libpng/png.c

/* png.c - location for general purpose libpng functions
 *
 * libpng version 1.0.6d - April 7, 2000
 * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
 * Copyright (c) 1996, 1997 Andreas Dilger
 * Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson
 *
 */

#define PNG_INTERNAL
#define PNG_NO_EXTERN
#include <assert.h>
#include "png.h"

/* Generate a compiler error if there is an old png.h in the search path. */
typedef version_1_0_6d Your_png_h_is_not_version_1_0_6d;

/* Version information for C files.  This had better match the version
 * string defined in png.h.  */

#ifdef PNG_USE_GLOBAL_ARRAYS
/* png_libpng_ver was changed to a function in version 1.0.5c */
char png_libpng_ver[12] = "1.0.6d";

/* png_sig was changed to a function in version 1.0.5c */
/* Place to hold the signature string for a PNG file. */
png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};

/* Invoke global declarations for constant strings for known chunk types */
PNG_IHDR;
PNG_IDAT;
PNG_IEND;
PNG_PLTE;
PNG_bKGD;
PNG_cHRM;
PNG_gAMA;
PNG_hIST;
PNG_iCCP;
PNG_iTXt;
PNG_oFFs;
PNG_pCAL;
PNG_sCAL;
PNG_pHYs;
PNG_sBIT;
PNG_sPLT;
PNG_sRGB;
PNG_tEXt;
PNG_tIME;
PNG_tRNS;
PNG_zTXt;

/* arrays to facilitate easy interlacing - use pass (0 - 6) as index */

/* start of interlace block */
int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};

/* offset to next interlace block */
int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};

/* start of interlace block in the y direction */
int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};

/* offset to next interlace block in the y direction */
int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};

/* width of interlace block (used in assembler routines only) */
#ifdef PNG_HAVE_ASSEMBLER_COMBINE_ROW
int FARDATA png_pass_width[] = {8, 4, 4, 2, 2, 1, 1};
#endif

/* Height of interlace block.  This is not currently used - if you need
 * it, uncomment it here and in png.h
int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
*/

/* Mask to determine which pixels are valid in a pass */
int FARDATA png_pass_mask[] = {0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff};

/* Mask to determine which pixels to overwrite while displaying */
int FARDATA png_pass_dsp_mask[] = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff};

#endif

/* Tells libpng that we have already handled the first "num_bytes" bytes
 * of the PNG file signature.  If the PNG data is embedded into another
 * stream we can set num_bytes = 8 so that libpng will not attempt to read
 * or write any of the magic bytes before it starts on the IHDR.
 */

void
png_set_sig_bytes(png_structp png_ptr, int num_bytes)
{
   png_debug(1, "in png_set_sig_bytes\n");
   if (num_bytes > 8)
      png_error(png_ptr, "Too many bytes for PNG signature.");

   png_ptr->sig_bytes = (png_byte)(num_bytes < 0 ? 0 : num_bytes);
}

/* Checks whether the supplied bytes match the PNG signature.  We allow
 * checking less than the full 8-byte signature so that those apps that
 * already read the first few bytes of a file to determine the file type
 * can simply check the remaining bytes for extra assurance.  Returns
 * an integer less than, equal to, or greater than zero if sig is found,
 * respectively, to be less than, to match, or be greater than the correct
 * PNG signature (this is the same behaviour as strcmp, memcmp, etc).
 */
int
png_sig_cmp(png_bytep sig, png_size_t start, png_size_t num_to_check)
{
   png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
   if (num_to_check > 8)
      num_to_check = 8;
   else if (num_to_check < 1)
      return (0);

   if (start > 7)
      return (0);

   if (start + num_to_check > 8)
      num_to_check = 8 - start;

   return ((int)(png_memcmp(&sig[start], &png_signature[start], num_to_check)));
}

/* (Obsolete) function to check signature bytes.  It does not allow one
 * to check a partial signature.  This function might be removed in the
 * future - use png_sig_cmp().  Returns true (nonzero) if the file is a PNG.
 */
int
png_check_sig(png_bytep sig, int num)
{
  return ((int)!png_sig_cmp(sig, (png_size_t)0, (png_size_t)num));
}

/* Function to allocate memory for zlib. */
voidpf
png_zalloc(voidpf png_ptr, uInt items, uInt size)
{
   png_uint_32 num_bytes = (png_uint_32)items * size;
   png_voidp ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes);

   if (num_bytes > (png_uint_32)0x8000L)
   {
      png_memset(ptr, 0, (png_size_t)0x8000L);
      png_memset((png_bytep)ptr + (png_size_t)0x8000L, 0,
         (png_size_t)(num_bytes - (png_uint_32)0x8000L));
   }
   else
   {
      png_memset(ptr, 0, (png_size_t)num_bytes);
   }
   return ((voidpf)ptr);
}

