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/***************************************************************************** |
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* |
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* XVID MPEG-4 VIDEO CODEC |
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* - Aligned Memory Allocator - |
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* |
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* Copyright(C) 2002-2003 Edouard Gomez <ed.gomez@free.fr> |
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* |
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* This program is free software ; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License as published by |
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* the Free Software Foundation ; either version 2 of the License, or |
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* (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY ; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License |
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* along with this program ; if not, write to the Free Software |
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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* |
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* $Id$ |
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* |
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****************************************************************************/ |
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#include <stdlib.h> |
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#include <stdio.h> |
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#include "mem_align.h" |
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/***************************************************************************** |
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* xvid_malloc |
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* |
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* This function allocates 'size' bytes (usable by the user) on the heap and |
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* takes care of the requested 'alignment'. |
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* In order to align the allocated memory block, the xvid_malloc allocates |
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* 'size' bytes + 'alignment' bytes. So try to keep alignment very small |
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* when allocating small pieces of memory. |
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* |
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* NB : a block allocated by xvid_malloc _must_ be freed with xvid_free |
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* (the libc free will return an error) |
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* |
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* Returned value : - NULL on error |
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* - Pointer to the allocated aligned block |
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* |
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****************************************************************************/ |
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void * |
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xvid_malloc(size_t size, |
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uint8_t alignment) |
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{ |
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uint8_t *mem_ptr; |
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if (!alignment) { |
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/* We have not to satisfy any alignment */ |
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if ((mem_ptr = (uint8_t *) malloc(size + 1)) != NULL) { |
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/* Store (mem_ptr - "real allocated memory") in *(mem_ptr-1) */ |
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*mem_ptr = (uint8_t)1; |
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/* Return the mem_ptr pointer */ |
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return ((void *)(mem_ptr+1)); |
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} |
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} else { |
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uint8_t *tmp; |
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/* Allocate the required size memory + alignment so we |
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* can realign the data if necessary */ |
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if ((tmp = (uint8_t *) malloc(size + alignment)) != NULL) { |
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/* Align the tmp pointer */ |
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mem_ptr = |
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(uint8_t *) ((ptr_t) (tmp + alignment - 1) & |
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(~(ptr_t) (alignment - 1))); |
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/* Special case where malloc have already satisfied the alignment |
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* We must add alignment to mem_ptr because we must store |
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* (mem_ptr - tmp) in *(mem_ptr-1) |
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* If we do not add alignment to mem_ptr then *(mem_ptr-1) points |
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* to a forbidden memory space */ |
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if (mem_ptr == tmp) |
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mem_ptr += alignment; |
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/* (mem_ptr - tmp) is stored in *(mem_ptr-1) so we are able to retrieve |
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* the real malloc block allocated and free it in xvid_free */ |
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*(mem_ptr - 1) = (uint8_t) (mem_ptr - tmp); |
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/* Return the aligned pointer */ |
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return ((void *)mem_ptr); |
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} |
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} |
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return(NULL); |
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} |
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/***************************************************************************** |
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* xvid_free |
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* |
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* Free a previously 'xvid_malloc' allocated block. Does not free NULL |
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* references. |
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* |
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* Returned value : None. |
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* |
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****************************************************************************/ |
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void |
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xvid_free(void *mem_ptr) |
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{ |
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uint8_t *ptr; |
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if (mem_ptr == NULL) |
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return; |
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/* Aligned pointer */ |
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ptr = mem_ptr; |
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/* *(ptr - 1) holds the offset to the real allocated block |
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* we sub that offset os we free the real pointer */ |
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ptr -= *(ptr - 1); |
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/* Free the memory */ |
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free(ptr); |
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} |