pngmem.c

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            ptr = NULL;
            png_ptr->offset_table_count_free++;
            break;
         }
      }
      if (png_ptr->offset_table_count_free == png_ptr->offset_table_count)
      {
         farfree(png_ptr->offset_table);
         farfree(png_ptr->offset_table_ptr);
         png_ptr->offset_table = NULL;
         png_ptr->offset_table_ptr = NULL;
      }
   }

   if (ptr != NULL)
   {
      farfree(ptr);
   }
}

#else /* Not the Borland DOS special memory handler */

/* Allocate memory for a png_struct or a png_info.  The malloc and
   memset can be replaced by a single call to calloc() if this is thought
   to improve performance noticably. */
png_voidp /* PRIVATE */
png_create_struct(int type)
{
#ifdef PNG_USER_MEM_SUPPORTED
   return (png_create_struct_2(type, png_malloc_ptr_NULL, png_voidp_NULL));
}

/* Allocate memory for a png_struct or a png_info.  The malloc and
   memset can be replaced by a single call to calloc() if this is thought
   to improve performance noticably. */
png_voidp /* PRIVATE */
png_create_struct_2(int type, png_malloc_ptr malloc_fn, png_voidp mem_ptr)
{
#endif /* PNG_USER_MEM_SUPPORTED */
   png_size_t size;
   png_voidp struct_ptr;

   if (type == PNG_STRUCT_INFO)
      size = png_sizeof(png_info);
   else if (type == PNG_STRUCT_PNG)
      size = png_sizeof(png_struct);
   else
      return (NULL);

#ifdef PNG_USER_MEM_SUPPORTED
   if(malloc_fn != NULL)
   {
      png_struct dummy_struct;
      png_structp png_ptr = &dummy_struct;
      png_ptr->mem_ptr=mem_ptr;
      struct_ptr = (*(malloc_fn))(png_ptr, size);
      if (struct_ptr != NULL)
         png_memset(struct_ptr, 0, size);
      return (struct_ptr);
   }
#endif /* PNG_USER_MEM_SUPPORTED */

#if defined(__TURBOC__) && !defined(__FLAT__)
   struct_ptr = (png_voidp)farmalloc(size);
#else
# if defined(_MSC_VER) && defined(MAXSEG_64K)
   struct_ptr = (png_voidp)halloc(size,1);
# else
   struct_ptr = (png_voidp)malloc(size);
# endif
#endif
   if (struct_ptr != NULL)
      png_memset(struct_ptr, 0, size);

   return (struct_ptr);
}


/* Free memory allocated by a png_create_struct() call */
void /* PRIVATE */
png_destroy_struct(png_voidp struct_ptr)
{
#ifdef PNG_USER_MEM_SUPPORTED
   png_destroy_struct_2(struct_ptr, png_free_ptr_NULL, png_voidp_NULL);
}

/* Free memory allocated by a png_create_struct() call */
void /* PRIVATE */
png_destroy_struct_2(png_voidp struct_ptr, png_free_ptr free_fn,
    png_voidp mem_ptr)
{
#endif /* PNG_USER_MEM_SUPPORTED */
   if (struct_ptr != NULL)
   {
#ifdef PNG_USER_MEM_SUPPORTED
      if(free_fn != NULL)
      {
         png_struct dummy_struct;
         png_structp png_ptr = &dummy_struct;
         png_ptr->mem_ptr=mem_ptr;
         (*(free_fn))(png_ptr, struct_ptr);
         return;
      }
#endif /* PNG_USER_MEM_SUPPORTED */
#if defined(__TURBOC__) && !defined(__FLAT__)
      farfree(struct_ptr);
#else
# if defined(_MSC_VER) && defined(MAXSEG_64K)
      hfree(struct_ptr);
# else
      free(struct_ptr);
# endif
#endif
   }
}

/* Allocate memory.  For reasonable files, size should never exceed
   64K.  However, zlib may allocate more then 64K if you don't tell
   it not to.  See zconf.h and png.h for more information.  zlib does
   need to allocate exactly 64K, so whatever you call here must
   have the ability to do that. */

png_voidp PNGAPI
png_malloc(png_structp png_ptr, png_uint_32 size)
{
   png_voidp ret;

#ifdef PNG_USER_MEM_SUPPORTED
   if (png_ptr == NULL || size == 0)
      return (NULL);

   if(png_ptr->malloc_fn != NULL)
       ret = ((png_voidp)(*(png_ptr->malloc_fn))(png_ptr, (png_size_t)size));
   else
       ret = (png_malloc_default(png_ptr, size));
   if (ret == NULL && (png_ptr->flags&PNG_FLAG_MALLOC_NULL_MEM_OK) == 0)
       png_error(png_ptr, "Out of Memory!");
   return (ret);
}

png_voidp PNGAPI
png_malloc_default(png_structp png_ptr, png_uint_32 size)
{
   png_voidp ret;
#endif /* PNG_USER_MEM_SUPPORTED */

   if (png_ptr == NULL || size == 0)
      return (NULL);

