1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
|
/* File I/O for GNU DIFF.
Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1998, 2001, 2002,
2004, 2006 Free Software Foundation, Inc.
This file is part of GNU DIFF.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "diff.h"
#include <cmpbuf.h>
#include <file-type.h>
#include <xalloc.h>
/* Rotate an unsigned value to the left. */
#define ROL(v, n) ((v) << (n) | (v) >> (sizeof (v) * CHAR_BIT - (n)))
/* Given a hash value and a new character, return a new hash value. */
#define HASH(h, c) ((c) + ROL (h, 7))
/* The type of a hash value. */
typedef size_t hash_value;
verify (! TYPE_SIGNED (hash_value));
/* Lines are put into equivalence classes of lines that match in lines_differ.
Each equivalence class is represented by one of these structures,
but only while the classes are being computed.
Afterward, each class is represented by a number. */
struct equivclass
{
lin next; /* Next item in this bucket. */
hash_value hash; /* Hash of lines in this class. */
char const *line; /* A line that fits this class. */
size_t length; /* That line's length, not counting its newline. */
};
/* Hash-table: array of buckets, each being a chain of equivalence classes.
buckets[-1] is reserved for incomplete lines. */
static lin *buckets;
/* Number of buckets in the hash table array, not counting buckets[-1]. */
static size_t nbuckets;
/* Array in which the equivalence classes are allocated.
The bucket-chains go through the elements in this array.
The number of an equivalence class is its index in this array. */
static struct equivclass *equivs;
/* Index of first free element in the array `equivs'. */
static lin equivs_index;
/* Number of elements allocated in the array `equivs'. */
static lin equivs_alloc;
/* Read a block of data into a file buffer, checking for EOF and error. */
void
file_block_read (struct file_data *current, size_t size)
{
if (size && ! current->eof)
{
size_t s = block_read (current->desc,
FILE_BUFFER (current) + current->buffered, size);
if (s == SIZE_MAX)
pfatal_with_name (current->name);
current->buffered += s;
current->eof = s < size;
}
}
/* Check for binary files and compare them for exact identity. */
/* Return 1 if BUF contains a non text character.
SIZE is the number of characters in BUF. */
#define binary_file_p(buf, size) (memchr (buf, 0, size) != 0)
/* Get ready to read the current file.
Return nonzero if SKIP_TEST is zero,
and if it appears to be a binary file. */
static bool
sip (struct file_data *current, bool skip_test)
{
/* If we have a nonexistent file at this stage, treat it as empty. */
if (current->desc < 0)
{
/* Leave room for a sentinel. */
current->bufsize = sizeof (word);
current->buffer = xmalloc (current->bufsize);
}
else
{
current->bufsize = buffer_lcm (sizeof (word),
STAT_BLOCKSIZE (current->stat),
PTRDIFF_MAX - 2 * sizeof (word));
current->buffer = xmalloc (current->bufsize);
if (! skip_test)
{
/* Check first part of file to see if it's a binary file. */
/* FIXME: if O_BINARY, this should revert to text mode
if the file is not binary. */
file_block_read (current, current->bufsize);
return binary_file_p (current->buffer, current->buffered);
}
}
current->buffered = 0;
current->eof = false;
return false;
}
/* Slurp the rest of the current file completely into memory. */
static void
slurp (struct file_data *current)
{
size_t cc;
if (current->desc < 0)
{
/* The file is nonexistent. */
return;
}
if (S_ISREG (current->stat.st_mode))
{
/* It's a regular file; slurp in the rest all at once. */
/* Get the size out of the stat block.
