src/png/png.c

   1
   2 /* png.c - location for general purpose libpng functions
   3  *
   4  * Last changed in libpng 1.2.19 August 19, 2007
   5  * For conditions of distribution and use, see copyright notice in png.h
   6  * Copyright (c) 1998-2007 Glenn Randers-Pehrson
   7  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   8  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
   9  */
  10
  11 #define PNG_INTERNAL
  12 #define PNG_NO_EXTERN
  13 #include "png.h"
  14
  15 /* Generate a compiler error if there is an old png.h in the search path. */
  16 typedef version_1_2_20 Your_png_h_is_not_version_1_2_20;
  17
  18 /* Version information for C files.  This had better match the version
  19  * string defined in png.h.  */
  20
  21 #ifdef PNG_USE_GLOBAL_ARRAYS
  22 /* png_libpng_ver was changed to a function in version 1.0.5c */
  23 PNG_CONST char png_libpng_ver[18] = PNG_LIBPNG_VER_STRING;
  24
  25 #ifdef PNG_READ_SUPPORTED
  26
  27 /* png_sig was changed to a function in version 1.0.5c */
  28 /* Place to hold the signature string for a PNG file. */
  29 PNG_CONST png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
  30 #endif /* PNG_READ_SUPPORTED */
  31
  32 /* Invoke global declarations for constant strings for known chunk types */
  33 PNG_IHDR;
  34 PNG_IDAT;
  35 PNG_IEND;
  36 PNG_PLTE;
  37 PNG_bKGD;
  38 PNG_cHRM;
  39 PNG_gAMA;
  40 PNG_hIST;
  41 PNG_iCCP;
  42 PNG_iTXt;
  43 PNG_oFFs;
  44 PNG_pCAL;
  45 PNG_sCAL;
  46 PNG_pHYs;
  47 PNG_sBIT;
  48 PNG_sPLT;
  49 PNG_sRGB;
  50 PNG_tEXt;
  51 PNG_tIME;
  52 PNG_tRNS;
  53 PNG_zTXt;
  54
  55 #ifdef PNG_READ_SUPPORTED
  56 /* arrays to facilitate easy interlacing - use pass (0 - 6) as index */
  57
  58 /* start of interlace block */
  59 PNG_CONST int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
  60
  61 /* offset to next interlace block */
  62 PNG_CONST int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
  63
  64 /* start of interlace block in the y direction */
  65 PNG_CONST int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
  66
  67 /* offset to next interlace block in the y direction */
  68 PNG_CONST int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
  69
  70 /* Height of interlace block.  This is not currently used - if you need
  71  * it, uncomment it here and in png.h
  72 PNG_CONST int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
  73 */
  74
  75 /* Mask to determine which pixels are valid in a pass */
  76 PNG_CONST int FARDATA png_pass_mask[] = {0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff};
  77
  78 /* Mask to determine which pixels to overwrite while displaying */
  79 PNG_CONST int FARDATA png_pass_dsp_mask[]
  80    = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff};
  81
  82 #endif /* PNG_READ_SUPPORTED */
  83 #endif /* PNG_USE_GLOBAL_ARRAYS */
  84
  85 /* Tells libpng that we have already handled the first "num_bytes" bytes
  86  * of the PNG file signature.  If the PNG data is embedded into another
  87  * stream we can set num_bytes = 8 so that libpng will not attempt to read
  88  * or write any of the magic bytes before it starts on the IHDR.
  89  */
  90
  91 #ifdef PNG_READ_SUPPORTED
  92 void PNGAPI
  93 png_set_sig_bytes(png_structp png_ptr, int num_bytes)
  94 {
  95    if(png_ptr == NULL) return;
  96    png_debug(1, "in png_set_sig_bytes\n");
  97    if (num_bytes > 8)
  98       png_error(png_ptr, "Too many bytes for PNG signature.");
  99
 100    png_ptr->sig_bytes = (png_byte)(num_bytes < 0 ? 0 : num_bytes);
 101 }
 102
 103 /* Checks whether the supplied bytes match the PNG signature.  We allow
 104  * checking less than the full 8-byte signature so that those apps that
 105  * already read the first few bytes of a file to determine the file type
 106  * can simply check the remaining bytes for extra assurance.  Returns
 107  * an integer less than, equal to, or greater than zero if sig is found,
 108  * respectively, to be less than, to match, or be greater than the correct
 109  * PNG signature (this is the same behaviour as strcmp, memcmp, etc).
