2 * realloc.c - dynamic memory allocation
4 * written by Vangelis Rokas, 2004 (vrokas@otenet.gr)
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the
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12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
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17 * along with this program; if not, write to the Free Software
18 * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
20 * In other words, you are welcome to use, share and improve this program.
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29 extern unsigned char _MALLOC_SPEC *heap;
31 unsigned char _MALLOC_SPEC *realloc(unsigned char _MALLOC_SPEC *mblock, unsigned char len)
33 _malloc_rec _MALLOC_SPEC *pHeap; /* pointer to block header */
34 _malloc_rec _MALLOC_SPEC *temp;
35 unsigned char bLen; /* size of block */
37 if(len >= MAX_BLOCK_SIZE)
38 return ((unsigned char _MALLOC_SPEC *)0);
40 /* if mblock is NULL, then same as malloc */
50 len++; /* increase to count header too */
52 pHeap = (_malloc_rec _MALLOC_SPEC *)((unsigned int)mblock - 1);
53 bLen = pHeap->bits.count;
55 /* new size is same as old, return pointer */
56 if(bLen == len)return (mblock);
59 /* new segment is smaller than the old one, that's easy! */
60 pHeap->bits.count = len;
61 temp = (_malloc_rec _MALLOC_SPEC *)((unsigned int)pHeap + len);
63 temp->bits.count = bLen - len;
65 return ((unsigned char _MALLOC_SPEC *)((unsigned int)pHeap + 1));
68 /* so, new segment has size bigger than the old one, we can return a
69 * valid pointer only when after the block there is an empty block that
70 * can be merged to produce a new block of the requested size, otherwise
72 temp = _mergeHeapBlock(pHeap, len);
75 /* no could not find a valid block, return NULL */
76 return ((unsigned char _MALLOC_SPEC *)0);
80 bLen = pHeap->bits.count;
82 /* allocate by filling the fields */
83 pHeap->bits.count = len;
84 pHeap->bits.alloc = 1;
87 /* if current block size is greater than the requested one,
88 * create a new empty block at the end of the newly allocated */
89 temp = (_malloc_rec _MALLOC_SPEC *)((unsigned int)pHeap + len);
90 temp->bits.count = bLen - len;
94 return ((unsigned char _MALLOC_SPEC *)((unsigned int)pHeap + 1));