Allocate just enough room for appended newline plus word sentinel,
plus word-alignment since we want the buffer word-aligned. */
size_t file_size = current->stat.st_size;
cc = file_size + 2 * sizeof (word) - file_size % sizeof (word);
if (file_size != current->stat.st_size || cc < file_size
|| PTRDIFF_MAX <= cc)
xalloc_die ();
if (current->bufsize < cc)
{
current->bufsize = cc;
current->buffer = xrealloc (current->buffer, cc);
}
/* Try to read at least 1 more byte than the size indicates, to
detect whether the file is growing. This is a nicety for
users who run 'diff' on files while they are changing. */
if (current->buffered <= file_size)
{
file_block_read (current, file_size + 1 - current->buffered);
if (current->buffered <= file_size)
return;
}
}
/* It's not a regular file, or it's a growing regular file; read it,
growing the buffer as needed. */
file_block_read (current, current->bufsize - current->buffered);
if (current->buffered)
{
while (current->buffered == current->bufsize)
{
if (PTRDIFF_MAX / 2 - sizeof (word) < current->bufsize)
xalloc_die ();
current->bufsize *= 2;
current->buffer = xrealloc (current->buffer, current->bufsize);
file_block_read (current, current->bufsize - current->buffered);
}
/* Allocate just enough room for appended newline plus word
sentinel, plus word-alignment. */
cc = current->buffered + 2 * sizeof (word);
current->bufsize = cc - cc % sizeof (word);
current->buffer = xrealloc (current->buffer, current->bufsize);
}
}
/* Split the file into lines, simultaneously computing the equivalence
class for each line. */
static void
find_and_hash_each_line (struct file_data *current)
{
hash_value h;
char const *p = current->prefix_end;
unsigned char c;
lin i, *bucket;
size_t length;
/* Cache often-used quantities in local variables to help the compiler. */
char const **linbuf = current->linbuf;
lin alloc_lines = current->alloc_lines;
lin line = 0;
lin linbuf_base = current->linbuf_base;
lin *cureqs = xmalloc (alloc_lines * sizeof *cureqs);
struct equivclass *eqs = equivs;
lin eqs_index = equivs_index;
lin eqs_alloc = equivs_alloc;
char const *suffix_begin = current->suffix_begin;
char const *bufend = FILE_BUFFER (current) + current->buffered;
bool diff_length_compare_anyway =
ignore_white_space != IGNORE_NO_WHITE_SPACE;
bool same_length_diff_contents_compare_anyway =
diff_length_compare_anyway | ignore_case;
while (p < suffix_begin)
{
char const *ip = p;
h = 0;
/* Hash this line until we find a newline. */
if (ignore_case)
switch (ignore_white_space)
{
case IGNORE_ALL_SPACE:
while ((c = *p++) != '\n')
if (! isspace (c))
h = HASH (h, tolower (c));
break;
case IGNORE_SPACE_CHANGE:
while ((c = *p++) != '\n')
{
if (isspace (c))
{
do
if ((c = *p++) == '\n')
goto hashing_done;
while (isspace (c));
h = HASH (h, ' ');
}
/* C is now the first non-space. */
h = HASH (h, tolower (c));
}
break;
case IGNORE_TAB_EXPANSION:
{
size_t column = 0;
while ((c = *p++) != '\n')
{
size_t repetitions = 1;
switch (c)
{
case '\b':
column -= 0 < column;
break;
case '\t':
c = ' ';
repetitions = tabsize - column % tabsize;
column = (column + repetitions < column
? 0
: column + repetitions);
break;
case '\r':
column = 0;
break;
default:
c = tolower (c);
column++;
break;
}
do
h = HASH (h, c);
while (--repetitions != 0);
}
}
break;
default:
while ((c = *p++) != '\n')
h = HASH (h, tolower (c));
break;
}
else
switch (ignore_white_space)
{
case IGNORE_ALL_SPACE:
while ((c = *p++) != '\n')
if (! isspace (c))
h = HASH (h, c);
break;
case IGNORE_SPACE_CHANGE:
while ((c = *p++) != '\n')
{
if (isspace (c))
{
do
