media/libpng/pngpread.c

   1
   2 /* pngpread.c - read a png file in push mode
   3  *
   4  * Copyright (c) 2018-2024 Cosmin Truta
   5  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
   6  * Copyright (c) 1996-1997 Andreas Dilger
   7  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
   8  *
   9  * This code is released under the libpng license.
  10  * For conditions of distribution and use, see the disclaimer
  11  * and license in png.h
  12  */
  13
  14 #include "pngpriv.h"
  15
  16 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
  17
  18 /* Push model modes */
  19 #define PNG_READ_SIG_MODE   0
  20 #define PNG_READ_CHUNK_MODE 1
  21 #define PNG_READ_IDAT_MODE  2
  22 #define PNG_READ_tEXt_MODE  4
  23 #define PNG_READ_zTXt_MODE  5
  24 #define PNG_READ_DONE_MODE  6
  25 #define PNG_READ_iTXt_MODE  7
  26 #define PNG_ERROR_MODE      8
  27
  28 #define PNG_PUSH_SAVE_BUFFER_IF_FULL \
  29 if (png_ptr->push_length + 4 > png_ptr->buffer_size) \
  30    { png_push_save_buffer(png_ptr); return; }
  31 #define PNG_PUSH_SAVE_BUFFER_IF_LT(N) \
  32 if (png_ptr->buffer_size < N) \
  33    { png_push_save_buffer(png_ptr); return; }
  34
  35 void PNGAPI
  36 png_process_data(png_structrp png_ptr, png_inforp info_ptr,
  37     png_bytep buffer, size_t buffer_size)
  38 {
  39    if (png_ptr == NULL || info_ptr == NULL)
  40       return;
  41
  42    png_push_restore_buffer(png_ptr, buffer, buffer_size);
  43
  44    while (png_ptr->buffer_size)
  45    {
  46       png_process_some_data(png_ptr, info_ptr);
  47    }
  48 }
  49
  50 size_t PNGAPI
  51 png_process_data_pause(png_structrp png_ptr, int save)
  52 {
  53    if (png_ptr != NULL)
  54    {
  55       /* It's easiest for the caller if we do the save; then the caller doesn't
  56        * have to supply the same data again:
  57        */
  58       if (save != 0)
  59          png_push_save_buffer(png_ptr);
  60       else
  61       {
  62          /* This includes any pending saved bytes: */
  63          size_t remaining = png_ptr->buffer_size;
  64          png_ptr->buffer_size = 0;
  65
  66          /* So subtract the saved buffer size, unless all the data
  67           * is actually 'saved', in which case we just return 0
  68           */
  69          if (png_ptr->save_buffer_size < remaining)
  70             return remaining - png_ptr->save_buffer_size;
  71       }
  72    }
  73
  74    return 0;
  75 }
  76
  77 png_uint_32 PNGAPI
  78 png_process_data_skip(png_structrp png_ptr)
  79 {
  80 /* TODO: Deprecate and remove this API.
  81  * Somewhere the implementation of this seems to have been lost,
  82  * or abandoned.  It was only to support some internal back-door access
  83  * to png_struct) in libpng-1.4.x.
  84  */
  85    png_app_warning(png_ptr,
  86 "png_process_data_skip is not implemented in any current version of libpng");
  87    return 0;
  88 }
  89
  90 /* What we do with the incoming data depends on what we were previously
  91  * doing before we ran out of data...
  92  */
  93 void /* PRIVATE */
  94 png_process_some_data(png_structrp png_ptr, png_inforp info_ptr)
  95 {
  96    if (png_ptr == NULL)
  97       return;
  98
  99    switch (png_ptr->process_mode)
 100    {
 101       case PNG_READ_SIG_MODE:
 102       {
 103          png_push_read_sig(png_ptr, info_ptr);
 104          break;
 105       }
 106
 107       case PNG_READ_CHUNK_MODE:
 108       {
 109          png_push_read_chunk(png_ptr, info_ptr);
 110          break;
 111       }
 112
 113       case PNG_READ_IDAT_MODE:
 114       {
 115          png_push_read_IDAT(png_ptr);
 116          break;
 117       }
 118
 119       default:
 120       {
 121          png_ptr->buffer_size = 0;
 122          break;
 123       }
 124    }
 125 }
 126
 127 /* Read any remaining signature bytes from the stream and compare them with
 128  * the correct PNG signature.  It is possible that this routine is called
 129  * with bytes already read from the signature, either because they have been
 130  * checked by the calling application, or because of multiple calls to this
 131  * routine.
 132  */
 133 void /* PRIVATE */
 134 png_push_read_sig(png_structrp png_ptr, png_inforp info_ptr)
 135 {
 136    size_t num_checked = png_ptr->sig_bytes; /* SAFE, does not exceed 8 */
 137    size_t num_to_check = 8 - num_checked;
 138
 139    if (png_ptr->buffer_size < num_to_check)
 140    {
 141       num_to_check = png_ptr->buffer_size;
 142    }
 143
 144    png_push_fill_buffer(png_ptr, &(info_ptr->signature[num_checked]),
 145        num_to_check);
 146    png_ptr->sig_bytes = (png_byte)(png_ptr->sig_bytes + num_to_check);
 147
 148    if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check) != 0)
 149    {
 150       if (num_checked < 4 &&
 151           png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4) != 0)
 152          png_error(png_ptr, "Not a PNG file");
 153
 154       else
 155          png_error(png_ptr, "PNG file corrupted by ASCII conversion");
 156    }
 157    else
 158    {
 159       if (png_ptr->sig_bytes >= 8)
 160       {
 161          png_ptr->process_mode = PNG_READ_CHUNK_MODE;
 162       }
 163    }
 164 }
 165
 166 void /* PRIVATE */
 167 png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
 168 {
 169    png_uint_32 chunk_name;
 170 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 171    int keep; /* unknown handling method */
 172 #endif
 173
 174    /* First we make sure we have enough data for the 4-byte chunk name
 175     * and the 4-byte chunk length before proceeding with decoding the
 176     * chunk data.  To fully decode each of these chunks, we also make
 177     * sure we have enough data in the buffer for the 4-byte CRC at the
 178     * end of every chunk (except IDAT, which is handled separately).
