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-rw-r--r--askama/src/lib.rs4
-rw-r--r--askama_derive/src/generator.rs136
2 files changed, 102 insertions, 38 deletions
diff --git a/askama/src/lib.rs b/askama/src/lib.rs
index d15d1b6..91ebdd3 100644
--- a/askama/src/lib.rs
+++ b/askama/src/lib.rs
@@ -423,7 +423,7 @@ pub use askama_escape::{Html, Text};
pub trait Template {
/// Helper method which allocates a new `String` and renders into it
fn render(&self) -> Result<String> {
- let mut buf = String::new();
+ let mut buf = String::with_capacity(Self::size_hint());
self.render_into(&mut buf)?;
Ok(buf)
}
@@ -433,6 +433,8 @@ pub trait Template {
fn extension() -> Option<&'static str>
where
Self: Sized;
+ /// Provides an conservative estimate of the expanded length of the rendered template
+ fn size_hint() -> usize;
}
pub use crate::shared::filters;
diff --git a/askama_derive/src/generator.rs b/askama_derive/src/generator.rs
index 955d588..e4261e9 100644
--- a/askama_derive/src/generator.rs
+++ b/askama_derive/src/generator.rs
@@ -123,11 +123,11 @@ impl<'a> Generator<'a> {
}
}
- if let Some(heritage) = self.heritage {
- self.handle(heritage.root, heritage.root.nodes, buf, AstLevel::Top);
+ let size_hint = if let Some(heritage) = self.heritage {
+ self.handle(heritage.root, heritage.root.nodes, buf, AstLevel::Top)
} else {
- self.handle(ctx, &ctx.nodes, buf, AstLevel::Top);
- }
+ self.handle(ctx, &ctx.nodes, buf, AstLevel::Top)
+ };
self.flush_ws(WS(false, false));
buf.writeln("Ok(())");
@@ -140,6 +140,10 @@ impl<'a> Generator<'a> {
));
buf.writeln("}");
+ buf.writeln("fn size_hint() -> usize {");
+ buf.writeln(&format!("{}", size_hint));
+ buf.writeln("}");
+
buf.writeln("}");
}
@@ -283,7 +287,14 @@ impl<'a> Generator<'a> {
/* Helper methods for handling node types */
- fn handle(&mut self, ctx: &'a Context, nodes: &'a [Node], buf: &mut Buffer, level: AstLevel) {
+ fn handle(
+ &mut self,
+ ctx: &'a Context,
+ nodes: &'a [Node],
+ buf: &mut Buffer,
+ level: AstLevel,
+ ) -> usize {
+ let mut size_hint = 0;
for n in nodes {
match *n {
Node::Lit(lws, val, rws) => {
@@ -322,10 +333,10 @@ impl<'a> Generator<'a> {
self.write_block(buf, Some(name), outer);
}
Node::Include(ws, path) => {
- self.handle_include(ctx, buf, ws, path);
+ size_hint += self.handle_include(ctx, buf, ws, path);
}
Node::Call(ws, scope, name, ref args) => {
- self.write_call(ctx, buf, ws, scope, name, args);
+ size_hint += self.write_call(ctx, buf, ws, scope, name, args);
}
Node::Macro(_, ref m) => {
if level != AstLevel::Top {
@@ -351,40 +362,72 @@ impl<'a> Generator<'a> {
}
if AstLevel::Top == level {
- self.write_buf_writable(buf);
+ size_hint += self.write_buf_writable(buf);
}
+ size_hint
}
- fn write_cond(&mut self, ctx: &'a Context, buf: &mut Buffer, conds: &'a [Cond], ws: WS) {
+ fn write_cond(
+ &mut self,
+ ctx: &'a Context,
+ buf: &mut Buffer,
+ conds: &'a [Cond],
+ ws: WS,
+ ) -> usize {
+ let mut flushed = 0;
+ let mut arm_size = 0;
+ let mut arm_sizes = Vec::new();
+ let mut has_else = false;
for (i, &(cws, ref cond, ref nodes)) in conds.iter().enumerate() {
self.handle_ws(cws);
- self.write_buf_writable(buf);
+
+ let size_hint = self.write_buf_writable(buf);
+ if i > 0 {
+ arm_size += size_hint;
+ } else {
+ flushed += size_hint;
+ }
+
match *cond {
Some(ref expr) => {
let expr_code = self.visit_expr_root(expr);
if i == 0 {
