summaryrefslogtreecommitdiff
path: root/Build/source/libs/libpng/libpng-src/pngerror.c
blob: ec3a709b9d2c5873995237679d6f7b3b4ffd1d84 (plain)
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
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963

/* pngerror.c - stub functions for i/o and memory allocation
 *
 * Copyright (c) 2018 Cosmin Truta
 * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
 * Copyright (c) 1996-1997 Andreas Dilger
 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
 *
 * This file provides a location for all error handling.  Users who
 * need special error handling are expected to write replacement functions
 * and use png_set_error_fn() to use those functions.  See the instructions
 * at each function.
 */

#include "pngpriv.h"

#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

static PNG_FUNCTION(void, png_default_error,PNGARG((png_const_structrp png_ptr,
    png_const_charp error_message)),PNG_NORETURN);

#ifdef PNG_WARNINGS_SUPPORTED
static void /* PRIVATE */
png_default_warning PNGARG((png_const_structrp png_ptr,
    png_const_charp warning_message));
#endif /* WARNINGS */

/* This function is called whenever there is a fatal error.  This function
 * should not be changed.  If there is a need to handle errors differently,
 * you should supply a replacement error function and use png_set_error_fn()
 * to replace the error function at run-time.
 */
#ifdef PNG_ERROR_TEXT_SUPPORTED
PNG_FUNCTION(void,PNGAPI
png_error,(png_const_structrp png_ptr, png_const_charp error_message),
    PNG_NORETURN)
{
#ifdef PNG_ERROR_NUMBERS_SUPPORTED
   char msg[16];
   if (png_ptr != NULL)
   {
      if ((png_ptr->flags &
         (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT)) != 0)
      {
         if (*error_message == PNG_LITERAL_SHARP)
         {
            /* Strip "#nnnn " from beginning of error message. */
            int offset;
            for (offset = 1; offset<15; offset++)
               if (error_message[offset] == ' ')
                  break;

            if ((png_ptr->flags & PNG_FLAG_STRIP_ERROR_TEXT) != 0)
            {
               int i;
               for (i = 0; i < offset - 1; i++)
                  msg[i] = error_message[i + 1];
               msg[i - 1] = '\0';
               error_message = msg;
            }

            else
               error_message += offset;
         }

         else
         {
            if ((png_ptr->flags & PNG_FLAG_STRIP_ERROR_TEXT) != 0)
            {
               msg[0] = '0';
               msg[1] = '\0';
               error_message = msg;
            }
         }
      }
   }
#endif
   if (png_ptr != NULL && png_ptr->error_fn != NULL)
      (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr),
          error_message);

   /* If the custom handler doesn't exist, or if it returns,
      use the default handler, which will not return. */
   png_default_error(png_ptr, error_message);
}
#else
PNG_FUNCTION(void,PNGAPI
png_err,(png_const_structrp png_ptr),PNG_NORETURN)
{
   /* Prior to 1.5.2 the error_fn received a NULL pointer, expressed
    * erroneously as '\0', instead of the empty string "".  This was
    * apparently an error, introduced in libpng-1.2.20, and png_default_error
    * will crash in this case.
    */
   if (png_ptr != NULL && png_ptr->error_fn != NULL)
      (*(png_ptr->error_fn))(png_constcast(png_structrp,png_ptr), "");

   /* If the custom handler doesn't exist, or if it returns,
      use the default handler, which will not return. */
   png_default_error(png_ptr, "");
}
#endif /* ERROR_TEXT */