 179     */
 180    if ((png_ptr->mode & PNG_HAVE_CHUNK_HEADER) == 0)
 181    {
 182       png_byte chunk_length[4];
 183       png_byte chunk_tag[4];
 184
 185       PNG_PUSH_SAVE_BUFFER_IF_LT(8)
 186       png_push_fill_buffer(png_ptr, chunk_length, 4);
 187       png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
 188       png_reset_crc(png_ptr);
 189       png_crc_read(png_ptr, chunk_tag, 4);
 190       png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(chunk_tag);
 191       png_check_chunk_name(png_ptr, png_ptr->chunk_name);
 192       png_check_chunk_length(png_ptr, png_ptr->push_length);
 193       png_ptr->mode |= PNG_HAVE_CHUNK_HEADER;
 194    }
 195
 196    chunk_name = png_ptr->chunk_name;
 197
 198 #ifdef PNG_READ_APNG_SUPPORTED
 199    if (png_ptr->num_frames_read > 0 &&
 200        png_ptr->num_frames_read < info_ptr->num_frames)
 201    {
 202       if (chunk_name == png_IDAT)
 203       {
 204          /* Discard trailing IDATs for the first frame */
 205          if ((png_ptr->mode & PNG_HAVE_fcTL) != 0 ||
 206              png_ptr->num_frames_read > 1)
 207             png_error(png_ptr, "out of place IDAT");
 208
 209          PNG_PUSH_SAVE_BUFFER_IF_FULL
 210          png_crc_finish(png_ptr, png_ptr->push_length);
 211          png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 212       }
 213
 214       else if (chunk_name == png_fdAT)
 215       {
 216          PNG_PUSH_SAVE_BUFFER_IF_LT(4)
 217          png_ensure_sequence_number(png_ptr, 4);
 218
 219          if ((png_ptr->mode & PNG_HAVE_fcTL) == 0)
 220          {
 221             /* Discard trailing fdATs for frames other than the first */
 222             if (png_ptr->num_frames_read < 2)
 223                png_error(png_ptr, "out of place fdAT");
 224
 225             PNG_PUSH_SAVE_BUFFER_IF_FULL
 226             png_crc_finish(png_ptr, png_ptr->push_length);
 227             png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 228          }
 229
 230          else
 231          {
 232             /* frame data follows */
 233             png_ptr->idat_size = png_ptr->push_length - 4;
 234             png_ptr->mode |= PNG_HAVE_IDAT;
 235             png_ptr->process_mode = PNG_READ_IDAT_MODE;
 236          }
 237       }
 238
 239       else if (chunk_name == png_fcTL)
 240       {
 241          PNG_PUSH_SAVE_BUFFER_IF_FULL
 242          png_read_reset(png_ptr);
 243          png_ptr->mode &= ~PNG_HAVE_fcTL;
 244
 245          png_handle_fcTL(png_ptr, info_ptr, png_ptr->push_length);
 246
 247          if ((png_ptr->mode & PNG_HAVE_fcTL) == 0)
 248             png_error(png_ptr, "missing required fcTL chunk");
 249
 250          png_read_reinit(png_ptr, info_ptr);
 251          png_progressive_read_reset(png_ptr);
 252
 253          if (png_ptr->frame_info_fn != NULL)
 254             (*(png_ptr->frame_info_fn))(png_ptr, png_ptr->num_frames_read);
 255
 256          png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 257       }
 258
 259       else if (chunk_name == png_IEND)
 260       {
 261          PNG_PUSH_SAVE_BUFFER_IF_FULL
 262          png_warning(png_ptr, "Number of actual frames fewer than expected");
 263          png_crc_finish(png_ptr, png_ptr->push_length);
 264          png_ptr->process_mode = PNG_READ_DONE_MODE;
 265          png_push_have_end(png_ptr, info_ptr);
 266       }
 267
 268       else
 269       {
 270          PNG_PUSH_SAVE_BUFFER_IF_FULL
 271          png_warning(png_ptr, "Skipped (ignored) a chunk "
 272                               "between APNG chunks");
 273          png_crc_finish(png_ptr, png_ptr->push_length);
 274          png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 275       }
 276
 277       return;
 278    }
 279 #endif /* READ_APNG */
 280
 281    if (chunk_name == png_IDAT)
 282    {
 283       if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
 284          png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
 285
 286       /* If we reach an IDAT chunk, this means we have read all of the
 287        * header chunks, and we can start reading the image (or if this
 288        * is called after the image has been read - we have an error).