 110  */
 111 int PNGAPI
 112 png_sig_cmp(png_bytep sig, png_size_t start, png_size_t num_to_check)
 113 {
 114    png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
 115    if (num_to_check > 8)
 116       num_to_check = 8;
 117    else if (num_to_check < 1)
 118       return (-1);
 119
 120    if (start > 7)
 121       return (-1);
 122
 123    if (start + num_to_check > 8)
 124       num_to_check = 8 - start;
 125
 126    return ((int)(png_memcmp(&sig[start], &png_signature[start], num_to_check)));
 127 }
 128
 129 #if defined(PNG_1_0_X) || defined(PNG_1_2_X)
 130 /* (Obsolete) function to check signature bytes.  It does not allow one
 131  * to check a partial signature.  This function might be removed in the
 132  * future - use png_sig_cmp().  Returns true (nonzero) if the file is PNG.
 133  */
 134 int PNGAPI
 135 png_check_sig(png_bytep sig, int num)
 136 {
 137   return ((int)!png_sig_cmp(sig, (png_size_t)0, (png_size_t)num));
 138 }
 139 #endif
 140 #endif /* PNG_READ_SUPPORTED */
 141
 142 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
 143 /* Function to allocate memory for zlib and clear it to 0. */
 144 #ifdef PNG_1_0_X
 145 voidpf PNGAPI
 146 #else
 147 voidpf /* private */
 148 #endif
 149 png_zalloc(voidpf png_ptr, uInt items, uInt size)
 150 {
 151    png_voidp ptr;
 152    png_structp p=(png_structp)png_ptr;
 153    png_uint_32 save_flags=p->flags;
 154    png_uint_32 num_bytes;
 155
 156    if(png_ptr == NULL) return (NULL);
 157    if (items > PNG_UINT_32_MAX/size)
 158    {
 159      png_warning (p, "Potential overflow in png_zalloc()");
 160      return (NULL);
 161    }
 162    num_bytes = (png_uint_32)items * size;
 163
 164    p->flags|=PNG_FLAG_MALLOC_NULL_MEM_OK;
 165    ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes);
 166    p->flags=save_flags;
 167
 168 #if defined(PNG_1_0_X) && !defined(PNG_NO_ZALLOC_ZERO)
 169    if (ptr == NULL)
 170        return ((voidpf)ptr);
 171
 172    if (num_bytes > (png_uint_32)0x8000L)
 173    {
 174       png_memset(ptr, 0, (png_size_t)0x8000L);
 175       png_memset((png_bytep)ptr + (png_size_t)0x8000L, 0,
 176          (png_size_t)(num_bytes - (png_uint_32)0x8000L));
 177    }
 178    else
 179    {
 180       png_memset(ptr, 0, (png_size_t)num_bytes);
 181    }
 182 #endif
 183    return ((voidpf)ptr);
 184 }
 185
 186 /* function to free memory for zlib */
 187 #ifdef PNG_1_0_X
 188 void PNGAPI
 189 #else
 190 void /* private */
 191 #endif
 192 png_zfree(voidpf png_ptr, voidpf ptr)
 193 {
 194    png_free((png_structp)png_ptr, (png_voidp)ptr);
 195 }
 196
 197 /* Reset the CRC variable to 32 bits of 1's.  Care must be taken
 198  * in case CRC is > 32 bits to leave the top bits 0.
 199  */
 200 void /* PRIVATE */
 201 png_reset_crc(png_structp png_ptr)
 202 {
 203    png_ptr->crc = crc32(0, Z_NULL, 0);
 204 }
 205
 206 /* Calculate the CRC over a section of data.  We can only pass as
 207  * much data to this routine as the largest single buffer size.  We
 208  * also check that this data will actually be used before going to the
 209  * trouble of calculating it.
