src/png/png.c

   1
   2 /* png.c - location for general purpose libpng functions
   3  *
   4  * libpng 1.0.1
   5  * For conditions of distribution and use, see copyright notice in png.h
   6  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
   7  * Copyright (c) 1996, 1997 Andreas Dilger
   8  * Copyright (c) 1998, Glenn Randers-Pehrson
   9  * March 15, 1998
  10  */
  11
  12 #define PNG_INTERNAL
  13 #define PNG_NO_EXTERN
  14 #include "png.h"
  15
  16 /* Version information for C files.  This had better match the version
  17  * string defined in png.h.
  18  */
  19 char png_libpng_ver[12] = "1.0.1";
  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 will be removed in the
 119  * future - use png_sig_cmp().
 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_voidp ptr;
 132    png_uint_32 num_bytes;
 133
 134    num_bytes = (png_uint_32)items * size;
 135    ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes);
 136    if (num_bytes > (png_uint_32)0x8000)
 137    {
 138       png_memset(ptr, 0, (png_size_t)0x8000L);
 139       png_memset((png_bytep)ptr + (png_size_t)0x8000L, 0,
 140          (png_size_t)(num_bytes - (png_uint_32)0x8000L));
 141    }
 142    else
 143    {
 144       png_memset(ptr, 0, (png_size_t)num_bytes);
 145    }
 146    return ((voidpf)ptr);
 147 }
 148
 149 /* function to free memory for zlib */
 150 void
 151 png_zfree(voidpf png_ptr, voidpf ptr)
 152 {
 153    png_free((png_structp)png_ptr, (png_voidp)ptr);
 154 }
 155
 156 /* Reset the CRC variable to 32 bits of 1's.  Care must be taken
 157  * in case CRC is > 32 bits to leave the top bits 0.
 158  */
 159 void
 160 png_reset_crc(png_structp png_ptr)
 161 {
 162    png_ptr->crc = crc32(0, Z_NULL, 0);
 163 }
 164
 165 /* Calculate the CRC over a section of data.  We can only pass as
 166  * much data to this routine as the largest single buffer size.  We
 167  * also check that this data will actually be used before going to the
 168  * trouble of calculating it.
 169  */
 170 void
 171 png_calculate_crc(png_structp png_ptr, png_bytep ptr, png_size_t length)
 172 {
 173    int need_crc = 1;
 174
 175    if (png_ptr->chunk_name[0] & 0x20)                     /* ancillary */
 176    {
 177       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
 178           (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
 179          need_crc = 0;
 180    }
 181    else                                                    /* critical */
 182    {
 183       if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)
 184          need_crc = 0;
 185    }
 186
 187    if (need_crc)
 188       png_ptr->crc = crc32(png_ptr->crc, ptr, (uInt)length);
 189 }
 190
 191 /* Allocate the memory for an info_struct for the application.  We don't
 192  * really need the png_ptr, but it could potentially be useful in the
 193  * future.  This should be used in favour of malloc(sizeof(png_info))
 194  * and png_info_init() so that applications that want to use a shared
 195  * libpng don't have to be recompiled if png_info changes size.
 196  */
 197 png_infop
 198 png_create_info_struct(png_structp png_ptr)
 199 {
 200    png_infop info_ptr;
 201
 202    png_debug(1, "in png_create_info_struct\n");
 203    if(png_ptr == NULL) return (NULL);
 204    if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL)
 205    {
 206       png_info_init(info_ptr);
 207    }
 208
 209    return (info_ptr);
 210 }
 211
 212 /* This function frees the memory associated with a single info struct.
 213  * Normally, one would use either png_destroy_read_struct() or
 214  * png_destroy_write_struct() to free an info struct, but this may be
 215  * useful for some applications.
 216  */
 217 void
 218 png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr)
 219 {
 220    png_infop info_ptr = NULL;
 221
 222    png_debug(1, "in png_destroy_info_struct\n");
 223    if (info_ptr_ptr != NULL)
 224       info_ptr = *info_ptr_ptr;
 225
 226    if (info_ptr != NULL)
 227    {
 228       png_info_destroy(png_ptr, info_ptr);
 229
 230       png_destroy_struct((png_voidp)info_ptr);
 231       *info_ptr_ptr = (png_infop)NULL;
 232    }
 233 }
 234
 235 /* Initialize the info structure.  This is now an internal function (0.89)
 236  * and applications using it are urged to use png_create_info_struct()
 237  * instead.
 238  */
 239 void
 240 png_info_init(png_infop info_ptr)
 241 {
 242    png_debug(1, "in png_info_init\n");
 243    /* set everything to 0 */
 244    png_memset(info_ptr, 0, sizeof (png_info));
 245 }
 246
 247 /* This is an internal routine to free any memory that the info struct is
 248  * pointing to before re-using it or freeing the struct itself.  Recall
 249  * that png_free() checks for NULL pointers for us.
 250  */
 251 void
 252 png_info_destroy(png_structp png_ptr, png_infop info_ptr)
 253 {
 254 #if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_READ_zTXt_SUPPORTED)
 255    int i;
 256
 257    png_debug(1, "in png_info_destroy\n");
 258    if (info_ptr->text != NULL)
 259    {
 260       for (i = 0; i < info_ptr->num_text; i++)
 261       {
 262          png_free(png_ptr, info_ptr->text[i].key);
 263       }
 264       png_free(png_ptr, info_ptr->text);
 265    }
 266 #endif
 267 #if defined(PNG_READ_pCAL_SUPPORTED)
 268    png_free(png_ptr, info_ptr->pcal_purpose);
 269    png_free(png_ptr, info_ptr->pcal_units);
 270    if (info_ptr->pcal_params != NULL)
 271    {
 272       for (i = 0; i < (int)info_ptr->pcal_nparams; i++)
 273       {
 274          png_free(png_ptr, info_ptr->pcal_params[i]);
 275       }
 276       png_free(png_ptr, info_ptr->pcal_params);
 277    }
 278 #endif
 279
 280    png_info_init(info_ptr);
 281 }
 282
 283 /* This function returns a pointer to the io_ptr associated with the user
 284  * functions.  The application should free any memory associated with this
 285  * pointer before png_write_destroy() or png_read_destroy() are called.
 286  */
 287 png_voidp
 288 png_get_io_ptr(png_structp png_ptr)
 289 {
 290    return (png_ptr->io_ptr);
 291 }
 292
 293 #if !defined(PNG_NO_STDIO)
 294 /* Initialize the default input/output functions for the PNG file.  If you
 295  * use your own read or write routines, you can call either png_set_read_fn()
 296  * or png_set_write_fn() instead of png_init_io().
 297  */
 298 void
 299 png_init_io(png_structp png_ptr, FILE *fp)
 300 {
 301    png_debug(1, "in png_init_io\n");
 302    png_ptr->io_ptr = (png_voidp)fp;
 303 }
 304 #endif