1//! Patience diff algorithm.
2//!
3//! * time: `O(N log N + M log M + (N+M)D)`
4//! * space: `O(N+M)`
5//!
6//! Tends to give more human-readable outputs. See [Bram Cohen's blog
7//! post](https://bramcohen.livejournal.com/73318.html) describing it.
8//!
9//! This is based on the patience implementation of [pijul](https://pijul.org/)
10//! by Pierre-Étienne Meunier.
11use std::hash::Hash;
12use std::ops::{Index, Range};
13use std::time::Instant;
14
15use crate::algorithms::{myers, DiffHook, NoFinishHook, Replace};
16
17use super::utils::{unique, UniqueItem};
18
19/// Patience diff algorithm.
20///
21/// Diff `old`, between indices `old_range` and `new` between indices `new_range`.
22pub fn diff<Old, New, D>(
23 d: &mut D,
24 old: &Old,
25 old_range: Range<usize>,
26 new: &New,
27 new_range: Range<usize>,
28) -> Result<(), D::Error>
29where
30 Old: Index<usize> + ?Sized,
31 New: Index<usize> + ?Sized,
32 Old::Output: Hash + Eq,
33 New::Output: PartialEq<Old::Output> + Hash + Eq,
34 D: DiffHook,
35{
36 diff_deadline(d, old, old_range, new, new_range, deadline:None)
37}
38
39/// Patience diff algorithm with deadline.
40///
41/// Diff `old`, between indices `old_range` and `new` between indices `new_range`.
42///
43/// This diff is done with an optional deadline that defines the maximal
44/// execution time permitted before it bails and falls back to an approximation.
45pub fn diff_deadline<Old, New, D>(
46 d: &mut D,
47 old: &Old,
48 old_range: Range<usize>,
49 new: &New,
50 new_range: Range<usize>,
51 deadline: Option<Instant>,
52) -> Result<(), D::Error>
53where
54 Old: Index<usize> + ?Sized,
55 New: Index<usize> + ?Sized,
56 Old::Output: Hash + Eq,
57 New::Output: PartialEq<Old::Output> + Hash + Eq,
58 D: DiffHook,
59{
60 let old_indexes = unique(old, old_range.clone());
61 let new_indexes = unique(new, new_range.clone());
62
63 let mut d = Replace::new(Patience {
64 d,
65 old,
66 old_current: old_range.start,
67 old_end: old_range.end,
68 old_indexes: &old_indexes,
69 new,
70 new_current: new_range.start,
71 new_end: new_range.end,
72 new_indexes: &new_indexes,
73 deadline,
74 });
75 myers::diff_deadline(
76 &mut d,
77 &old_indexes,
78 0..old_indexes.len(),
79 &new_indexes,
80 0..new_indexes.len(),
81 deadline,
82 )?;
83 Ok(())
84}
85
86struct Patience<'old, 'new, 'd, Old: ?Sized, New: ?Sized, D> {
87 d: &'d mut D,
88 old: &'old Old,
89 old_current: usize,
90 old_end: usize,
91 old_indexes: &'old [UniqueItem<'old, Old>],
92 new: &'new New,
93 new_current: usize,
94 new_end: usize,
95 new_indexes: &'new [UniqueItem<'new, New>],
96 deadline: Option<Instant>,
97}
98
99impl<'old, 'new, 'd, Old, New, D> DiffHook for Patience<'old, 'new, 'd, Old, New, D>
100where
101 D: DiffHook + 'd,
102 Old: Index<usize> + ?Sized + 'old,
103 New: Index<usize> + ?Sized + 'new,
104 New::Output: PartialEq<Old::Output>,
105{
106 type Error = D::Error;
107 fn equal(&mut self, old: usize, new: usize, len: usize) -> Result<(), D::Error> {
108 for (old, new) in (old..old + len).zip(new..new + len) {
109 let a0 = self.old_current;
110 let b0 = self.new_current;
111 while self.old_current < self.old_indexes[old].original_index()
112 && self.new_current < self.new_indexes[new].original_index()
113 && self.new[self.new_current] == self.old[self.old_current]
114 {
115 self.old_current += 1;
116 self.new_current += 1;
117 }
118 if self.old_current > a0 {
119 self.d.equal(a0, b0, self.old_current - a0)?;
120 }
121 let mut no_finish_d = NoFinishHook::new(&mut self.d);
122 myers::diff_deadline(
123 &mut no_finish_d,
124 self.old,
125 self.old_current..self.old_indexes[old].original_index(),
126 self.new,
127 self.new_current..self.new_indexes[new].original_index(),
128 self.deadline,
129 )?;
130 self.old_current = self.old_indexes[old].original_index();
131 self.new_current = self.new_indexes[new].original_index();
132 }
133 Ok(())
134 }
135
136 fn finish(&mut self) -> Result<(), D::Error> {
137 myers::diff_deadline(
138 self.d,
139 self.old,
140 self.old_current..self.old_end,
141 self.new,
142 self.new_current..self.new_end,
143 self.deadline,
144 )
145 }
146}
147
148#[test]
149fn test_patience() {
150 let a: &[usize] = &[11, 1, 2, 2, 3, 4, 4, 4, 5, 47, 19];
151 let b: &[usize] = &[10, 1, 2, 2, 8, 9, 4, 4, 7, 47, 18];
152
153 let mut d = Replace::new(crate::algorithms::Capture::new());
154 diff(&mut d, a, 0..a.len(), b, 0..b.len()).unwrap();
155
156 insta::assert_debug_snapshot!(d.into_inner().ops());
157}
158
159#[test]
160fn test_patience_out_of_bounds_bug() {
161 // this used to be a bug
162 let a: &[usize] = &[1, 2, 3, 4];
163 let b: &[usize] = &[1, 2, 3];
164
165 let mut d = Replace::new(crate::algorithms::Capture::new());
166 diff(&mut d, a, 0..a.len(), b, 0..b.len()).unwrap();
167
168 insta::assert_debug_snapshot!(d.into_inner().ops());
169}
170
171#[test]
172fn test_finish_called() {
173 struct HasRunFinish(bool);
174
175 impl DiffHook for HasRunFinish {
176 type Error = ();
177 fn finish(&mut self) -> Result<(), Self::Error> {
178 self.0 = true;
179 Ok(())
180 }
181 }
182
183 let mut d = HasRunFinish(false);
184 let slice = &[1, 2];
185 let slice2 = &[1, 2, 3];
186 diff(&mut d, slice, 0..slice.len(), slice2, 0..slice2.len()).unwrap();
187 assert!(d.0);
188
189 let mut d = HasRunFinish(false);
190 let slice = &[1, 2];
191 diff(&mut d, slice, 0..slice.len(), slice, 0..slice.len()).unwrap();
192 assert!(d.0);
193
194 let mut d = HasRunFinish(false);
195 let slice: &[u8] = &[];
196 diff(&mut d, slice, 0..slice.len(), slice, 0..slice.len()).unwrap();
197 assert!(d.0);
198}
199