src/png/png.c

   1
   2 /* png.c - location for general purpose libpng functions
   3  *
   4  * libpng version 1.0.3 - January 14, 1999
   5  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
   6  * Copyright (c) 1996, 1997 Andreas Dilger
   7  * Copyright (c) 1998, 1999 Glenn Randers-Pehrson
   8  *
   9  */
  10
  11 #define PNG_INTERNAL
  12 #define PNG_NO_EXTERN
  13 #include "png.h"
  14
  15 /* Version information for C files.  This had better match the version
  16  * string defined in png.h.
  17  */
  18
  19 char png_libpng_ver[12] = "1.0.3";
  20
  21 /* Place to hold the signature string for a PNG file. */
  22 png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
  23
  24 /* Constant strings for known chunk types.  If you need to add a chunk,
  25  * add a string holding the name here.  If you want to make the code
  26  * portable to EBCDIC machines, use ASCII numbers, not characters.
  27  */
  28 png_byte FARDATA png_IHDR[5] = { 73,  72,  68,  82, '\0'};
  29 png_byte FARDATA png_IDAT[5] = { 73,  68,  65,  84, '\0'};
  30 png_byte FARDATA png_IEND[5] = { 73,  69,  78,  68, '\0'};
  31 png_byte FARDATA png_PLTE[5] = { 80,  76,  84,  69, '\0'};
  32 png_byte FARDATA png_bKGD[5] = { 98,  75,  71,  68, '\0'};
  33 png_byte FARDATA png_cHRM[5] = { 99,  72,  82,  77, '\0'};
  34 png_byte FARDATA png_gAMA[5] = {103,  65,  77,  65, '\0'};
  35 png_byte FARDATA png_hIST[5] = {104,  73,  83,  84, '\0'};
  36 png_byte FARDATA png_oFFs[5] = {111,  70,  70, 115, '\0'};
  37 png_byte FARDATA png_pCAL[5] = {112,  67,  65,  76, '\0'};
  38 png_byte FARDATA png_pHYs[5] = {112,  72,  89, 115, '\0'};
  39 png_byte FARDATA png_sBIT[5] = {115,  66,  73,  84, '\0'};
  40 png_byte FARDATA png_sRGB[5] = {115,  82,  71,  66, '\0'};
  41 png_byte FARDATA png_tEXt[5] = {116,  69,  88, 116, '\0'};
  42 png_byte FARDATA png_tIME[5] = {116,  73,  77,  69, '\0'};
  43 png_byte FARDATA png_tRNS[5] = {116,  82,  78,  83, '\0'};
  44 png_byte FARDATA png_zTXt[5] = {122,  84,  88, 116, '\0'};
  45
  46 /* arrays to facilitate easy interlacing - use pass (0 - 6) as index */
  47
  48 /* start of interlace block */
  49 int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
  50
  51 /* offset to next interlace block */
  52 int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
  53
  54 /* start of interlace block in the y direction */
  55 int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
  56
  57 /* offset to next interlace block in the y direction */
  58 int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
  59
  60 /* Width of interlace block.  This is not currently used - if you need
  61  * it, uncomment it here and in png.h
  62 int FARDATA png_pass_width[] = {8, 4, 4, 2, 2, 1, 1};
  63 */
  64
  65 /* Height of interlace block.  This is not currently used - if you need
  66  * it, uncomment it here and in png.h
  67 int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
  68 */
  69
  70 /* Mask to determine which pixels are valid in a pass */
  71 int FARDATA png_pass_mask[] = {0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff};
  72
  73 /* Mask to determine which pixels to overwrite while displaying */
  74 int FARDATA png_pass_dsp_mask[] = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff};
  75
  76
  77 /* Tells libpng that we have already handled the first "num_bytes" bytes
  78  * of the PNG file signature.  If the PNG data is embedded into another
  79  * stream we can set num_bytes = 8 so that libpng will not attempt to read
  80  * or write any of the magic bytes before it starts on the IHDR.
  81  */
  82 void
  83 png_set_sig_bytes(png_structp png_ptr, int num_bytes)
  84 {
  85    png_debug(1, "in png_set_sig_bytes\n");
  86    if (num_bytes > 8)
  87       png_error(png_ptr, "Too many bytes for PNG signature.");
  88
  89    png_ptr->sig_bytes = num_bytes < 0 ? 0 : num_bytes;
  90 }
  91
  92 /* Checks whether the supplied bytes match the PNG signature.  We allow
  93  * checking less than the full 8-byte signature so that those apps that
  94  * already read the first few bytes of a file to determine the file type
  95  * can simply check the remaining bytes for extra assurance.  Returns
  96  * an integer less than, equal to, or greater than zero if sig is found,
  97  * respectively, to be less than, to match, or be greater than the correct
  98  * PNG signature (this is the same behaviour as strcmp, memcmp, etc).
