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//! Patience diff algorithm.
//!
//! * time: `O(N log N + M log M + (N+M)D)`
//! * space: `O(N+M)`
//!
//! Tends to give more human-readable outputs. See [Bram Cohen's blog
//! post](https://bramcohen.livejournal.com/73318.html) describing it.
//!
//! This is based on the patience implementation of [pijul](https://pijul.org/)
//! by Pierre-Étienne Meunier.
use std::hash::Hash;
use std::ops::{Index, Range};
use std::time::Instant;
use crate::algorithms::{myers, DiffHook, NoFinishHook, Replace};
use super::utils::{unique, UniqueItem};
/// Patience diff algorithm.
///
/// Diff `old`, between indices `old_range` and `new` between indices `new_range`.
pub fn diff<Old, New, D>(
d: &mut D,
old: &Old,
old_range: Range<usize>,
new: &New,
new_range: Range<usize>,
) -> Result<(), D::Error>
where
Old: Index<usize> + ?Sized,
New: Index<usize> + ?Sized,
Old::Output: Hash + Eq,
New::Output: PartialEq<Old::Output> + Hash + Eq,
D: DiffHook,
{
diff_deadline(d, old, old_range, new, new_range, None)
}
/// Patience diff algorithm with deadline.
///
/// Diff `old`, between indices `old_range` and `new` between indices `new_range`.
///
/// This diff is done with an optional deadline that defines the maximal
/// execution time permitted before it bails and falls back to an approximation.
pub fn diff_deadline<Old, New, D>(
d: &mut D,
old: &Old,
old_range: Range<usize>,
new: &New,
new_range: Range<usize>,
deadline: Option<Instant>,
) -> Result<(), D::Error>
where
Old: Index<usize> + ?Sized,
New: Index<usize> + ?Sized,
Old::Output: Hash + Eq,
New::Output: PartialEq<Old::Output> + Hash + Eq,
D: DiffHook,
{
let old_indexes = unique(old, old_range.clone());
let new_indexes = unique(new, new_range.clone());
let mut d = Replace::new(Patience {
d,
old,
old_current: old_range.start,
old_end: old_range.end,
old_indexes: &old_indexes,
new,
new_current: new_range.start,
new_end: new_range.end,
new_indexes: &new_indexes,
deadline,
});
myers::diff_deadline(
&mut d,
&old_indexes,
0..old_indexes.len(),
&new_indexes,
0..new_indexes.len(),
deadline,
)?;
Ok(())
}
struct Patience<'old, 'new, 'd, Old: ?Sized, New: ?Sized, D> {
d: &'d mut D,
old: &'old Old,
old_current: usize,
old_end: usize,
old_indexes: &'old [UniqueItem<'old, Old>],
new: &'new New,
new_current: usize,
new_end: usize,
new_indexes: &'new [UniqueItem<'new, New>],
deadline: Option<Instant>,
}
impl<'old, 'new, 'd, Old, New, D> DiffHook for Patience<'old, 'new, 'd, Old, New, D>
where
D: DiffHook + 'd,
Old: Index<usize> + ?Sized + 'old,
New: Index<usize> + ?Sized + 'new,
New::Output: PartialEq<Old::Output>,
{
type Error = D::Error;
fn equal(&mut self, old: usize, new: usize, len: usize) -> Result<(), D::Error> {
for (old, new) in (old..old + len).zip(new..new + len) {
let a0 = self.old_current;
let b0 = self.new_current;
while self.old_current < self.old_indexes[old].original_index()
&& self.new_current < self.new_indexes[new].original_index()
&& self.new[self.new_current] == self.old[self.old_current]
{
self.old_current += 1;
self.new_current += 1;
}
if self.old_current > a0 {
self.d.equal(a0, b0, self.old_current - a0)?;
}
let mut no_finish_d = NoFinishHook::new(&mut self.d);
myers::diff_deadline(
&mut no_finish_d,
self.old,
self.old_current..self.old_indexes[old].original_index(),
self.new,
self.new_current..self.new_indexes[new].original_index(),
self.deadline,
)?;
self.old_current = self.old_indexes[old].original_index();
self.new_current = self.new_indexes[new].original_index();
}
Ok(())
}
fn finish(&mut self) -> Result<(), D::Error> {
myers::diff_deadline(
self.d,
self.old,
self.old_current..self.old_end,
self.new,
self.new_current..self.new_end,
self.deadline,
)
}
}
#[test]
fn test_patience() {
let a: &[usize] = &[11, 1, 2, 2, 3, 4, 4, 4, 5, 47, 19];
let b: &[usize] = &[10, 1, 2, 2, 8, 9, 4, 4, 7, 47, 18];
let mut d = Replace::new(crate::algorithms::Capture::new());
diff(&mut d, a, 0..a.len(), b, 0..b.len()).unwrap();
insta::assert_debug_snapshot!(d.into_inner().ops());
}
#[test]
fn test_patience_out_of_bounds_bug() {
// this used to be a bug
let a: &[usize] = &[1, 2, 3, 4];
let b: &[usize] = &[1, 2, 3];
let mut d = Replace::new(crate::algorithms::Capture::new());
diff(&mut d, a, 0..a.len(), b, 0..b.len()).unwrap();
insta::assert_debug_snapshot!(d.into_inner().ops());
}
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