 289        */
 290       if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
 291          png_error(png_ptr, "Missing IHDR before IDAT");
 292
 293       else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
 294           (png_ptr->mode & PNG_HAVE_PLTE) == 0)
 295          png_error(png_ptr, "Missing PLTE before IDAT");
 296
 297       png_ptr->process_mode = PNG_READ_IDAT_MODE;
 298
 299       if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
 300          if ((png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) == 0)
 301             if (png_ptr->push_length == 0)
 302                return;
 303
 304       png_ptr->mode |= PNG_HAVE_IDAT;
 305
 306       if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
 307          png_benign_error(png_ptr, "Too many IDATs found");
 308    }
 309
 310    if (chunk_name == png_IHDR)
 311    {
 312       if (png_ptr->push_length != 13)
 313          png_error(png_ptr, "Invalid IHDR length");
 314
 315       PNG_PUSH_SAVE_BUFFER_IF_FULL
 316       png_handle_IHDR(png_ptr, info_ptr, png_ptr->push_length);
 317    }
 318
 319    else if (chunk_name == png_IEND)
 320    {
 321       PNG_PUSH_SAVE_BUFFER_IF_FULL
 322       png_handle_IEND(png_ptr, info_ptr, png_ptr->push_length);
 323
 324       png_ptr->process_mode = PNG_READ_DONE_MODE;
 325       png_push_have_end(png_ptr, info_ptr);
 326    }
 327
 328 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 329    else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
 330    {
 331       PNG_PUSH_SAVE_BUFFER_IF_FULL
 332       png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length, keep);
 333
 334       if (chunk_name == png_PLTE)
 335          png_ptr->mode |= PNG_HAVE_PLTE;
 336    }
 337 #endif
 338
 339    else if (chunk_name == png_PLTE)
 340    {
 341       PNG_PUSH_SAVE_BUFFER_IF_FULL
 342       png_handle_PLTE(png_ptr, info_ptr, png_ptr->push_length);
 343    }
 344
 345    else if (chunk_name == png_IDAT)
 346    {
 347 #ifdef PNG_READ_APNG_SUPPORTED
 348       png_have_info(png_ptr, info_ptr);
 349 #endif
 350       png_ptr->idat_size = png_ptr->push_length;
 351       png_ptr->process_mode = PNG_READ_IDAT_MODE;
 352       png_push_have_info(png_ptr, info_ptr);
 353       png_ptr->zstream.avail_out =
 354           (uInt) PNG_ROWBYTES(png_ptr->pixel_depth,
 355           png_ptr->iwidth) + 1;
 356       png_ptr->zstream.next_out = png_ptr->row_buf;
 357       return;
 358    }
 359
 360 #ifdef PNG_READ_gAMA_SUPPORTED
 361    else if (png_ptr->chunk_name == png_gAMA)
 362    {
 363       PNG_PUSH_SAVE_BUFFER_IF_FULL
 364       png_handle_gAMA(png_ptr, info_ptr, png_ptr->push_length);
 365    }
 366
 367 #endif
 368 #ifdef PNG_READ_sBIT_SUPPORTED
 369    else if (png_ptr->chunk_name == png_sBIT)
 370    {
 371       PNG_PUSH_SAVE_BUFFER_IF_FULL
 372       png_handle_sBIT(png_ptr, info_ptr, png_ptr->push_length);
 373    }
 374
 375 #endif
 376 #ifdef PNG_READ_cHRM_SUPPORTED
 377    else if (png_ptr->chunk_name == png_cHRM)
 378    {
 379       PNG_PUSH_SAVE_BUFFER_IF_FULL
 380       png_handle_cHRM(png_ptr, info_ptr, png_ptr->push_length);
 381    }
 382
 383 #endif
 384 #ifdef PNG_READ_eXIf_SUPPORTED
 385    else if (png_ptr->chunk_name == png_eXIf)
 386    {
 387       PNG_PUSH_SAVE_BUFFER_IF_FULL
 388       png_handle_eXIf(png_ptr, info_ptr, png_ptr->push_length);
 389    }
 390
 391 #endif
 392 #ifdef PNG_READ_sRGB_SUPPORTED
 393    else if (chunk_name == png_sRGB)
 394    {
 395       PNG_PUSH_SAVE_BUFFER_IF_FULL
 396       png_handle_sRGB(png_ptr, info_ptr, png_ptr->push_length);
 397    }
 398
 399 #endif
 400 #ifdef PNG_READ_iCCP_SUPPORTED
 401    else if (png_ptr->chunk_name == png_iCCP)
 402    {
 403       PNG_PUSH_SAVE_BUFFER_IF_FULL
 404       png_handle_iCCP(png_ptr, info_ptr, png_ptr->push_length);
 405    }
 406
 407 #endif
 408 #ifdef PNG_READ_sPLT_SUPPORTED
 409    else if (chunk_name == png_sPLT)
 410    {
 411       PNG_PUSH_SAVE_BUFFER_IF_FULL
 412       png_handle_sPLT(png_ptr, info_ptr, png_ptr->push_length);
 413    }
 414
 415 #endif
 416 #ifdef PNG_READ_tRNS_SUPPORTED
 417    else if (chunk_name == png_tRNS)
 418    {
 419       PNG_PUSH_SAVE_BUFFER_IF_FULL
 420       png_handle_tRNS(png_ptr, info_ptr, png_ptr->push_length);
 421    }
 422
 423 #endif
 424 #ifdef PNG_READ_bKGD_SUPPORTED
 425    else if (chunk_name == png_bKGD)
 426    {
 427       PNG_PUSH_SAVE_BUFFER_IF_FULL
 428       png_handle_bKGD(png_ptr, info_ptr, png_ptr->push_length);
 429    }
 430
 431 #endif
 432 #ifdef PNG_READ_hIST_SUPPORTED
 433    else if (chunk_name == png_hIST)
 434    {
 435       PNG_PUSH_SAVE_BUFFER_IF_FULL
 436       png_handle_hIST(png_ptr, info_ptr, png_ptr->push_length);
 437    }
 438
 439 #endif
 440 #ifdef PNG_READ_pHYs_SUPPORTED
 441    else if (chunk_name == png_pHYs)
 442    {
 443       PNG_PUSH_SAVE_BUFFER_IF_FULL
 444       png_handle_pHYs(png_ptr, info_ptr, png_ptr->push_length);
 445    }
 446
 447 #endif
 448 #ifdef PNG_READ_oFFs_SUPPORTED
 449    else if (chunk_name == png_oFFs)
 450    {
 451       PNG_PUSH_SAVE_BUFFER_IF_FULL
 452       png_handle_oFFs(png_ptr, info_ptr, png_ptr->push_length);