if ((c = *p++) == '\n')
goto hashing_done;
while (isspace (c));
h = HASH (h, ' ');
}
/* C is now the first non-space. */
h = HASH (h, c);
}
break;
case IGNORE_TAB_EXPANSION:
{
size_t column = 0;
while ((c = *p++) != '\n')
{
size_t repetitions = 1;
switch (c)
{
case '\b':
column -= 0 < column;
break;
case '\t':
c = ' ';
repetitions = tabsize - column % tabsize;
column = (column + repetitions < column
? 0
: column + repetitions);
break;
case '\r':
column = 0;
break;
default:
column++;
break;
}
do
h = HASH (h, c);
while (--repetitions != 0);
}
}
break;
default:
while ((c = *p++) != '\n')
h = HASH (h, c);
break;
}
hashing_done:;
bucket = &buckets[h % nbuckets];
length = p - ip - 1;
if (p == bufend
&& current->missing_newline
&& ROBUST_OUTPUT_STYLE (output_style))
{
/* This line is incomplete. If this is significant,
put the line into buckets[-1]. */
if (ignore_white_space < IGNORE_SPACE_CHANGE)
bucket = &buckets[-1];
/* Omit the inserted newline when computing linbuf later. */
p--;
bufend = suffix_begin = p;
}
for (i = *bucket; ; i = eqs[i].next)
if (!i)
{
/* Create a new equivalence class in this bucket. */
i = eqs_index++;
if (i == eqs_alloc)
{
if (PTRDIFF_MAX / (2 * sizeof *eqs) <= eqs_alloc)
xalloc_die ();
eqs_alloc *= 2;
eqs = xrealloc (eqs, eqs_alloc * sizeof *eqs);
}
eqs[i].next = *bucket;
eqs[i].hash = h;
eqs[i].line = ip;
eqs[i].length = length;
*bucket = i;
break;
}
else if (eqs[i].hash == h)
{
char const *eqline = eqs[i].line;
/* Reuse existing class if lines_differ reports the lines
equal. */
if (eqs[i].length == length)
{
/* Reuse existing equivalence class if the lines are identical.
This detects the common case of exact identity
faster than lines_differ would. */
if (memcmp (eqline, ip, length) == 0)
break;
if (!same_length_diff_contents_compare_anyway)
continue;
}
else if (!diff_length_compare_anyway)
continue;
if (! lines_differ (eqline, ip))
break;
}
/* Maybe increase the size of the line table. */
if (line == alloc_lines)
{
/* Double (alloc_lines - linbuf_base) by adding to alloc_lines. */
if (PTRDIFF_MAX / 3 <= alloc_lines
|| PTRDIFF_MAX / sizeof *cureqs <= 2 * alloc_lines - linbuf_base
|| PTRDIFF_MAX / sizeof *linbuf <= alloc_lines - linbuf_base)
xalloc_die ();
alloc_lines = 2 * alloc_lines - linbuf_base;
cureqs = xrealloc (cureqs, alloc_lines * sizeof *cureqs);
linbuf += linbuf_base;
linbuf = xrealloc (linbuf,
(alloc_lines - linbuf_base) * sizeof *linbuf);
linbuf -= linbuf_base;
}
linbuf[line] = ip;
cureqs[line] = i;
++line;
}
current->buffered_lines = line;
for (i = 0; ; i++)
{
/* Record the line start for lines in the suffix that we care about.
Record one more line start than lines,
so that we can compute the length of any buffered line. */
if (line == alloc_lines)
{
/* Double (alloc_lines - linbuf_base) by adding to alloc_lines. */
if (PTRDIFF_MAX / 3 <= alloc_lines
|| PTRDIFF_MAX / sizeof *cureqs <= 2 * alloc_lines - linbuf_base
|| PTRDIFF_MAX / sizeof *linbuf <= alloc_lines - linbuf_base)
xalloc_die ();
alloc_lines = 2 * alloc_lines - linbuf_base;
linbuf += linbuf_base;
linbuf = xrealloc (linbuf,
(alloc_lines - linbuf_base) * sizeof *linbuf);
linbuf -= linbuf_base;
}
linbuf[line] = p;
if (p == bufend)
break;
if (context <= i && no_diff_means_no_output)
break;
line++;
while (*p++ != '\n')
continue;
}
/* Done with cache in local variables. */
current->linbuf = linbuf;
current->valid_lines = line;
current->alloc_lines = alloc_lines;
current->equivs = cureqs;
equivs = eqs;
equivs_alloc = eqs_alloc;
equivs_index = eqs_index;
}
/* Prepare the text. Make sure the text end is initialized.