/* function to free memory for zlib */
void
png_zfree(voidpf png_ptr, voidpf ptr)
{
   png_free((png_structp)png_ptr, (png_voidp)ptr);
}

/* Reset the CRC variable to 32 bits of 1's.  Care must be taken
 * in case CRC is > 32 bits to leave the top bits 0.
 */
void
png_reset_crc(png_structp png_ptr)
{
   png_ptr->crc = crc32(0, Z_NULL, 0);
}

/* Calculate the CRC over a section of data.  We can only pass as
 * much data to this routine as the largest single buffer size.  We
 * also check that this data will actually be used before going to the
 * trouble of calculating it.
 */
void
png_calculate_crc(png_structp png_ptr, png_bytep ptr, png_size_t length)
{
   int need_crc = 1;

   if (png_ptr->chunk_name[0] & 0x20)                     /* ancillary */
   {
      if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
          (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
         need_crc = 0;
   }
   else                                                    /* critical */
   {
      if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)
         need_crc = 0;
   }

   if (need_crc)
      png_ptr->crc = crc32(png_ptr->crc, ptr, (uInt)length);
}

/* Allocate the memory for an info_struct for the application.  We don't
 * really need the png_ptr, but it could potentially be useful in the
 * future.  This should be used in favour of malloc(sizeof(png_info))
 * and png_info_init() so that applications that want to use a shared
 * libpng don't have to be recompiled if png_info changes size.
 */
png_infop
png_create_info_struct(png_structp png_ptr)
{
   png_infop info_ptr;

   png_debug(1, "in png_create_info_struct\n");
   if(png_ptr == NULL) return (NULL);
#ifdef PNG_USER_MEM_SUPPORTED
   if ((info_ptr = (png_infop)png_create_struct_2(PNG_STRUCT_INFO,
      png_ptr->malloc_fn)) != NULL)
#else
   if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL)
#endif
   {
      png_info_init(info_ptr);
   }

   return (info_ptr);
}

/* This function frees the memory associated with a single info struct.
 * Normally, one would use either png_destroy_read_struct() or
 * png_destroy_write_struct() to free an info struct, but this may be
 * useful for some applications.
 */
void
png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr)
{
   png_infop info_ptr = NULL;

   png_debug(1, "in png_destroy_info_struct\n");
   if (info_ptr_ptr != NULL)
      info_ptr = *info_ptr_ptr;

   if (info_ptr != NULL)
   {
      png_info_destroy(png_ptr, info_ptr);

#ifdef PNG_USER_MEM_SUPPORTED
      png_destroy_struct_2((png_voidp)info_ptr, png_ptr->free_fn);
#else
      png_destroy_struct((png_voidp)info_ptr);
#endif
      *info_ptr_ptr = (png_infop)NULL;
   }
}

/* Initialize the info structure.  This is now an internal function (0.89)
 * and applications using it are urged to use png_create_info_struct()
 * instead.
 */
void
png_info_init(png_infop info_ptr)
{
   png_debug(1, "in png_info_init\n");
   /* set everything to 0 */
   png_memset(info_ptr, 0, sizeof (png_info));
}

void
png_free_data(png_structp png_ptr, png_infop info_ptr, png_uint_32 mask, int num)
{
   if (png_ptr == NULL || info_ptr == NULL)
      return;

#if defined(PNG_TEXT_SUPPORTED)
/* free text item num or (if num == -1) all text items */
if (mask & info_ptr->free_me & PNG_FREE_TEXT)
{
   if (num != -1)
   {
     if (info_ptr->text[num].key)
     {
         png_free(png_ptr, info_ptr->text[num].key);
         info_ptr->text[num].key = NULL;
     }
   }
   else if (info_ptr->text != NULL)
   {
     int i;
     for (i = 0; i < info_ptr->num_text; i++)
         png_free_data(png_ptr, info_ptr, PNG_FREE_TEXT, i);
     png_free(png_ptr, info_ptr->text);
     info_ptr->text = NULL;
     info_ptr->num_text=0;
   }
}
#endif

#if defined(PNG_tRNS_SUPPORTED)
/* free any tRNS entry */
if (mask & PNG_FREE_TRNS)
{
   if (info_ptr->valid & PNG_INFO_tRNS)
   {
       if (info_ptr->free_me & PNG_FREE_TRNS)
         png_free(png_ptr, info_ptr->trans);
       info_ptr->valid &= ~PNG_INFO_tRNS;
   }
}
#endif

