BLI_memarena.c

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/*
 * $Id: BLI_memarena.c 35246 2011-02-27 20:37:56Z jesterking $
 *
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): none yet.
 *
 * ***** END GPL LICENSE BLOCK *****
 * Efficient memory allocation for lots of similar small chunks.
 */

#include "MEM_guardedalloc.h"

#include "BLI_memarena.h"
#include "BLI_linklist.h"

struct MemArena {
        unsigned char *curbuf;
        int bufsize, cursize;
        const char *name;
        
        int use_calloc; 
        int align;
        
        LinkNode *bufs;
};

MemArena *BLI_memarena_new(int bufsize, const char *name) {
        MemArena *ma= MEM_callocN(sizeof(*ma), "memarena");
        ma->bufsize= bufsize;
        ma->align = 8;
        ma->name= name;
        
        return ma;
}

void BLI_memarena_use_calloc(MemArena *ma) {
        ma->use_calloc= 1;
}

void BLI_memarena_use_malloc(MemArena *ma) {
        ma->use_calloc= 0;
}

void BLI_memarena_use_align(struct MemArena *ma, int align) {
        /* align should be a power of two */
        ma->align = align;
}

void BLI_memarena_free(MemArena *ma) {
        BLI_linklist_free(ma->bufs, (void(*)(void*)) MEM_freeN);
        MEM_freeN(ma);
}

        /* amt must be power of two */
#define PADUP(num, amt) ((num+(amt-1))&~(amt-1))

void *BLI_memarena_alloc(MemArena *ma, int size) {
        void *ptr;

                /* ensure proper alignment by rounding
                 * size up to multiple of 8 */  
        size= PADUP(size, ma->align);
        
        if (size>ma->cursize) {
                unsigned char *tmp;
                
                if(size > ma->bufsize - (ma->align - 1))
                {
                        ma->cursize = PADUP(size+1, ma->align);
                }
                else ma->cursize = ma->bufsize;

                if(ma->use_calloc)
                        ma->curbuf= MEM_callocN(ma->cursize, ma->name);
                else
                        ma->curbuf= MEM_mallocN(ma->cursize, ma->name);
                
                BLI_linklist_prepend(&ma->bufs, ma->curbuf);

                /* align alloc'ed memory (needed if align > 8) */
                tmp = (unsigned char*)PADUP( (intptr_t) ma->curbuf, ma->align);
                ma->cursize -= (tmp - ma->curbuf);
                ma->curbuf = tmp;               
        }
        
        ptr= ma->curbuf;
        ma->curbuf+= size;
        ma->cursize-= size;
        
        return ptr;
}