Make sure text ends in a newline,
but remember that we had to add one.
Strip trailing CRs, if that was requested. */
static void
prepare_text (struct file_data *current)
{
size_t buffered = current->buffered;
char *p = FILE_BUFFER (current);
char *dst;
if (buffered == 0 || p[buffered - 1] == '\n')
current->missing_newline = false;
else
{
p[buffered++] = '\n';
current->missing_newline = true;
}
if (!p)
return;
/* Don't use uninitialized storage when planting or using sentinels. */
memset (p + buffered, 0, sizeof (word));
if (strip_trailing_cr && (dst = memchr (p, '\r', buffered)))
{
char const *src = dst;
char const *srclim = p + buffered;
do
dst += ! ((*dst = *src++) == '\r' && *src == '\n');
while (src < srclim);
buffered -= src - dst;
}
current->buffered = buffered;
}
/* We have found N lines in a buffer of size S; guess the
proportionate number of lines that will be found in a buffer of
size T. However, do not guess a number of lines so large that the
resulting line table might cause overflow in size calculations. */
static lin
guess_lines (lin n, size_t s, size_t t)
{
size_t guessed_bytes_per_line = n < 10 ? 32 : s / (n - 1);
lin guessed_lines = MAX (1, t / guessed_bytes_per_line);
return MIN (guessed_lines, PTRDIFF_MAX / (2 * sizeof (char *) + 1) - 5) + 5;
}
/* Given a vector of two file_data objects, find the identical
prefixes and suffixes of each object. */
static void
find_identical_ends (struct file_data filevec[])
{
word *w0, *w1;
char *p0, *p1, *buffer0, *buffer1;
char const *end0, *beg0;
char const **linbuf0, **linbuf1;
lin i, lines;
size_t n0, n1;
lin alloc_lines0, alloc_lines1;
lin buffered_prefix, prefix_count, prefix_mask;
lin middle_guess, suffix_guess;
slurp (&filevec[0]);
prepare_text (&filevec[0]);
if (filevec[0].desc != filevec[1].desc)
{
slurp (&filevec[1]);
prepare_text (&filevec[1]);
}
else
{
filevec[1].buffer = filevec[0].buffer;
filevec[1].bufsize = filevec[0].bufsize;
filevec[1].buffered = filevec[0].buffered;
filevec[1].missing_newline = filevec[0].missing_newline;
}
/* Find identical prefix. */
w0 = filevec[0].buffer;
w1 = filevec[1].buffer;
p0 = buffer0 = (char *) w0;
p1 = buffer1 = (char *) w1;
n0 = filevec[0].buffered;
n1 = filevec[1].buffered;
if (p0 == p1)
/* The buffers are the same; sentinels won't work. */
p0 = p1 += n1;
else
{
/* Insert end sentinels, in this case characters that are guaranteed
to make the equality test false, and thus terminate the loop. */
if (n0 < n1)
p0[n0] = ~p1[n0];
else
p1[n1] = ~p0[n1];
/* Loop until first mismatch, or to the sentinel characters. */
/* Compare a word at a time for speed. */
while (*w0 == *w1)
w0++, w1++;
/* Do the last few bytes of comparison a byte at a time. */
p0 = (char *) w0;
p1 = (char *) w1;
while (*p0 == *p1)
p0++, p1++;
/* Don't mistakenly count missing newline as part of prefix. */
if (ROBUST_OUTPUT_STYLE (output_style)
&& ((buffer0 + n0 - filevec[0].missing_newline < p0)
!=
(buffer1 + n1 - filevec[1].missing_newline < p1)))
p0--, p1--;
}
/* Now P0 and P1 point at the first nonmatching characters. */
/* Skip back to last line-beginning in the prefix,
and then discard up to HORIZON_LINES lines from the prefix. */
i = horizon_lines;
while (p0 != buffer0 && (p0[-1] != '\n' || i--))
p0--, p1--;