 210  */
 211 void /* PRIVATE */
 212 png_calculate_crc(png_structp png_ptr, png_bytep ptr, png_size_t length)
 213 {
 214    int need_crc = 1;
 215
 216    if (png_ptr->chunk_name[0] & 0x20)                     /* ancillary */
 217    {
 218       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
 219           (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
 220          need_crc = 0;
 221    }
 222    else                                                    /* critical */
 223    {
 224       if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)
 225          need_crc = 0;
 226    }
 227
 228    if (need_crc)
 229       png_ptr->crc = crc32(png_ptr->crc, ptr, (uInt)length);
 230 }
 231
 232 /* Allocate the memory for an info_struct for the application.  We don't
 233  * really need the png_ptr, but it could potentially be useful in the
 234  * future.  This should be used in favour of malloc(png_sizeof(png_info))
 235  * and png_info_init() so that applications that want to use a shared
 236  * libpng don't have to be recompiled if png_info changes size.
 237  */
 238 png_infop PNGAPI
 239 png_create_info_struct(png_structp png_ptr)
 240 {
 241    png_infop info_ptr;
 242
 243    png_debug(1, "in png_create_info_struct\n");
 244    if(png_ptr == NULL) return (NULL);
 245 #ifdef PNG_USER_MEM_SUPPORTED
 246    info_ptr = (png_infop)png_create_struct_2(PNG_STRUCT_INFO,
 247       png_ptr->malloc_fn, png_ptr->mem_ptr);
 248 #else
 249    info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO);
 250 #endif
 251    if (info_ptr != NULL)
 252       png_info_init_3(&info_ptr, png_sizeof(png_info));
 253
 254    return (info_ptr);
 255 }
 256
 257 /* This function frees the memory associated with a single info struct.
 258  * Normally, one would use either png_destroy_read_struct() or
 259  * png_destroy_write_struct() to free an info struct, but this may be
 260  * useful for some applications.
 261  */
 262 void PNGAPI
 263 png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr)
 264 {
 265    png_infop info_ptr = NULL;
 266    if(png_ptr == NULL) return;
 267
 268    png_debug(1, "in png_destroy_info_struct\n");
 269    if (info_ptr_ptr != NULL)
 270       info_ptr = *info_ptr_ptr;
 271
 272    if (info_ptr != NULL)
 273    {
 274       png_info_destroy(png_ptr, info_ptr);
 275
 276 #ifdef PNG_USER_MEM_SUPPORTED
 277       png_destroy_struct_2((png_voidp)info_ptr, png_ptr->free_fn,
 278           png_ptr->mem_ptr);
 279 #else
 280       png_destroy_struct((png_voidp)info_ptr);
 281 #endif
 282       *info_ptr_ptr = NULL;
 283    }
 284 }
 285
 286 /* Initialize the info structure.  This is now an internal function (0.89)
 287  * and applications using it are urged to use png_create_info_struct()
 288  * instead.