/* Utility to safely appends strings to a buffer.  This never errors out so
 * error checking is not required in the caller.
 */
size_t
png_safecat(png_charp buffer, size_t bufsize, size_t pos,
    png_const_charp string)
{
   if (buffer != NULL && pos < bufsize)
   {
      if (string != NULL)
         while (*string != '\0' && pos < bufsize-1)
           buffer[pos++] = *string++;

      buffer[pos] = '\0';
   }

   return pos;
}

#if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_TIME_RFC1123_SUPPORTED)
/* Utility to dump an unsigned value into a buffer, given a start pointer and
 * and end pointer (which should point just *beyond* the end of the buffer!)
 * Returns the pointer to the start of the formatted string.
 */
png_charp
png_format_number(png_const_charp start, png_charp end, int format,
    png_alloc_size_t number)
{
   int count = 0;    /* number of digits output */
   int mincount = 1; /* minimum number required */
   int output = 0;   /* digit output (for the fixed point format) */

   *--end = '\0';

   /* This is written so that the loop always runs at least once, even with
    * number zero.
    */
   while (end > start && (number != 0 || count < mincount))
   {

      static const char digits[] = "0123456789ABCDEF";

      switch (format)
      {
         case PNG_NUMBER_FORMAT_fixed:
            /* Needs five digits (the fraction) */
            mincount = 5;
            if (output != 0 || number % 10 != 0)
            {
               *--end = digits[number % 10];
               output = 1;
            }
            number /= 10;
            break;

         case PNG_NUMBER_FORMAT_02u:
            /* Expects at least 2 digits. */
            mincount = 2;
            /* FALLTHROUGH */

         case PNG_NUMBER_FORMAT_u:
            *--end = digits[number % 10];
            number /= 10;
            break;

         case PNG_NUMBER_FORMAT_02x:
            /* This format expects at least two digits */
            mincount = 2;
            /* FALLTHROUGH */

         case PNG_NUMBER_FORMAT_x:
            *--end = digits[number & 0xf];
            number >>= 4;
            break;

         default: /* an error */
            number = 0;
            break;
      }

      /* Keep track of the number of digits added */
      ++count;

      /* Float a fixed number here: */
      if ((format == PNG_NUMBER_FORMAT_fixed) && (count == 5) && (end > start))
      {
         /* End of the fraction, but maybe nothing was output?  In that case
          * drop the decimal point.  If the number is a true zero handle that
          * here.
          */
         if (output != 0)
            *--end = '.';
         else if (number == 0) /* and !output */
            *--end = '0';
      }
   }

   return end;
}
#endif

#ifdef PNG_WARNINGS_SUPPORTED
/* This function is called whenever there is a non-fatal error.  This function
 * should not be changed.  If there is a need to handle warnings differently,
 * you should supply a replacement warning function and use
 * png_set_error_fn() to replace the warning function at run-time.
 */
void PNGAPI
png_warning(png_const_structrp png_ptr, png_const_charp warning_message)
{
   int offset = 0;
   if (png_ptr != NULL)
   {
#ifdef PNG_ERROR_NUMBERS_SUPPORTED
   if ((png_ptr->flags &
       (PNG_FLAG_STRIP_ERROR_NUMBERS|PNG_FLAG_STRIP_ERROR_TEXT)) != 0)
#endif
      {
         if (*warning_message == PNG_LITERAL_SHARP)
         {
            for (offset = 1; offset < 15; offset++)
               if (warning_message[offset] == ' ')
                  break;
         }
      }
   }
   if (png_ptr != NULL && png_ptr->warning_fn != NULL)
      (*(png_ptr->warning_fn))(png_constcast(png_structrp,png_ptr),
          warning_message + offset);
   else
      png_default_warning(png_ptr, warning_message + offset);
}

