memmisc.c

sdcc是为51等小型嵌入式cpu设计的c语言编译器支持数种不同类型的cpu

/*
 * memmisc.c - heap handling functions
 *
 * written by Vangelis Rokas, 2005 <vrokas AT otenet.gr>
 *
 * 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, 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 * 
 * In other words, you are welcome to use, share and improve this program.
 * You are forbidden to forbid anyone else to use, share and improve
 * what you give them.   Help stamp out software-hoarding!  
 *
 * $Id: memmisc.c 3835 2005-08-07 20:09:11Z tecodev $
 */

#include <malloc.h>

void _initHeap(unsigned char _MALLOC_SPEC *dheap, unsigned int heapsize)
{
  _malloc_rec _MALLOC_SPEC *pHeap;
  unsigned int hsize=0;
  int bsize;
  
    pHeap = (_malloc_rec _MALLOC_SPEC *)dheap;
    if (heapsize == 0) return;
    /* we need one byte as the end of block list marker */
    heapsize--;
    
    while (hsize < heapsize) {
      /* a guess of the next block size */
      bsize = (heapsize - hsize); /* thus: bsize > 0 */
      if(bsize > MAX_BLOCK_SIZE) bsize = MAX_BLOCK_SIZE;
      
      /* now we can create the block */
      pHeap->datum = bsize;
      pHeap = (_malloc_rec _MALLOC_SPEC *)((unsigned int)pHeap + bsize);

      hsize += bsize;
    }

    /* mark end of block list */
    pHeap->datum = 0;
}

/* search heap starting from sBlock for a block of size bSize, merging
 * adjacent blocks if necessery */
_malloc_rec _MALLOC_SPEC *_mergeHeapBlock(_malloc_rec _MALLOC_SPEC *sBlock, unsigned char bSize)
{
  _malloc_rec _MALLOC_SPEC *temp;
  unsigned char bLen;
  unsigned char eLen;
  unsigned char dat;
  
    bLen = sBlock->bits.count;
  
    /* current block is not enough, see if we can merge some adjacent memory
     * blocks to make it fit */
    temp = (_malloc_rec _MALLOC_SPEC *)((unsigned int)sBlock + bLen);	//sBlock->bits.count);
    eLen = bLen;
    while((temp->datum) && (!temp->bits.alloc) && (eLen <= bSize)) {
      eLen += (dat=temp->bits.count);
      temp = (_malloc_rec _MALLOC_SPEC *)((unsigned int)temp + dat);
    }

    if(eLen > bSize) {
      unsigned char i;
            
        /* yes, there are some free blocks that can be merged, so merge them... */
        temp = sBlock;
        while(eLen > 0) {
          if(eLen > MAX_BLOCK_SIZE)i = MAX_BLOCK_SIZE;
            else i = eLen;
          temp->datum = i;
          temp = (_malloc_rec _MALLOC_SPEC *)((unsigned int)temp + i);
          eLen -= i;
        }

        /* return block starts at the old block start address */
        return (sBlock);
    } else {
      
      /* no, there are no free blocks after sBlock, so return NULL */
      return ((_malloc_rec _MALLOC_SPEC *)0);
    }
}