| Lang. | Library | Diff Avg. | Patch Avg. | Bencher | Mode | Correct |

|:-------:|:----------------------------------------------------------------------------------------:|:---------:|:----------:|:----------:|:-----------:|:-------:|

| `node` | [diff-match-patch](https://www.npmjs.com/package/diff-match-patch)[^1] | 246.90 ms | 1.07 ms | tinybench | - | ❌ |

| `python`| [diff-match-patch](https://pypi.org/project/diff-match-patch/) | 1.01 s | 0.25 ms | timeit | - | ✅ |

Self(op, data.to_vec())

}

pub fn delete(data: &[T]) -> Self {

Self::new(Ops::Delete, data)

}

pub fn insert(data: &[T]) -> Self {

Self::new(Ops::Insert, data)

}

pub fn equal(data: &[T]) -> Self {

Self::new(Ops::Equal, data)

}

pub fn op(&self) -> Ops {

self.0

}

pub fn data(&self) -> &[T] {

&self.1[..]

}

}

// Trim common prefix

// Restore the prefix and suffix.

let mut d = vec![Diff::equal(&old_t[..common_prefix])];

d.append(&mut diffs);

diffs = d;

}

}

Self::cleanup_merge(&mut diffs);

};

// found a subsequence which contains the short text

// Shorter text is inside the longer text (speedup).

let op = if old_gt_new { Ops::Delete } else { Ops::Insert };

let diffs = vec![

}

// First check if the second quarter is the seed for a half-match.

// Check again based on the third quarter.

if hm1.is_none() && hm2.is_none() {

return None;

// Add a dummy entry at the end.

diffs.push(Diff::equal(&[]));

let mut pointer = 0_usize;

// count of bytes inserted

let idxstart = pointer - delete_n - insert_n;

let idxend = idxstart + delete_n + insert_n;

pointer = idxstart;

}

// Trim common prefix

diffs.insert(0, Diff::equal(&old[..common_prefix]));

}

}

Self::cleanup_merge(&mut diffs);

};

// found a subsequence which contains the short text

// Shorter text is inside the longer text (speedup).

let op = if old_gt_new { Ops::Delete } else { Ops::Insert };

let diffs = vec![

// Does a substring of shorttext exist within longtext such that the substring

// is at least half the length of longtext?

// idx Start index of quarter length substring within longtext.

fn half_match_i<'a, T: DType>(

long: &'a [T],

short: &'a [T],

idx: usize,

) -> Option<HalfMatch<'a, T>> {

// Start with a 1/4 length substring at position i as a seed.

let mut j = 0;

let mut best_common: &[T] = &[];

let mut best_short_a: &[T] = &[];

let mut best_short_b: &[T] = &[];

}

if (best_common.len() << 1) >= long.len() {

// We are doing a binary search here, and I've observed similar performance as noted by https://neil.fraser.name/news/2007/10/09/

// Some benchmark code can be found in benches/prefix.rs

// Reverse prefix is suffix

fn common_prefix<T: DType>(lhs: &[T], rhs: &[T], reverse: bool) -> usize {

if lhs.is_empty()

|| rhs.is_empty()

)

};

pointmin = pointmid;

pointstart = pointmin;

} else {

pointmid

}

fn common_overlap<T: DType>(lhs: &[T], rhs: &[T]) -> usize {

if lhs.is_empty() || rhs.is_empty() {

return 0;

let mut len = 1;

let mut best = 0;

len += found;

if found == 0 || l[l.len() - len..] == r[..len] {

best = len;

}

// Reduce the number of edits by eliminating semantically trivial equalities

fn cleanup_semantic<T: DType>(diffs: &mut Vec<Diff<T>>) {

let mut changes = false;

let mut insert_len_post = 0_usize;

let mut delete_len_post = 0_usize;

let mut diff_mod = false;

if diffs[pointer].op() == Ops::Equal {

equalities.push(pointer);

diffs.insert(last, Diff::delete(last_eq));

// Change the other copy to insert

diffs[last + 1].0 = Ops::Insert;

// Throw away the equality we just deleted.

equalities.pop();

Self::cleanup_semantic_lossless(diffs);

// Find any overlaps between deletions and insertions.