/* These functions support 'formatted' warning messages with up to
 * PNG_WARNING_PARAMETER_COUNT parameters.  In the format string the parameter
 * is introduced by @<number>, where 'number' starts at 1.  This follows the
 * standard established by X/Open for internationalizable error messages.
 */
void
png_warning_parameter(png_warning_parameters p, int number,
    png_const_charp string)
{
   if (number > 0 && number <= PNG_WARNING_PARAMETER_COUNT)
      (void)png_safecat(p[number-1], (sizeof p[number-1]), 0, string);
}

void
png_warning_parameter_unsigned(png_warning_parameters p, int number, int format,
    png_alloc_size_t value)
{
   char buffer[PNG_NUMBER_BUFFER_SIZE];
   png_warning_parameter(p, number, PNG_FORMAT_NUMBER(buffer, format, value));
}

void
png_warning_parameter_signed(png_warning_parameters p, int number, int format,
    png_int_32 value)
{
   png_alloc_size_t u;
   png_charp str;
   char buffer[PNG_NUMBER_BUFFER_SIZE];

   /* Avoid overflow by doing the negate in a png_alloc_size_t: */
   u = (png_alloc_size_t)value;
   if (value < 0)
      u = ~u + 1;

   str = PNG_FORMAT_NUMBER(buffer, format, u);

   if (value < 0 && str > buffer)
      *--str = '-';

   png_warning_parameter(p, number, str);
}

void
png_formatted_warning(png_const_structrp png_ptr, png_warning_parameters p,
    png_const_charp message)
{
   /* The internal buffer is just 192 bytes - enough for all our messages,
    * overflow doesn't happen because this code checks!  If someone figures
    * out how to send us a message longer than 192 bytes, all that will
    * happen is that the message will be truncated appropriately.
    */
   size_t i = 0; /* Index in the msg[] buffer: */
   char msg[192];

   /* Each iteration through the following loop writes at most one character
    * to msg[i++] then returns here to validate that there is still space for
    * the trailing '\0'.  It may (in the case of a parameter) read more than
    * one character from message[]; it must check for '\0' and continue to the
    * test if it finds the end of string.
    */
   while (i<(sizeof msg)-1 && *message != '\0')
   {
      /* '@' at end of string is now just printed (previously it was skipped);
       * it is an error in the calling code to terminate the string with @.
       */
      if (p != NULL && *message == '@' && message[1] != '\0')
      {
         int parameter_char = *++message; /* Consume the '@' */
         static const char valid_parameters[] = "123456789";
         int parameter = 0;

         /* Search for the parameter digit, the index in the string is the
          * parameter to use.
          */
         while (valid_parameters[parameter] != parameter_char &&
            valid_parameters[parameter] != '\0')
            ++parameter;

         /* If the parameter digit is out of range it will just get printed. */
         if (parameter < PNG_WARNING_PARAMETER_COUNT)
         {
            /* Append this parameter */
            png_const_charp parm = p[parameter];
            png_const_charp pend = p[parameter] + (sizeof p[parameter]);

            /* No need to copy the trailing '\0' here, but there is no guarantee
             * that parm[] has been initialized, so there is no guarantee of a
             * trailing '\0':
             */
            while (i<(sizeof msg)-1 && *parm != '\0' && parm < pend)
               msg[i++] = *parm++;

            /* Consume the parameter digit too: */
            ++message;
            continue;
         }

         /* else not a parameter and there is a character after the @ sign; just
          * copy that.  This is known not to be '\0' because of the test above.
          */
      }

      /* At this point *message can't be '\0', even in the bad parameter case
       * above where there is a lone '@' at the end of the message string.
       */
      msg[i++] = *message++;
   }

   /* i is always less than (sizeof msg), so: */
   msg[i] = '\0';

   /* And this is the formatted message. It may be larger than
    * PNG_MAX_ERROR_TEXT, but that is only used for 'chunk' errors and these
    * are not (currently) formatted.
    */
   png_warning(png_ptr, msg);
}
#endif /* WARNINGS */

#ifdef PNG_BENIGN_ERRORS_SUPPORTED
void PNGAPI
png_benign_error(png_const_structrp png_ptr, png_const_charp error_message)
{
   if ((png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN) != 0)
   {
#     ifdef PNG_READ_SUPPORTED
         if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
            png_ptr->chunk_name != 0)
            png_chunk_warning(png_ptr, error_message);
         else
#     endif
      png_warning(png_ptr, error_message);
   }

   else
   {
#     ifdef PNG_READ_SUPPORTED
         if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
            png_ptr->chunk_name != 0)
            png_chunk_error(png_ptr, error_message);
         else
#     endif
      png_error(png_ptr, error_message);
   }

