// Copyright 2014-2017 The html5ever Project Developers. See the
// COPYRIGHT file at the top-level directory of this distribution.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::collections::VecDeque;
use tendril::StrTendril;
pub use self::SetResult::{FromSet, NotFromSet};
use util::smallcharset::SmallCharSet;
/// Result from `pop_except_from`.
#[derive(PartialEq, Eq, Debug)]
pub enum SetResult {
FromSet(char),
NotFromSet(StrTendril),
}
/// A queue of owned string buffers, which supports incrementally
/// consuming characters.
pub struct BufferQueue {
/// Buffers to process.
buffers: VecDeque<StrTendril>,
}
impl BufferQueue {
/// Create an empty BufferQueue.
pub fn new() -> BufferQueue {
BufferQueue {
buffers: VecDeque::with_capacity(16),
}
}
/// Returns whether the queue is empty.
pub fn is_empty(&self) -> bool {
self.buffers.is_empty()
}
/// Get the tendril at the beginning of the queue.
pub fn pop_front(&mut self) -> Option<StrTendril> {
self.buffers.pop_front()
}
/// Add a buffer to the beginning of the queue.
pub fn push_front(&mut self, buf: StrTendril) {
if buf.len32() == 0 {
return;
}
self.buffers.push_front(buf);
}
/// Add a buffer to the end of the queue.
pub fn push_back(&mut self, buf: StrTendril) {
if buf.len32() == 0 {
return;
}
self.buffers.push_back(buf);
}
/// Look at the next available character, if any.
pub fn peek(&self) -> Option<char> {
// Invariant: all buffers in the queue are non-empty.
self.buffers.front().map(|b| b.chars().next().unwrap())
}
/// Get the next character, if one is available.
pub fn next(&mut self) -> Option<char> {
let (result, now_empty) = match self.buffers.front_mut() {
None => (None, false),
Some(buf) => {
let c = buf.pop_front_char().expect("empty buffer in queue");
(Some(c), buf.is_empty())
}
};
if now_empty {
self.buffers.pop_front();
}
result
}
/// Pops and returns either a single character from the given set, or
/// a `StrTendril` of characters none of which are in the set. The set
/// is represented as a bitmask and so can only contain the first 64
/// ASCII characters.
pub fn pop_except_from(&mut self, set: SmallCharSet) -> Option<SetResult> {
let (result, now_empty) = match self.buffers.front_mut() {
None => (None, false),
Some(buf) => {
let n = set.nonmember_prefix_len(&buf);
if n > 0 {
let out;
unsafe {
out = buf.unsafe_subtendril(0, n);
buf.unsafe_pop_front(n);
}
(Some(NotFromSet(out)), buf.is_empty())
} else {
let c = buf.pop_front_char().expect("empty buffer in queue");
(Some(FromSet(c)), buf.is_empty())
}
}
};
// Unborrow self for this part.
if now_empty {
self.buffers.pop_front();
}
result
}
// Check if the next characters are an ASCII case-insensitive match for
// `pat`, which must be non-empty.
//
// If so, consume them and return Some(true).
// If they do not match, return Some(false).
// If not enough characters are available to know, return None.
pub fn eat<F: Fn(&u8, &u8) -> bool>(&mut self, pat: &str, eq: F) -> Option<bool> {
let mut buffers_exhausted = 0;
let mut consumed_from_last = 0;
if self.buffers.front().is_none() {
return None;
}
for pattern_byte in pat.bytes() {
if buffers_exhausted >= self.buffers.len() {
return None;
}
let ref buf = self.buffers[buffers_exhausted];
if !eq(&buf.as_bytes()[consumed_from_last], &pattern_byte) {
return Some(false)
}
consumed_from_last += 1;
if consumed_from_last >= buf.len() {
buffers_exhausted += 1;
consumed_from_last = 0;
}
}
// We have a match. Commit changes to the BufferQueue.
for _ in 0 .. buffers_exhausted {
self.buffers.pop_front();
}
match self.buffers.front_mut() {
None => assert_eq!(consumed_from_last, 0),
Some(ref mut buf) => buf.pop_front(consumed_from_last as u32),
}
Some(true)
}
}