse_state.bytes, &self.point) {
             CharAction::Ignore => {
                 self.point.index += 1;
             }
-            CharAction::Insert(char) => {
-                self.previous = Some(char);
+            CharAction::Insert(byte) => {
+                self.previous = Some(byte);
                 self.point.column += 1;
                 self.point.vs += 1;
             }
-            CharAction::Normal(char) => {
-                self.previous = Some(char);
+            CharAction::Normal(byte) => {
+                self.previous = Some(byte);
                 self.point.vs = 0;
                 self.point.index += 1;
 
-                if char == '\n' {
+                if byte == b'\n' {
                     self.point.line += 1;
                     self.point.column = 1;
 
@@ -355,7 +355,7 @@ impl<'a> Tokenizer<'a> {
         }
     }
 
-    /// Move (virtual) characters.
+    /// Move (virtual) bytes.
     pub fn move_to(&mut self, to: (usize, usize)) {
         let (to_index, to_vs) = to;
         while self.point.index < to_index || self.point.index == to_index && self.point.vs < to_vs {
@@ -382,10 +382,10 @@ impl<'a> Tokenizer<'a> {
     pub fn enter_with_link(&mut self, token_type: Token, link: Option<Link>) {
         let mut point = self.point.clone();
 
-        // Move back past ignored chars.
+        // Move back past ignored bytes.
         while point.index > 0 {
             point.index -= 1;
-            let action = char_action(&self.parse_state.chars, &point);
+            let action = byte_action(self.parse_state.bytes, &point);
             if !matches!(action, CharAction::Ignore) {
                 point.index += 1;
                 break;
@@ -432,13 +432,13 @@ impl<'a> Tokenizer<'a> {
 
         // A bit weird, but if we exit right after a line ending, we *don’t* want to consider
         // potential skips.
-        if matches!(self.previous, Some('\n')) {
+        if matches!(self.previous, Some(b'\n')) {
             point = self.line_start.clone();
         } else {
-            // Move back past ignored chars.
+            // Move back past ignored bytes.
             while point.index > 0 {
                 point.index -= 1;
-                let action = char_action(&self.parse_state.chars, &point);
+                let action = byte_action(self.parse_state.bytes, &point);
                 if !matches!(action, CharAction::Ignore) {
                     point.index += 1;
                     break;
@@ -520,7 +520,7 @@ impl<'a> Tokenizer<'a> {
     pub fn go_until(
         &mut self,
         state_fn: impl FnOnce(&mut Tokenizer) -> State + 'static,
-        until: impl Fn(Option<char>) -> bool + 'static,
+        until: impl Fn(Option<u8>) -> bool + 'static,
         done: impl FnOnce(State) -> Box<StateFn> + 'static,
     ) -> Box<StateFn> {
         attempt_impl(
@@ -653,21 +653,19 @@ impl<'a> Tokenizer<'a> {
         while self.point.index < max {
             match state {
                 State::Ok | State::Nok => break,
-                State::Fn(func) => match char_action(&self.parse_state.chars, &self.point) {
+                State::Fn(func) => match byte_action(self.parse_state.bytes, &self.point) {
                     CharAction::Ignore => {
                         state = State::Fn(Box::new(func));
                         self.move_one();
                     }
-                    CharAction::Insert(char) => {
-                        log::debug!("main: passing (fake): `{:?}` ({:?})", char, self.point);
-                        self.expect(Some(char));
+                    CharAction::Insert(byte) => {
+                        log::debug!("main: passing (fake): `{:?}` ({:?})", byte, self.point);
+                        self.expect(Some(byte));
                         state = func(self);
-                        // self.point.column += 1;
-                        // self.point.vs += 1;
                     }
-                    CharAction::Normal(char) => {
-                        log::debug!("main: passing: `{:?}` ({:?})", char, self.point);
-                        self.expect(Some(char));
+                    CharAction::Normal(byte) => {
+                        log::debug!("main: passing: `{:?}` ({:?})", byte, self.point);
+                        self.expect(Some(byte));
                         state = func(self);
                     }
                 },
@@ -690,28 +688,28 @@ impl<'a> Tokenizer<'a> {
                     // To do: clean this?
                     // We sometimes move back when flushing, so then we use those codes.
                     if self.point.index == max {
-                        let char = None;
-                        log::debug!("main: flushing eof: `{:?}` ({:?})", char, self.point);
-                        self.expect(char);
+                        let byte = None;
+                        log::debug!("main: flushing eof: `{:?}` ({:?})", byte, self.point);
+                        self.expect(byte);
                         state = func(self);
                     } else {
-                        match char_action(&self.parse_state.chars, &self.point) {
+                        match byte_action(self.parse_state.bytes, &self.point) {
                             CharAction::Ignore => {
                                 state = State::Fn(Box::new(func));
                                 self.move_one();
                             }
-                            CharAction::Insert(char) => {
+                            CharAction::Insert(byte) => {
                                 log::debug!(
                                     "main: flushing (fake): `{:?}` ({:?})",
-                                    char,
+                                    byte,
                                     self.point
                                 );
-                                self.expect(Some(char));
+                                self.expect(Some(byte));
                                 state = func(self);
                             }
-                            CharAction::Normal(char) => {
-                                log::debug!("main: flushing: `{:?}` ({:?})", char, self.point);
-                                self.expect(Some(char));
+                            CharAction::Normal(byte) => {
+                                log::debug!("main: flushing: `{:?}` ({:?})", byte, self.point);
+                                self.expect(Some(byte));
                                 state = func(self);
                             }
                         }
@@ -735,22 +733,20 @@ impl<'a> Tokenizer<'a> {
     }
 }
 