 453    }
 454 #endif
 455
 456 #ifdef PNG_READ_pCAL_SUPPORTED
 457    else if (chunk_name == png_pCAL)
 458    {
 459       PNG_PUSH_SAVE_BUFFER_IF_FULL
 460       png_handle_pCAL(png_ptr, info_ptr, png_ptr->push_length);
 461    }
 462
 463 #endif
 464 #ifdef PNG_READ_sCAL_SUPPORTED
 465    else if (chunk_name == png_sCAL)
 466    {
 467       PNG_PUSH_SAVE_BUFFER_IF_FULL
 468       png_handle_sCAL(png_ptr, info_ptr, png_ptr->push_length);
 469    }
 470
 471 #endif
 472 #ifdef PNG_READ_tIME_SUPPORTED
 473    else if (chunk_name == png_tIME)
 474    {
 475       PNG_PUSH_SAVE_BUFFER_IF_FULL
 476       png_handle_tIME(png_ptr, info_ptr, png_ptr->push_length);
 477    }
 478
 479 #endif
 480 #ifdef PNG_READ_tEXt_SUPPORTED
 481    else if (chunk_name == png_tEXt)
 482    {
 483       PNG_PUSH_SAVE_BUFFER_IF_FULL
 484       png_handle_tEXt(png_ptr, info_ptr, png_ptr->push_length);
 485    }
 486
 487 #endif
 488 #ifdef PNG_READ_zTXt_SUPPORTED
 489    else if (chunk_name == png_zTXt)
 490    {
 491       PNG_PUSH_SAVE_BUFFER_IF_FULL
 492       png_handle_zTXt(png_ptr, info_ptr, png_ptr->push_length);
 493    }
 494
 495 #endif
 496 #ifdef PNG_READ_iTXt_SUPPORTED
 497    else if (chunk_name == png_iTXt)
 498    {
 499       PNG_PUSH_SAVE_BUFFER_IF_FULL
 500       png_handle_iTXt(png_ptr, info_ptr, png_ptr->push_length);
 501    }
 502 #endif
 503
 504 #ifdef PNG_READ_APNG_SUPPORTED
 505    else if (chunk_name == png_acTL)
 506    {
 507       PNG_PUSH_SAVE_BUFFER_IF_FULL
 508       png_handle_acTL(png_ptr, info_ptr, png_ptr->push_length);
 509    }
 510
 511    else if (chunk_name == png_fcTL)
 512    {
 513       PNG_PUSH_SAVE_BUFFER_IF_FULL
 514       png_handle_fcTL(png_ptr, info_ptr, png_ptr->push_length);
 515    }
 516
 517 #endif /* READ_APNG */
 518    else
 519    {
 520       PNG_PUSH_SAVE_BUFFER_IF_FULL
 521       png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length,
 522           PNG_HANDLE_CHUNK_AS_DEFAULT);
 523    }
 524
 525    png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 526 }
 527
 528 void PNGCBAPI
 529 png_push_fill_buffer(png_structp png_ptr, png_bytep buffer, size_t length)
 530 {
 531    png_bytep ptr;
 532
 533    if (png_ptr == NULL)
 534       return;
 535
 536    ptr = buffer;
 537    if (png_ptr->save_buffer_size != 0)
 538    {
 539       size_t save_size;
 540
 541       if (length < png_ptr->save_buffer_size)
 542          save_size = length;
 543
 544       else
 545          save_size = png_ptr->save_buffer_size;
 546
 547       memcpy(ptr, png_ptr->save_buffer_ptr, save_size);
 548       length -= save_size;
 549       ptr += save_size;
 550       png_ptr->buffer_size -= save_size;
 551       png_ptr->save_buffer_size -= save_size;
 552       png_ptr->save_buffer_ptr += save_size;
 553    }
 554    if (length != 0 && png_ptr->current_buffer_size != 0)
 555    {
 556       size_t save_size;
 557
 558       if (length < png_ptr->current_buffer_size)
 559          save_size = length;
 560
 561       else
 562          save_size = png_ptr->current_buffer_size;
 563
 564       memcpy(ptr, png_ptr->current_buffer_ptr, save_size);
 565       png_ptr->buffer_size -= save_size;
 566       png_ptr->current_buffer_size -= save_size;
 567       png_ptr->current_buffer_ptr += save_size;
 568    }
 569 }
 570
 571 void /* PRIVATE */
 572 png_push_save_buffer(png_structrp png_ptr)
 573 {
 574    if (png_ptr->save_buffer_size != 0)
 575    {
 576       if (png_ptr->save_buffer_ptr != png_ptr->save_buffer)
 577       {
 578          size_t i, istop;
 579          png_bytep sp;
 580          png_bytep dp;
 581
 582          istop = png_ptr->save_buffer_size;
 583          for (i = 0, sp = png_ptr->save_buffer_ptr, dp = png_ptr->save_buffer;
 584              i < istop; i++, sp++, dp++)
 585          {
 586             *dp = *sp;
 587          }
 588       }
 589    }
 590    if (png_ptr->save_buffer_size + png_ptr->current_buffer_size >
 591        png_ptr->save_buffer_max)
 592    {
 593       size_t new_max;
 594       png_bytep old_buffer;
 595
 596       if (png_ptr->save_buffer_size > PNG_SIZE_MAX -
 597           (png_ptr->current_buffer_size + 256))
 598       {
 599          png_error(png_ptr, "Potential overflow of save_buffer");
 600       }
 601
 602       new_max = png_ptr->save_buffer_size + png_ptr->current_buffer_size + 256;
 603       old_buffer = png_ptr->save_buffer;
 604       png_ptr->save_buffer = (png_bytep)png_malloc_warn(png_ptr,
 605           (size_t)new_max);
 606
 607       if (png_ptr->save_buffer == NULL)
 608       {
 609          png_free(png_ptr, old_buffer);
 610          png_error(png_ptr, "Insufficient memory for save_buffer");
 611       }
 612
 613       if (old_buffer)
 614          memcpy(png_ptr->save_buffer, old_buffer, png_ptr->save_buffer_size);
 615       else if (png_ptr->save_buffer_size)
 616          png_error(png_ptr, "save_buffer error");
 617       png_free(png_ptr, old_buffer);
 618       png_ptr->save_buffer_max = new_max;
 619    }
 620    if (png_ptr->current_buffer_size)
 621    {
 622       memcpy(png_ptr->save_buffer + png_ptr->save_buffer_size,
