1: <?php
2: /**
3: * Class used internally by Horde_Text_Diff to actually compute the diffs.
4: *
5: * This class is implemented using native PHP code.
6: *
7: * The algorithm used here is mostly lifted from the perl module
8: * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
9: * http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
10: *
11: * More ideas are taken from: http://www.ics.uci.edu/~eppstein/161/960229.html
12: *
13: * Some ideas (and a bit of code) are taken from analyze.c, of GNU
14: * diffutils-2.7, which can be found at:
15: * ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
16: *
17: * Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from
18: * Geoffrey T. Dairiki <dairiki@dairiki.org>. The original PHP version of this
19: * code was written by him, and is used/adapted with his permission.
20: *
21: * Copyright 2004-2012 Horde LLC (http://www.horde.org/)
22: *
23: * See the enclosed file COPYING for license information (LGPL). If you did
24: * not receive this file, see http://www.horde.org/licenses/lgpl21.
25: *
26: * @author Geoffrey T. Dairiki <dairiki@dairiki.org>
27: * @package Text_Diff
28: */
29: class Horde_Text_Diff_Engine_Native
30: {
31: public function diff($from_lines, $to_lines)
32: {
33: array_walk($from_lines, array('Horde_Text_Diff', 'trimNewlines'));
34: array_walk($to_lines, array('Horde_Text_Diff', 'trimNewlines'));
35:
36: $n_from = count($from_lines);
37: $n_to = count($to_lines);
38:
39: $this->xchanged = $this->ychanged = array();
40: $this->xv = $this->yv = array();
41: $this->xind = $this->yind = array();
42: unset($this->seq);
43: unset($this->in_seq);
44: unset($this->lcs);
45:
46: // Skip leading common lines.
47: for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
48: if ($from_lines[$skip] !== $to_lines[$skip]) {
49: break;
50: }
51: $this->xchanged[$skip] = $this->ychanged[$skip] = false;
52: }
53:
54: // Skip trailing common lines.
55: $xi = $n_from; $yi = $n_to;
56: for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
57: if ($from_lines[$xi] !== $to_lines[$yi]) {
58: break;
59: }
60: $this->xchanged[$xi] = $this->ychanged[$yi] = false;
61: }
62:
63: // Ignore lines which do not exist in both files.
64: for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
65: $xhash[$from_lines[$xi]] = 1;
66: }
67: for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
68: $line = $to_lines[$yi];
69: if (($this->ychanged[$yi] = empty($xhash[$line]))) {
70: continue;
71: }
72: $yhash[$line] = 1;
73: $this->yv[] = $line;
74: $this->yind[] = $yi;
75: }
76: for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
77: $line = $from_lines[$xi];
78: if (($this->xchanged[$xi] = empty($yhash[$line]))) {
79: continue;
80: }
81: $this->xv[] = $line;
82: $this->xind[] = $xi;
83: }
84:
85: // Find the LCS.
86: $this->_compareseq(0, count($this->xv), 0, count($this->yv));
87:
88: // Merge edits when possible.
89: $this->_shiftBoundaries($from_lines, $this->xchanged, $this->ychanged);
90: $this->_shiftBoundaries($to_lines, $this->ychanged, $this->xchanged);
91:
92: // Compute the edit operations.
93: $edits = array();
94: $xi = $yi = 0;
95: while ($xi < $n_from || $yi < $n_to) {
96: assert($yi < $n_to || $this->xchanged[$xi]);
97: assert($xi < $n_from || $this->ychanged[$yi]);
98:
99: // Skip matching "snake".
100: $copy = array();
101: while ($xi < $n_from && $yi < $n_to
102: && !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
103: $copy[] = $from_lines[$xi++];
104: ++$yi;
105: }
106: if ($copy) {
107: $edits[] = new Horde_Text_Diff_Op_Copy($copy);
108: }
109:
110: // Find deletes & adds.
111: $delete = array();
112: while ($xi < $n_from && $this->xchanged[$xi]) {
113: $delete[] = $from_lines[$xi++];
114: }
115:
116: $add = array();
117: while ($yi < $n_to && $this->ychanged[$yi]) {
118: $add[] = $to_lines[$yi++];
119: }
120:
121: if ($delete && $add) {
122: $edits[] = new Horde_Text_Diff_Op_Change($delete, $add);
123: } elseif ($delete) {
124: $edits[] = new Horde_Text_Diff_Op_Delete($delete);
125: } elseif ($add) {
126: $edits[] = new Horde_Text_Diff_Op_Add($add);
127: }
128: }
129:
130: return $edits;
131: }
132:
133: /**
134: * Divides the Largest Common Subsequence (LCS) of the sequences (XOFF,
135: * XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized
136: * segments.
