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/*******************************************************************************
Key portions of code below was borrowed from:
https://github.com/Swatinem/diff
License is LGPL3 (thanks!) as per:
https://github.com/Swatinem/diff/blob/b58391504759/README.md
I chose to pick this implementation over
https://github.com/google/diff-match-patch as suggested by CodeMirror
because:
- Code is clean and simple to read -- useful when unfamiliar with the diff
algorithm, this makes changing the code easier if/when needed.
- Smaller -- diff_match_patch comes with an extended API most of which is
of no use to the current project.
- diff_match_patch uncompressed: 74.7 KB
- Swatinem's diff uncompressed: 3.66 KB
- I can easily adapt Swatinem's diff to deal with arrays of strings, which
is best suited for the current project -- it natively work with arrays.
I removed portions of code which are of no use for the current project.
I modified the diff script generator (Diff.prototype.editscript) since I
need to generate a script which is compatible with the output of the
diff_match_patch, as expected by CodeMirror.
2018-12-20 gorhill:
===================
There was an issue causing the wrong diff data to be issued, for instance
when diff-ing these two URLs on a character granularity basis (failure
point is marked):
|
/articles/5c1a7aae1854f30006cb26f7/lede/1545239527833-shutterstock_726 01757 2-copy.jpeg?crop=0.8889xw%3A0.9988xh%3B0.1089xw%2C0xh&resize=650%3A*&output-quality=55
/articles/5c1a* 1854f30006cb2* /lede/15452* -shutterstock_* 017* 2-copy.jpeg?crop=0.* xw%3A* h%3B0.0* xw%2C0xh&resize=650%3A*&output-quality=55
/articles/5c1aaea91854f30006cb2f1e/lede/1545253629235-shutterstock_106399017 2-copy.jpeg?crop=0.7749xw%3A1 xh%3B0.0391xw%2C0xh&resize=650%3A*&output-quality=55
|
Investigating, I found what appears to be the original source on which the
code below is based:
- "An O(ND) Difference Algorithm for C#" by Matthias Hertel
- http://www.mathertel.de/Diff/ViewSrc.aspx
- https://github.com/mathertel
There was a difference; code had been commented out in the original source:
http://www.mathertel.de/Diff/DiffTest.aspx?oldfile=Diff.cs.v1&newfile=Diff.cs.v2
The developer noted:
> There have been overlapping boxes; that where analyzed partial differently.
> One return-point is enough.
After applying the changes to the code below, the problematic diff-ing went
away:
|
/articles/5c1a7aae1854f30006cb26f7/lede/1545239527833-shutterstock_726 01757 2-copy.jpeg?crop=0.8889xw%3A0.9988xh%3B0.1089xw%2C0xh&resize=650%3A*&output-quality=55
/articles/5c1a* 1854f30006cb2* /lede/15452* -shutterstock_* 017* 2-copy.jpeg?crop=0.* 9xw%3A* xh%3B0.* xw%2C0xh&resize=650%3A*&output-quality=55
/articles/5c1aaea91854f30006cb2f1e/lede/1545253629235-shutterstock_106399017 2-copy.jpeg?crop=0.7749xw%3A1 xh%3B0.0391xw%2C0xh&resize=650%3A*&output-quality=55
|
So I will assume this was the issue.
2021-07-17 gorhill:
===================
Added pure diff() method which natively deals with arrays and other minor
changes related to ES6.
