pngmem.c File Reference

#include "pngpriv.h"

Functions
void	png_destroy_png_struct (png_structrp png_ptr)
	PNG_FUNCTION (png_voidp, PNGAPI png_calloc,(png_const_structrp png_ptr, png_alloc_size_t size), PNG_ALLOCATED)
	PNG_FUNCTION (png_voidp, png_malloc_base,(png_const_structrp png_ptr, png_alloc_size_t size), PNG_ALLOCATED)
static png_voidp	png_malloc_array_checked (png_const_structrp png_ptr, int nelements, size_t element_size)
	PNG_FUNCTION (png_voidp, png_malloc_array,(png_const_structrp png_ptr, int nelements, size_t element_size), PNG_ALLOCATED)
	PNG_FUNCTION (png_voidp, png_realloc_array,(png_const_structrp png_ptr, png_const_voidp old_array, int old_elements, int add_elements, size_t element_size), PNG_ALLOCATED)
void PNGAPI	png_free (png_const_structrp png_ptr, png_voidp ptr)
	PNG_FUNCTION (void, PNGAPI png_free_default,(png_const_structrp png_ptr, png_voidp ptr), PNG_DEPRECATED)
void PNGAPI	png_set_mem_fn (png_structrp png_ptr, png_voidp mem_ptr, png_malloc_ptr malloc_fn, png_free_ptr free_fn)
png_voidp PNGAPI	png_get_mem_ptr (png_const_structrp png_ptr)

Function Documentation

png_destroy_png_struct()

void png_destroy_png_struct

(

png_structrp

png_ptr

)

{
   if (png_ptr != NULL)
   {
      /* png_free might call png_error and may certainly call
       * png_get_mem_ptr, so fake a temporary png_struct to support this.
       */
      png_struct dummy_struct = *png_ptr;
      memset(png_ptr, 0, (sizeof *png_ptr));
      png_free(&dummy_struct, png_ptr);
 
#     ifdef PNG_SETJMP_SUPPORTED
         /* We may have a jmp_buf left to deallocate. */
         png_free_jmpbuf(&dummy_struct);
#     endif
   }
}

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PNG_FUNCTION() [1/5]

PNG_FUNCTION	(	png_voidp	,
		PNGAPI	png_calloc,
		(png_const_structrp png_ptr, png_alloc_size_t size)	,
		PNG_ALLOCATED	PNG_DEPRECATED
	)

{
   png_voidp ret;
 
   ret = png_malloc(png_ptr, size);
 
   if (ret != NULL)
      memset(ret, 0, size);
 
   return ret;
}

PNG_FUNCTION() [2/5]

PNG_FUNCTION	(	png_voidp	,
		png_malloc_base	,
		(png_const_structrp png_ptr, png_alloc_size_t size)	,
		PNG_ALLOCATED
	)

{
   /* Moved to png_malloc_base from png_malloc_default in 1.6.0; the DOS
    * allocators have also been removed in 1.6.0, so any 16-bit system now has
    * to implement a user memory handler.  This checks to be sure it isn't
    * called with big numbers.
    */
#ifndef PNG_USER_MEM_SUPPORTED
   PNG_UNUSED(png_ptr)
#endif
 
   /* Some compilers complain that this is always true.  However, it
    * can be false when integer overflow happens.
    */
   if (size > 0 && size <= PNG_SIZE_MAX
#     ifdef PNG_MAX_MALLOC_64K
         && size <= 65536U
#     endif
      )
   {
#ifdef PNG_USER_MEM_SUPPORTED
      if (png_ptr != NULL && png_ptr->malloc_fn != NULL)
         return png_ptr->malloc_fn(png_constcast(png_structrp,png_ptr), size);
 
      else
#endif
         return malloc((size_t)size); /* checked for truncation above */
   }
 
   else
      return NULL;
}

png_malloc_array_checked()

static png_voidp png_malloc_array_checked ( png_const_structrp  png_ptr, int  nelements, size_t  element_size  )

static

{
   png_alloc_size_t req = (png_alloc_size_t)nelements; /* known to be > 0 */
 
   if (req <= PNG_SIZE_MAX/element_size)
      return png_malloc_base(png_ptr, req * element_size);
 
   /* The failure case when the request is too large */
   return NULL;
}

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PNG_FUNCTION() [3/5]

PNG_FUNCTION	(	png_voidp	,
		png_malloc_array	,
		(png_const_structrp png_ptr, int nelements, size_t element_size)	,
		PNG_ALLOCATED
	)

{
   if (nelements <= 0 || element_size == 0)
      png_error(png_ptr, "internal error: array alloc");
 
   return png_malloc_array_checked(png_ptr, nelements, element_size);
}

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PNG_FUNCTION() [4/5]

PNG_FUNCTION	(	png_voidp	,
		png_realloc_array	,
		(png_const_structrp png_ptr, png_const_voidp old_array, int old_elements, int add_elements, size_t element_size)	,
		PNG_ALLOCATED
	)

{
   /* These are internal errors: */
   if (add_elements <= 0 || element_size == 0 || old_elements < 0 ||
      (old_array == NULL && old_elements > 0))
      png_error(png_ptr, "internal error: array realloc");
 
   /* Check for overflow on the elements count (so the caller does not have to
    * check.)
    */
   if (add_elements <= INT_MAX - old_elements)
   {
      png_voidp new_array = png_malloc_array_checked(png_ptr,
          old_elements+add_elements, element_size);
 
      if (new_array != NULL)
      {
         /* Because png_malloc_array worked the size calculations below cannot
          * overflow.
          */
         if (old_elements > 0)
            memcpy(new_array, old_array, element_size*(unsigned)old_elements);
 
         memset((char*)new_array + element_size*(unsigned)old_elements, 0,
             element_size*(unsigned)add_elements);
 
         return new_array;
      }
   }
 
   return NULL; /* error */
}

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png_free()

void PNGAPI png_free	(	png_const_structrp	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_constcast(png_structrp,png_ptr), ptr);
 
   else
      png_free_default(png_ptr, ptr);
}

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PNG_FUNCTION() [5/5]

PNG_FUNCTION	(	void	,
		PNGAPI	png_free_default,
		(png_const_structrp png_ptr, png_voidp ptr)	,
		PNG_DEPRECATED
	)

{
   if (png_ptr == NULL || ptr == NULL)
      return;
#endif /* USER_MEM */
 
   free(ptr);
}

png_set_mem_fn()

void PNGAPI png_set_mem_fn	(	png_structrp	png_ptr,
		png_voidp	mem_ptr,
		png_malloc_ptr	malloc_fn,
		png_free_ptr	free_fn
	)

{
   if (png_ptr != NULL)
   {
      png_ptr->mem_ptr = mem_ptr;
      png_ptr->malloc_fn = malloc_fn;
      png_ptr->free_fn = free_fn;
   }
}

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png_get_mem_ptr()

png_voidp PNGAPI png_get_mem_ptr

(

png_const_structrp

png_ptr

)

{
   if (png_ptr == NULL)
      return NULL;
 
   return png_ptr->mem_ptr;
}