// e.g: <del>abcxxx</del><ins>xxxdef</ins>

// -> <del>abc</del>xxx<ins>def</ins>

// -> <ins>def</ins>xxx<del>abc</del>

// Only extract an overlap if it is as big as the edit ahead or behind it.

pointer = 1;

if diffs[pointer - 1].op() == Ops::Delete && diffs[pointer].op() == Ops::Insert {

let delete = diffs[pointer - 1].data().to_vec();

let insert = diffs[pointer].data().to_vec();

diffs.insert(pointer, Diff::equal(&insert[..overlap_1]));

diffs[pointer - 1].1 = delete[..delete.len() - overlap_1].to_vec();

diffs[pointer + 1].1 = insert[overlap_1..].to_vec();

pointer += 1;

} else if overlap_2 >= delete_thres || overlap_2 >= insert_thres {

// Reverse overlap

diffs[pointer - 1] = Diff::insert(&insert[..insert.len() - overlap_2]);

diffs[pointer + 1] = Diff::delete(&delete[overlap_2..]);

pointer += 1;

}

pointer += 1;

// Look for single edits surrounded on both sides by equalities

// e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.

fn cleanup_semantic_lossless<T: DType>(diffs: &mut Vec<Diff<T>>) {

let mut pointer = 1_usize;

// Intentionally ignore the first and last element (don't need checking).

// an edit surrounded by equalities

if diffs[pointer - 1].op() == Ops::Equal && diffs[pointer + 1].op() == Ops::Equal {

// Shift the edit as far left as possible

let (mut equality_prev, mut edit, mut equality_next) = {

let commonlen =

let mut best_score = Self::cleanup_semantic_score(&equality_prev[..], &edit[..])

+ Self::cleanup_semantic_score(&edit[..], &equality_next[..]);

equality_prev.push(edit[0]);

edit.remove(0);

edit.push(equality_next[0]);

} else {

diffs.remove(pointer - 1);

pointer -= 1;

}

diffs[pointer].1.clone_from(&best_edit);

} else {

diffs.remove(pointer + 1);

pointer -= 1;

}

}

}

// Given two strings, compute a score representing whether the internal

// boundary falls on logical boundaries

// Scores range from 6 (best) to 0 (worst)

fn cleanup_semantic_score<T: DType>(one: &[T], two: &[T]) -> u8 {

let (char1, char2) = if let (Some(&char1), Some(&char2)) = (one.last(), two.first()) {

if let (Some(c1), Some(c2)) = (char1.as_char(), char2.as_char()) {

fn cleanup_merge<T: DType>(diffs: &mut Vec<Diff<T>>) {

Self::cleanup_merge_first(diffs);

Self::cleanup_merge(diffs);

}

}

pointer += 1;

}

Ops::Equal => {

diffs,

insert_n,

delete_n,

changes

}

diffs: &mut Vec<Diff<T>>,

insert_n: usize,

delete_n: usize,

}

// Reduce the number of edits by eliminating operationally trivial equalities.

fn cleanup_efficiency<T: DType>(&self, diffs: &mut Vec<Diff<T>>) {

if diffs.is_empty() {

return;

&& pre_ins as u8 + pre_del as u8 + post_ins as u8 + post_del as u8 == 3)

{

// Duplicate record.

last_eq = None;

changes = true;

continue;

};

post_ins = false;

post_del = false;

}

let mut linehash: HashMap<&'a [T], usize> = HashMap::new();

// Allocate 2/3rds of the UTF16::MAX (65535) value space for text1, the rest for text2.

let mut maxlines = 40000;

let chars_old = Self::lines_to_chars_internal(old, &mut lines, &mut linehash, maxlines);

// This basically represents the U16::MAX value

maxlines = 65535;

let chars_new = Self::lines_to_chars_internal(new, &mut lines, &mut linehash, maxlines);

LineToChars {

}

}

fn lines_to_chars_internal<'a, T: DType>(

text: &'a [T],

array: &mut Vec<&'a [T]>,

) -> Vec<usize> {

let take = maxlines - array.len();

let mut charlist = Vec::with_capacity(take);

let mut broke = false;

});

// We broke at max lines, so we'll account for the remaining text

let line = &text[cursor..];

let e = hash.entry(line).or_insert(array.len());

// Fresh insert

charlist

}

fn chars_to_lines<T: DType>(diffs: &[Diff<usize>], lines: &[&[T]]) -> Vec<Diff<T>> {

diffs

.iter()

.map(|d| {

})

.collect::<Vec<_>>()

}

}

// Is there a nearby exact match? (speedup)

if let Some(best_loc) = text

.windows(pattern.len())

.skip(loc)

.position(|p| p == pattern)

.map(|pos| pos + loc)

// best_loc = text.lastIndexOf(pattern, loc + pattern.length);

if let Some(best_loc_rev) = text

.windows(pattern.len())

.skip(loc)

.rev()

.position(|p| p == pattern)