 289  */
 290 #if defined(PNG_1_0_X) || defined(PNG_1_2_X)
 291 #undef png_info_init
 292 void PNGAPI
 293 png_info_init(png_infop info_ptr)
 294 {
 295    /* We only come here via pre-1.0.12-compiled applications */
 296    png_info_init_3(&info_ptr, 0);
 297 }
 298 #endif
 299
 300 void PNGAPI
 301 png_info_init_3(png_infopp ptr_ptr, png_size_t png_info_struct_size)
 302 {
 303    png_infop info_ptr = *ptr_ptr;
 304
 305    if(info_ptr == NULL) return;
 306
 307    png_debug(1, "in png_info_init_3\n");
 308
 309    if(png_sizeof(png_info) > png_info_struct_size)
 310      {
 311        png_destroy_struct(info_ptr);
 312        info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO);
 313        *ptr_ptr = info_ptr;
 314      }
 315
 316    /* set everything to 0 */
 317    png_memset(info_ptr, 0, png_sizeof (png_info));
 318 }
 319
 320 #ifdef PNG_FREE_ME_SUPPORTED
 321 void PNGAPI
 322 png_data_freer(png_structp png_ptr, png_infop info_ptr,
 323    int freer, png_uint_32 mask)
 324 {
 325    png_debug(1, "in png_data_freer\n");
 326    if (png_ptr == NULL || info_ptr == NULL)
 327       return;
 328    if(freer == PNG_DESTROY_WILL_FREE_DATA)
 329       info_ptr->free_me |= mask;
 330    else if(freer == PNG_USER_WILL_FREE_DATA)
 331       info_ptr->free_me &= ~mask;
 332    else
 333       png_warning(png_ptr,
 334          "Unknown freer parameter in png_data_freer.");
 335 }
 336 #endif
 337
 338 void PNGAPI
 339 png_free_data(png_structp png_ptr, png_infop info_ptr, png_uint_32 mask,
 340    int num)
 341 {
 342    png_debug(1, "in png_free_data\n");
 343    if (png_ptr == NULL || info_ptr == NULL)
 344       return;
 345
 346 #if defined(PNG_TEXT_SUPPORTED)
 347 /* free text item num or (if num == -1) all text items */
 348 #ifdef PNG_FREE_ME_SUPPORTED
 349 if ((mask & PNG_FREE_TEXT) & info_ptr->free_me)
 350 #else
 351 if (mask & PNG_FREE_TEXT)
 352 #endif
 353 {
 354    if (num != -1)
 355    {
 356      if (info_ptr->text && info_ptr->text[num].key)
 357      {
 358          png_free(png_ptr, info_ptr->text[num].key);
 359          info_ptr->text[num].key = NULL;
 360      }
 361    }
 362    else
 363    {
 364        int i;
 365        for (i = 0; i < info_ptr->num_text; i++)
 366            png_free_data(png_ptr, info_ptr, PNG_FREE_TEXT, i);
 367        png_free(png_ptr, info_ptr->text);
 368        info_ptr->text = NULL;
 369        info_ptr->num_text=0;
 370    }
 371 }
 372 #endif
 373
 374 #if defined(PNG_tRNS_SUPPORTED)
 375 /* free any tRNS entry */
 376 #ifdef PNG_FREE_ME_SUPPORTED
 377 if ((mask & PNG_FREE_TRNS) & info_ptr->free_me)
 378 #else
 379 if ((mask & PNG_FREE_TRNS) && (png_ptr->flags & PNG_FLAG_FREE_TRNS))
 380 #endif
 381 {
 382     png_free(png_ptr, info_ptr->trans);
 383     info_ptr->valid &= ~PNG_INFO_tRNS;
 384 #ifndef PNG_FREE_ME_SUPPORTED
 385     png_ptr->flags &= ~PNG_FLAG_FREE_TRNS;
 386 #endif
 387     info_ptr->trans = NULL;
 388 }
 389 #endif
 390
 391 #if defined(PNG_sCAL_SUPPORTED)
 392 /* free any sCAL entry */
 393 #ifdef PNG_FREE_ME_SUPPORTED
 394 if ((mask & PNG_FREE_SCAL) & info_ptr->free_me)
 395 #else
 396 if (mask & PNG_FREE_SCAL)
 397 #endif
 398 {
 399 #if defined(PNG_FIXED_POINT_SUPPORTED) && !defined(PNG_FLOATING_POINT_SUPPORTED)
 400     png_free(png_ptr, info_ptr->scal_s_width);