buf.write("if ");
} else {
- self.write_buf_writable(buf);
+ arm_size += self.write_buf_writable(buf);
+ arm_sizes.push(arm_size);
+ arm_size = 0;
+
buf.dedent();
buf.write("} else if ");
}
buf.write(&expr_code);
}
None => {
- self.write_buf_writable(buf);
+ arm_size += self.write_buf_writable(buf);
+ arm_sizes.push(arm_size);
+ arm_size = 0;
+
buf.dedent();
buf.write("} else");
+ has_else = true;
}
}
buf.writeln(" {");
self.locals.push();
- self.handle(ctx, nodes, buf, AstLevel::Nested);
+ arm_size += self.handle(ctx, nodes, buf, AstLevel::Nested);
self.locals.pop();
}
+
self.handle_ws(ws);
- self.write_buf_writable(buf);
+ arm_size += self.write_buf_writable(buf);
+ arm_sizes.push(arm_size);
buf.writeln("}");
+
+ if !has_else {
+ arm_sizes.push(0);
+ }
+ flushed + median(&mut arm_sizes)
}
fn write_match(
@@ -396,9 +439,10 @@ impl<'a> Generator<'a> {
inter: Option<&'a str>,
arms: &'a [When],
ws2: WS,
- ) {
+ ) -> usize {
self.flush_ws(ws1);
- self.write_buf_writable(buf);
+ let flushed = self.write_buf_writable(buf);
+ let mut arm_sizes = Vec::new();
if let Some(inter) = inter {
if !inter.is_empty() {
self.next_ws = Some(inter);
@@ -456,14 +500,15 @@ impl<'a> Generator<'a> {
}
buf.writeln(" => {");
self.handle_ws(ws);
- self.handle(ctx, body, buf, AstLevel::Nested);
- self.write_buf_writable(buf);
+ let arm_size = self.handle(ctx, body, buf, AstLevel::Nested);
+ arm_sizes.push(arm_size + self.write_buf_writable(buf));
buf.writeln("}");
self.locals.pop();
}
buf.writeln("}");
self.handle_ws(ws2);
+ flushed + median(&mut arm_sizes)
}
fn write_loop(
@@ -475,13 +520,13 @@ impl<'a> Generator<'a> {
iter: &Expr,
body: &'a [Node],
ws2: WS,
- ) {
+ ) -> usize {
self.handle_ws(ws1);
self.locals.push();
let expr_code = self.visit_expr_root(iter);
- self.write_buf_writable(buf);
+ let flushed = self.write_buf_writable(buf);
buf.write("for (");
self.visit_target(buf, var);
match iter {
@@ -495,12 +540,13 @@ impl<'a> Generator<'a> {
)),
};
- self.handle(ctx, body, buf, AstLevel::Nested);
+ let mut size_hint = self.handle(ctx, body, buf, AstLevel::Nested);
self.handle_ws(ws2);
- self.write_buf_writable(buf);
+ size_hint += self.write_buf_writable(buf);
buf.writeln("}");
self.locals.pop();
+ flushed + (size_hint * 3)
}
fn write_call(
@@ -511,10 +557,9 @@ impl<'a> Generator<'a> {
scope: Option<&str>,
name: &str,
args: &[Expr],
- ) {
+ ) -> usize {
if name == "super" {
- self.write_block(buf, None, ws);
- return;
+ return self.write_block(buf, None, ws);
}
let (def, own_ctx) = if let Some(s) = scope {
@@ -556,16 +601,17 @@ impl<'a> Generator<'a> {
self.locals.insert(arg);
}
- self.handle(own_ctx, &def.nodes, buf, AstLevel::Nested);
+ let mut size_hint = self.handle(own_ctx, &def.nodes, buf, AstLevel::Nested);
self.flush_ws(def.ws2);
- self.write_buf_writable(buf);
+ size_hint += self.write_buf_writable(buf);
buf.writeln("}");
self.locals.pop();
self.prepare_ws(ws);
+ size_hint
}
- fn handle_include(&mut self, ctx: &'a Context, buf: &mut Buffer, ws: WS, path: &str) {
+ fn handle_include(&mut self, ctx: &'a Context, buf: &mut Buffer, ws: WS, path: &str) -> usize {
self.flush_ws(ws);
self.write_buf_writable(buf);
let path = self
@@ -583,14 +629,16 @@ impl<'a> Generator<'a> {
}.to_string());
}
- {
+ let size_hint = {
// Since nodes must not outlive the Generator, we instantiate
// a nested Generator here to handle the include's nodes.