 623          png_ptr->current_buffer_ptr, png_ptr->current_buffer_size);
 624       png_ptr->save_buffer_size += png_ptr->current_buffer_size;
 625       png_ptr->current_buffer_size = 0;
 626    }
 627    png_ptr->save_buffer_ptr = png_ptr->save_buffer;
 628    png_ptr->buffer_size = 0;
 629 }
 630
 631 void /* PRIVATE */
 632 png_push_restore_buffer(png_structrp png_ptr, png_bytep buffer,
 633     size_t buffer_length)
 634 {
 635    png_ptr->current_buffer = buffer;
 636    png_ptr->current_buffer_size = buffer_length;
 637    png_ptr->buffer_size = buffer_length + png_ptr->save_buffer_size;
 638    png_ptr->current_buffer_ptr = png_ptr->current_buffer;
 639 }
 640
 641 void /* PRIVATE */
 642 png_push_read_IDAT(png_structrp png_ptr)
 643 {
 644    if ((png_ptr->mode & PNG_HAVE_CHUNK_HEADER) == 0)
 645    {
 646       png_byte chunk_length[4];
 647       png_byte chunk_tag[4];
 648
 649       /* TODO: this code can be commoned up with the same code in push_read */
 650 #ifdef PNG_READ_APNG_SUPPORTED
 651       PNG_PUSH_SAVE_BUFFER_IF_LT(12)
 652 #else
 653       PNG_PUSH_SAVE_BUFFER_IF_LT(8)
 654 #endif
 655       png_push_fill_buffer(png_ptr, chunk_length, 4);
 656       png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
 657       png_reset_crc(png_ptr);
 658       png_crc_read(png_ptr, chunk_tag, 4);
 659       png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(chunk_tag);
 660       png_ptr->mode |= PNG_HAVE_CHUNK_HEADER;
 661
 662 #ifdef PNG_READ_APNG_SUPPORTED
 663       if (png_ptr->chunk_name != png_fdAT && png_ptr->num_frames_read > 0)
 664       {
 665           if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) != 0)
 666           {
 667               png_ptr->process_mode = PNG_READ_CHUNK_MODE;
 668               if (png_ptr->frame_end_fn != NULL)
 669                  (*(png_ptr->frame_end_fn))(png_ptr, png_ptr->num_frames_read);
 670               png_ptr->num_frames_read++;
 671               return;
 672           }
 673           else
 674           {
 675               if (png_ptr->chunk_name == png_IEND)
 676                   png_error(png_ptr, "Not enough image data");
 677               PNG_PUSH_SAVE_BUFFER_IF_FULL
 678               png_warning(png_ptr, "Skipping (ignoring) a chunk between "
 679                                    "APNG chunks");
 680               png_crc_finish(png_ptr, png_ptr->push_length);
 681               png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 682               return;
 683           }
 684       }
 685       else
 686 #endif
 687 #ifdef PNG_READ_APNG_SUPPORTED
 688       if (png_ptr->chunk_name != png_IDAT && png_ptr->num_frames_read == 0)
 689 #else
 690       if (png_ptr->chunk_name != png_IDAT)
 691 #endif
 692       {
 693          png_ptr->process_mode = PNG_READ_CHUNK_MODE;
 694
 695          if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
 696             png_error(png_ptr, "Not enough compressed data");
 697
 698 #ifdef PNG_READ_APNG_SUPPORTED
 699          if (png_ptr->frame_end_fn != NULL)
 700             (*(png_ptr->frame_end_fn))(png_ptr, png_ptr->num_frames_read);
 701          png_ptr->num_frames_read++;
 702 #endif
 703
 704          return;
 705       }
 706
 707       png_ptr->idat_size = png_ptr->push_length;
 708
 709 #ifdef PNG_READ_APNG_SUPPORTED
 710       if (png_ptr->num_frames_read > 0)
 711       {
 712          png_ensure_sequence_number(png_ptr, 4);
 713          png_ptr->idat_size -= 4;
 714       }
 715 #endif
 716    }
 717
 718    if (png_ptr->idat_size != 0 && png_ptr->save_buffer_size != 0)
 719    {
 720       size_t save_size = png_ptr->save_buffer_size;
 721       png_uint_32 idat_size = png_ptr->idat_size;
 722
 723       /* We want the smaller of 'idat_size' and 'current_buffer_size', but they
 724        * are of different types and we don't know which variable has the fewest
 725        * bits.  Carefully select the smaller and cast it to the type of the
 726        * larger - this cannot overflow.  Do not cast in the following test - it
 727        * will break on either 16-bit or 64-bit platforms.
 728        */
 729       if (idat_size < save_size)
 730          save_size = (size_t)idat_size;
 731
 732       else
 733          idat_size = (png_uint_32)save_size;
 734
 735       png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);
 736
 737       png_process_IDAT_data(png_ptr, png_ptr->save_buffer_ptr, save_size);
 738
 739       png_ptr->idat_size -= idat_size;
 740       png_ptr->buffer_size -= save_size;
 741       png_ptr->save_buffer_size -= save_size;
 742       png_ptr->save_buffer_ptr += save_size;
 743    }
 744
 745    if (png_ptr->idat_size != 0 && png_ptr->current_buffer_size != 0)
 746    {
 747       size_t save_size = png_ptr->current_buffer_size;
 748       png_uint_32 idat_size = png_ptr->idat_size;
 749
 750       /* We want the smaller of 'idat_size' and 'current_buffer_size', but they
 751        * are of different types and we don't know which variable has the fewest
 752        * bits.  Carefully select the smaller and cast it to the type of the
 753        * larger - this cannot overflow.