#if defined(PNG_sCAL_SUPPORTED)
/* free any sCAL entry */
if (mask & PNG_FREE_SCAL)
{
   if (info_ptr->valid & PNG_INFO_sCAL)
   {
#if defined(PNG_FIXED_POINT_SUPPORTED) && !defined(PNG_FLOATING_POINT_SUPPORTED)
       png_free(png_ptr, info_ptr->scal_s_width);
       png_free(png_ptr, info_ptr->scal_s_height);
#endif
          info_ptr->valid &= ~PNG_INFO_sCAL;
   }
}
#endif

#if defined(PNG_pCAL_SUPPORTED)
/* free any pCAL entry */
if (mask & PNG_FREE_PCAL)
{
   if (info_ptr->valid & PNG_INFO_pCAL)
   {
       png_free(png_ptr, info_ptr->pcal_purpose);
       png_free(png_ptr, info_ptr->pcal_units);
       if (info_ptr->pcal_params != NULL)
       {
           int i;
           for (i = 0; i < (int)info_ptr->pcal_nparams; i++)
             {
             png_free(png_ptr, info_ptr->pcal_params[i]);
             }
           png_free(png_ptr, info_ptr->pcal_params);
       }
       info_ptr->valid &= ~PNG_INFO_pCAL;
   }
}
#endif

#if defined(PNG_iCCP_SUPPORTED)
/* free any iCCP entry */
if (mask & PNG_FREE_ICCP)
{
   if (info_ptr->valid & PNG_INFO_iCCP)
   {
       if (info_ptr->free_me & PNG_FREE_ICCP)
       {
         png_free(png_ptr, info_ptr->iccp_name);
         png_free(png_ptr, info_ptr->iccp_profile);
       }
       info_ptr->valid &= ~PNG_INFO_iCCP;
   }
}
#endif

#if defined(PNG_sPLT_SUPPORTED)
/* free a given sPLT entry, or (if num == -1) all sPLT entries */
if (mask & PNG_FREE_SPLT)
{
   if (num != -1)
   {
       png_free(png_ptr, info_ptr->splt_palettes[num].name);
       png_free(png_ptr, info_ptr->splt_palettes[num].entries);
       info_ptr->valid &= ~PNG_INFO_sPLT;
   }
   else
   {
       if(info_ptr->splt_palettes_num)
       {
         int i;
         for (i = 0; i < (int)info_ptr->splt_palettes_num; i++)
            png_free_data(png_ptr, info_ptr, PNG_FREE_SPLT, i);

         png_free(png_ptr, info_ptr->splt_palettes);
         info_ptr->splt_palettes_num = 0;
       }
   }
}
#endif

#if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
if (mask & PNG_FREE_UNKN)
{
   if (num != -1)
   {
       png_free(png_ptr, info_ptr->unknown_chunks[num].data);
       info_ptr->unknown_chunks[num].data = NULL;
   }
   else
   {
       int i;

       if(info_ptr->unknown_chunks_num)
       {
         for (i = 0; i < (int)info_ptr->unknown_chunks_num; i++)
            png_free_data(png_ptr, info_ptr, PNG_FREE_UNKN, i);

         png_free(png_ptr, info_ptr->unknown_chunks);
         info_ptr->unknown_chunks_num = 0;
       }
   }
}
#endif

#if defined(PNG_hIST_SUPPORTED)
/* free any hIST entry */
if (mask & PNG_FREE_HIST)
{
   if (info_ptr->valid & PNG_INFO_hIST)
   {
       if (info_ptr->free_me & PNG_FREE_HIST)
         png_free(png_ptr, info_ptr->hist);
       info_ptr->valid &= ~PNG_INFO_hIST;
   }
}
#endif

/* free any PLTE entry that was internally allocated */
if (mask & PNG_FREE_PLTE)
{
   if (info_ptr->valid & PNG_INFO_PLTE)
   {
       if (info_ptr->free_me & PNG_FREE_PLTE)
          png_zfree(png_ptr, info_ptr->palette);
       info_ptr->valid &= ~(PNG_INFO_PLTE);
       info_ptr->num_palette = 0;
   }
}

#if defined(PNG_INFO_IMAGE_SUPPORTED)
/* free any image bits attached to the info structure */
if (mask & PNG_FREE_ROWS)
{
   if (info_ptr->free_me & PNG_FREE_ROWS)
   {
       int row;

       for (row = 0; row < (int)info_ptr->height; row++)
          png_free(png_ptr, info_ptr->row_pointers[row]);
       png_free(png_ptr, info_ptr->row_pointers);
   }
}
#endif
   if(num == -1)
     info_ptr->free_me &= ~mask;
}

/* This is an internal routine to free any memory that the info struct is
 * pointing to before re-using it or freeing the struct itself.  Recall
 * that png_free() checks for NULL pointers for us.
 */
void
png_info_destroy(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_info_destroy\n");

   png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);
    