 401     png_free(png_ptr, info_ptr->scal_s_height);
 402     info_ptr->scal_s_width = NULL;
 403     info_ptr->scal_s_height = NULL;
 404 #endif
 405     info_ptr->valid &= ~PNG_INFO_sCAL;
 406 }
 407 #endif
 408
 409 #if defined(PNG_pCAL_SUPPORTED)
 410 /* free any pCAL entry */
 411 #ifdef PNG_FREE_ME_SUPPORTED
 412 if ((mask & PNG_FREE_PCAL) & info_ptr->free_me)
 413 #else
 414 if (mask & PNG_FREE_PCAL)
 415 #endif
 416 {
 417     png_free(png_ptr, info_ptr->pcal_purpose);
 418     png_free(png_ptr, info_ptr->pcal_units);
 419     info_ptr->pcal_purpose = NULL;
 420     info_ptr->pcal_units = NULL;
 421     if (info_ptr->pcal_params != NULL)
 422     {
 423         int i;
 424         for (i = 0; i < (int)info_ptr->pcal_nparams; i++)
 425         {
 426           png_free(png_ptr, info_ptr->pcal_params[i]);
 427           info_ptr->pcal_params[i]=NULL;
 428         }
 429         png_free(png_ptr, info_ptr->pcal_params);
 430         info_ptr->pcal_params = NULL;
 431     }
 432     info_ptr->valid &= ~PNG_INFO_pCAL;
 433 }
 434 #endif
 435
 436 #if defined(PNG_iCCP_SUPPORTED)
 437 /* free any iCCP entry */
 438 #ifdef PNG_FREE_ME_SUPPORTED
 439 if ((mask & PNG_FREE_ICCP) & info_ptr->free_me)
 440 #else
 441 if (mask & PNG_FREE_ICCP)
 442 #endif
 443 {
 444     png_free(png_ptr, info_ptr->iccp_name);
 445     png_free(png_ptr, info_ptr->iccp_profile);
 446     info_ptr->iccp_name = NULL;
 447     info_ptr->iccp_profile = NULL;
 448     info_ptr->valid &= ~PNG_INFO_iCCP;
 449 }
 450 #endif
 451
 452 #if defined(PNG_sPLT_SUPPORTED)
 453 /* free a given sPLT entry, or (if num == -1) all sPLT entries */
 454 #ifdef PNG_FREE_ME_SUPPORTED
 455 if ((mask & PNG_FREE_SPLT) & info_ptr->free_me)
 456 #else
 457 if (mask & PNG_FREE_SPLT)
 458 #endif
 459 {
 460    if (num != -1)
 461    {
 462       if(info_ptr->splt_palettes)
 463       {
 464           png_free(png_ptr, info_ptr->splt_palettes[num].name);
 465           png_free(png_ptr, info_ptr->splt_palettes[num].entries);
 466           info_ptr->splt_palettes[num].name = NULL;
 467           info_ptr->splt_palettes[num].entries = NULL;
 468       }
 469    }
 470    else
 471    {
 472        if(info_ptr->splt_palettes_num)
 473        {
 474          int i;
 475          for (i = 0; i < (int)info_ptr->splt_palettes_num; i++)
 476             png_free_data(png_ptr, info_ptr, PNG_FREE_SPLT, i);
 477
 478          png_free(png_ptr, info_ptr->splt_palettes);
 479          info_ptr->splt_palettes = NULL;
 480          info_ptr->splt_palettes_num = 0;
 481        }
 482        info_ptr->valid &= ~PNG_INFO_sPLT;
 483    }
 484 }
 485 #endif
 486
 487 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
 488   if(png_ptr->unknown_chunk.data)
 489   {
 490     png_free(png_ptr, png_ptr->unknown_chunk.data);
 491     png_ptr->unknown_chunk.data = NULL;
 492   }
 493 #ifdef PNG_FREE_ME_SUPPORTED
 494 if ((mask & PNG_FREE_UNKN) & info_ptr->free_me)
 495 #else
 496 if (mask & PNG_FREE_UNKN)
 497 #endif
 498 {
 499    if (num != -1)
 500    {
 501        if(info_ptr->unknown_chunks)
 502        {
 503           png_free(png_ptr, info_ptr->unknown_chunks[num].data);
 504           info_ptr->unknown_chunks[num].data = NULL;
 505        }
 506    }
 507    else
 508    {
 509        int i;
 510
 511        if(info_ptr->unknown_chunks_num)
 512        {