137: *
138: * Returns (LCS, PTS). LCS is the length of the LCS. PTS is an array of
139: * NCHUNKS+1 (X, Y) indexes giving the diving points between sub
140: * sequences. The first sub-sequence is contained in (X0, X1), (Y0, Y1),
141: * the second in (X1, X2), (Y1, Y2) and so on. Note that (X0, Y0) ==
142: * (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
143: *
144: * This public function assumes that the first lines of the specified portions of
145: * the two files do not match, and likewise that the last lines do not
146: * match. The caller must trim matching lines from the beginning and end
147: * of the portions it is going to specify.
148: */
149: protected function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
150: {
151: $flip = false;
152:
153: if ($xlim - $xoff > $ylim - $yoff) {
154: /* Things seems faster (I'm not sure I understand why) when the
155: * shortest sequence is in X. */
156: $flip = true;
157: list ($xoff, $xlim, $yoff, $ylim)
158: = array($yoff, $ylim, $xoff, $xlim);
159: }
160:
161: if ($flip) {
162: for ($i = $ylim - 1; $i >= $yoff; $i--) {
163: $ymatches[$this->xv[$i]][] = $i;
164: }
165: } else {
166: for ($i = $ylim - 1; $i >= $yoff; $i--) {
167: $ymatches[$this->yv[$i]][] = $i;
168: }
169: }
170:
171: $this->lcs = 0;
172: $this->seq[0]= $yoff - 1;
173: $this->in_seq = array();
174: $ymids[0] = array();
175:
176: $numer = $xlim - $xoff + $nchunks - 1;
177: $x = $xoff;
178: for ($chunk = 0; $chunk < $nchunks; $chunk++) {
179: if ($chunk > 0) {
180: for ($i = 0; $i <= $this->lcs; $i++) {
181: $ymids[$i][$chunk - 1] = $this->seq[$i];
182: }
183: }
184:
185: $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $chunk) / $nchunks);
186: for (; $x < $x1; $x++) {
187: $line = $flip ? $this->yv[$x] : $this->xv[$x];
188: if (empty($ymatches[$line])) {
189: continue;
190: }
191: $matches = $ymatches[$line];
192: reset($matches);
193: while (list(, $y) = each($matches)) {
194: if (empty($this->in_seq[$y])) {
195: $k = $this->_lcsPos($y);
196: assert($k > 0);
197: $ymids[$k] = $ymids[$k - 1];
198: break;
199: }
200: }
201: while (list(, $y) = each($matches)) {
202: if ($y > $this->seq[$k - 1]) {
203: assert($y <= $this->seq[$k]);
204: /* Optimization: this is a common case: next match is
205: * just replacing previous match. */
206: $this->in_seq[$this->seq[$k]] = false;
207: $this->seq[$k] = $y;
208: $this->in_seq[$y] = 1;
209: } elseif (empty($this->in_seq[$y])) {
210: $k = $this->_lcsPos($y);
211: assert($k > 0);
212: $ymids[$k] = $ymids[$k - 1];
213: }
214: }
215: }
216: }
217:
218: $seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
219: $ymid = $ymids[$this->lcs];
220: for ($n = 0; $n < $nchunks - 1; $n++) {
221: $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
222: $y1 = $ymid[$n] + 1;
223: $seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
224: }
225: $seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);
226:
227: return array($this->lcs, $seps);
228: }
229:
230: protected function _lcsPos($ypos)
231: {
232: $end = $this->lcs;
233: if ($end == 0 || $ypos > $this->seq[$end]) {
234: $this->seq[++$this->lcs] = $ypos;
235: $this->in_seq[$ypos] = 1;
236: return $this->lcs;
237: }
238:
239: $beg = 1;
240: while ($beg < $end) {
241: $mid = (int)(($beg + $end) / 2);
242: if ($ypos > $this->seq[$mid]) {
243: $beg = $mid + 1;
244: } else {
245: $end = $mid;
246: }
247: }
248:
249: assert($ypos != $this->seq[$end]);
250:
251: $this->in_seq[$this->seq[$end]] = false;
252: $this->seq[$end] = $ypos;
253: $this->in_seq[$ypos] = 1;
254: return $end;
255: }
256:
257: /**
258: * Finds LCS of two sequences.
259: *
260: * The results are recorded in the vectors $this->{x,y}changed[], by
261: * storing a 1 in the element for each line that is an insertion or
262: * deletion (ie. is not in the LCS).
263: *
264: * The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
265: *
266: * Note that XLIM, YLIM are exclusive bounds. All line numbers are
267: * origin-0 and discarded lines are not counted.