#  ifndef PNG_ERROR_TEXT_SUPPORTED
      PNG_UNUSED(error_message)
#  endif
}

void /* PRIVATE */
png_app_warning(png_const_structrp png_ptr, png_const_charp error_message)
{
   if ((png_ptr->flags & PNG_FLAG_APP_WARNINGS_WARN) != 0)
      png_warning(png_ptr, error_message);
   else
      png_error(png_ptr, error_message);

#  ifndef PNG_ERROR_TEXT_SUPPORTED
      PNG_UNUSED(error_message)
#  endif
}

void /* PRIVATE */
png_app_error(png_const_structrp png_ptr, png_const_charp error_message)
{
   if ((png_ptr->flags & PNG_FLAG_APP_ERRORS_WARN) != 0)
      png_warning(png_ptr, error_message);
   else
      png_error(png_ptr, error_message);

#  ifndef PNG_ERROR_TEXT_SUPPORTED
      PNG_UNUSED(error_message)
#  endif
}
#endif /* BENIGN_ERRORS */

#define PNG_MAX_ERROR_TEXT 196 /* Currently limited by profile_error in png.c */
#if defined(PNG_WARNINGS_SUPPORTED) || \
   (defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED))
/* These utilities are used internally to build an error message that relates
 * to the current chunk.  The chunk name comes from png_ptr->chunk_name,
 * which is used to prefix the message.  The message is limited in length
 * to 63 bytes. The name characters are output as hex digits wrapped in []
 * if the character is invalid.
 */
#define isnonalpha(c) ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
static const char png_digit[16] = {
   '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
   'A', 'B', 'C', 'D', 'E', 'F'
};

static void /* PRIVATE */
png_format_buffer(png_const_structrp png_ptr, png_charp buffer, png_const_charp
    error_message)
{
   png_uint_32 chunk_name = png_ptr->chunk_name;
   int iout = 0, ishift = 24;

   while (ishift >= 0)
   {
      int c = (int)(chunk_name >> ishift) & 0xff;

      ishift -= 8;
      if (isnonalpha(c) != 0)
      {
         buffer[iout++] = PNG_LITERAL_LEFT_SQUARE_BRACKET;
         buffer[iout++] = png_digit[(c & 0xf0) >> 4];
         buffer[iout++] = png_digit[c & 0x0f];
         buffer[iout++] = PNG_LITERAL_RIGHT_SQUARE_BRACKET;
      }

      else
      {
         buffer[iout++] = (char)c;
      }
   }

   if (error_message == NULL)
      buffer[iout] = '\0';

   else
   {
      int iin = 0;

      buffer[iout++] = ':';
      buffer[iout++] = ' ';

      while (iin < PNG_MAX_ERROR_TEXT-1 && error_message[iin] != '\0')
         buffer[iout++] = error_message[iin++];

      /* iin < PNG_MAX_ERROR_TEXT, so the following is safe: */
      buffer[iout] = '\0';
   }
}
#endif /* WARNINGS || ERROR_TEXT */

#if defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
PNG_FUNCTION(void,PNGAPI
png_chunk_error,(png_const_structrp png_ptr, png_const_charp error_message),
    PNG_NORETURN)
{
   char msg[18+PNG_MAX_ERROR_TEXT];
   if (png_ptr == NULL)
      png_error(png_ptr, error_message);

   else
   {
      png_format_buffer(png_ptr, msg, error_message);
      png_error(png_ptr, msg);
   }
}
#endif /* READ && ERROR_TEXT */