 513          for (i = 0; i < (int)info_ptr->unknown_chunks_num; i++)
 514             png_free_data(png_ptr, info_ptr, PNG_FREE_UNKN, i);
 515
 516          png_free(png_ptr, info_ptr->unknown_chunks);
 517          info_ptr->unknown_chunks = NULL;
 518          info_ptr->unknown_chunks_num = 0;
 519        }
 520    }
 521 }
 522 #endif
 523
 524 #if defined(PNG_hIST_SUPPORTED)
 525 /* free any hIST entry */
 526 #ifdef PNG_FREE_ME_SUPPORTED
 527 if ((mask & PNG_FREE_HIST)  & info_ptr->free_me)
 528 #else
 529 if ((mask & PNG_FREE_HIST) && (png_ptr->flags & PNG_FLAG_FREE_HIST))
 530 #endif
 531 {
 532     png_free(png_ptr, info_ptr->hist);
 533     info_ptr->hist = NULL;
 534     info_ptr->valid &= ~PNG_INFO_hIST;
 535 #ifndef PNG_FREE_ME_SUPPORTED
 536     png_ptr->flags &= ~PNG_FLAG_FREE_HIST;
 537 #endif
 538 }
 539 #endif
 540
 541 /* free any PLTE entry that was internally allocated */
 542 #ifdef PNG_FREE_ME_SUPPORTED
 543 if ((mask & PNG_FREE_PLTE) & info_ptr->free_me)
 544 #else
 545 if ((mask & PNG_FREE_PLTE) && (png_ptr->flags & PNG_FLAG_FREE_PLTE))
 546 #endif
 547 {
 548     png_zfree(png_ptr, info_ptr->palette);
 549     info_ptr->palette = NULL;
 550     info_ptr->valid &= ~PNG_INFO_PLTE;
 551 #ifndef PNG_FREE_ME_SUPPORTED
 552     png_ptr->flags &= ~PNG_FLAG_FREE_PLTE;
 553 #endif
 554     info_ptr->num_palette = 0;
 555 }
 556
 557 #if defined(PNG_INFO_IMAGE_SUPPORTED)
 558 /* free any image bits attached to the info structure */
 559 #ifdef PNG_FREE_ME_SUPPORTED
 560 if ((mask & PNG_FREE_ROWS) & info_ptr->free_me)
 561 #else
 562 if (mask & PNG_FREE_ROWS)
 563 #endif
 564 {
 565     if(info_ptr->row_pointers)
 566     {
 567        int row;
 568        for (row = 0; row < (int)info_ptr->height; row++)
 569        {
 570           png_free(png_ptr, info_ptr->row_pointers[row]);
 571           info_ptr->row_pointers[row]=NULL;
 572        }
 573        png_free(png_ptr, info_ptr->row_pointers);
 574        info_ptr->row_pointers=NULL;
 575     }
 576     info_ptr->valid &= ~PNG_INFO_IDAT;
 577 }
 578 #endif
 579
 580 #ifdef PNG_FREE_ME_SUPPORTED
 581    if(num == -1)
 582      info_ptr->free_me &= ~mask;
 583    else
 584      info_ptr->free_me &= ~(mask & ~PNG_FREE_MUL);
 585 #endif
 586 }
 587
 588 /* This is an internal routine to free any memory that the info struct is
 589  * pointing to before re-using it or freeing the struct itself.  Recall
 590  * that png_free() checks for NULL pointers for us.
 591  */
 592 void /* PRIVATE */
 593 png_info_destroy(png_structp png_ptr, png_infop info_ptr)
 594 {
 595    png_debug(1, "in png_info_destroy\n");
 596
 597    png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);
 598
 599 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
 600    if (png_ptr->num_chunk_list)
 601    {
 602        png_free(png_ptr, png_ptr->chunk_list);
 603        png_ptr->chunk_list=NULL;
 604        png_ptr->num_chunk_list=0;
 605    }
 606 #endif
 607
 608    png_info_init_3(&info_ptr, png_sizeof(png_info));
 609 }
 610 #endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
 611
 612 /* This function returns a pointer to the io_ptr associated with the user
 613  * functions.  The application should free any memory associated with this
 614  * pointer before png_write_destroy() or png_read_destroy() are called.
