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// Copyright 2017 Google Inc. All rights reserved.
//
// Licensed under either of MIT or Apache License, Version 2.0,
// at your option.
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Simple recognizer combinators.
// This version is similar to a similar one in the "lang" module of
// xi-editor, but is stripped down to only the needed combinators.
use std::ops;
pub trait Recognize {
fn p(&self, s: &[u8]) -> Option<usize>;
}
impl<F: Fn(&[u8]) -> Option<usize>> Recognize for F {
#[inline(always)]
fn p(&self, s: &[u8]) -> Option<usize> {
self(s)
}
}
pub struct OneByte<F>(pub F);
impl<F: Fn(u8) -> bool> Recognize for OneByte<F> {
#[inline(always)]
fn p(&self, s: &[u8]) -> Option<usize> {
if s.is_empty() || !self.0(s[0]) {
None
} else {
Some(1)
}
}
}
impl Recognize for u8 {
#[inline(always)]
fn p(&self, s: &[u8]) -> Option<usize> {
OneByte(|b| b == *self).p(s)
}
}
/// Use Inclusive(a..b) to indicate an inclusive range. When a...b syntax becomes
/// stable, we can get rid of this and switch to that.
pub struct Inclusive<T>(pub T);
impl Recognize for Inclusive<ops::Range<u8>> {
#[inline(always)]
fn p(&self, s: &[u8]) -> Option<usize> {
OneByte(|x| x >= self.0.start && x <= self.0.end).p(s)
}
}
impl<'a> Recognize for &'a [u8] {
#[inline(always)]
fn p(&self, s: &[u8]) -> Option<usize> {
let len = self.len();
if s.len() >= len && &s[..len] == *self {
Some(len)
} else {
None
}
}
}
impl<'a> Recognize for &'a str {
#[inline(always)]
fn p(&self, s: &[u8]) -> Option<usize> {
self.as_bytes().p(s)
}
}
impl<P1: Recognize, P2: Recognize> Recognize for (P1, P2) {
#[inline(always)]
fn p(&self, s: &[u8]) -> Option<usize> {
self.0.p(s).and_then(|len1|
self.1.p(&s[len1..]).map(|len2|
len1 + len2))
}
}
/// Choice from two heterogeneous alternatives.
pub struct Alt<P1, P2>(pub P1, pub P2);
impl<P1: Recognize, P2: Recognize> Recognize for Alt<P1, P2> {
#[inline(always)]
fn p(&self, s: &[u8]) -> Option<usize> {
self.0.p(s).or_else(|| self.1.p(s))
}
}
/// Choice from a homogenous slice of parsers.
pub struct OneOf<'a, P: 'a>(pub &'a [P]);
impl<'a, P: Recognize> Recognize for OneOf<'a, P> {
#[inline]
fn p(&self, s: &[u8]) -> Option<usize> {
for ref p in self.0 {
if let Some(len) = p.p(s) {
return Some(len);
}
}
None
}
}
pub struct OneOrMore<P>(pub P);
impl<P: Recognize> Recognize for OneOrMore<P> {
#[inline]
fn p(&self, s: &[u8]) -> Option<usize> {
let mut i = 0;
let mut count = 0;
while let Some(len) = self.0.p(&s[i..]) {
i += len;
count += 1;
}
if count >= 1 {
Some(i)
} else {
None
}
}
}
pub struct ZeroOrMore<P>(pub P);
impl<P: Recognize> Recognize for ZeroOrMore<P> {
#[inline]
fn p(&self, s: &[u8]) -> Option<usize> {
let mut i = 0;
while let Some(len) = self.0.p(&s[i..]) {
i += len;
}
Some(i)
}
}
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