pest/position.rs
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// pest. The Elegant Parser
// Copyright (c) 2018 Dragoș Tiselice
//
// 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. All files in the project carrying such notice may not be copied,
// modified, or distributed except according to those terms.
use core::cmp::Ordering;
use core::fmt;
use core::hash::{Hash, Hasher};
use core::ops::Range;
use core::ptr;
use core::str;
use crate::span;
/// A cursor position in a `&str` which provides useful methods to manually parse that string.
#[derive(Clone, Copy)]
pub struct Position<'i> {
input: &'i str,
pos: usize,
}
impl<'i> Position<'i> {
/// Create a new `Position` without checking invariants. (Checked with `debug_assertions`.)
pub(crate) fn new_internal(input: &str, pos: usize) -> Position<'_> {
debug_assert!(input.get(pos..).is_some());
Position { input, pos }
}
/// Attempts to create a new `Position` at the given position. If the specified position is
/// an invalid index, or the specified position is not a valid UTF8 boundary, then None is
/// returned.
///
/// # Examples
/// ```
/// # use pest::Position;
/// let cheart = '💖';
/// let heart = "💖";
/// assert_eq!(Position::new(heart, 1), None);
/// assert_ne!(Position::new(heart, cheart.len_utf8()), None);
/// ```
pub fn new(input: &str, pos: usize) -> Option<Position<'_>> {
input.get(pos..).map(|_| Position { input, pos })
}
/// Creates a `Position` at the start of a `&str`.
///
/// # Examples
///
/// ```
/// # use pest::Position;
/// let start = Position::from_start("");
/// assert_eq!(start.pos(), 0);
/// ```
#[inline]
pub fn from_start(input: &'i str) -> Position<'i> {
// Position 0 is always safe because it's always a valid UTF-8 border.
Position { input, pos: 0 }
}
/// Returns the byte position of this `Position` as a `usize`.
///
/// # Examples
///
/// ```
/// # use pest::Position;
/// let input = "ab";
/// let mut start = Position::from_start(input);
///
/// assert_eq!(start.pos(), 0);
/// ```
#[inline]
pub fn pos(&self) -> usize {
self.pos
}
/// Creates a `Span` from two `Position`s.
///
/// # Panics
///
/// Panics if the positions come from different inputs.
///
/// # Examples
///
/// ```
/// # use pest::Position;
/// let input = "ab";
/// let start = Position::from_start(input);
/// let span = start.span(&start.clone());
///
/// assert_eq!(span.start(), 0);
/// assert_eq!(span.end(), 0);
/// ```
#[inline]
pub fn span(&self, other: &Position<'i>) -> span::Span<'i> {
if ptr::eq(self.input, other.input)
/* && self.input.get(self.pos..other.pos).is_some() */
{
span::Span::new_internal(self.input, self.pos, other.pos)
} else {
// TODO: maybe a panic if self.pos < other.pos
panic!("span created from positions from different inputs")
}
}
/// Returns the line and column number of this `Position`.
///
/// This is an O(n) operation, where n is the number of chars in the input.
/// You better use [`pair.line_col()`](struct.Pair.html#method.line_col) instead.
///
/// # Examples
///
/// ```
/// # use pest;
/// # #[allow(non_camel_case_types)]
/// # #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
/// enum Rule {}
///
/// let input = "\na";
/// let mut state: Box<pest::ParserState<'_, Rule>> = pest::ParserState::new(input);
/// let mut result = state.match_string("\na");
/// assert!(result.is_ok());
/// assert_eq!(result.unwrap().position().line_col(), (2, 2));
/// ```
#[inline]
pub fn line_col(&self) -> (usize, usize) {
if self.pos > self.input.len() {
panic!("position out of bounds");
}
let mut pos = self.pos;
let slice = &self.input[..pos];
let mut chars = slice.chars().peekable();
let mut line_col = (1, 1);
while pos != 0 {
match chars.next() {
Some('\r') => {
if let Some(&'\n') = chars.peek() {
chars.next();
if pos == 1 {
pos -= 1;
} else {
pos -= 2;
}
line_col = (line_col.0 + 1, 1);
} else {
pos -= 1;
line_col = (line_col.0, line_col.1 + 1);
}
}
Some('\n') => {
pos -= 1;
line_col = (line_col.0 + 1, 1);
}
Some(c) => {
pos -= c.len_utf8();
line_col = (line_col.0, line_col.1 + 1);
}
None => unreachable!(),
}
}
line_col
}
/// Returns the entire line of the input that contains this `Position`.
