// Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// 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::ops;
use char::Char;
use prefix::Prefix;
/// Represents a location in the input.
#[derive(Clone, Copy, Debug)]
pub struct InputAt {
pos: usize,
c: Char,
len: usize,
}
impl InputAt {
/// Returns true iff this position is at the beginning of the input.
pub fn is_beginning(&self) -> bool {
self.pos == 0
}
/// Returns the character at this position.
///
/// If this position is just before or after the input, then an absent
/// character is returned.
pub fn char(&self) -> Char {
self.c
}
/// Returns the UTF-8 width of the character at this position.
pub fn len(&self) -> usize {
self.len
}
/// Returns the byte offset of this position.
pub fn pos(&self) -> usize {
self.pos
}
/// Returns the byte offset of the next position in the input.
pub fn next_pos(&self) -> usize {
self.pos + self.len
}
}
/// An abstraction over input used in the matching engines.
pub trait Input {
/// Return an encoding of the position at byte offset `i`.
fn at(&self, i: usize) -> InputAt;
/// Return an encoding of the char position just prior to byte offset `i`.
fn previous_at(&self, i: usize) -> InputAt;
/// Scan the input for a matching prefix.
fn prefix_at(&self, prefixes: &Prefix, at: InputAt) -> Option<InputAt>;
}
/// An input reader over characters.
///
/// (This is the only implementation of `Input` at the moment.)
#[derive(Debug)]
pub struct CharInput<'t>(&'t str);
impl<'t> CharInput<'t> {
/// Return a new character input reader for the given string.
pub fn new(s: &'t str) -> CharInput<'t> {
CharInput(s)
}
}
impl<'t> ops::Deref for CharInput<'t> {
type Target = str;
fn deref(&self) -> &str {
self.0
}
}
impl<'t> Input for CharInput<'t> {
// This `inline(always)` increases throughput by almost 25% on the `hard`
// benchmarks over a normal `inline` annotation.
//
// I'm not sure why `#[inline]` isn't enough to convince LLVM, but it is
// used *a lot* in the guts of the matching engines.
#[inline(always)]
fn at(&self, i: usize) -> InputAt {
let c = self[i..].chars().next().into();
InputAt {
pos: i,
c: c,
len: c.len_utf8(),
}
}
fn previous_at(&self, i: usize) -> InputAt {
let c: Char = self[..i].chars().rev().next().into();
let len = c.len_utf8();
InputAt {
pos: i - len,
c: c,
len: len,
}
}
fn prefix_at(&self, prefixes: &Prefix, at: InputAt) -> Option<InputAt> {
prefixes.find(&self[at.pos()..]).map(|(s, _)| self.at(at.pos() + s))
}
}