 615  */
 616 png_voidp PNGAPI
 617 png_get_io_ptr(png_structp png_ptr)
 618 {
 619    if(png_ptr == NULL) return (NULL);
 620    return (png_ptr->io_ptr);
 621 }
 622
 623 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
 624 #if !defined(PNG_NO_STDIO)
 625 /* Initialize the default input/output functions for the PNG file.  If you
 626  * use your own read or write routines, you can call either png_set_read_fn()
 627  * or png_set_write_fn() instead of png_init_io().  If you have defined
 628  * PNG_NO_STDIO, you must use a function of your own because "FILE *" isn't
 629  * necessarily available.
 630  */
 631 void PNGAPI
 632 png_init_io(png_structp png_ptr, png_FILE_p fp)
 633 {
 634    png_debug(1, "in png_init_io\n");
 635    if(png_ptr == NULL) return;
 636    png_ptr->io_ptr = (png_voidp)fp;
 637 }
 638 #endif
 639
 640 #if defined(PNG_TIME_RFC1123_SUPPORTED)
 641 /* Convert the supplied time into an RFC 1123 string suitable for use in
 642  * a "Creation Time" or other text-based time string.
 643  */
 644 png_charp PNGAPI
 645 png_convert_to_rfc1123(png_structp png_ptr, png_timep ptime)
 646 {
 647    static PNG_CONST char short_months[12][4] =
 648         {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
 649          "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
 650
 651    if(png_ptr == NULL) return (NULL);
 652    if (png_ptr->time_buffer == NULL)
 653    {
 654       png_ptr->time_buffer = (png_charp)png_malloc(png_ptr, (png_uint_32)(29*
 655          png_sizeof(char)));
 656    }
 657
 658 #if defined(_WIN32_WCE)
 659    {
 660       wchar_t time_buf[29];
 661       wsprintf(time_buf, TEXT("%d %S %d %02d:%02d:%02d +0000"),
 662           ptime->day % 32, short_months[(ptime->month - 1) % 12],
 663         ptime->year, ptime->hour % 24, ptime->minute % 60,
 664           ptime->second % 61);
 665       WideCharToMultiByte(CP_ACP, 0, time_buf, -1, png_ptr->time_buffer, 29,
 666           NULL, NULL);
 667    }
 668 #else
 669 #ifdef USE_FAR_KEYWORD
 670    {
 671       char near_time_buf[29];
 672       png_snprintf6(near_time_buf,29,"%d %s %d %02d:%02d:%02d +0000",
 673           ptime->day % 32, short_months[(ptime->month - 1) % 12],
 674           ptime->year, ptime->hour % 24, ptime->minute % 60,
 675           ptime->second % 61);
 676       png_memcpy(png_ptr->time_buffer, near_time_buf,
 677           29*png_sizeof(char));
 678    }
 679 #else
 680    png_snprintf6(png_ptr->time_buffer,29,"%d %s %d %02d:%02d:%02d +0000",
 681        ptime->day % 32, short_months[(ptime->month - 1) % 12],
 682        ptime->year, ptime->hour % 24, ptime->minute % 60,
 683        ptime->second % 61);
 684 #endif
 685 #endif /* _WIN32_WCE */
 686    return ((png_charp)png_ptr->time_buffer);
 687 }
 688 #endif /* PNG_TIME_RFC1123_SUPPORTED */
 689
 690 #endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
 691
 692 png_charp PNGAPI
 693 png_get_copyright(png_structp png_ptr)
 694 {
 695    png_ptr = png_ptr;  /* silence compiler warning about unused png_ptr */
 696    return ((png_charp) "\n libpng version 1.2.20 - September 8, 2007\n\
 697    Copyright (c) 1998-2007 Glenn Randers-Pehrson\n\
 698    Copyright (c) 1996-1997 Andreas Dilger\n\
 699    Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.\n");
 700 }
 701
 702 /* The following return the library version as a short string in the
 703  * format 1.0.0 through 99.99.99zz.  To get the version of *.h files
 704  * used with your application, print out PNG_LIBPNG_VER_STRING, which
 705  * is defined in png.h.