#if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
   if (png_ptr->num_chunk_list)
   {
       png_free(png_ptr, png_ptr->chunk_list);
       png_ptr->num_chunk_list=0;
   }
#endif

   png_info_init(info_ptr);
}

/* This function returns a pointer to the io_ptr associated with the user
 * functions.  The application should free any memory associated with this
 * pointer before png_write_destroy() or png_read_destroy() are called.
 */
png_voidp
png_get_io_ptr(png_structp png_ptr)
{
   return (png_ptr->io_ptr);
}

#if !defined(PNG_NO_STDIO)
/* Initialize the default input/output functions for the PNG file.  If you
 * use your own read or write routines, you can call either png_set_read_fn()
 * or png_set_write_fn() instead of png_init_io().
 */
void
png_init_io(png_structp png_ptr, FILE *fp)
{
   png_debug(1, "in png_init_io\n");
   png_ptr->io_ptr = (png_voidp)fp;
}
#endif

#if defined(PNG_TIME_RFC1123_SUPPORTED)
/* Convert the supplied time into an RFC 1123 string suitable for use in
 * a "Creation Time" or other text-based time string.
 */
png_charp
png_convert_to_rfc1123(png_structp png_ptr, png_timep ptime)
{
   static PNG_CONST char short_months[12][4] =
        {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
         "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};

   if (png_ptr->time_buffer == NULL)
   {
      png_ptr->time_buffer = (png_charp)png_malloc(png_ptr, (png_uint_32)(29*
         sizeof(char)));
   }

#ifdef USE_FAR_KEYWORD
   {
      char near_time_buf[29];
      sprintf(near_time_buf, "%d %s %d %02d:%02d:%02d +0000",
               ptime->day % 32, short_months[(ptime->month - 1) % 12],
               ptime->year, ptime->hour % 24, ptime->minute % 60,
               ptime->second % 61);
      png_memcpy(png_ptr->time_buffer, near_time_buf,
      29*sizeof(char));
   }
#else
   sprintf(png_ptr->time_buffer, "%d %s %d %02d:%02d:%02d +0000",
               ptime->day % 32, short_months[(ptime->month - 1) % 12],
               ptime->year, ptime->hour % 24, ptime->minute % 60,
               ptime->second % 61);
#endif
   return ((png_charp)png_ptr->time_buffer);
}
#endif /* PNG_TIME_RFC1123_SUPPORTED */

#if 0
/* Signature string for a PNG file. */
png_bytep
png_sig_bytes(void)
{
   return ((png_bytep)"\211\120\116\107\015\012\032\012");
}
#endif

png_charp
png_get_copyright(png_structp png_ptr)
{
   if (png_ptr != NULL || png_ptr == NULL)  /* silence compiler warning */
   return ("\n libpng version 1.0.6d - April 7, 2000\n\
   Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.\n\
   Copyright (c) 1996, 1997 Andreas Dilger\n\
   Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson\n");
   return ("");
}

/* The following return the library version as a short string in the
 * format 1.0.0 through 99.99.99zz.  To get the version of *.h files used
 * with your application, print out PNG_LIBPNG_VER_STRING, which is defined
 * in png.h.
 */

png_charp
png_get_libpng_ver(png_structp png_ptr)
{
   /* Version of *.c files used when building libpng */
   if(png_ptr != NULL) /* silence compiler warning about unused png_ptr */
      return("1.0.6d");
   return("1.0.6d");
}

png_charp
png_get_header_ver(png_structp png_ptr)
{
   /* Version of *.h files used when building libpng */
   if(png_ptr != NULL) /* silence compiler warning about unused png_ptr */
      return(PNG_LIBPNG_VER_STRING);
   return(PNG_LIBPNG_VER_STRING);
}

png_charp
png_get_header_version(png_structp png_ptr)
{
   /* Returns longer string containing both version and date */
   if(png_ptr != NULL) /* silence compiler warning about unused png_ptr */
      return(PNG_HEADER_VERSION_STRING);
   return(PNG_HEADER_VERSION_STRING);
}

#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
int
png_handle_as_unknown(png_structp png_ptr, png_bytep chunk_name)
{
   /* check chunk_name and return "keep" value if it's on the list, else 0 */
   int i;
   png_bytep p;
   if((png_ptr == NULL && chunk_name == NULL) || png_ptr->num_chunk_list<=0)
      return 0;
   p=png_ptr->chunk_list+png_ptr->num_chunk_list*5-5;
   for (i = png_ptr->num_chunk_list; i; i--, p-=5)
      if (!png_memcmp(chunk_name, p, 4))
        return ((int)*(p+4));
   return 0;
}
#endif