 754        */
 755       if (idat_size < save_size)
 756          save_size = (size_t)idat_size;
 757
 758       else
 759          idat_size = (png_uint_32)save_size;
 760
 761       png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);
 762
 763       png_process_IDAT_data(png_ptr, png_ptr->current_buffer_ptr, save_size);
 764
 765       png_ptr->idat_size -= idat_size;
 766       png_ptr->buffer_size -= save_size;
 767       png_ptr->current_buffer_size -= save_size;
 768       png_ptr->current_buffer_ptr += save_size;
 769    }
 770
 771    if (png_ptr->idat_size == 0)
 772    {
 773       PNG_PUSH_SAVE_BUFFER_IF_LT(4)
 774       png_crc_finish(png_ptr, 0);
 775       png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 776       png_ptr->mode |= PNG_AFTER_IDAT;
 777       png_ptr->zowner = 0;
 778    }
 779 }
 780
 781 void /* PRIVATE */
 782 png_process_IDAT_data(png_structrp png_ptr, png_bytep buffer,
 783     size_t buffer_length)
 784 {
 785    /* The caller checks for a non-zero buffer length. */
 786    if (!(buffer_length > 0) || buffer == NULL)
 787       png_error(png_ptr, "No IDAT data (internal error)");
 788
 789 #ifdef PNG_READ_APNG_SUPPORTED
 790    /* If the app is not APNG-aware, decode only the first frame */
 791    if ((png_ptr->apng_flags & PNG_APNG_APP) == 0 &&
 792       png_ptr->num_frames_read > 0)
 793    {
 794       png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
 795       return;
 796    }
 797 #endif
 798
 799    /* This routine must process all the data it has been given
 800     * before returning, calling the row callback as required to
 801     * handle the uncompressed results.
 802     */
 803    png_ptr->zstream.next_in = buffer;
 804    /* TODO: WARNING: TRUNCATION ERROR: DANGER WILL ROBINSON: */
 805    png_ptr->zstream.avail_in = (uInt)buffer_length;
 806
 807    /* Keep going until the decompressed data is all processed
 808     * or the stream marked as finished.
 809     */
 810    while (png_ptr->zstream.avail_in > 0 &&
 811       (png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
 812    {
 813       int ret;
 814
 815       /* We have data for zlib, but we must check that zlib
 816        * has someplace to put the results.  It doesn't matter
 817        * if we don't expect any results -- it may be the input
 818        * data is just the LZ end code.
 819        */
 820       if (!(png_ptr->zstream.avail_out > 0))
 821       {
 822          /* TODO: WARNING: TRUNCATION ERROR: DANGER WILL ROBINSON: */
 823          png_ptr->zstream.avail_out = (uInt)(PNG_ROWBYTES(png_ptr->pixel_depth,
 824              png_ptr->iwidth) + 1);
 825
 826          png_ptr->zstream.next_out = png_ptr->row_buf;
 827       }
 828
 829       /* Using Z_SYNC_FLUSH here means that an unterminated
 830        * LZ stream (a stream with a missing end code) can still
 831        * be handled, otherwise (Z_NO_FLUSH) a future zlib
 832        * implementation might defer output and therefore
 833        * change the current behavior (see comments in inflate.c
 834        * for why this doesn't happen at present with zlib 1.2.5).
 835        */
 836       ret = PNG_INFLATE(png_ptr, Z_SYNC_FLUSH);
 837
 838       /* Check for any failure before proceeding. */
 839       if (ret != Z_OK && ret != Z_STREAM_END)
 840       {
 841          /* Terminate the decompression. */
 842          png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
 843          png_ptr->zowner = 0;
 844
 845          /* This may be a truncated stream (missing or
 846           * damaged end code).  Treat that as a warning.
 847           */
 848          if (png_ptr->row_number >= png_ptr->num_rows ||
 849              png_ptr->pass > 6)
 850             png_warning(png_ptr, "Truncated compressed data in IDAT");
 851
 852          else
 853          {
 854             if (ret == Z_DATA_ERROR)
 855                png_benign_error(png_ptr, "IDAT: ADLER32 checksum mismatch");
 856             else
 857                png_error(png_ptr, "Decompression error in IDAT");
 858          }
 859
 860          /* Skip the check on unprocessed input */
 861          return;
 862       }
 863
 864       /* Did inflate output any data? */
 865       if (png_ptr->zstream.next_out != png_ptr->row_buf)
 866       {
 867          /* Is this unexpected data after the last row?
 868           * If it is, artificially terminate the LZ output
 869           * here.
 870           */
 871          if (png_ptr->row_number >= png_ptr->num_rows ||
 872              png_ptr->pass > 6)
 873          {
 874             /* Extra data. */
 875             png_warning(png_ptr, "Extra compressed data in IDAT");
 876             png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
 877             png_ptr->zowner = 0;
 878
 879             /* Do no more processing; skip the unprocessed
 880              * input check below.
 881              */
 882             return;
 883          }
 884
 885          /* Do we have a complete row? */
 886          if (png_ptr->zstream.avail_out == 0)
 887             png_push_process_row(png_ptr);
 888       }
 889
 890       /* And check for the end of the stream. */
 891       if (ret == Z_STREAM_END)
 892          png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
 893    }
 894
 895    /* All the data should have been processed, if anything
 896     * is left at this point we have bytes of IDAT data
 897     * after the zlib end code.