///
/// # Examples
///
/// ```
/// # use pest;
/// # #[allow(non_camel_case_types)]
/// # #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
/// enum Rule {}
///
/// let input = "\na";
/// let mut state: Box<pest::ParserState<'_, Rule>> = pest::ParserState::new(input);
/// let mut result = state.match_string("\na");
/// assert!(result.is_ok());
/// assert_eq!(result.unwrap().position().line_of(), "a");
/// ```
#[inline]
pub fn line_of(&self) -> &'i str {
if self.pos > self.input.len() {
panic!("position out of bounds");
};
// Safe since start and end can only be valid UTF-8 borders.
&self.input[self.find_line_start()..self.find_line_end()]
}
pub(crate) fn find_line_start(&self) -> usize {
if self.input.is_empty() {
return 0;
};
// Position's pos is always a UTF-8 border.
let start = self
.input
.char_indices()
.rev()
.skip_while(|&(i, _)| i >= self.pos)
.find(|&(_, c)| c == '\n');
match start {
Some((i, _)) => i + 1,
None => 0,
}
}
pub(crate) fn find_line_end(&self) -> usize {
if self.input.is_empty() {
0
} else if self.pos == self.input.len() - 1 {
self.input.len()
} else {
// Position's pos is always a UTF-8 border.
let end = self
.input
.char_indices()
.skip_while(|&(i, _)| i < self.pos)
.find(|&(_, c)| c == '\n');
match end {
Some((i, _)) => i + 1,
None => self.input.len(),
}
}
}
/// Returns `true` when the `Position` points to the start of the input `&str`.
#[inline]
pub(crate) fn at_start(&self) -> bool {
self.pos == 0
}
/// Returns `true` when the `Position` points to the end of the input `&str`.
#[inline]
pub(crate) fn at_end(&self) -> bool {
self.pos == self.input.len()
}
/// Skips `n` `char`s from the `Position` and returns `true` if the skip was possible or `false`
/// otherwise. If the return value is `false`, `pos` will not be updated.
#[inline]
pub(crate) fn skip(&mut self, n: usize) -> bool {
let skipped = {
let mut len = 0;
// Position's pos is always a UTF-8 border.
let mut chars = self.input[self.pos..].chars();
for _ in 0..n {
if let Some(c) = chars.next() {
len += c.len_utf8();
} else {
return false;
}
}
len
};
self.pos += skipped;
true
}
/// Goes back `n` `char`s from the `Position` and returns `true` if the skip was possible or `false`
/// otherwise. If the return value is `false`, `pos` will not be updated.
#[inline]
pub(crate) fn skip_back(&mut self, n: usize) -> bool {
let skipped = {
let mut len = 0;
// Position's pos is always a UTF-8 border.
let mut chars = self.input[..self.pos].chars().rev();
for _ in 0..n {
if let Some(c) = chars.next() {
len += c.len_utf8();
} else {
return false;
}
}
len
};
self.pos -= skipped;
true
}
/// Skips until one of the given `strings` is found. If none of the `strings` can be found,
/// this function will return `false` but its `pos` will *still* be updated.
#[inline]
pub(crate) fn skip_until(&mut self, strings: &[&str]) -> bool {
#[cfg(not(feature = "memchr"))]
{
self.skip_until_basic(strings)
}
#[cfg(feature = "memchr")]
{
match strings {
[] => (),
[s1] => {
if let Some(from) =
memchr::memmem::find(&self.input.as_bytes()[self.pos..], s1.as_bytes())
{
self.pos += from;
return true;
}
}
[s1, s2] if !s1.is_empty() && !s2.is_empty() => {
let b1 = s1.as_bytes()[0];
let b2 = s2.as_bytes()[0];
let miter = memchr::memchr2_iter(b1, b2, &self.input.as_bytes()[self.pos..]);
for from in miter {
let start = &self.input[self.pos + from..];
if start.starts_with(s1) || start.starts_with(s2) {
self.pos += from;
return true;
}
}
}
[s1, s2, s3] if !s1.is_empty() && !s2.is_empty() && s3.is_empty() => {
let b1 = s1.as_bytes()[0];
let b2 = s2.as_bytes()[0];
let b3 = s2.as_bytes()[0];
let miter =
memchr::memchr3_iter(b1, b2, b3, &self.input.as_bytes()[self.pos..]);
for from in miter {
let start = &self.input[self.pos + from..];
if start.starts_with(s1) || start.starts_with(s2) || start.starts_with(s3) {
self.pos += from;
return true;
}
}
}
_ => {
return self.skip_until_basic(strings);
}
}
self.pos = self.input.len();
false
}
}
#[inline]
fn skip_until_basic(&mut self, strings: &[&str]) -> bool {
// TODO: optimize with Aho-Corasick, e.g. https://crates.io/crates/daachorse?
for from in self.pos..self.input.len() {
let bytes = if let Some(string) = self.input.get(from..) {
string.as_bytes()
} else {
continue;
};
for slice in strings.iter() {
let to = slice.len();
if Some(slice.as_bytes()) == bytes.get(0..to) {
self.pos = from;
return true;
}
}
}
self.pos = self.input.len();
false
}
/// Matches the char at the `Position` against a specified character and returns `true` if a match
/// was made. If no match was made, returns `false`.