let mut gen = self.child();
- gen.handle(ctx, &nodes, buf, AstLevel::Nested);
- gen.write_buf_writable(buf);
- }
+ let mut size_hint = gen.handle(ctx, &nodes, buf, AstLevel::Nested);
+ size_hint += gen.write_buf_writable(buf);
+ size_hint
+ };
self.prepare_ws(ws);
+ size_hint
}
fn write_let_decl(&mut self, buf: &mut Buffer, ws: WS, var: &'a Target) {
@@ -644,7 +692,7 @@ impl<'a> Generator<'a> {
// If `name` is `Some`, this is a call to a block definition, and we have to find
// the first block for that name from the ancestry chain. If name is `None`, this
// is from a `super()` call, and we can get the name from `self.super_block`.
- fn write_block(&mut self, buf: &mut Buffer, name: Option<&'a str>, outer: WS) {
+ fn write_block(&mut self, buf: &mut Buffer, name: Option<&'a str>, outer: WS) -> usize {
// Flush preceding whitespace according to the outer WS spec
self.flush_ws(outer);
@@ -687,7 +735,7 @@ impl<'a> Generator<'a> {
// Handle inner whitespace suppression spec and process block nodes
self.prepare_ws(*ws1);
self.locals.push();
- self.handle(ctx, nodes, buf, AstLevel::Block);
+ let size_hint = self.handle(ctx, nodes, buf, AstLevel::Block);
self.locals.pop();
self.flush_ws(*ws2);
@@ -695,6 +743,7 @@ impl<'a> Generator<'a> {
// succeeding whitespace according to the outer WS spec
self.super_block = prev_block;
self.prepare_ws(outer);
+ size_hint
}
fn write_expr(&mut self, ws: WS, s: &'a Expr<'a>) {
@@ -703,9 +752,9 @@ impl<'a> Generator<'a> {
}
// Write expression buffer and empty
- fn write_buf_writable(&mut self, buf: &mut Buffer) {
+ fn write_buf_writable(&mut self, buf: &mut Buffer) -> usize {
if self.buf_writable.is_empty() {
- return;
+ return 0;
}
if self.buf_writable.iter().all(|w| match w {
@@ -719,9 +768,10 @@ impl<'a> Generator<'a> {
};
}
buf.writeln(&format!("writer.write_str({:#?})?;", &buf_lit.buf));
- return;
+ return buf_lit.buf.len();
}
+ let mut size_hint = 0;
let mut buf_format = Buffer::new(0);
let mut buf_expr = Buffer::new(buf.indent + 1);
let mut expr_cache = HashMap::with_capacity(self.buf_writable.len());
@@ -729,6 +779,7 @@ impl<'a> Generator<'a> {
match s {
Writable::Lit(s) => {
buf_format.write(&s.replace("{", "{{").replace("}", "}}"));
+ size_hint += s.len();
}
Writable::Expr(s) => {
use self::DisplayWrap::*;
@@ -755,6 +806,7 @@ impl<'a> Generator<'a> {
});
buf_format.write(&format!("{{expr{}}}", id));
+ size_hint += 3;
}
}
}
@@ -766,6 +818,7 @@ impl<'a> Generator<'a> {
buf.writeln(buf_expr.buf.trim());
buf.dedent();
buf.writeln(")?;");
+ size_hint
}
fn visit_lit(&mut self, lws: &'a str, val: &'a str, rws: &'a str) {
@@ -1221,6 +1274,15 @@ where
}
}
+fn median(sizes: &mut [usize]) -> usize {
+ sizes.sort();
+ if sizes.len() % 2 == 1 {
+ sizes[sizes.len() / 2]
+ } else {
+ (sizes[sizes.len() / 2 - 1] + sizes[sizes.len() / 2]) / 2
+ }
+}
+
#[derive(Clone, PartialEq)]
enum AstLevel {
Top,
generated by cgit (git 2.34.1) at 2024-11-25 16:15:30 +0000