DiffEngine.php in Service Container 7
Same filename and directory in other branches
Contains \Drupal\Component\Diff\Engine\DiffEngine.
Namespace
Drupal\Component\Diff\EngineFile
lib/Drupal/Component/Diff/Engine/DiffEngine.phpView source
<?php
/**
* @file
* Contains \Drupal\Component\Diff\Engine\DiffEngine.
*/
namespace Drupal\Component\Diff\Engine;
use Drupal\Component\Utility\Unicode;
/**
* Class used internally by Diff to actually compute the diffs.
*
* The algorithm used here is mostly lifted from the perl module
* Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
* http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
*
* More ideas are taken from:
* http://www.ics.uci.edu/~eppstein/161/960229.html
*
* Some ideas (and a bit of code) are from analyze.c, from GNU
* diffutils-2.7, which can be found at:
* ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
*
* closingly, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
* are my own.
*
* Line length limits for robustness added by Tim Starling, 2005-08-31
*
* @author Geoffrey T. Dairiki, Tim Starling
* @private
* @subpackage DifferenceEngine
*/
class DiffEngine {
const USE_ASSERTS = FALSE;
const MAX_XREF_LENGTH = 10000;
public function diff($from_lines, $to_lines) {
$n_from = sizeof($from_lines);
$n_to = sizeof($to_lines);
$this->xchanged = $this->ychanged = array();
$this->xv = $this->yv = array();
$this->xind = $this->yind = array();
unset($this->seq);
unset($this->in_seq);
unset($this->lcs);
// Skip leading common lines.
for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
if ($from_lines[$skip] !== $to_lines[$skip]) {
break;
}
$this->xchanged[$skip] = $this->ychanged[$skip] = FALSE;
}
// Skip trailing common lines.
$xi = $n_from;
$yi = $n_to;
for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
if ($from_lines[$xi] !== $to_lines[$yi]) {
break;
}
$this->xchanged[$xi] = $this->ychanged[$yi] = FALSE;
}
// Ignore lines which do not exist in both files.
for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
$xhash[$this
->_line_hash($from_lines[$xi])] = 1;
}
for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
$line = $to_lines[$yi];
if ($this->ychanged[$yi] = empty($xhash[$this
->_line_hash($line)])) {
continue;
}
$yhash[$this
->_line_hash($line)] = 1;
$this->yv[] = $line;
$this->yind[] = $yi;
}
for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
$line = $from_lines[$xi];
if ($this->xchanged[$xi] = empty($yhash[$this
->_line_hash($line)])) {
continue;
}
$this->xv[] = $line;
$this->xind[] = $xi;
}
// Find the LCS.
$this
->_compareseq(0, sizeof($this->xv), 0, sizeof($this->yv));
// Merge edits when possible
$this
->_shift_boundaries($from_lines, $this->xchanged, $this->ychanged);
$this
->_shift_boundaries($to_lines, $this->ychanged, $this->xchanged);
// Compute the edit operations.
$edits = array();
$xi = $yi = 0;
while ($xi < $n_from || $yi < $n_to) {
$this::USE_ASSERTS && assert($yi < $n_to || $this->xchanged[$xi]);
$this::USE_ASSERTS && assert($xi < $n_from || $this->ychanged[$yi]);
// Skip matching "snake".
$copy = array();
while ($xi < $n_from && $yi < $n_to && !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
$copy[] = $from_lines[$xi++];
++$yi;
}
if ($copy) {
$edits[] = new DiffOpCopy($copy);
}
// Find deletes & adds.
$delete = array();
while ($xi < $n_from && $this->xchanged[$xi]) {
$delete[] = $from_lines[$xi++];
}
$add = array();
while ($yi < $n_to && $this->ychanged[$yi]) {
$add[] = $to_lines[$yi++];
}
if ($delete && $add) {
$edits[] = new DiffOpChange($delete, $add);
}
elseif ($delete) {
$edits[] = new DiffOpDelete($delete);
}
elseif ($add) {
$edits[] = new DiffOpAdd($add);
}
}
return $edits;
}
/**
* Returns the whole line if it's small enough, or the MD5 hash otherwise.
*/
protected function _line_hash($line) {
if (Unicode::strlen($line) > $this::MAX_XREF_LENGTH) {
return md5($line);
}
else {
return $line;
}
}
/**
* Divide the Largest Common Subsequence (LCS) of the sequences
* [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
* sized segments.
*
* Returns (LCS, PTS). LCS is the length of the LCS. PTS is an
* array of NCHUNKS+1 (X, Y) indexes giving the diving points between
* sub sequences. The first sub-sequence is contained in [X0, X1),
* [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on. Note
* that (X0, Y0) == (XOFF, YOFF) and
* (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
*
* This function assumes that the first lines of the specified portions
* of the two files do not match, and likewise that the last lines do not
* match. The caller must trim matching lines from the beginning and end
* of the portions it is going to specify.
*/
protected function _diag($xoff, $xlim, $yoff, $ylim, $nchunks) {
$flip = FALSE;
if ($xlim - $xoff > $ylim - $yoff) {
// Things seems faster (I'm not sure I understand why)
// when the shortest sequence in X.
$flip = TRUE;
list($xoff, $xlim, $yoff, $ylim) = array(
$yoff,
$ylim,
$xoff,
$xlim,
);
}
if ($flip) {
for ($i = $ylim - 1; $i >= $yoff; $i--) {
$ymatches[$this->xv[$i]][] = $i;
}
}
else {
for ($i = $ylim - 1; $i >= $yoff; $i--) {
$ymatches[$this->yv[$i]][] = $i;
}
}
$this->lcs = 0;
$this->seq[0] = $yoff - 1;
$this->in_seq = array();
$ymids[0] = array();
$numer = $xlim - $xoff + $nchunks - 1;
$x = $xoff;
for ($chunk = 0; $chunk < $nchunks; $chunk++) {
if ($chunk > 0) {
for ($i = 0; $i <= $this->lcs; $i++) {
$ymids[$i][$chunk - 1] = $this->seq[$i];
}
}
$x1 = $xoff + (int) (($numer + ($xlim - $xoff) * $chunk) / $nchunks);
for (; $x < $x1; $x++) {
$line = $flip ? $this->yv[$x] : $this->xv[$x];
if (empty($ymatches[$line])) {
continue;
}
$matches = $ymatches[$line];
reset($matches);
while (list($junk, $y) = each($matches)) {
if (empty($this->in_seq[$y])) {
$k = $this
->_lcs_pos($y);
$this::USE_ASSERTS && assert($k > 0);
$ymids[$k] = $ymids[$k - 1];
break;
}
}
while (list($junk, $y) = each($matches)) {
if ($y > $this->seq[$k - 1]) {
$this::USE_ASSERTS && assert($y < $this->seq[$k]);
// Optimization: this is a common case:
// next match is just replacing previous match.
$this->in_seq[$this->seq[$k]] = FALSE;
$this->seq[$k] = $y;
$this->in_seq[$y] = 1;
}
elseif (empty($this->in_seq[$y])) {
$k = $this
->_lcs_pos($y);
$this::USE_ASSERTS && assert($k > 0);
$ymids[$k] = $ymids[$k - 1];
}
}
}
}
$seps[] = $flip ? array(
$yoff,
$xoff,
) : array(
$xoff,
$yoff,
);
$ymid = $ymids[$this->lcs];
for ($n = 0; $n < $nchunks - 1; $n++) {
$x1 = $xoff + (int) (($numer + ($xlim - $xoff) * $n) / $nchunks);
$y1 = $ymid[$n] + 1;
$seps[] = $flip ? array(
$y1,
$x1,
) : array(
$x1,
$y1,
);
}
$seps[] = $flip ? array(
$ylim,
$xlim,
) : array(
$xlim,
$ylim,
);
return array(
$this->lcs,
$seps,
);
}
protected function _lcs_pos($ypos) {
$end = $this->lcs;
if ($end == 0 || $ypos > $this->seq[$end]) {
$this->seq[++$this->lcs] = $ypos;
$this->in_seq[$ypos] = 1;
return $this->lcs;
}
$beg = 1;
while ($beg < $end) {
$mid = (int) (($beg + $end) / 2);
if ($ypos > $this->seq[$mid]) {
$beg = $mid + 1;
}
else {
$end = $mid;
}
}
$this::USE_ASSERTS && assert($ypos != $this->seq[$end]);
$this->in_seq[$this->seq[$end]] = FALSE;
$this->seq[$end] = $ypos;
$this->in_seq[$ypos] = 1;
return $end;
}
/**
* Find LCS of two sequences.
*
* The results are recorded in the vectors $this->{x,y}changed[], by
* storing a 1 in the element for each line that is an insertion
* or deletion (ie. is not in the LCS).
*
* The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
*
* Note that XLIM, YLIM are exclusive bounds.
* All line numbers are origin-0 and discarded lines are not counted.