#ifdef PNG_WARNINGS_SUPPORTED
void PNGAPI
png_chunk_warning(png_const_structrp png_ptr, png_const_charp warning_message)
{
   char msg[18+PNG_MAX_ERROR_TEXT];
   if (png_ptr == NULL)
      png_warning(png_ptr, warning_message);

   else
   {
      png_format_buffer(png_ptr, msg, warning_message);
      png_warning(png_ptr, msg);
   }
}
#endif /* WARNINGS */

#ifdef PNG_READ_SUPPORTED
#ifdef PNG_BENIGN_ERRORS_SUPPORTED
void PNGAPI
png_chunk_benign_error(png_const_structrp png_ptr, png_const_charp
    error_message)
{
   if ((png_ptr->flags & PNG_FLAG_BENIGN_ERRORS_WARN) != 0)
      png_chunk_warning(png_ptr, error_message);

   else
      png_chunk_error(png_ptr, error_message);

#  ifndef PNG_ERROR_TEXT_SUPPORTED
      PNG_UNUSED(error_message)
#  endif
}
#endif
#endif /* READ */

void /* PRIVATE */
png_chunk_report(png_const_structrp png_ptr, png_const_charp message, int error)
{
#  ifndef PNG_WARNINGS_SUPPORTED
      PNG_UNUSED(message)
#  endif

   /* This is always supported, but for just read or just write it
    * unconditionally does the right thing.
    */
#  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
      if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0)
#  endif

#  ifdef PNG_READ_SUPPORTED
      {
         if (error < PNG_CHUNK_ERROR)
            png_chunk_warning(png_ptr, message);

         else
            png_chunk_benign_error(png_ptr, message);
      }
#  endif

#  if defined(PNG_READ_SUPPORTED) && defined(PNG_WRITE_SUPPORTED)
      else if ((png_ptr->mode & PNG_IS_READ_STRUCT) == 0)
#  endif

#  ifdef PNG_WRITE_SUPPORTED
      {
         if (error < PNG_CHUNK_WRITE_ERROR)
            png_app_warning(png_ptr, message);

         else
            png_app_error(png_ptr, message);
      }
#  endif
}

#ifdef PNG_ERROR_TEXT_SUPPORTED
#ifdef PNG_FLOATING_POINT_SUPPORTED
PNG_FUNCTION(void,
png_fixed_error,(png_const_structrp png_ptr, png_const_charp name),PNG_NORETURN)
{
#  define fixed_message "fixed point overflow in "
#  define fixed_message_ln ((sizeof fixed_message)-1)
   unsigned int  iin;
   char msg[fixed_message_ln+PNG_MAX_ERROR_TEXT];
   memcpy(msg, fixed_message, fixed_message_ln);
   iin = 0;
   if (name != NULL)
      while (iin < (PNG_MAX_ERROR_TEXT-1) && name[iin] != 0)
      {
         msg[fixed_message_ln + iin] = name[iin];
         ++iin;
      }
   msg[fixed_message_ln + iin] = 0;
   png_error(png_ptr, msg);
}
#endif
#endif

#ifdef PNG_SETJMP_SUPPORTED
/* This API only exists if ANSI-C style error handling is used,
 * otherwise it is necessary for png_default_error to be overridden.
 */
jmp_buf* PNGAPI
png_set_longjmp_fn(png_structrp png_ptr, png_longjmp_ptr longjmp_fn,
    size_t jmp_buf_size)
{
   /* From libpng 1.6.0 the app gets one chance to set a 'jmpbuf_size' value
    * and it must not change after that.  Libpng doesn't care how big the
    * buffer is, just that it doesn't change.
    *
    * If the buffer size is no *larger* than the size of jmp_buf when libpng is
    * compiled a built in jmp_buf is returned; this preserves the pre-1.6.0
    * semantics that this call will not fail.  If the size is larger, however,
    * the buffer is allocated and this may fail, causing the function to return
    * NULL.
    */
   if (png_ptr == NULL)
      return NULL;