  99  */
 100 int
 101 png_sig_cmp(png_bytep sig, png_size_t start, png_size_t num_to_check)
 102 {
 103    if (num_to_check > 8)
 104       num_to_check = 8;
 105    else if (num_to_check < 1)
 106       return (0);
 107
 108    if (start > 7)
 109       return (0);
 110
 111    if (start + num_to_check > 8)
 112       num_to_check = 8 - start;
 113
 114    return ((int)(png_memcmp(&sig[start], &png_sig[start], num_to_check)));
 115 }
 116
 117 /* (Obsolete) function to check signature bytes.  It does not allow one
 118  * to check a partial signature.  This function might be removed in the
 119  * future - use png_sig_cmp().  Returns true (nonzero) if the file is a PNG.
 120  */
 121 int
 122 png_check_sig(png_bytep sig, int num)
 123 {
 124   return ((int)!png_sig_cmp(sig, (png_size_t)0, (png_size_t)num));
 125 }
 126
 127 /* Function to allocate memory for zlib. */
 128 voidpf
 129 png_zalloc(voidpf png_ptr, uInt items, uInt size)
 130 {
 131    png_uint_32 num_bytes = (png_uint_32)items * size;
 132    png_voidp ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes);
 133
 134    if (num_bytes > (png_uint_32)0x8000L)
 135    {
 136       png_memset(ptr, 0, (png_size_t)0x8000L);
 137       png_memset((png_bytep)ptr + (png_size_t)0x8000L, 0,
 138          (png_size_t)(num_bytes - (png_uint_32)0x8000L));
 139    }
 140    else
 141    {
 142       png_memset(ptr, 0, (png_size_t)num_bytes);
 143    }
 144    return ((voidpf)ptr);
 145 }
 146
 147 /* function to free memory for zlib */
 148 void
 149 png_zfree(voidpf png_ptr, voidpf ptr)
 150 {
 151    png_free((png_structp)png_ptr, (png_voidp)ptr);
 152 }
 153
 154 /* Reset the CRC variable to 32 bits of 1's.  Care must be taken
 155  * in case CRC is > 32 bits to leave the top bits 0.
 156  */
 157 void
 158 png_reset_crc(png_structp png_ptr)
 159 {
 160    png_ptr->crc = crc32(0, Z_NULL, 0);
 161 }
 162
 163 /* Calculate the CRC over a section of data.  We can only pass as
 164  * much data to this routine as the largest single buffer size.  We
 165  * also check that this data will actually be used before going to the
 166  * trouble of calculating it.
 167  */
 168 void
 169 png_calculate_crc(png_structp png_ptr, png_bytep ptr, png_size_t length)
 170 {
 171    int need_crc = 1;
 172
 173    if (png_ptr->chunk_name[0] & 0x20)                     /* ancillary */
 174    {
 175       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
 176           (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
 177          need_crc = 0;
 178    }
 179    else                                                    /* critical */
 180    {
 181       if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)
 182          need_crc = 0;
 183    }
 184
 185    if (need_crc)
 186       png_ptr->crc = crc32(png_ptr->crc, ptr, (uInt)length);
 187 }
 188
 189 /* Allocate the memory for an info_struct for the application.  We don't
 190  * really need the png_ptr, but it could potentially be useful in the
 191  * future.  This should be used in favour of malloc(sizeof(png_info))
 192  * and png_info_init() so that applications that want to use a shared
 193  * libpng don't have to be recompiled if png_info changes size.
 194  */
 195 png_infop
 196 png_create_info_struct(png_structp png_ptr)
 197 {
 198    png_infop info_ptr;
 199
 200    png_debug(1, "in png_create_info_struct\n");
 201    if(png_ptr == NULL) return (NULL);
 202 #ifdef PNG_USER_MEM_SUPPORTED
 203    if ((info_ptr = (png_infop)png_create_struct_2(PNG_STRUCT_INFO,
 204       png_ptr->malloc_fn)) != NULL)
 205 #else
 206    if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL)
 207 #endif
 208    {
 209       png_info_init(info_ptr);
 210    }
 211
 212    return (info_ptr);
 213 }
 214
 215 /* This function frees the memory associated with a single info struct.
 216  * Normally, one would use either png_destroy_read_struct() or
 217  * png_destroy_write_struct() to free an info struct, but this may be
 218  * useful for some applications.
 219  */
 220 void
 221 png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr)
 222 {
 223    png_infop info_ptr = NULL;
 224
 225    png_debug(1, "in png_destroy_info_struct\n");
 226    if (info_ptr_ptr != NULL)
 227       info_ptr = *info_ptr_ptr;
 228
 229    if (info_ptr != NULL)
 230    {
 231       png_info_destroy(png_ptr, info_ptr);
 232
 233 #ifdef PNG_USER_MEM_SUPPORTED
 234       png_destroy_struct_2((png_voidp)info_ptr, png_ptr->free_fn);
 235 #else
 236       png_destroy_struct((png_voidp)info_ptr);
 237 #endif
 238       *info_ptr_ptr = (png_infop)NULL;
 239    }
 240 }
 241
 242 /* Initialize the info structure.  This is now an internal function (0.89)
 243  * and applications using it are urged to use png_create_info_struct()
 244  * instead.
