/* pngmem.c - stub functions for memory allocation

 *

 * Copyright (c) 2018-2025 Cosmin Truta

 * Copyright (c) 1998-2002,2004,2006-2014,2016 Glenn Randers-Pehrson

 * Copyright (c) 1996-1997 Andreas Dilger

 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.

 *

 * This code is released under the libpng license.

 * For conditions of distribution and use, see the disclaimer

 * and license in png.h

 *

 * This file provides a location for all memory allocation.  Users who

 * need special memory handling are expected to supply replacement

 * functions for png_malloc() and png_free(), and to use

 * png_create_read_struct_2() and png_create_write_struct_2() to

 * identify the replacement functions.

 */

#include "pngpriv.h"

#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

/* Free a png_struct */

void /* PRIVATE */

png_destroy_png_struct(png_struct *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

   }

}

/* Allocate memory.  For reasonable files, size should never exceed

 * 64K.  However, zlib may allocate more than 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_FUNCTION(void *,

png_calloc,(const png_struct *png_ptr, png_alloc_size_t size),

    PNG_ALLOCATED)

{

   void *ret;

   ret = png_malloc(png_ptr, size);

   if (ret != NULL)

      memset(ret, 0, size);

   return ret;

}

/* png_malloc_base, an internal function added at libpng 1.6.0, does the work of

 * allocating memory, taking into account limits and PNG_USER_MEM_SUPPORTED.

 * Checking and error handling must happen outside this routine; it returns NULL

 * if the allocation cannot be done (for any reason.)

 */

PNG_FUNCTION(void * /* PRIVATE */,

png_malloc_base,(const png_struct *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.

    */

#  ifdef PNG_MAX_MALLOC_64K

      /* This is support for legacy systems which had segmented addressing

       * limiting the maximum allocation size to 65536.  It takes precedence

       * over PNG_SIZE_MAX which is set to 65535 on true 16-bit systems.

       *

       * TODO: libpng-1.8: finally remove both cases.

       */

      if (size > 65536U) return NULL;

#  endif

   /* This is checked too because the system malloc call below takes a (size_t).

    */

   if (size > PNG_SIZE_MAX) return NULL;

#  ifdef PNG_USER_MEM_SUPPORTED

      if (png_ptr != NULL && png_ptr->malloc_fn != NULL)

         return png_ptr->malloc_fn(png_constcast(png_struct *,png_ptr), size);

#  else

      PNG_UNUSED(png_ptr)

#  endif

   /* Use the system malloc */

   return malloc((size_t)/*SAFE*/size); /* checked for truncation above */

}

#if defined(PNG_TEXT_SUPPORTED) || defined(PNG_sPLT_SUPPORTED) ||\

   defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED)

/* This is really here only to work round a spurious warning in GCC 4.6 and 4.7

 * that arises because of the checks in png_realloc_array that are repeated in

 * png_malloc_array.

 */

static void *

png_malloc_array_checked(const png_struct *png_ptr, int nelements,

    size_t element_size)

{

   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;

}

PNG_FUNCTION(void * /* PRIVATE */,

png_malloc_array,(const png_struct *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);

}

PNG_FUNCTION(void * /* PRIVATE */,

png_realloc_array,(const png_struct *png_ptr, const void *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)

   {

      void *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 */

}

#endif /* TEXT || sPLT || STORE_UNKNOWN_CHUNKS */

/* Various functions that have different error handling are derived from this.

 * png_malloc always exists, but if PNG_USER_MEM_SUPPORTED is defined a separate

 * function png_malloc_default is also provided.

 */

PNG_FUNCTION(void *,

png_malloc,(const png_struct *png_ptr, png_alloc_size_t size),

    PNG_ALLOCATED)

{

   void *ret;

   if (png_ptr == NULL)

      return NULL;

   ret = png_malloc_base(png_ptr, size);

   if (ret == NULL)

       png_error(png_ptr, "Out of memory"); /* 'm' means png_malloc */

   return ret;

}

#ifdef PNG_USER_MEM_SUPPORTED

PNG_FUNCTION(void *,

png_malloc_default,(const png_struct *png_ptr, png_alloc_size_t size),

    PNG_ALLOCATED PNG_DEPRECATED)

{

   void *ret;

   if (png_ptr == NULL)

      return NULL;

   /* Passing 'NULL' here bypasses the application provided memory handler. */

   ret = png_malloc_base(NULL/*use malloc*/, size);

   if (ret == NULL)

      png_error(png_ptr, "Out of Memory"); /* 'M' means png_malloc_default */

   return ret;

}

#endif /* USER_MEM */

/* This function was added at libpng version 1.2.3.  The png_malloc_warn()

 * function will issue a png_warning and return NULL instead of issuing a

 * png_error, if it fails to allocate the requested memory.

 */

PNG_FUNCTION(void *,

png_malloc_warn,(const png_struct *png_ptr, png_alloc_size_t size),

    PNG_ALLOCATED)

{

   if (png_ptr != NULL)

   {

      void *ret = png_malloc_base(png_ptr, size);

      if (ret != NULL)

         return ret;

      png_warning(png_ptr, "Out of memory");

   }

   return NULL;

}

/* Free a pointer allocated by png_malloc().  If ptr is NULL, return

 * without taking any action.

 */

void

png_free(const png_struct *png_ptr, void *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_struct *,png_ptr), ptr);

   else

      png_free_default(png_ptr, ptr);

}

PNG_FUNCTION(void,

png_free_default,(const png_struct *png_ptr, void *ptr),

    PNG_DEPRECATED)

{

   if (png_ptr == NULL || ptr == NULL)

      return;

#endif /* USER_MEM */

   free(ptr);

}

#ifdef PNG_USER_MEM_SUPPORTED

/* This function is called when the application wants to use another method

 * of allocating and freeing memory.

 */

void

png_set_mem_fn(png_struct *png_ptr, void *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;

   }

}

/* 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.

 */

void *

png_get_mem_ptr(const png_struct *png_ptr)

{

   if (png_ptr == NULL)

      return NULL;

   return png_ptr->mem_ptr;

}

#endif /* USER_MEM */

#endif /* READ || WRITE */