   if (png_ptr->jmp_buf_ptr == NULL)
   {
      png_ptr->jmp_buf_size = 0; /* not allocated */

      if (jmp_buf_size <= (sizeof png_ptr->jmp_buf_local))
         png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local;

      else
      {
         png_ptr->jmp_buf_ptr = png_voidcast(jmp_buf *,
             png_malloc_warn(png_ptr, jmp_buf_size));

         if (png_ptr->jmp_buf_ptr == NULL)
            return NULL; /* new NULL return on OOM */

         png_ptr->jmp_buf_size = jmp_buf_size;
      }
   }

   else /* Already allocated: check the size */
   {
      size_t size = png_ptr->jmp_buf_size;

      if (size == 0)
      {
         size = (sizeof png_ptr->jmp_buf_local);
         if (png_ptr->jmp_buf_ptr != &png_ptr->jmp_buf_local)
         {
            /* This is an internal error in libpng: somehow we have been left
             * with a stack allocated jmp_buf when the application regained
             * control.  It's always possible to fix this up, but for the moment
             * this is a png_error because that makes it easy to detect.
             */
            png_error(png_ptr, "Libpng jmp_buf still allocated");
            /* png_ptr->jmp_buf_ptr = &png_ptr->jmp_buf_local; */
         }
      }

      if (size != jmp_buf_size)
      {
         png_warning(png_ptr, "Application jmp_buf size changed");
         return NULL; /* caller will probably crash: no choice here */
      }
   }

   /* Finally fill in the function, now we have a satisfactory buffer. It is
    * valid to change the function on every call.
    */
   png_ptr->longjmp_fn = longjmp_fn;
   return png_ptr->jmp_buf_ptr;
}

void /* PRIVATE */
png_free_jmpbuf(png_structrp png_ptr)
{
   if (png_ptr != NULL)
   {
      jmp_buf *jb = png_ptr->jmp_buf_ptr;

      /* A size of 0 is used to indicate a local, stack, allocation of the
       * pointer; used here and in png.c
       */
      if (jb != NULL && png_ptr->jmp_buf_size > 0)
      {

         /* This stuff is so that a failure to free the error control structure
          * does not leave libpng in a state with no valid error handling: the
          * free always succeeds, if there is an error it gets ignored.
          */
         if (jb != &png_ptr->jmp_buf_local)
         {
            /* Make an internal, libpng, jmp_buf to return here */
            jmp_buf free_jmp_buf;

            if (!setjmp(free_jmp_buf))
            {
               png_ptr->jmp_buf_ptr = &free_jmp_buf; /* come back here */
               png_ptr->jmp_buf_size = 0; /* stack allocation */
               png_ptr->longjmp_fn = longjmp;
               png_free(png_ptr, jb); /* Return to setjmp on error */
            }
         }
      }

      /* *Always* cancel everything out: */
      png_ptr->jmp_buf_size = 0;
      png_ptr->jmp_buf_ptr = NULL;
      png_ptr->longjmp_fn = 0;
   }
}
#endif

/* This is the default error handling function.  Note that replacements for
 * this function MUST NOT RETURN, or the program will likely crash.  This
 * function is used by default, or if the program supplies NULL for the
 * error function pointer in png_set_error_fn().
 */
static PNG_FUNCTION(void /* PRIVATE */,
png_default_error,(png_const_structrp png_ptr, png_const_charp error_message),
    PNG_NORETURN)
{
#ifdef PNG_CONSOLE_IO_SUPPORTED
#ifdef PNG_ERROR_NUMBERS_SUPPORTED
   /* Check on NULL only added in 1.5.4 */
   if (error_message != NULL && *error_message == PNG_LITERAL_SHARP)
   {
      /* Strip "#nnnn " from beginning of error message. */
      int offset;
      char error_number[16];
      for (offset = 0; offset<15; offset++)
      {
         error_number[offset] = error_message[offset + 1];
         if (error_message[offset] == ' ')
            break;
      }