-fn char_action(chars: &[char], point: &Point) -> CharAction {
-    if point.index < chars.len() {
-        let char = chars[point.index];
+fn byte_action(bytes: &[u8], point: &Point) -> CharAction {
+    if point.index < bytes.len() {
+        let byte = bytes[point.index];
 
-        if char == '\0' {
-            CharAction::Normal(char::REPLACEMENT_CHARACTER)
-        } else if char == '\r' {
+        if byte == b'\r' {
             // CRLF.
-            if point.index < chars.len() - 1 && chars[point.index + 1] == '\n' {
+            if point.index < bytes.len() - 1 && bytes[point.index + 1] == b'\n' {
                 CharAction::Ignore
             }
             // CR.
             else {
-                CharAction::Normal('\n')
+                CharAction::Normal(b'\n')
             }
-        } else if char == '\t' {
+        } else if byte == b'\t' {
             let remainder = point.column % TAB_SIZE;
             let vs = if remainder == 0 {
                 0
@@ -761,19 +757,19 @@ fn char_action(chars: &[char], point: &Point) -> CharAction {
             // On the tab itself, first send it.
             if point.vs == 0 {
                 if vs == 0 {
-                    CharAction::Normal(char)
+                    CharAction::Normal(byte)
                 } else {
-                    CharAction::Insert(char)
+                    CharAction::Insert(byte)
                 }
             } else if vs == 0 {
-                CharAction::Normal(' ')
+                CharAction::Normal(b' ')
             } else {
-                CharAction::Insert(' ')
+                CharAction::Insert(b' ')
             }
         }
         // VS?
         else {
-            CharAction::Normal(char)
+            CharAction::Normal(byte)
         }
     } else {
         unreachable!("out of bounds")
@@ -786,7 +782,7 @@ fn char_action(chars: &[char], point: &Point) -> CharAction {
 /// Used in [`Tokenizer::attempt`][Tokenizer::attempt] and  [`Tokenizer::check`][Tokenizer::check].
 fn attempt_impl(
     state: impl FnOnce(&mut Tokenizer) -> State + 'static,
-    pause: Option<Box<dyn Fn(Option<char>) -> bool + 'static>>,
+    pause: Option<Box<dyn Fn(Option<u8>) -> bool + 'static>>,
     start: usize,
     done: impl FnOnce(&mut Tokenizer, State) -> State + 'static,
 ) -> Box<StateFn> {
diff --git a/src/util/slice.rs b/src/util/slice.rs
index 14fd527..cd3641e 100644
--- a/src/util/slice.rs
+++ b/src/util/slice.rs
@@ -48,17 +48,21 @@ impl<'a> Position<'a> {
 /// Includes information on virtual spaces before and after the chars.
 #[derive(Debug)]
 pub struct Slice<'a> {
-    pub chars: &'a [char],
+    pub bytes: &'a [u8],
     pub before: usize,
     pub after: usize,
 }
 
 impl<'a> Slice<'a> {
     /// Get the slice belonging to a position.
-    pub fn from_point(list: &'a [char], point: &Point) -> Slice<'a> {
+    pub fn from_point(bytes: &'a [u8], point: &Point) -> Slice<'a> {
         let mut before = point.vs;
         let mut start = point.index;
-        let end = if start < list.len() { start + 1 } else { start };
+        let end = if start < bytes.len() {
+            start + 1
+        } else {
+            start
+        };
 
         // If we have virtual spaces before, it means we are past the actual
         // character at that index, and those virtual spaces.
@@ -68,14 +72,14 @@ impl<'a> Slice<'a> {
         };
 
         Slice {
-            chars: if start < end { &list[start..end] } else { &[] },
+            bytes: if start < end { &bytes[start..end] } else { &[] },
             before,
             after: 0,
         }
     }
 
     /// Get the slice belonging to a position.
-    pub fn from_position(list: &'a [char], position: &Position) -> Slice<'a> {
+    pub fn from_position(bytes: &'a [u8], position: &Position) -> Slice<'a> {
         let mut before = position.start.vs;
         let mut after = position.end.vs;
         let mut start = position.start.index;
@@ -96,15 +100,16 @@ impl<'a> Slice<'a> {
         }
 
         Slice {
-            chars: &list[start..end],
+            bytes: &bytes[start..end],
             before,
             after,
         }
     }
 
     /// To do.
+    // To do: rename to `len`?
     pub fn size(&self) -> usize {
-        self.chars.len() + self.before + self.after
+        self.bytes.len() + self.before + self.after
     }
 
     // To do:
@@ -112,27 +117,13 @@ impl<'a> Slice<'a> {
     // to implement an `as_str`.
 
     /// To do.
-    pub fn head(&self) -> Option<char> {
+    pub fn head(&self) -> Option<u8> {
         if self.before > 0 {
-            Some(' ')
-        } else if self.chars.is_empty() {
+            Some(b' ')
+        } else if self.bytes.is_empty() {
             None
         } else {
-            Some(self.chars[0])
-        }
-    }
-
-    /// To do.
-    pub fn tail(&self) -> Option<char> {
-        if self.after > 0 {
-            Some(' ')
-        } else {
-            let index = self.chars.len();
-            if index > 0 {
-                Some(self.chars[index - 1])
-            } else {
-                None
-            }
+            Some(self.bytes[0])
         }
     }
 
@@ -144,7 +135,8 @@ impl<'a> Slice<'a> {
             string.push(' ');
             index -= 1;
         }
-        string.push_str(&self.chars.iter().collect::<String>());
+        // To do: invalid UTF8?
+        string.push_str(std::str::from_utf8(self.bytes).unwrap());
         index = self.after;
         while index > 0 {
             string.push(' ');
-- 
cgit