?? mem_align.c
字號:
// --------------------------------------------------------------------// just rename xvid_malloc, xvid_free in xvid to mp4_malloc, mp4_free// --------------------------------------------------------------------#include <stdlib.h>#include <stdio.h>#include "../portab.h"#include "mem_align.h"#if defined(MP4LIB_MASTER) || defined(MP4LIB_HOST)/***************************************************************************** * mp4_malloc * * This function allocates 'size' bytes (usable by the user) on the heap and * takes care of the requested 'alignment'. * In order to align the allocated memory block, the mp4_malloc allocates * 'size' bytes + 'alignment' bytes. So try to keep alignment very small * when allocating small pieces of memory. * * NB : a block allocated by mp4_malloc _must_ be freed with mp4_free * (the libc free will return an error) * * Returned value : - NULL on error * - Pointer to the allocated aligned block * ****************************************************************************/void *mp4_malloc(size_t size, uint8_t alignment){ uint8_t *mem_ptr; if (!alignment) { /* We have not to satisfy any alignment */ if ((mem_ptr = (uint8_t *) MALLOC(size + 1)) != NULL) { /* Store (mem_ptr - "real allocated memory") in *(mem_ptr-1) */ *mem_ptr = 1; /* Return the mem_ptr pointer */ return (void *)(mem_ptr+1); } } else { uint8_t *tmp; /* * Allocate the required size memory + alignment so we * can realign the data if necessary */ if ((tmp = (uint8_t *) MALLOC(size + alignment)) != NULL) { /* Align the tmp pointer */ mem_ptr = (uint8_t *) ((ptr_t) (tmp + alignment - 1) & (~(ptr_t) (alignment - 1))); /* * Special case where malloc have already satisfied the alignment * We must add alignment to mem_ptr because we must store * (mem_ptr - tmp) in *(mem_ptr-1) * If we do not add alignment to mem_ptr then *(mem_ptr-1) points * to a forbidden memory space */ if (mem_ptr == tmp) mem_ptr += alignment; /* * (mem_ptr - tmp) is stored in *(mem_ptr-1) so we are able to retrieve * the real malloc block allocated and free it in mp4_free */ *(mem_ptr - 1) = (uint8_t) (mem_ptr - tmp); /* Return the aligned pointer */ return (void *) mem_ptr; } } return NULL;}/***************************************************************************** * mp4_free * * Free a previously 'mp4_malloc' allocated block. Does not free NULL * references. * * Returned value : None. * ****************************************************************************/voidmp4_free(void *mem_ptr){ /* *(mem_ptr - 1) give us the offset to the real malloc block */ if (mem_ptr) FREE((uint8_t *) mem_ptr - *((uint8_t *) mem_ptr - 1));}#endif
?? 快捷鍵說明
復制代碼
Ctrl + C
搜索代碼
Ctrl + F
全屏模式
F11
切換主題
Ctrl + Shift + D
顯示快捷鍵
?
增大字號
Ctrl + =
減小字號
Ctrl + -