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|
//! Utilities to deal with lists of events.
use crate::token::Token;
use crate::tokenizer::{Event, EventType};
/// Skip from `index`, optionally past `token_types`.
pub fn opt(events: &[Event], index: usize, token_types: &[Token]) -> usize {
skip_opt_impl(events, index, token_types, true)
}
/// Skip from `index`, optionally past `token_types`, backwards.
pub fn opt_back(events: &[Event], index: usize, token_types: &[Token]) -> usize {
skip_opt_impl(events, index, token_types, false)
}
pub fn to_back(events: &[Event], index: usize, token_types: &[Token]) -> usize {
to_impl(events, index, token_types, false)
}
pub fn to(events: &[Event], index: usize, token_types: &[Token]) -> usize {
to_impl(events, index, token_types, true)
}
pub fn to_impl(events: &[Event], mut index: usize, token_types: &[Token], forward: bool) -> usize {
while index < events.len() {
let current = &events[index].token_type;
if token_types.contains(current) {
break;
}
index = if forward { index + 1 } else { index - 1 };
}
index
}
/// Skip internals.
fn skip_opt_impl(
events: &[Event],
mut index: usize,
token_types: &[Token],
forward: bool,
) -> usize {
let mut balance = 0;
let open = if forward {
EventType::Enter
} else {
EventType::Exit
};
while index < events.len() {
let current = &events[index].token_type;
if !token_types.contains(current) || events[index].event_type != open {
break;
}
index = if forward { index + 1 } else { index - 1 };
balance += 1;
loop {
balance = if events[index].event_type == open {
balance + 1
} else {
balance - 1
};
if events[index].token_type == *current && balance == 0 {
index = if forward { index + 1 } else { index - 1 };
break;
}
index = if forward { index + 1 } else { index - 1 };
}
}
index
}
|
