// 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 std::fmt;
use std::hash::{Hash, Hasher};
use std::ptr;
use std::str;
use position;
/// A span over a `&str`. It is created from either [two `Position`s] or from a [`Pair`].
///
/// [two `Position`s]: struct.Position.html#method.span
/// [`Pair`]: ../iterators/struct.Pair.html#method.span
#[derive(Clone)]
pub struct Span<'i> {
input: &'i str,
/// # Safety
///
/// Must be a valid character boundary index into `input`.
start: usize,
/// # Safety
///
/// Must be a valid character boundary index into `input`.
end: usize,
}
impl<'i> Span<'i> {
/// Create a new `Span` without checking invariants. (Checked with `debug_assertions`.)
///
/// # Safety
///
/// `input[start..end]` must be a valid subslice; that is, said indexing should not panic.
pub(crate) unsafe fn new_unchecked(input: &str, start: usize, end: usize) -> Span {
debug_assert!(input.get(start..end).is_some());
Span { input, start, end }
}
/// Attempts to create a new span. Will return `None` if `input[start..end]` is an invalid index
/// into `input`.
///
/// # Examples
///
/// ```
/// # use pest::Span;
/// let input = "Hello!";
/// assert_eq!(None, Span::new(input, 100, 0));
/// assert!(Span::new(input, 0, input.len()).is_some());
/// ```
#[allow(clippy::new_ret_no_self)]
pub fn new(input: &str, start: usize, end: usize) -> Option<Span> {
if input.get(start..end).is_some() {
Some(Span { input, start, end })
} else {
None
}
}
/// Returns the `Span`'s start byte position as a `usize`.
///
/// # Examples
///
/// ```
/// # use pest::Position;
/// let input = "ab";
/// let start = Position::from_start(input);
/// let end = start.clone();
/// let span = start.span(&end);
///
/// assert_eq!(span.start(), 0);
/// ```
#[inline]
pub fn start(&self) -> usize {
self.start
}
/// Returns the `Span`'s end byte position as a `usize`.
///
/// # Examples
///
/// ```
/// # use pest::Position;
/// let input = "ab";
/// let start = Position::from_start(input);
/// let end = start.clone();
/// let span = start.span(&end);
///
/// assert_eq!(span.end(), 0);
/// ```
#[inline]
pub fn end(&self) -> usize {
self.end
}
/// Returns the `Span`'s start `Position`.
///
/// # Examples
///
/// ```
/// # use pest::Position;
/// let input = "ab";
/// let start = Position::from_start(input);
/// let end = start.clone();
/// let span = start.clone().span(&end);
///
/// assert_eq!(span.start_pos(), start);
/// ```
#[inline]
pub fn start_pos(&self) -> position::Position<'i> {
// Span's start position is always a UTF-8 border.
unsafe { position::Position::new_unchecked(self.input, self.start) }
}
/// Returns the `Span`'s end `Position`.
///
/// # Examples
///
/// ```
/// # use pest::Position;
/// let input = "ab";
/// let start = Position::from_start(input);
/// let end = start.clone();
/// let span = start.span(&end);
///
/// assert_eq!(span.end_pos(), end);
/// ```
#[inline]
pub fn end_pos(&self) -> position::Position<'i> {
// Span's end position is always a UTF-8 border.
unsafe { position::Position::new_unchecked(self.input, self.end) }
}
/// Splits the `Span` into a pair of `Position`s.
///
/// # Examples
///
/// ```
/// # use pest::Position;
/// let input = "ab";
/// let start = Position::from_start(input);
/// let end = start.clone();
/// let span = start.clone().span(&end);
///
/// assert_eq!(span.split(), (start, end));
/// ```
#[inline]
pub fn split(self) -> (position::Position<'i>, position::Position<'i>) {
// Span's start and end positions are always a UTF-8 borders.
let pos1 = unsafe { position::Position::new_unchecked(self.input, self.start) };
let pos2 = unsafe { position::Position::new_unchecked(self.input, self.end) };
(pos1, pos2)
}
/// Captures a slice from the `&str` defined by the `Span`.