 898     */
 899    if (png_ptr->zstream.avail_in > 0)
 900       png_warning(png_ptr, "Extra compression data in IDAT");
 901 }
 902
 903 void /* PRIVATE */
 904 png_push_process_row(png_structrp png_ptr)
 905 {
 906    /* 1.5.6: row_info moved out of png_struct to a local here. */
 907    png_row_info row_info;
 908
 909    row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
 910    row_info.color_type = png_ptr->color_type;
 911    row_info.bit_depth = png_ptr->bit_depth;
 912    row_info.channels = png_ptr->channels;
 913    row_info.pixel_depth = png_ptr->pixel_depth;
 914    row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
 915
 916    if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
 917    {
 918       if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
 919          png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
 920             png_ptr->prev_row + 1, png_ptr->row_buf[0]);
 921       else
 922          png_error(png_ptr, "bad adaptive filter value");
 923    }
 924
 925    /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
 926     * 1.5.6, while the buffer really is this big in current versions of libpng
 927     * it may not be in the future, so this was changed just to copy the
 928     * interlaced row count:
 929     */
 930    memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
 931
 932 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
 933    if (png_ptr->transformations != 0)
 934       png_do_read_transformations(png_ptr, &row_info);
 935 #endif
 936
 937    /* The transformed pixel depth should match the depth now in row_info. */
 938    if (png_ptr->transformed_pixel_depth == 0)
 939    {
 940       png_ptr->transformed_pixel_depth = row_info.pixel_depth;
 941       if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
 942          png_error(png_ptr, "progressive row overflow");
 943    }
 944
 945    else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
 946       png_error(png_ptr, "internal progressive row size calculation error");
 947
 948
 949 #ifdef PNG_READ_INTERLACING_SUPPORTED
 950    /* Expand interlaced rows to full size */
 951    if (png_ptr->interlaced != 0 &&
 952        (png_ptr->transformations & PNG_INTERLACE) != 0)
 953    {
 954       if (png_ptr->pass < 6)
 955          png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
 956              png_ptr->transformations);
 957
 958       switch (png_ptr->pass)
 959       {
 960          case 0:
 961          {
 962             int i;
 963             for (i = 0; i < 8 && png_ptr->pass == 0; i++)
 964             {
 965                png_push_have_row(png_ptr, png_ptr->row_buf + 1);
 966                png_read_push_finish_row(png_ptr); /* Updates png_ptr->pass */
 967             }
 968
 969             if (png_ptr->pass == 2) /* Pass 1 might be empty */
 970             {
 971                for (i = 0; i < 4 && png_ptr->pass == 2; i++)
 972                {
 973                   png_push_have_row(png_ptr, NULL);
 974                   png_read_push_finish_row(png_ptr);
 975                }
 976             }
 977
 978             if (png_ptr->pass == 4 && png_ptr->height <= 4)
 979             {
 980                for (i = 0; i < 2 && png_ptr->pass == 4; i++)
 981                {
 982                   png_push_have_row(png_ptr, NULL);
 983                   png_read_push_finish_row(png_ptr);
 984                }
 985             }
 986
 987             if (png_ptr->pass == 6 && png_ptr->height <= 4)
 988             {
 989                 png_push_have_row(png_ptr, NULL);
 990                 png_read_push_finish_row(png_ptr);
 991             }
 992
 993             break;
 994          }
 995
 996          case 1:
 997          {
 998             int i;
 999             for (i = 0; i < 8 && png_ptr->pass == 1; i++)
1000             {
1001                png_push_have_row(png_ptr, png_ptr->row_buf + 1);
1002                png_read_push_finish_row(png_ptr);
1003             }
1004
1005             if (png_ptr->pass == 2) /* Skip top 4 generated rows */
1006             {
1007                for (i = 0; i < 4 && png_ptr->pass == 2; i++)
1008                {
1009                   png_push_have_row(png_ptr, NULL);
1010                   png_read_push_finish_row(png_ptr);
1011                }
1012             }
1013
1014             break;
1015          }
1016
1017          case 2:
1018          {
1019             int i;
1020
1021             for (i = 0; i < 4 && png_ptr->pass == 2; i++)
1022             {
1023                png_push_have_row(png_ptr, png_ptr->row_buf + 1);
1024                png_read_push_finish_row(png_ptr);
1025             }
1026
1027             for (i = 0; i < 4 && png_ptr->pass == 2; i++)
1028             {
1029                png_push_have_row(png_ptr, NULL);
1030                png_read_push_finish_row(png_ptr);
1031             }
1032
1033             if (png_ptr->pass == 4) /* Pass 3 might be empty */
1034             {
1035                for (i = 0; i < 2 && png_ptr->pass == 4; i++)
1036                {
1037                   png_push_have_row(png_ptr, NULL);
1038                   png_read_push_finish_row(png_ptr);
1039                }
1040             }
1041
1042             break;
1043          }
1044
1045          case 3:
1046          {
1047             int i;
1048
1049             for (i = 0; i < 4 && png_ptr->pass == 3; i++)
1050             {
1051                png_push_have_row(png_ptr, png_ptr->row_buf + 1);
1052                png_read_push_finish_row(png_ptr);
1053             }
1054
1055             if (png_ptr->pass == 4) /* Skip top two generated rows */
1056             {
1057                for (i = 0; i < 2 && png_ptr->pass == 4; i++)
1058                {
1059                   png_push_have_row(png_ptr, NULL);
1060                   png_read_push_finish_row(png_ptr);
1061                }
1062             }
1063
1064             break;
1065          }
1066
1067          case 4:
1068          {
1069             int i;
1070
1071             for (i = 0; i < 2 && png_ptr->pass == 4; i++)
1072             {
1073                png_push_have_row(png_ptr, png_ptr->row_buf + 1);
1074                png_read_push_finish_row(png_ptr);
1075             }
1076