 245  */
 246 void
 247 png_info_init(png_infop info_ptr)
 248 {
 249    png_debug(1, "in png_info_init\n");
 250    /* set everything to 0 */
 251    png_memset(info_ptr, 0, sizeof (png_info));
 252 }
 253
 254 /* This is an internal routine to free any memory that the info struct is
 255  * pointing to before re-using it or freeing the struct itself.  Recall
 256  * that png_free() checks for NULL pointers for us.
 257  */
 258 void
 259 png_info_destroy(png_structp png_ptr, png_infop info_ptr)
 260 {
 261 #if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_READ_zTXt_SUPPORTED)
 262    png_debug(1, "in png_info_destroy\n");
 263    if (info_ptr->text != NULL)
 264    {
 265       int i;
 266       for (i = 0; i < info_ptr->num_text; i++)
 267       {
 268          png_free(png_ptr, info_ptr->text[i].key);
 269       }
 270       png_free(png_ptr, info_ptr->text);
 271    }
 272 #endif
 273 #if defined(PNG_READ_pCAL_SUPPORTED)
 274    png_free(png_ptr, info_ptr->pcal_purpose);
 275    png_free(png_ptr, info_ptr->pcal_units);
 276    if (info_ptr->pcal_params != NULL)
 277    {
 278       int i;
 279       for (i = 0; i < (int)info_ptr->pcal_nparams; i++)
 280       {
 281          png_free(png_ptr, info_ptr->pcal_params[i]);
 282       }
 283       png_free(png_ptr, info_ptr->pcal_params);
 284    }
 285 #endif
 286
 287    png_info_init(info_ptr);
 288 }
 289
 290 /* This function returns a pointer to the io_ptr associated with the user
 291  * functions.  The application should free any memory associated with this
 292  * pointer before png_write_destroy() or png_read_destroy() are called.
 293  */
 294 png_voidp
 295 png_get_io_ptr(png_structp png_ptr)
 296 {
 297    return (png_ptr->io_ptr);
 298 }
 299
 300 #if !defined(PNG_NO_STDIO)
 301 /* Initialize the default input/output functions for the PNG file.  If you
 302  * use your own read or write routines, you can call either png_set_read_fn()
 303  * or png_set_write_fn() instead of png_init_io().
 304  */
 305 void
 306 png_init_io(png_structp png_ptr, FILE *fp)
 307 {
 308    png_debug(1, "in png_init_io\n");
 309    png_ptr->io_ptr = (png_voidp)fp;
 310 }
 311 #endif
 312
 313 #if defined(PNG_TIME_RFC1123_SUPPORTED)
 314 /* Convert the supplied time into an RFC 1123 string suitable for use in
 315  * a "Creation Time" or other text-based time string.
 316  */
 317 png_charp
 318 png_convert_to_rfc1123(png_structp png_ptr, png_timep ptime)
 319 {
 320    static PNG_CONST char short_months[12][4] =
 321         {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
 322          "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
 323
 324    if (png_ptr->time_buffer == NULL)
 325    {
 326       png_ptr->time_buffer = (png_charp)png_malloc(png_ptr, (png_uint_32)(29*
 327          sizeof(char)));
 328    }
 329
 330 #ifdef USE_FAR_KEYWORD
 331    {
 332       char near_time_buf[29];
 333       sprintf(near_time_buf, "%d %s %d %02d:%02d:%02d +0000",
 334                ptime->day % 32, short_months[(ptime->month - 1) % 12],
 335                ptime->year, ptime->hour % 24, ptime->minute % 60,
 336                ptime->second % 61);
 337       png_memcpy(png_ptr->time_buffer, near_time_buf,
 338       29*sizeof(char));
 339    }
 340 #else
 341    sprintf(png_ptr->time_buffer, "%d %s %d %02d:%02d:%02d +0000",
 342                ptime->day % 32, short_months[(ptime->month - 1) % 12],
 343                ptime->year, ptime->hour % 24, ptime->minute % 60,
 344                ptime->second % 61);
 345 #endif
 346    return ((png_charp)png_ptr->time_buffer);
 347 }
 348 #endif /* PNG_TIME_RFC1123_SUPPORTED */
 349
 350 png_charp
 351 png_get_copyright(png_structp png_ptr)
 352 {
 353    if(png_ptr == NULL)
 354      /* silence compiler warning about unused png_ptr */ ;
 355    return("\n libpng version 1.0.3 - January 14, 1999\n\
 356    Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.\n\
 357    Copyright (c) 1996, 1997 Andreas Dilger\n\
 358    Copyright (c) 1998, 1999, Glenn Randers-Pehrson\n");
 359 }