/* Record the prefix. */
filevec[0].prefix_end = p0;
filevec[1].prefix_end = p1;
/* Find identical suffix. */
/* P0 and P1 point beyond the last chars not yet compared. */
p0 = buffer0 + n0;
p1 = buffer1 + n1;
if (! ROBUST_OUTPUT_STYLE (output_style)
|| filevec[0].missing_newline == filevec[1].missing_newline)
{
end0 = p0; /* Addr of last char in file 0. */
/* Get value of P0 at which we should stop scanning backward:
this is when either P0 or P1 points just past the last char
of the identical prefix. */
beg0 = filevec[0].prefix_end + (n0 < n1 ? 0 : n0 - n1);
/* Scan back until chars don't match or we reach that point. */
while (p0 != beg0)
if (*--p0 != *--p1)
{
/* Point at the first char of the matching suffix. */
++p0, ++p1;
beg0 = p0;
break;
}
/* Are we at a line-beginning in both files? If not, add the rest of
this line to the main body. Discard up to HORIZON_LINES lines from
the identical suffix. Also, discard one extra line,
because shift_boundaries may need it. */
i = horizon_lines + !((buffer0 == p0 || p0[-1] == '\n')
&&
(buffer1 == p1 || p1[-1] == '\n'));
while (i-- && p0 != end0)
while (*p0++ != '\n')
continue;
p1 += p0 - beg0;
}
/* Record the suffix. */
filevec[0].suffix_begin = p0;
filevec[1].suffix_begin = p1;
/* Calculate number of lines of prefix to save.
prefix_count == 0 means save the whole prefix;
we need this for options like -D that output the whole file,
or for enormous contexts (to avoid worrying about arithmetic overflow).
We also need it for options like -F that output some preceding line;
at least we will need to find the last few lines,
but since we don't know how many, it's easiest to find them all.
Otherwise, prefix_count != 0. Save just prefix_count lines at start
of the line buffer; they'll be moved to the proper location later.
Handle 1 more line than the context says (because we count 1 too many),
rounded up to the next power of 2 to speed index computation. */
if (no_diff_means_no_output && ! function_regexp.fastmap
&& context < LIN_MAX / 4 && context < n0)
{
middle_guess = guess_lines (0, 0, p0 - filevec[0].prefix_end);
suffix_guess = guess_lines (0, 0, buffer0 + n0 - p0);
for (prefix_count = 1; prefix_count <= context; prefix_count *= 2)
continue;
alloc_lines0 = (prefix_count + middle_guess
+ MIN (context, suffix_guess));
}
else
{
prefix_count = 0;
alloc_lines0 = guess_lines (0, 0, n0);
}
prefix_mask = prefix_count - 1;
lines = 0;
linbuf0 = xmalloc (alloc_lines0 * sizeof *linbuf0);
p0 = buffer0;
/* If the prefix is needed, find the prefix lines. */
if (! (no_diff_means_no_output
&& filevec[0].prefix_end == p0
&& filevec[1].prefix_end == p1))
{
end0 = filevec[0].prefix_end;
while (p0 != end0)
{
lin l = lines++ & prefix_mask;
if (l == alloc_lines0)
{
if (PTRDIFF_MAX / (2 * sizeof *linbuf0) <= alloc_lines0)
xalloc_die ();
alloc_lines0 *= 2;
linbuf0 = xrealloc (linbuf0, alloc_lines0 * sizeof *linbuf0);
}
linbuf0[l] = p0;
while (*p0++ != '\n')
continue;
}
}
buffered_prefix = prefix_count && context < lines ? context : lines;
/* Allocate line buffer 1. */
middle_guess = guess_lines (lines, p0 - buffer0, p1 - filevec[1].prefix_end);
suffix_guess = guess_lines (lines, p0 - buffer0, buffer1 + n1 - p1);
alloc_lines1 = buffered_prefix + middle_guess + MIN (context, suffix_guess);