/// `pos` will not be updated in either case.
#[inline]
pub(crate) fn match_char(&self, c: char) -> bool {
matches!(self.input[self.pos..].chars().next(), Some(cc) if c == cc)
}
/// Matches the char at the `Position` against a filter function and returns `true` if a match
/// was made. If no match was made, returns `false` and `pos` will not be updated.
#[inline]
pub(crate) fn match_char_by<F>(&mut self, f: F) -> bool
where
F: FnOnce(char) -> bool,
{
if let Some(c) = self.input[self.pos..].chars().next() {
if f(c) {
self.pos += c.len_utf8();
true
} else {
false
}
} else {
false
}
}
/// Matches `string` from the `Position` and returns `true` if a match was made or `false`
/// otherwise. If no match was made, `pos` will not be updated.
#[inline]
pub(crate) fn match_string(&mut self, string: &str) -> bool {
let to = self.pos + string.len();
if Some(string.as_bytes()) == self.input.as_bytes().get(self.pos..to) {
self.pos = to;
true
} else {
false
}
}
/// Case-insensitively matches `string` from the `Position` and returns `true` if a match was
/// made or `false` otherwise. If no match was made, `pos` will not be updated.
#[inline]
pub(crate) fn match_insensitive(&mut self, string: &str) -> bool {
let matched = {
let slice = &self.input[self.pos..];
if let Some(slice) = slice.get(0..string.len()) {
slice.eq_ignore_ascii_case(string)
} else {
false
}
};
if matched {
self.pos += string.len();
true
} else {
false
}
}
/// Matches `char` `range` from the `Position` and returns `true` if a match was made or `false`
/// otherwise. If no match was made, `pos` will not be updated.
#[inline]
pub(crate) fn match_range(&mut self, range: Range<char>) -> bool {
if let Some(c) = self.input[self.pos..].chars().next() {
if range.start <= c && c <= range.end {
self.pos += c.len_utf8();
return true;
}
}
false
}
}
impl<'i> fmt::Debug for Position<'i> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Position").field("pos", &self.pos).finish()
}
}
impl<'i> PartialEq for Position<'i> {
fn eq(&self, other: &Position<'i>) -> bool {
ptr::eq(self.input, other.input) && self.pos == other.pos
}
}
impl<'i> Eq for Position<'i> {}
#[allow(clippy::non_canonical_partial_ord_impl)]
impl<'i> PartialOrd for Position<'i> {
fn partial_cmp(&self, other: &Position<'i>) -> Option<Ordering> {
if ptr::eq(self.input, other.input) {
self.pos.partial_cmp(&other.pos)
} else {
None
}
}
}
impl<'i> Ord for Position<'i> {
fn cmp(&self, other: &Position<'i>) -> Ordering {
self.partial_cmp(other)
.expect("cannot compare positions from different strs")
}
}
impl<'i> Hash for Position<'i> {
fn hash<H: Hasher>(&self, state: &mut H) {
(self.input as *const str).hash(state);
self.pos.hash(state);
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn empty() {
let input = "";
assert!(Position::new(input, 0).unwrap().match_string(""));
assert!(!Position::new(input, 0).unwrap().match_string("a"));
}
#[test]
fn parts() {
let input = "asdasdf";
assert!(Position::new(input, 0).unwrap().match_string("asd"));
assert!(Position::new(input, 3).unwrap().match_string("asdf"));
}
#[test]
fn line_col() {
let input = "a\rb\nc\r\nd嗨";
assert_eq!(Position::new(input, 0).unwrap().line_col(), (1, 1));
assert_eq!(Position::new(input, 1).unwrap().line_col(), (1, 2));
assert_eq!(Position::new(input, 2).unwrap().line_col(), (1, 3));
assert_eq!(Position::new(input, 3).unwrap().line_col(), (1, 4));
assert_eq!(Position::new(input, 4).unwrap().line_col(), (2, 1));
assert_eq!(Position::new(input, 5).unwrap().line_col(), (2, 2));