268: */
269: protected function _compareseq ($xoff, $xlim, $yoff, $ylim)
270: {
271: /* Slide down the bottom initial diagonal. */
272: while ($xoff < $xlim && $yoff < $ylim
273: && $this->xv[$xoff] == $this->yv[$yoff]) {
274: ++$xoff;
275: ++$yoff;
276: }
277:
278: /* Slide up the top initial diagonal. */
279: while ($xlim > $xoff && $ylim > $yoff
280: && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
281: --$xlim;
282: --$ylim;
283: }
284:
285: if ($xoff == $xlim || $yoff == $ylim) {
286: $lcs = 0;
287: } else {
288: /* This is ad hoc but seems to work well. $nchunks =
289: * sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5); $nchunks =
290: * max(2,min(8,(int)$nchunks)); */
291: $nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
292: list($lcs, $seps)
293: = $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
294: }
295:
296: if ($lcs == 0) {
297: /* X and Y sequences have no common subsequence: mark all
298: * changed. */
299: while ($yoff < $ylim) {
300: $this->ychanged[$this->yind[$yoff++]] = 1;
301: }
302: while ($xoff < $xlim) {
303: $this->xchanged[$this->xind[$xoff++]] = 1;
304: }
305: } else {
306: /* Use the partitions to split this problem into subproblems. */
307: reset($seps);
308: $pt1 = $seps[0];
309: while ($pt2 = next($seps)) {
310: $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
311: $pt1 = $pt2;
312: }
313: }
314: }
315:
316: /**
317: * Adjusts inserts/deletes of identical lines to join changes as much as
318: * possible.
319: *
320: * We do something when a run of changed lines include a line at one end
321: * and has an excluded, identical line at the other. We are free to
322: * choose which identical line is included. `compareseq' usually chooses
323: * the one at the beginning, but usually it is cleaner to consider the
324: * following identical line to be the "change".
325: *
326: * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
327: */
328: protected function _shiftBoundaries($lines, &$changed, $other_changed)
329: {
330: $i = 0;
331: $j = 0;
332:
333: assert('count($lines) == count($changed)');
334: $len = count($lines);
335: $other_len = count($other_changed);
336:
337: while (1) {
338: /* Scan forward to find the beginning of another run of
339: * changes. Also keep track of the corresponding point in the
340: * other file.
341: *
342: * Throughout this code, $i and $j are adjusted together so that
343: * the first $i elements of $changed and the first $j elements of
344: * $other_changed both contain the same number of zeros (unchanged
345: * lines).
346: *
347: * Furthermore, $j is always kept so that $j == $other_len or
348: * $other_changed[$j] == false. */
349: while ($j < $other_len && $other_changed[$j]) {
350: $j++;
351: }
352:
353: while ($i < $len && ! $changed[$i]) {
354: assert('$j < $other_len && ! $other_changed[$j]');
355: $i++; $j++;
356: while ($j < $other_len && $other_changed[$j]) {
357: $j++;
358: }
359: }
360:
361: if ($i == $len) {
362: break;
363: }
364:
365: $start = $i;
366:
367: /* Find the end of this run of changes. */
368: while (++$i < $len && $changed[$i]) {
369: continue;
370: }
371:
372: do {
373: /* Record the length of this run of changes, so that we can
374: * later determine whether the run has grown. */
375: $runlength = $i - $start;
376:
377: /* Move the changed region back, so long as the previous
378: * unchanged line matches the last changed one. This merges
379: * with previous changed regions. */
380: while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
381: $changed[--$start] = 1;
382: $changed[--$i] = false;
383: while ($start > 0 && $changed[$start - 1]) {
384: $start--;
385: }
386: assert('$j > 0');
387: while ($other_changed[--$j]) {
388: continue;
389: }
390: assert('$j >= 0 && !$other_changed[$j]');
391: }
392:
393: /* Set CORRESPONDING to the end of the changed run, at the
394: * last point where it corresponds to a changed run in the
395: * other file. CORRESPONDING == LEN means no such point has
396: * been found. */
397: $corresponding = $j < $other_len ? $i : $len;
398:
399: /* Move the changed region forward, so long as the first
400: * changed line matches the following unchanged one. This
401: * merges with following changed regions. Do this second, so
402: * that if there are no merges, the changed region is moved
403: * forward as far as possible. */
404: while ($i < $len && $lines[$start] == $lines[$i]) {
405: $changed[$start++] = false;
406: $changed[$i++] = 1;
407: while ($i < $len && $changed[$i]) {
408: $i++;
409: }
410:
411: assert('$j < $other_len && ! $other_changed[$j]');
412: $j++;
413: if ($j < $other_len && $other_changed[$j]) {
414: $corresponding = $i;
415: while ($j < $other_len && $other_changed[$j]) {
416: $j++;
417: }
418: }
419: }
420: } while ($runlength != $i - $start);
421:
422: /* If possible, move the fully-merged run of changes back to a
423: * corresponding run in the other file. */
424: while ($corresponding < $i) {
425: $changed[--$start] = 1;
426: $changed[--$i] = 0;
427: assert('$j > 0');
428: while ($other_changed[--$j]) {
429: continue;
430: }
431: assert('$j >= 0 && !$other_changed[$j]');
432: }
433: }
434: }
435: }
436: