FFmpeg/libavutil/mem.h

/*
 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of Libav.
 *
 * Libav is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Libav is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * memory handling functions
 */

#ifndef AVUTIL_MEM_H
#define AVUTIL_MEM_H

#include <limits.h>
#include <stdint.h>

#include "attributes.h"
#include "avutil.h"

/**
 * @addtogroup lavu_mem
 * @{
 */


#if defined(__ICC) && __ICC < 1200 || defined(__SUNPRO_C)
    #define DECLARE_ALIGNED(n,t,v)      t __attribute__ ((aligned (n))) v
    #define DECLARE_ASM_CONST(n,t,v)    const t __attribute__ ((aligned (n))) v
#elif defined(__GNUC__) || defined(__clang__)
    #define DECLARE_ALIGNED(n,t,v)      t __attribute__ ((aligned (n))) v
    #define DECLARE_ASM_CONST(n,t,v)    static const t av_used __attribute__ ((aligned (n))) v
#elif defined(_MSC_VER)
    #define DECLARE_ALIGNED(n,t,v)      __declspec(align(n)) t v
    #define DECLARE_ASM_CONST(n,t,v)    __declspec(align(n)) static const t v
#else
    #define DECLARE_ALIGNED(n,t,v)      t v
    #define DECLARE_ASM_CONST(n,t,v)    static const t v
#endif

#if AV_GCC_VERSION_AT_LEAST(3,1)
    #define av_malloc_attrib __attribute__((__malloc__))
#else
    #define av_malloc_attrib
#endif

#if AV_GCC_VERSION_AT_LEAST(4,3)
    #define av_alloc_size(...) __attribute__((alloc_size(__VA_ARGS__)))
#else
    #define av_alloc_size(...)
#endif

/**
 * Allocate a block of size bytes with alignment suitable for all
 * memory accesses (including vectors if available on the CPU).
 * @param size Size in bytes for the memory block to be allocated.
 * @return Pointer to the allocated block, NULL if the block cannot
 * be allocated.
 * @see av_mallocz()
 */
void *av_malloc(size_t size) av_malloc_attrib av_alloc_size(1);

/**
 * Allocate a block of size * nmemb bytes with av_malloc().
 * @param nmemb Number of elements
 * @param size Size of the single element
 * @return Pointer to the allocated block, NULL if the block cannot
 * be allocated.
 * @see av_malloc()
 */
av_alloc_size(1, 2) void *av_malloc_array(size_t nmemb, size_t size);

/**
 * Allocate or reallocate a block of memory.
 * If ptr is NULL and size > 0, allocate a new block. If
 * size is zero, free the memory block pointed to by ptr.
 * @param ptr Pointer to a memory block already allocated with
 * av_realloc() or NULL.
 * @param size Size in bytes of the memory block to be allocated or
 * reallocated.
 * @return Pointer to a newly-reallocated block or NULL if the block
 * cannot be reallocated or the function is used to free the memory block.
 * @warning Pointers originating from the av_malloc() family of functions must
 *          not be passed to av_realloc(). The former can be implemented using
 *          memalign() (or other functions), and there is no guarantee that
 *          pointers from such functions can be passed to realloc() at all.
 *          The situation is undefined according to POSIX and may crash with
 *          some libc implementations.
 * @see av_fast_realloc()
 */
void *av_realloc(void *ptr, size_t size) av_alloc_size(2);

/**
 * Allocate or reallocate a block of memory.
 * If *ptr is NULL and size > 0, allocate a new block. If
 * size is zero, free the memory block pointed to by ptr.
 * @param   ptr Pointer to a pointer to a memory block already allocated
 *          with av_realloc(), or pointer to a pointer to NULL.
 *          The pointer is updated on success, or freed on failure.
 * @param   size Size in bytes for the memory block to be allocated or
 *          reallocated
 * @return  Zero on success, an AVERROR error code on failure.
 * @warning Pointers originating from the av_malloc() family of functions must
 *          not be passed to av_reallocp(). The former can be implemented using
 *          memalign() (or other functions), and there is no guarantee that
 *          pointers from such functions can be passed to realloc() at all.
 *          The situation is undefined according to POSIX and may crash with
 *          some libc implementations.
 */
int av_reallocp(void *ptr, size_t size);

/**
 * Allocate or reallocate an array.
 * If ptr is NULL and nmemb > 0, allocate a new block. If
 * nmemb is zero, free the memory block pointed to by ptr.
 * @param ptr Pointer to a memory block already allocated with
 * av_realloc() or NULL.
 * @param nmemb Number of elements
 * @param size Size of the single element
 * @return Pointer to a newly-reallocated block or NULL if the block
 * cannot be reallocated or the function is used to free the memory block.
 * @warning Pointers originating from the av_malloc() family of functions must
 *          not be passed to av_realloc(). The former can be implemented using
 *          memalign() (or other functions), and there is no guarantee that
 *          pointers from such functions can be passed to realloc() at all.
 *          The situation is undefined according to POSIX and may crash with
 *          some libc implementations.
 */
av_alloc_size(2, 3) void *av_realloc_array(void *ptr, size_t nmemb, size_t size);

/**
 * Allocate or reallocate an array through a pointer to a pointer.
 * If *ptr is NULL and nmemb > 0, allocate a new block. If
 * nmemb is zero, free the memory block pointed to by ptr.
 * @param ptr Pointer to a pointer to a memory block already allocated
 * with av_realloc(), or pointer to a pointer to NULL.
 * The pointer is updated on success, or freed on failure.
 * @param nmemb Number of elements
 * @param size Size of the single element
 * @return Zero on success, an AVERROR error code on failure.
 * @warning Pointers originating from the av_malloc() family of functions must
 *          not be passed to av_realloc(). The former can be implemented using
 *          memalign() (or other functions), and there is no guarantee that
 *          pointers from such functions can be passed to realloc() at all.
 *          The situation is undefined according to POSIX and may crash with
 *          some libc implementations.
 */
av_alloc_size(2, 3) int av_reallocp_array(void *ptr, size_t nmemb, size_t size);

/**
 * Free a memory block which has been allocated with av_malloc(z)() or
 * av_realloc().
 * @param ptr Pointer to the memory block which should be freed.
 * @note ptr = NULL is explicitly allowed.
 * @note It is recommended that you use av_freep() instead.
 * @see av_freep()
 */
void av_free(void *ptr);

/**
 * Allocate a block of size bytes with alignment suitable for all
 * memory accesses (including vectors if available on the CPU) and
 * zero all the bytes of the block.
 * @param size Size in bytes for the memory block to be allocated.
 * @return Pointer to the allocated block, NULL if it cannot be allocated.
 * @see av_malloc()
 */
void *av_mallocz(size_t size) av_malloc_attrib av_alloc_size(1);

/**
 * Allocate a block of size * nmemb bytes with av_mallocz().
 * @param nmemb Number of elements
 * @param size Size of the single element
 * @return Pointer to the allocated block, NULL if the block cannot
 * be allocated.
 * @see av_mallocz()
 * @see av_malloc_array()
 */
av_alloc_size(1, 2) void *av_mallocz_array(size_t nmemb, size_t size);

/**
 * Duplicate the string s.
 * @param s string to be duplicated
 * @return Pointer to a newly-allocated string containing a
 * copy of s or NULL if the string cannot be allocated.
 */
char *av_strdup(const char *s) av_malloc_attrib;

/**
 * Duplicate a substring of the string s.
 * @param s string to be duplicated
 * @param len the maximum length of the resulting string (not counting the
 *            terminating byte).
 * @return Pointer to a newly-allocated string containing a
 * copy of s or NULL if the string cannot be allocated.
 */
char *av_strndup(const char *s, size_t len) av_malloc_attrib;

/**
 * Free a memory block which has been allocated with av_malloc(z)() or
 * av_realloc() and set the pointer pointing to it to NULL.
 * @param ptr Pointer to the pointer to the memory block which should
 * be freed.
 * @see av_free()
 */
void av_freep(void *ptr);

/**
 * deliberately overlapping memcpy implementation
 * @param dst destination buffer
 * @param back how many bytes back we start (the initial size of the overlapping window)
 * @param cnt number of bytes to copy, must be >= 0
 *
 * cnt > back is valid, this will copy the bytes we just copied,
 * thus creating a repeating pattern with a period length of back.
 */
void av_memcpy_backptr(uint8_t *dst, int back, int cnt);

/**
 * Reallocate the given block if it is not large enough, otherwise do nothing.
 *
 * @see av_realloc
 */
void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size);

/**
 * Allocate a buffer, reusing the given one if large enough.
 *
 * Contrary to av_fast_realloc the current buffer contents might not be
 * preserved and on error the old buffer is freed, thus no special
 * handling to avoid memleaks is necessary.
 *
 * @param ptr pointer to pointer to already allocated buffer, overwritten with pointer to new buffer
 * @param size size of the buffer *ptr points to
 * @param min_size minimum size of *ptr buffer after returning, *ptr will be NULL and
 *                 *size 0 if an error occurred.
 */
void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size);

/**
 * @}
 */

#endif /* AVUTIL_MEM_H */