      if ((offset > 1) && (offset < 15))
      {
         error_number[offset - 1] = '\0';
         fprintf(stderr, "libpng error no. %s: %s",
             error_number, error_message + offset + 1);
         fprintf(stderr, PNG_STRING_NEWLINE);
      }

      else
      {
         fprintf(stderr, "libpng error: %s, offset=%d",
             error_message, offset);
         fprintf(stderr, PNG_STRING_NEWLINE);
      }
   }
   else
#endif
   {
      fprintf(stderr, "libpng error: %s", error_message ? error_message :
         "undefined");
      fprintf(stderr, PNG_STRING_NEWLINE);
   }
#else
   PNG_UNUSED(error_message) /* Make compiler happy */
#endif
   png_longjmp(png_ptr, 1);
}

PNG_FUNCTION(void,PNGAPI
png_longjmp,(png_const_structrp png_ptr, int val),PNG_NORETURN)
{
#ifdef PNG_SETJMP_SUPPORTED
   if (png_ptr != NULL && png_ptr->longjmp_fn != NULL &&
       png_ptr->jmp_buf_ptr != NULL)
      png_ptr->longjmp_fn(*png_ptr->jmp_buf_ptr, val);
#else
   PNG_UNUSED(png_ptr)
   PNG_UNUSED(val)
#endif

   /* If control reaches this point, png_longjmp() must not return. The only
    * choice is to terminate the whole process (or maybe the thread); to do
    * this the ANSI-C abort() function is used unless a different method is
    * implemented by overriding the default configuration setting for
    * PNG_ABORT().
    */
   PNG_ABORT();
}

#ifdef PNG_WARNINGS_SUPPORTED
/* This function is called when there is a warning, but the library thinks
 * it can continue anyway.  Replacement functions don't have to do anything
 * here if you don't want them to.  In the default configuration, png_ptr is
 * not used, but it is passed in case it may be useful.
 */
static void /* PRIVATE */
png_default_warning(png_const_structrp png_ptr, png_const_charp warning_message)
{
#ifdef PNG_CONSOLE_IO_SUPPORTED
#  ifdef PNG_ERROR_NUMBERS_SUPPORTED
   if (*warning_message == PNG_LITERAL_SHARP)
   {
      int offset;
      char warning_number[16];
      for (offset = 0; offset < 15; offset++)
      {
         warning_number[offset] = warning_message[offset + 1];
         if (warning_message[offset] == ' ')
            break;
      }

      if ((offset > 1) && (offset < 15))
      {
         warning_number[offset + 1] = '\0';
         fprintf(stderr, "libpng warning no. %s: %s",
             warning_number, warning_message + offset);
         fprintf(stderr, PNG_STRING_NEWLINE);
      }

      else
      {
         fprintf(stderr, "libpng warning: %s",
             warning_message);
         fprintf(stderr, PNG_STRING_NEWLINE);
      }
   }
   else
#  endif

   {
      fprintf(stderr, "libpng warning: %s", warning_message);
      fprintf(stderr, PNG_STRING_NEWLINE);
   }
#else
   PNG_UNUSED(warning_message) /* Make compiler happy */
#endif
   PNG_UNUSED(png_ptr) /* Make compiler happy */
}
#endif /* WARNINGS */

/* This function is called when the application wants to use another method
 * of handling errors and warnings.  Note that the error function MUST NOT
 * return to the calling routine or serious problems will occur.  The return
 * method used in the default routine calls longjmp(png_ptr->jmp_buf_ptr, 1)
 */
void PNGAPI
png_set_error_fn(png_structrp png_ptr, png_voidp error_ptr,
    png_error_ptr error_fn, png_error_ptr warning_fn)
{
   if (png_ptr == NULL)
      return;

   png_ptr->error_ptr = error_ptr;
   png_ptr->error_fn = error_fn;
#ifdef PNG_WARNINGS_SUPPORTED
   png_ptr->warning_fn = warning_fn;
#else
   PNG_UNUSED(warning_fn)
#endif
}