*/
protected function _compareseq($xoff, $xlim, $yoff, $ylim) {
// Slide down the bottom initial diagonal.
while ($xoff < $xlim && $yoff < $ylim && $this->xv[$xoff] == $this->yv[$yoff]) {
++$xoff;
++$yoff;
}
// Slide up the top initial diagonal.
while ($xlim > $xoff && $ylim > $yoff && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
--$xlim;
--$ylim;
}
if ($xoff == $xlim || $yoff == $ylim) {
$lcs = 0;
}
else {
// This is ad hoc but seems to work well.
//$nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
//$nchunks = max(2, min(8, (int)$nchunks));
$nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
list($lcs, $seps) = $this
->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
}
if ($lcs == 0) {
// X and Y sequences have no common subsequence:
// mark all changed.
while ($yoff < $ylim) {
$this->ychanged[$this->yind[$yoff++]] = 1;
}
while ($xoff < $xlim) {
$this->xchanged[$this->xind[$xoff++]] = 1;
}
}
else {
// Use the partitions to split this problem into subproblems.
reset($seps);
$pt1 = $seps[0];
while ($pt2 = next($seps)) {
$this
->_compareseq($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
$pt1 = $pt2;
}
}
}
/**
* Adjust inserts/deletes of identical lines to join changes
* as much as possible.
*
* We do something when a run of changed lines include a
* line at one end and has an excluded, identical line at the other.
* We are free to choose which identical line is included.
* `compareseq' usually chooses the one at the beginning,
* but usually it is cleaner to consider the following identical line
* to be the "change".
*
* This is extracted verbatim from analyze.c (GNU diffutils-2.7).
*/
protected function _shift_boundaries($lines, &$changed, $other_changed) {
$i = 0;
$j = 0;
$this::USE_ASSERTS && assert('sizeof($lines) == sizeof($changed)');
$len = sizeof($lines);
$other_len = sizeof($other_changed);
while (1) {
/*
* Scan forwards to find beginning of another run of changes.
* Also keep track of the corresponding point in the other file.
*
* Throughout this code, $i and $j are adjusted together so that
* the first $i elements of $changed and the first $j elements
* of $other_changed both contain the same number of zeros
* (unchanged lines).
* Furthermore, $j is always kept so that $j == $other_len or
* $other_changed[$j] == FALSE.
*/
while ($j < $other_len && $other_changed[$j]) {
$j++;
}
while ($i < $len && !$changed[$i]) {
$this::USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
$i++;
$j++;
while ($j < $other_len && $other_changed[$j]) {
$j++;
}
}
if ($i == $len) {
break;
}
$start = $i;
// Find the end of this run of changes.
while (++$i < $len && $changed[$i]) {
continue;
}
do {
/*
* Record the length of this run of changes, so that
* we can later determine whether the run has grown.
*/
$runlength = $i - $start;
/*
* Move the changed region back, so long as the
* previous unchanged line matches the last changed one.
* This merges with previous changed regions.
*/
while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
$changed[--$start] = 1;
$changed[--$i] = FALSE;
while ($start > 0 && $changed[$start - 1]) {
$start--;
}
$this::USE_ASSERTS && assert('$j > 0');
while ($other_changed[--$j]) {
continue;
}
$this::USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
}
/*
* Set CORRESPONDING to the end of the changed run, at the last
* point where it corresponds to a changed run in the other file.
* CORRESPONDING == LEN means no such point has been found.
*/
$corresponding = $j < $other_len ? $i : $len;
/*
* Move the changed region forward, so long as the
* first changed line matches the following unchanged one.
* This merges with following changed regions.
* Do this second, so that if there are no merges,
* the changed region is moved forward as far as possible.
*/
while ($i < $len && $lines[$start] == $lines[$i]) {
$changed[$start++] = FALSE;
$changed[$i++] = 1;
while ($i < $len && $changed[$i]) {
$i++;
}
$this::USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
$j++;
if ($j < $other_len && $other_changed[$j]) {
$corresponding = $i;
while ($j < $other_len && $other_changed[$j]) {
$j++;
}
}
}
} while ($runlength != $i - $start);
/*
* If possible, move the fully-merged run of changes
* back to a corresponding run in the other file.
*/
while ($corresponding < $i) {
$changed[--$start] = 1;
$changed[--$i] = 0;
$this::USE_ASSERTS && assert('$j > 0');
while ($other_changed[--$j]) {
continue;
}
$this::USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
}
}
}
}Classes
Name |
Description |
|---|---|
| DiffEngine | Class used internally by Diff to actually compute the diffs. |