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/***************************************************************************** * * XVID MPEG-4 VIDEO CODEC * - Aligned memory allocator - * * Copyright(C) 2002 Michael Militzer <isibaar@xvid.org> * 2002 Edouard Gomez * * This file is part of XviD, a free MPEG-4 video encoder/decoder * * XviD is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program 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 General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * * Under section 8 of the GNU General Public License, the copyright * holders of XVID explicitly forbid distribution in the following * countries: * * - Japan * - United States of America * * Linking XviD statically or dynamically with other modules is making a * combined work based on XviD. Thus, the terms and conditions of the * GNU General Public License cover the whole combination. * * As a special exception, the copyright holders of XviD give you * permission to link XviD with independent modules that communicate with * XviD solely through the VFW1.1 and DShow interfaces, regardless of the * license terms of these independent modules, and to copy and distribute * the resulting combined work under terms of your choice, provided that * every copy of the combined work is accompanied by a complete copy of * the source code of XviD (the version of XviD used to produce the * combined work), being distributed under the terms of the GNU General * Public License plus this exception. An independent module is a module * which is not derived from or based on XviD. * * Note that people who make modified versions of XviD are not obligated * to grant this special exception for their modified versions; it is * their choice whether to do so. The GNU General Public License gives * permission to release a modified version without this exception; this * exception also makes it possible to release a modified version which * carries forward this exception. * * $Id: mem_align.c,v 1.11 2002/11/17 00:51:11 edgomez Exp $ * ****************************************************************************/ #include <stdlib.h> #include <stdio.h> #include "mem_align.h" /***************************************************************************** * xvid_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 xvid_malloc allocates * 'size' bytes + 'alignment' bytes. So try to keep alignment very small * when allocating small pieces of memory. * * NB : a block allocated by xvid_malloc _must_ be freed with xvid_free * (the libc free will return an error) * * Returned value : - NULL on error * - Pointer to the allocated aligned block * ****************************************************************************/ 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)); }
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