/* This function returns a pointer to the error_ptr associated with the user
 * functions.  The application should free any memory associated with this
 * pointer before png_write_destroy and png_read_destroy are called.
 */
png_voidp PNGAPI
png_get_error_ptr(png_const_structrp png_ptr)
{
   if (png_ptr == NULL)
      return NULL;

   return ((png_voidp)png_ptr->error_ptr);
}


#ifdef PNG_ERROR_NUMBERS_SUPPORTED
void PNGAPI
png_set_strip_error_numbers(png_structrp png_ptr, png_uint_32 strip_mode)
{
   if (png_ptr != NULL)
   {
      png_ptr->flags &=
         ((~(PNG_FLAG_STRIP_ERROR_NUMBERS |
         PNG_FLAG_STRIP_ERROR_TEXT))&strip_mode);
   }
}
#endif

#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
   defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
   /* Currently the above both depend on SETJMP_SUPPORTED, however it would be
    * possible to implement without setjmp support just so long as there is some
    * way to handle the error return here:
    */
PNG_FUNCTION(void /* PRIVATE */, (PNGCBAPI
png_safe_error),(png_structp png_nonconst_ptr, png_const_charp error_message),
    PNG_NORETURN)
{
   png_const_structrp png_ptr = png_nonconst_ptr;
   png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);

   /* An error is always logged here, overwriting anything (typically a warning)
    * that is already there:
    */
   if (image != NULL)
   {
      png_safecat(image->message, (sizeof image->message), 0, error_message);
      image->warning_or_error |= PNG_IMAGE_ERROR;

      /* Retrieve the jmp_buf from within the png_control, making this work for
       * C++ compilation too is pretty tricky: C++ wants a pointer to the first
       * element of a jmp_buf, but C doesn't tell us the type of that.
       */
      if (image->opaque != NULL && image->opaque->error_buf != NULL)
         longjmp(png_control_jmp_buf(image->opaque), 1);

      /* Missing longjmp buffer, the following is to help debugging: */
      {
         size_t pos = png_safecat(image->message, (sizeof image->message), 0,
             "bad longjmp: ");
         png_safecat(image->message, (sizeof image->message), pos,
             error_message);
      }
   }

   /* Here on an internal programming error. */
   abort();
}

#ifdef PNG_WARNINGS_SUPPORTED
void /* PRIVATE */ PNGCBAPI
png_safe_warning(png_structp png_nonconst_ptr, png_const_charp warning_message)
{
   png_const_structrp png_ptr = png_nonconst_ptr;
   png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);

   /* A warning is only logged if there is no prior warning or error. */
   if (image->warning_or_error == 0)
   {
      png_safecat(image->message, (sizeof image->message), 0, warning_message);
      image->warning_or_error |= PNG_IMAGE_WARNING;
   }
}
#endif

int /* PRIVATE */
png_safe_execute(png_imagep image_in, int (*function)(png_voidp), png_voidp arg)
{
   volatile png_imagep image = image_in;
   volatile int result;
   volatile png_voidp saved_error_buf;
   jmp_buf safe_jmpbuf;

   /* Safely execute function(arg) with png_error returning to this function. */
   saved_error_buf = image->opaque->error_buf;
   result = setjmp(safe_jmpbuf) == 0;

   if (result != 0)
   {

      image->opaque->error_buf = safe_jmpbuf;
      result = function(arg);
   }

   image->opaque->error_buf = saved_error_buf;

   /* And do the cleanup prior to any failure return. */
   if (result == 0)
      png_image_free(image);

   return result;
}
#endif /* SIMPLIFIED READ || SIMPLIFIED_WRITE */
#endif /* READ || WRITE */