1077             for (i = 0; i < 2 && png_ptr->pass == 4; i++)
1078             {
1079                png_push_have_row(png_ptr, NULL);
1080                png_read_push_finish_row(png_ptr);
1081             }
1082
1083             if (png_ptr->pass == 6) /* Pass 5 might be empty */
1084             {
1085                png_push_have_row(png_ptr, NULL);
1086                png_read_push_finish_row(png_ptr);
1087             }
1088
1089             break;
1090          }
1091
1092          case 5:
1093          {
1094             int i;
1095
1096             for (i = 0; i < 2 && png_ptr->pass == 5; i++)
1097             {
1098                png_push_have_row(png_ptr, png_ptr->row_buf + 1);
1099                png_read_push_finish_row(png_ptr);
1100             }
1101
1102             if (png_ptr->pass == 6) /* Skip top generated row */
1103             {
1104                png_push_have_row(png_ptr, NULL);
1105                png_read_push_finish_row(png_ptr);
1106             }
1107
1108             break;
1109          }
1110
1111          default:
1112          case 6:
1113          {
1114             png_push_have_row(png_ptr, png_ptr->row_buf + 1);
1115             png_read_push_finish_row(png_ptr);
1116
1117             if (png_ptr->pass != 6)
1118                break;
1119
1120             png_push_have_row(png_ptr, NULL);
1121             png_read_push_finish_row(png_ptr);
1122          }
1123       }
1124    }
1125    else
1126 #endif
1127    {
1128       png_push_have_row(png_ptr, png_ptr->row_buf + 1);
1129       png_read_push_finish_row(png_ptr);
1130    }
1131 }
1132
1133 void /* PRIVATE */
1134 png_read_push_finish_row(png_structrp png_ptr)
1135 {
1136 #ifdef PNG_READ_INTERLACING_SUPPORTED
1137    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
1138
1139    /* Start of interlace block */
1140    static const png_byte png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
1141
1142    /* Offset to next interlace block */
1143    static const png_byte png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
1144
1145    /* Start of interlace block in the y direction */
1146    static const png_byte png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
1147
1148    /* Offset to next interlace block in the y direction */
1149    static const png_byte png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
1150
1151    /* Height of interlace block.  This is not currently used - if you need
1152     * it, uncomment it here and in png.h
1153    static const png_byte png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
1154    */
1155 #endif
1156
1157    png_ptr->row_number++;
1158    if (png_ptr->row_number < png_ptr->num_rows)
1159       return;
1160
1161 #ifdef PNG_READ_INTERLACING_SUPPORTED
1162    if (png_ptr->interlaced != 0)
1163    {
1164       png_ptr->row_number = 0;
1165       memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
1166
1167       do
1168       {
1169          png_ptr->pass++;
1170          if ((png_ptr->pass == 1 && png_ptr->width < 5) ||
1171              (png_ptr->pass == 3 && png_ptr->width < 3) ||
1172              (png_ptr->pass == 5 && png_ptr->width < 2))
1173             png_ptr->pass++;
1174
1175          if (png_ptr->pass > 7)
1176             png_ptr->pass--;
1177
1178          if (png_ptr->pass >= 7)
1179             break;
1180
1181          png_ptr->iwidth = (png_ptr->width +
1182              png_pass_inc[png_ptr->pass] - 1 -
1183              png_pass_start[png_ptr->pass]) /
1184              png_pass_inc[png_ptr->pass];
1185
1186          if ((png_ptr->transformations & PNG_INTERLACE) != 0)
1187             break;
1188
1189          png_ptr->num_rows = (png_ptr->height +
1190              png_pass_yinc[png_ptr->pass] - 1 -
1191              png_pass_ystart[png_ptr->pass]) /
1192              png_pass_yinc[png_ptr->pass];
1193
1194       } while (png_ptr->iwidth == 0 || png_ptr->num_rows == 0);
1195    }
1196 #endif /* READ_INTERLACING */
1197 }
1198
1199 void /* PRIVATE */
1200 png_push_have_info(png_structrp png_ptr, png_inforp info_ptr)
1201 {
1202    if (png_ptr->info_fn != NULL)
1203       (*(png_ptr->info_fn))(png_ptr, info_ptr);
1204 }
1205
1206 void /* PRIVATE */
1207 png_push_have_end(png_structrp png_ptr, png_inforp info_ptr)
1208 {
1209    if (png_ptr->end_fn != NULL)
1210       (*(png_ptr->end_fn))(png_ptr, info_ptr);
1211 }
1212
1213 void /* PRIVATE */
1214 png_push_have_row(png_structrp png_ptr, png_bytep row)
1215 {
1216    if (png_ptr->row_fn != NULL)
1217       (*(png_ptr->row_fn))(png_ptr, row, png_ptr->row_number,
1218           (int)png_ptr->pass);
1219 }
1220
1221 #ifdef PNG_READ_INTERLACING_SUPPORTED
1222 void PNGAPI
1223 png_progressive_combine_row(png_const_structrp png_ptr, png_bytep old_row,
1224     png_const_bytep new_row)
1225 {
1226    if (png_ptr == NULL)
1227       return;
1228
1229    /* new_row is a flag here - if it is NULL then the app callback was called
1230     * from an empty row (see the calls to png_struct::row_fn below), otherwise
1231     * it must be png_ptr->row_buf+1
1232     */
1233    if (new_row != NULL)
1234       png_combine_row(png_ptr, old_row, 1/*blocky display*/);
1235 }
1236 #endif /* READ_INTERLACING */
1237
1238 void PNGAPI
1239 png_set_progressive_read_fn(png_structrp png_ptr, png_voidp progressive_ptr,
1240     png_progressive_info_ptr info_fn, png_progressive_row_ptr row_fn,
1241     png_progressive_end_ptr end_fn)
1242 {
1243    if (png_ptr == NULL)
1244       return;
1245
1246    png_ptr->info_fn = info_fn;
1247    png_ptr->row_fn = row_fn;
1248    png_ptr->end_fn = end_fn;
1249
1250    png_set_read_fn(png_ptr, progressive_ptr, png_push_fill_buffer);
1251 }
1252
1253 #ifdef PNG_READ_APNG_SUPPORTED
1254 void PNGAPI
1255 png_set_progressive_frame_fn(png_structp png_ptr,
1256    png_progressive_frame_ptr frame_info_fn,
1257    png_progressive_frame_ptr frame_end_fn)
1258 {
1259    png_ptr->frame_info_fn = frame_info_fn;
1260    png_ptr->frame_end_fn = frame_end_fn;
1261    png_ptr->apng_flags |= PNG_APNG_APP;
1262 }
1263 #endif
1264
1265 png_voidp PNGAPI
1266 png_get_progressive_ptr(png_const_structrp png_ptr)
1267 {
1268    if (png_ptr == NULL)
1269       return NULL;
1270
1271    return png_ptr->io_ptr;
1272 }
1273 #endif /* PROGRESSIVE_READ */