基于Linux的ffmepg decoder

#include <stdlib.h>
#include <stdio.h>
#include "mem_align.h"
#include "../../faraday_mpeg4_common/dev_mem.h"


void *
xvid_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 = 0;

			/* Return the mem_ptr pointer */
			return (void *) ++mem_ptr;

		}

	} 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 xvid_free
			 */
			*(mem_ptr - 1) = (uint8_t) (mem_ptr - tmp);

			/* Return the aligned pointer */
			return (void *) mem_ptr;

		}
	}

	return NULL;

}

/*****************************************************************************
 * xvid_free
 *
 * Free a previously 'xvid_malloc' allocated block. Does not free NULL
 * references.
 *
 * Returned value : None.
 *
 ****************************************************************************/

void
xvid_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));

}

void *
xvid_dma_malloc(size_t size,
			uint8_t alignment, void ** phy)
{
	uint8_t *virt_mem_ptr;
	uint32_t tsize;
	if (!alignment) {
	    tsize = size + 5 + CACHE_LINE;
	   	if (dma_malloc(tsize, phy, (void **)&virt_mem_ptr) == 0) {
			/* Store (mem_ptr - "real allocated memory") in *(mem_ptr-5) */
			*virt_mem_ptr ++ = 5;
			/* Store (malloc size) in *(mem_ptr-4) ~ *(mem_ptr-1)*/
			*virt_mem_ptr ++ = (tsize >> 24) & 0xFF;
			*virt_mem_ptr ++ = (tsize >> 16) & 0xFF;
			*virt_mem_ptr ++ = (tsize >> 8) & 0xFF;
			*virt_mem_ptr ++ = (tsize >> 0) & 0xFF;
			*(uint32_t *)phy += 5;
			/* Return the mem_ptr pointer */
			return (void *) virt_mem_ptr;
		}
	} else {
		uint8_t *tmp;

		/*
		 * Allocate the required size memory + alignment so we
		 * can realign the data if necessary
		 */

	    tsize = size + alignment + 4 + CACHE_LINE;
	   	if (dma_malloc(size + alignment + CACHE_LINE, phy, (void **)&tmp) == 0) {

			/* Align the tmp pointer */
			virt_mem_ptr =
				(uint8_t *) ((ptr_t) (tmp + 4 + 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
			 */
			while ((virt_mem_ptr - tmp) < 4)
				virt_mem_ptr += alignment;
			*phy += (virt_mem_ptr - tmp);

			/*
			 * (mem_ptr - tmp) is stored in *(mem_ptr-1) so we are able to retrieve
			 * the real malloc block allocated and free it in xvid_free
			 */
			*(virt_mem_ptr - 5) = (uint8_t) (virt_mem_ptr - tmp);
			*(virt_mem_ptr - 4) = (tsize >> 24) & 0xFF;
			*(virt_mem_ptr - 3) = (tsize >> 16) & 0xFF;
			*(virt_mem_ptr - 2) = (tsize >> 8) & 0xFF;
			*(virt_mem_ptr - 1) = (tsize >> 0) & 0xFF;

			/* Return the aligned pointer */
			return (void *) virt_mem_ptr;

		}
	}

	return NULL;

}

/*****************************************************************************
 * xvid_free
 *
 * Free a previously 'xvid_malloc' allocated block. Does not free NULL
 * references.
 *
 * Returned value : None.
 *
 ****************************************************************************/

void
xvid_dma_free(void *virt_mem_ptr, void * phy_ptr)
{
	uint32_t tsize;

	/* *(virt_mem_ptr - 1) give us the offset to the real malloc block */
	if (virt_mem_ptr) {

	    tsize = (*(uint8_t *)(virt_mem_ptr - 4) << 24) +
	    	  	(*(uint8_t *)(virt_mem_ptr - 3) << 16) +
	    	  	(*(uint8_t *)(virt_mem_ptr - 2) << 8) +
	    	  	(*(uint8_t *)(virt_mem_ptr - 1) << 0);
		dma_free(tsize, (void *)((uint32_t) virt_mem_ptr - *((uint8_t *) virt_mem_ptr - 5)), phy_ptr);
 	}
}