#ifdef PNG_MAX_MALLOC_64K
   if (size > (png_uint_32)65536L)
   {
#ifndef PNG_USER_MEM_SUPPORTED
      if(png_ptr->flags&PNG_FLAG_MALLOC_NULL_MEM_OK) == 0)
         png_error(png_ptr, "Cannot Allocate > 64K");
      else
#endif
         return NULL;
   }
#endif

 /* Check for overflow */
#if defined(__TURBOC__) && !defined(__FLAT__)
 if (size != (unsigned long)size)
   ret = NULL;
 else
   ret = farmalloc(size);
#else
# if defined(_MSC_VER) && defined(MAXSEG_64K)
 if (size != (unsigned long)size)
   ret = NULL;
 else
   ret = halloc(size, 1);
# else
 if (size != (size_t)size)
   ret = NULL;
 else
   ret = malloc((size_t)size);
# endif
#endif

#ifndef PNG_USER_MEM_SUPPORTED
   if (ret == NULL && (png_ptr->flags&PNG_FLAG_MALLOC_NULL_MEM_OK) == 0)
      png_error(png_ptr, "Out of Memory");
#endif

   return (ret);
}

/* Free a pointer allocated by png_malloc().  If ptr is NULL, return
   without taking any action. */
void PNGAPI
png_free(png_structp png_ptr, png_voidp ptr)
{
   if (png_ptr == NULL || ptr == NULL)
      return;

#ifdef PNG_USER_MEM_SUPPORTED
   if (png_ptr->free_fn != NULL)
   {
      (*(png_ptr->free_fn))(png_ptr, ptr);
      return;
   }
   else png_free_default(png_ptr, ptr);
}
void PNGAPI
png_free_default(png_structp png_ptr, png_voidp ptr)
{
   if (png_ptr == NULL || ptr == NULL)
      return;

#endif /* PNG_USER_MEM_SUPPORTED */

#if defined(__TURBOC__) && !defined(__FLAT__)
   farfree(ptr);
#else
# if defined(_MSC_VER) && defined(MAXSEG_64K)
   hfree(ptr);
# else
   free(ptr);
# endif
#endif
}

#endif /* Not Borland DOS special memory handler */

#if defined(PNG_1_0_X)
#  define png_malloc_warn png_malloc
#else
/* This function was added at libpng version 1.2.3.  The png_malloc_warn()
 * function will set up png_malloc() to issue a png_warning and return NULL
 * instead of issuing a png_error, if it fails to allocate the requested
 * memory.
 */
png_voidp PNGAPI
png_malloc_warn(png_structp png_ptr, png_uint_32 size)
{
   png_voidp ptr;
   png_uint_32 save_flags=png_ptr->flags;

   png_ptr->flags|=PNG_FLAG_MALLOC_NULL_MEM_OK;
   ptr = (png_voidp)png_malloc((png_structp)png_ptr, size);
   png_ptr->flags=save_flags;
   return(ptr);
}
#endif

png_voidp PNGAPI
png_memcpy_check (png_structp png_ptr, png_voidp s1, png_voidp s2,
   png_uint_32 length)
{
   png_size_t size;

   size = (png_size_t)length;
   if ((png_uint_32)size != length)
      png_error(png_ptr,"Overflow in png_memcpy_check.");

   return(png_memcpy (s1, s2, size));
}

png_voidp PNGAPI
png_memset_check (png_structp png_ptr, png_voidp s1, int value,
   png_uint_32 length)
{
   png_size_t size;

   size = (png_size_t)length;
   if ((png_uint_32)size != length)
      png_error(png_ptr,"Overflow in png_memset_check.");

   return (png_memset (s1, value, size));

}

#ifdef PNG_USER_MEM_SUPPORTED
/* This function is called when the application wants to use another method
 * of allocating and freeing memory.
 */
void PNGAPI
png_set_mem_fn(png_structp png_ptr, png_voidp mem_ptr, png_malloc_ptr
  malloc_fn, png_free_ptr free_fn)
{
   png_ptr->mem_ptr = mem_ptr;
   png_ptr->malloc_fn = malloc_fn;
   png_ptr->free_fn = free_fn;
}

/* This function returns a pointer to the mem_ptr associated with the user
 * functions.  The application should free any memory associated with this
 * pointer before png_write_destroy and png_read_destroy are called.
 */
png_voidp PNGAPI
png_get_mem_ptr(png_structp png_ptr)
{
   return ((png_voidp)png_ptr->mem_ptr);
}
#endif /* PNG_USER_MEM_SUPPORTED */