if (alloc_lines1 < buffered_prefix
|| PTRDIFF_MAX / sizeof *linbuf1 <= alloc_lines1)
xalloc_die ();
linbuf1 = xmalloc (alloc_lines1 * sizeof *linbuf1);
if (buffered_prefix != lines)
{
/* Rotate prefix lines to proper location. */
for (i = 0; i < buffered_prefix; i++)
linbuf1[i] = linbuf0[(lines - context + i) & prefix_mask];
for (i = 0; i < buffered_prefix; i++)
linbuf0[i] = linbuf1[i];
}
/* Initialize line buffer 1 from line buffer 0. */
for (i = 0; i < buffered_prefix; i++)
linbuf1[i] = linbuf0[i] - buffer0 + buffer1;
/* Record the line buffer, adjusted so that
linbuf[0] points at the first differing line. */
filevec[0].linbuf = linbuf0 + buffered_prefix;
filevec[1].linbuf = linbuf1 + buffered_prefix;
filevec[0].linbuf_base = filevec[1].linbuf_base = - buffered_prefix;
filevec[0].alloc_lines = alloc_lines0 - buffered_prefix;
filevec[1].alloc_lines = alloc_lines1 - buffered_prefix;
filevec[0].prefix_lines = filevec[1].prefix_lines = lines;
}
/* If 1 < k, then (2**k - prime_offset[k]) is the largest prime less
than 2**k. This table is derived from Chris K. Caldwell's list
<http://www.utm.edu/research/primes/lists/2small/>. */
static unsigned char const prime_offset[] =
{
0, 0, 1, 1, 3, 1, 3, 1, 5, 3, 3, 9, 3, 1, 3, 19, 15, 1, 5, 1, 3, 9, 3,
15, 3, 39, 5, 39, 57, 3, 35, 1, 5, 9, 41, 31, 5, 25, 45, 7, 87, 21,
11, 57, 17, 55, 21, 115, 59, 81, 27, 129, 47, 111, 33, 55, 5, 13, 27,
55, 93, 1, 57, 25
};
/* Verify that this host's size_t is not too wide for the above table. */
verify (sizeof (size_t) * CHAR_BIT <= sizeof prime_offset);
/* Given a vector of two file_data objects, read the file associated
with each one, and build the table of equivalence classes.
Return nonzero if either file appears to be a binary file.
If PRETEND_BINARY is nonzero, pretend they are binary regardless. */
bool
read_files (struct file_data filevec[], bool pretend_binary)
{
int i;
bool skip_test = text | pretend_binary;
bool appears_binary = pretend_binary | sip (&filevec[0], skip_test);
if (filevec[0].desc != filevec[1].desc)
appears_binary |= sip (&filevec[1], skip_test | appears_binary);
else
{
filevec[1].buffer = filevec[0].buffer;
filevec[1].bufsize = filevec[0].bufsize;
filevec[1].buffered = filevec[0].buffered;
}
if (appears_binary)
{
/* FIXME: If O_BINARY, this should set both files to binary mode. */
return true;
}
find_identical_ends (filevec);
equivs_alloc = filevec[0].alloc_lines + filevec[1].alloc_lines + 1;
if (PTRDIFF_MAX / sizeof *equivs <= equivs_alloc)
xalloc_die ();
equivs = xmalloc (equivs_alloc * sizeof *equivs);
/* Equivalence class 0 is permanently safe for lines that were not
hashed. Real equivalence classes start at 1. */
equivs_index = 1;
/* Allocate (one plus) a prime number of hash buckets. Use a prime
number between 1/3 and 2/3 of the value of equiv_allocs,
approximately. */
for (i = 9; (size_t) 1 << i < equivs_alloc / 3; i++)
continue;
nbuckets = ((size_t) 1 << i) - prime_offset[i];
if (PTRDIFF_MAX / sizeof *buckets <= nbuckets)
xalloc_die ();
buckets = zalloc ((nbuckets + 1) * sizeof *buckets);
buckets++;
for (i = 0; i < 2; i++)
find_and_hash_each_line (&filevec[i]);
filevec[0].equiv_max = filevec[1].equiv_max = equivs_index;
free (equivs);
free (buckets - 1);
return false;
}
|