assert_eq!(Position::new(input, 6).unwrap().line_col(), (2, 3));
assert_eq!(Position::new(input, 7).unwrap().line_col(), (3, 1));
assert_eq!(Position::new(input, 8).unwrap().line_col(), (3, 2));
assert_eq!(Position::new(input, 11).unwrap().line_col(), (3, 3));
let input = "abcd嗨";
assert_eq!(Position::new(input, 7).unwrap().line_col(), (1, 6));
}
#[test]
fn line_of() {
let input = "a\rb\nc\r\nd嗨";
assert_eq!(Position::new(input, 0).unwrap().line_of(), "a\rb\n");
assert_eq!(Position::new(input, 1).unwrap().line_of(), "a\rb\n");
assert_eq!(Position::new(input, 2).unwrap().line_of(), "a\rb\n");
assert_eq!(Position::new(input, 3).unwrap().line_of(), "a\rb\n");
assert_eq!(Position::new(input, 4).unwrap().line_of(), "c\r\n");
assert_eq!(Position::new(input, 5).unwrap().line_of(), "c\r\n");
assert_eq!(Position::new(input, 6).unwrap().line_of(), "c\r\n");
assert_eq!(Position::new(input, 7).unwrap().line_of(), "d嗨");
assert_eq!(Position::new(input, 8).unwrap().line_of(), "d嗨");
assert_eq!(Position::new(input, 11).unwrap().line_of(), "d嗨");
}
#[test]
fn line_of_empty() {
let input = "";
assert_eq!(Position::new(input, 0).unwrap().line_of(), "");
}
#[test]
fn line_of_new_line() {
let input = "\n";
assert_eq!(Position::new(input, 0).unwrap().line_of(), "\n");
}
#[test]
fn line_of_between_new_line() {
let input = "\n\n";
assert_eq!(Position::new(input, 1).unwrap().line_of(), "\n");
}
fn measure_skip(input: &str, pos: usize, n: usize) -> Option<usize> {
let mut p = Position::new(input, pos).unwrap();
if p.skip(n) {
Some(p.pos - pos)
} else {
None
}
}
#[test]
fn skip_empty() {
let input = "";
assert_eq!(measure_skip(input, 0, 0), Some(0));
assert_eq!(measure_skip(input, 0, 1), None);
}
#[test]
fn skip() {
let input = "d嗨";
assert_eq!(measure_skip(input, 0, 0), Some(0));
assert_eq!(measure_skip(input, 0, 1), Some(1));
assert_eq!(measure_skip(input, 1, 1), Some(3));
}
#[test]
fn skip_until() {
let input = "ab ac";
let pos = Position::from_start(input);
let mut test_pos = pos;
test_pos.skip_until(&["a", "b"]);
assert_eq!(test_pos.pos(), 0);
test_pos = pos;
test_pos.skip_until(&["b"]);
assert_eq!(test_pos.pos(), 1);
test_pos = pos;
test_pos.skip_until(&["ab"]);
assert_eq!(test_pos.pos(), 0);
test_pos = pos;
test_pos.skip_until(&["ac", "z"]);
assert_eq!(test_pos.pos(), 3);
test_pos = pos;
assert!(!test_pos.skip_until(&["z"]));
assert_eq!(test_pos.pos(), 5);
}
#[test]
fn match_range() {
let input = "b";
assert!(Position::new(input, 0).unwrap().match_range('a'..'c'));
assert!(Position::new(input, 0).unwrap().match_range('b'..'b'));
assert!(!Position::new(input, 0).unwrap().match_range('a'..'a'));
assert!(!Position::new(input, 0).unwrap().match_range('c'..'c'));
assert!(Position::new(input, 0).unwrap().match_range('a'..'嗨'));
}
#[test]
fn match_insensitive() {
let input = "AsdASdF";
assert!(Position::new(input, 0).unwrap().match_insensitive("asd"));
assert!(Position::new(input, 3).unwrap().match_insensitive("asdf"));
}
#[test]
fn cmp() {
let input = "a";
let start = Position::from_start(input);
let mut end = start;
assert!(end.skip(1));
let result = start.cmp(&end);
assert_eq!(result, Ordering::Less);
}
#[test]
#[should_panic]
fn cmp_panic() {
let input1 = "a";
let input2 = "b";
let pos1 = Position::from_start(input1);
let pos2 = Position::from_start(input2);
let _ = pos1.cmp(&pos2);
}
#[test]
#[cfg(feature = "std")]
fn hash() {
use std::collections::HashSet;
let input = "a";
let start = Position::from_start(input);
let mut positions = HashSet::new();
positions.insert(start);
}
}