BLI_memarena.c

Go to the documentation of this file.

/*
 * ***** 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;
}