**/
'use strict';
(function(context) {
// CodeMirror expect these globals:
context.DIFF_INSERT = 1;
context.DIFF_DELETE = -1;
context.DIFF_EQUAL = 0;
context.diff_match_patch = function(){};
context.diff_match_patch.prototype.diff_main = function(a, b) {
if ( a === b ) { return [ [ 0, a ] ]; }
const aa = a.match(/\n|[^\n]+\n?/g) || [];
const bb = b.match(/\n|[^\n]+\n?/g) || [];
const d = new Diff(aa, bb);
return d.editscript();
};
context.diff_match_patch.prototype.diff = function(a, b) {
const d = new Diff(a, b);
return d.editscript();
};
const eqlDefault = (a, b) => a === b;
function Diff(a, b, eql = eqlDefault) {
this.a = a;
this.b = b;
this.eql = eql;
this.moda = Array.apply(null, new Array(a.length)).map(true.valueOf, false);
this.modb = Array.apply(null, new Array(b.length)).map(true.valueOf, false);
// just to save some allocations:
this.down = {};
this.up = {};
this.lcs(0, a.length, 0, b.length);
}
Diff.prototype.editscript = function Diff_editscript() {
const moda = this.moda, modb = this.modb;
var astart = 0, aend = moda.length;
var bstart = 0, bend = modb.length;
const result = [];
while (astart < aend || bstart < bend) {
if (astart < aend && bstart < bend) {
if (!moda[astart] && !modb[bstart]) {
result.push([ 0, this.a[astart] ]);
astart++; bstart++;
continue;
} else if (moda[astart] && modb[bstart]) {
result.push([ -1, this.a[astart] ]);
result.push([ 1, this.b[bstart] ]);
astart++; bstart++;
continue;
}
}
if (astart < aend && (bstart >= bend || moda[astart])) {
result.push([ -1, this.a[astart] ]);
astart++;
}
if (bstart < bend && (astart >= aend || modb[bstart])) {
result.push([ 1, this.b[bstart] ]);
bstart++;
}
}
return result;
};
Diff.prototype.lcs = function Diff_lcs(astart, aend, bstart, bend) {
const a = this.a, b = this.b, eql = this.eql;
// separate common head
while (astart < aend && bstart < bend && eql(a[astart], b[bstart])) {
astart++; bstart++;
}
// separate common tail
while (astart < aend && bstart < bend && eql(a[aend - 1], b[bend - 1])) {
aend--; bend--;
}
if (astart === aend) {
// only insertions
while (bstart < bend) {
this.modb[bstart] = true;
bstart++;
}
} else if (bend === bstart) {
// only deletions
while (astart < aend) {
this.moda[astart] = true;
astart++;
}
} else {
const snake = this.snake(astart, aend, bstart, bend);
this.lcs(astart, snake.x, bstart, snake.y);
this.lcs(snake.x, aend, snake.y, bend);
}
};
Diff.prototype.snake = function Diff_snake(astart, aend, bstart, bend) {
const a = this.a, b = this.b, eql = this.eql;
const N = aend - astart;
const M = bend - bstart;
const kdown = astart - bstart;
const kup = aend - bend;
const delta = N - M;
const deltaOdd = delta & 1;
const down = this.down;
down[kdown + 1] = astart;
const up = this.up;
up[kup - 1] = aend;
const Dmax = (N + M + 1) / 2;
for (let D = 0; D <= Dmax; D++) {
// forward path
for (let k = kdown - D; k <= kdown + D; k += 2) {
let x;
if (k === kdown - D) {
x = down[k + 1]; // down
} else {
x = down[k - 1] + 1; // right
if ((k < kdown + D) && (down[k + 1] >= x)) {
x = down[k + 1]; // down
}
}
let y = x - k;
while (x < aend && y < bend && eql(a[x], b[y])) {
x++; y++; // diagonal
}
down[k] = x;
if (deltaOdd && (kup - D < k) && (k < kup + D) &&
up[k] <= down[k]) {
return {
x: down[k],
y: down[k] - k,
// u: up[k],
// v: up[k] - k,
};
}
}
// reverse path
for (let k = kup - D; k <= kup + D; k += 2) {
let x;
if (k === kup + D) {
x = up[k - 1]; // up
} else {
x = up[k + 1] - 1; // left
if ((k > kup - D) && (up[k - 1] < x)) {
x = up[k - 1]; // up
}
}
let y = x - k;
while (x > astart && y > bstart && eql(a[x - 1], b[y - 1])) {
x--; y--; // diagonal
}
up[k] = x;
if (!deltaOdd && (kdown - D <= k) && (k <= kdown + D) &&
up[k] <= down[k]) {
return {
x: down[k],
y: down[k] - k,
// u: up[k],
// v: up[k] - k,
};
}
}
}
};
return Diff;
})(self);
/*******************************************************************************
DO NOT:
- Remove the following code
- Add code beyond the following code
Reason:
- https://github.com/gorhill/uBlock/pull/3721
- uBO never uses the return value from injected content scripts
**/
void 0;
|