///
/// # Examples
///
/// ```
/// # use pest;
/// # #[allow(non_camel_case_types)]
/// # #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
/// enum Rule {}
///
/// let input = "abc";
/// let mut state: Box<pest::ParserState<Rule>> = pest::ParserState::new(input).skip(1).unwrap();
/// let start_pos = state.position().clone();
/// state = state.match_string("b").unwrap();
/// let span = start_pos.span(&state.position().clone());
/// assert_eq!(span.as_str(), "b");
/// ```
#[inline]
pub fn as_str(&self) -> &'i str {
// Span's start and end positions are always a UTF-8 borders.
&self.input[self.start..self.end]
}
/// Iterates over all lines (partially) covered by this span.
///
/// # Examples
///
/// ```
/// # use pest;
/// # #[allow(non_camel_case_types)]
/// # #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
/// enum Rule {}
///
/// let input = "a\nb\nc";
/// let mut state: Box<pest::ParserState<Rule>> = pest::ParserState::new(input).skip(2).unwrap();
/// let start_pos = state.position().clone();
/// state = state.match_string("b\nc").unwrap();
/// let span = start_pos.span(&state.position().clone());
/// assert_eq!(span.lines().collect::<Vec<_>>(), vec!["b\n", "c"]);
/// ```
#[inline]
pub fn lines(&self) -> Lines {
Lines {
span: self,
pos: self.start,
}
}
}
impl<'i> fmt::Debug for Span<'i> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("Span")
.field("str", &self.as_str())
.field("start", &self.start)
.field("end", &self.end)
.finish()
}
}
impl<'i> PartialEq for Span<'i> {
fn eq(&self, other: &Span<'i>) -> bool {
ptr::eq(self.input, other.input) && self.start == other.start && self.end == other.end
}
}
impl<'i> Eq for Span<'i> {}
impl<'i> Hash for Span<'i> {
fn hash<H: Hasher>(&self, state: &mut H) {
(self.input as *const str).hash(state);
self.start.hash(state);
self.end.hash(state);
}
}
/// Line iterator for Spans, created by [`Span::lines()`].
///
/// Iterates all lines that are at least partially covered by the span.
///
/// [`Span::lines()`]: struct.Span.html#method.lines
pub struct Lines<'i> {
span: &'i Span<'i>,
pos: usize,
}
impl<'i> Iterator for Lines<'i> {
type Item = &'i str;
fn next(&mut self) -> Option<&'i str> {
if self.pos > self.span.end {
return None;
}
let pos = position::Position::new(self.span.input, self.pos)?;
if pos.at_end() {
return None;
}
let line = pos.line_of();
self.pos = pos.find_line_end();
Some(line)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn split() {
let input = "a";
let start = position::Position::from_start(input);
let mut end = start.clone();
assert!(end.skip(1));
let span = start.clone().span(&end.clone());
assert_eq!(span.split(), (start, end));
}
#[test]
fn lines_mid() {
let input = "abc\ndef\nghi";
let span = Span::new(input, 1, 7).unwrap();
let lines: Vec<_> = span.lines().collect();
println!("{:?}", lines);
assert_eq!(lines.len(), 2);
assert_eq!(lines[0], "abc\n".to_owned());
assert_eq!(lines[1], "def\n".to_owned());
}
#[test]
fn lines_eof() {
let input = "abc\ndef\nghi";
let span = Span::new(input, 5, 11).unwrap();
assert!(span.end_pos().at_end());
let lines: Vec<_> = span.lines().collect();
println!("{:?}", lines);
assert_eq!(lines.len(), 2);
assert_eq!(lines[0], "def\n".to_owned());
assert_eq!(lines[1], "ghi".to_owned());
}
}