 706  * Note: now there is no difference between png_get_libpng_ver() and
 707  * png_get_header_ver().  Due to the version_nn_nn_nn typedef guard,
 708  * it is guaranteed that png.c uses the correct version of png.h.
 709  */
 710 png_charp PNGAPI
 711 png_get_libpng_ver(png_structp png_ptr)
 712 {
 713    /* Version of *.c files used when building libpng */
 714    png_ptr = png_ptr;  /* silence compiler warning about unused png_ptr */
 715    return ((png_charp) PNG_LIBPNG_VER_STRING);
 716 }
 717
 718 png_charp PNGAPI
 719 png_get_header_ver(png_structp png_ptr)
 720 {
 721    /* Version of *.h files used when building libpng */
 722    png_ptr = png_ptr;  /* silence compiler warning about unused png_ptr */
 723    return ((png_charp) PNG_LIBPNG_VER_STRING);
 724 }
 725
 726 png_charp PNGAPI
 727 png_get_header_version(png_structp png_ptr)
 728 {
 729    /* Returns longer string containing both version and date */
 730    png_ptr = png_ptr;  /* silence compiler warning about unused png_ptr */
 731    return ((png_charp) PNG_HEADER_VERSION_STRING
 732 #ifndef PNG_READ_SUPPORTED
 733    "     (NO READ SUPPORT)"
 734 #endif
 735    "\n");
 736 }
 737
 738 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
 739 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 740 int PNGAPI
 741 png_handle_as_unknown(png_structp png_ptr, png_bytep chunk_name)
 742 {
 743    /* check chunk_name and return "keep" value if it's on the list, else 0 */
 744    int i;
 745    png_bytep p;
 746    if(png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list<=0)
 747       return 0;
 748    p=png_ptr->chunk_list+png_ptr->num_chunk_list*5-5;
 749    for (i = png_ptr->num_chunk_list; i; i--, p-=5)
 750       if (!png_memcmp(chunk_name, p, 4))
 751         return ((int)*(p+4));
 752    return 0;
 753 }
 754 #endif
 755
 756 /* This function, added to libpng-1.0.6g, is untested. */
 757 int PNGAPI
 758 png_reset_zstream(png_structp png_ptr)
 759 {
 760    if (png_ptr == NULL) return Z_STREAM_ERROR;
 761    return (inflateReset(&png_ptr->zstream));
 762 }
 763 #endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
 764
 765 /* This function was added to libpng-1.0.7 */
 766 png_uint_32 PNGAPI
 767 png_access_version_number(void)
 768 {
 769    /* Version of *.c files used when building libpng */
 770    return((png_uint_32) PNG_LIBPNG_VER);
 771 }
 772
 773
 774 #if defined(PNG_READ_SUPPORTED) && defined(PNG_ASSEMBLER_CODE_SUPPORTED)
 775 #if !defined(PNG_1_0_X)
 776 /* this function was added to libpng 1.2.0 */
 777 int PNGAPI
 778 png_mmx_support(void)
 779 {
 780    /* obsolete, to be removed from libpng-1.4.0 */
 781     return -1;
 782 }
 783 #endif /* PNG_1_0_X */
 784 #endif /* PNG_READ_SUPPORTED && PNG_ASSEMBLER_CODE_SUPPORTED */
 785
 786 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
 787 #ifdef PNG_SIZE_T
 788 /* Added at libpng version 1.2.6 */
 789    PNG_EXTERN png_size_t PNGAPI png_convert_size PNGARG((size_t size));
 790 png_size_t PNGAPI
 791 png_convert_size(size_t size)
 792 {
 793   if (size > (png_size_t)-1)
 794      PNG_ABORT();  /* We haven't got access to png_ptr, so no png_error() */
 795   return ((png_size_t)size);
 796 }
 797 #endif /* PNG_SIZE_T */
 798 #endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */