327 lines
9.4 KiB
C
327 lines
9.4 KiB
C
/* Memory allocator `malloc'.
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Copyright 1990, 1991, 1992 Free Software Foundation
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Written May 1989 by Mike Haertel.
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Heavily modified Mar 1992 by Fred Fish for mmap'c version.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA.
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The author may be reached (Email) at the address mike@ai.mit.edu,
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or (US mail) as Mike Haertel c/o Free Software Foundation. */
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#include "mmalloc.h"
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/* Prototypes for local functions */
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static int initialize PARAMS ((struct mdesc *));
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static PTR morecore PARAMS ((struct mdesc *, size_t));
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static PTR align PARAMS ((struct mdesc *, size_t));
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/* Aligned allocation. */
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static PTR
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align (mdp, size)
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struct mdesc *mdp;
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size_t size;
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{
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PTR result;
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unsigned long int adj;
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result = mdp -> morecore (mdp, size);
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adj = RESIDUAL (result, BLOCKSIZE);
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if (adj != 0)
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{
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adj = BLOCKSIZE - adj;
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(void) mdp -> morecore (mdp, adj);
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result = (char *) result + adj;
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}
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return (result);
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}
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/* Set everything up and remember that we have. */
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static int
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initialize (mdp)
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struct mdesc *mdp;
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{
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mdp -> heapsize = HEAP / BLOCKSIZE;
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mdp -> heapinfo = (malloc_info *)
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align (mdp, mdp -> heapsize * sizeof (malloc_info));
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if (mdp -> heapinfo == NULL)
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{
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return (0);
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}
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memset ((PTR)mdp -> heapinfo, 0, mdp -> heapsize * sizeof (malloc_info));
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mdp -> heapinfo[0].free.size = 0;
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mdp -> heapinfo[0].free.next = mdp -> heapinfo[0].free.prev = 0;
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mdp -> heapindex = 0;
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mdp -> heapbase = (char *) mdp -> heapinfo;
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mdp -> flags |= MMALLOC_INITIALIZED;
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return (1);
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}
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/* Get neatly aligned memory, initializing or
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growing the heap info table as necessary. */
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static PTR
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morecore (mdp, size)
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struct mdesc *mdp;
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size_t size;
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{
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PTR result;
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malloc_info *newinfo, *oldinfo;
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size_t newsize;
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result = align (mdp, size);
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if (result == NULL)
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{
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return (NULL);
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}
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/* Check if we need to grow the info table. */
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if ((size_t) BLOCK ((char *) result + size) > mdp -> heapsize)
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{
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newsize = mdp -> heapsize;
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while ((size_t) BLOCK ((char *) result + size) > newsize)
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{
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newsize *= 2;
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}
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newinfo = (malloc_info *) align (mdp, newsize * sizeof (malloc_info));
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if (newinfo == NULL)
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{
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mdp -> morecore (mdp, -size);
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return (NULL);
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}
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memset ((PTR)newinfo, 0, newsize * sizeof (malloc_info));
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memcpy ((PTR)newinfo, (PTR)mdp -> heapinfo,
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mdp -> heapsize * sizeof (malloc_info));
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oldinfo = mdp -> heapinfo;
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newinfo[BLOCK (oldinfo)].busy.type = 0;
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newinfo[BLOCK (oldinfo)].busy.info.size
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= BLOCKIFY (mdp -> heapsize * sizeof (malloc_info));
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mdp -> heapinfo = newinfo;
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__mmalloc_free (mdp, (PTR)oldinfo);
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mdp -> heapsize = newsize;
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}
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mdp -> heaplimit = BLOCK ((char *) result + size);
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return (result);
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}
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/* Allocate memory from the heap. */
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PTR
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mmalloc (md, size)
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PTR md;
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size_t size;
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{
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struct mdesc *mdp;
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PTR result;
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size_t block, blocks, lastblocks, start;
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register size_t i;
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struct list *next;
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register size_t log;
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if (size == 0)
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{
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return (NULL);
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}
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mdp = MD_TO_MDP (md);
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if (mdp -> mmalloc_hook != NULL)
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{
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return ((*mdp -> mmalloc_hook) (md, size));
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}
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if (!(mdp -> flags & MMALLOC_INITIALIZED))
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{
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if (!initialize (mdp))
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{
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return (NULL);
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}
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}
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if (size < sizeof (struct list))
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{
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size = sizeof (struct list);
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}
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/* Determine the allocation policy based on the request size. */
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if (size <= BLOCKSIZE / 2)
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{
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/* Small allocation to receive a fragment of a block.
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Determine the logarithm to base two of the fragment size. */
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log = 1;
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--size;
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while ((size /= 2) != 0)
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{
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++log;
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}
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/* Look in the fragment lists for a
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free fragment of the desired size. */
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next = mdp -> fraghead[log].next;
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if (next != NULL)
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{
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/* There are free fragments of this size.
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Pop a fragment out of the fragment list and return it.
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Update the block's nfree and first counters. */
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result = (PTR) next;
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next -> prev -> next = next -> next;
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if (next -> next != NULL)
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{
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next -> next -> prev = next -> prev;
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}
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block = BLOCK (result);
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if (--mdp -> heapinfo[block].busy.info.frag.nfree != 0)
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{
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mdp -> heapinfo[block].busy.info.frag.first =
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RESIDUAL (next -> next, BLOCKSIZE) >> log;
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}
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/* Update the statistics. */
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mdp -> heapstats.chunks_used++;
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mdp -> heapstats.bytes_used += 1 << log;
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mdp -> heapstats.chunks_free--;
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mdp -> heapstats.bytes_free -= 1 << log;
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}
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else
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{
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/* No free fragments of the desired size, so get a new block
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and break it into fragments, returning the first. */
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result = mmalloc (md, BLOCKSIZE);
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if (result == NULL)
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{
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return (NULL);
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}
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/* Link all fragments but the first into the free list. */
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for (i = 1; i < (size_t) (BLOCKSIZE >> log); ++i)
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{
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next = (struct list *) ((char *) result + (i << log));
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next -> next = mdp -> fraghead[log].next;
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next -> prev = &mdp -> fraghead[log];
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next -> prev -> next = next;
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if (next -> next != NULL)
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{
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next -> next -> prev = next;
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}
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}
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/* Initialize the nfree and first counters for this block. */
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block = BLOCK (result);
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mdp -> heapinfo[block].busy.type = log;
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mdp -> heapinfo[block].busy.info.frag.nfree = i - 1;
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mdp -> heapinfo[block].busy.info.frag.first = i - 1;
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mdp -> heapstats.chunks_free += (BLOCKSIZE >> log) - 1;
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mdp -> heapstats.bytes_free += BLOCKSIZE - (1 << log);
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mdp -> heapstats.bytes_used -= BLOCKSIZE - (1 << log);
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}
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}
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else
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{
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/* Large allocation to receive one or more blocks.
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Search the free list in a circle starting at the last place visited.
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If we loop completely around without finding a large enough
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space we will have to get more memory from the system. */
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blocks = BLOCKIFY(size);
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start = block = MALLOC_SEARCH_START;
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while (mdp -> heapinfo[block].free.size < blocks)
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{
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block = mdp -> heapinfo[block].free.next;
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if (block == start)
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{
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/* Need to get more from the system. Check to see if
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the new core will be contiguous with the final free
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block; if so we don't need to get as much. */
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block = mdp -> heapinfo[0].free.prev;
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lastblocks = mdp -> heapinfo[block].free.size;
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if (mdp -> heaplimit != 0 &&
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block + lastblocks == mdp -> heaplimit &&
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mdp -> morecore (mdp, 0) == ADDRESS(block + lastblocks) &&
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(morecore (mdp, (blocks - lastblocks) * BLOCKSIZE)) != NULL)
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{
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mdp -> heapinfo[block].free.size = blocks;
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mdp -> heapstats.bytes_free +=
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(blocks - lastblocks) * BLOCKSIZE;
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continue;
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}
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result = morecore(mdp, blocks * BLOCKSIZE);
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if (result == NULL)
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{
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return (NULL);
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}
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block = BLOCK (result);
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mdp -> heapinfo[block].busy.type = 0;
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mdp -> heapinfo[block].busy.info.size = blocks;
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mdp -> heapstats.chunks_used++;
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mdp -> heapstats.bytes_used += blocks * BLOCKSIZE;
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return (result);
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}
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}
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/* At this point we have found a suitable free list entry.
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Figure out how to remove what we need from the list. */
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result = ADDRESS(block);
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if (mdp -> heapinfo[block].free.size > blocks)
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{
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/* The block we found has a bit left over,
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so relink the tail end back into the free list. */
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mdp -> heapinfo[block + blocks].free.size
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= mdp -> heapinfo[block].free.size - blocks;
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mdp -> heapinfo[block + blocks].free.next
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= mdp -> heapinfo[block].free.next;
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mdp -> heapinfo[block + blocks].free.prev
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= mdp -> heapinfo[block].free.prev;
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mdp -> heapinfo[mdp -> heapinfo[block].free.prev].free.next
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= mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.prev
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= mdp -> heapindex = block + blocks;
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}
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else
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{
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/* The block exactly matches our requirements,
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so just remove it from the list. */
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mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.prev
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= mdp -> heapinfo[block].free.prev;
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mdp -> heapinfo[mdp -> heapinfo[block].free.prev].free.next
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= mdp -> heapindex = mdp -> heapinfo[block].free.next;
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mdp -> heapstats.chunks_free--;
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}
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mdp -> heapinfo[block].busy.type = 0;
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mdp -> heapinfo[block].busy.info.size = blocks;
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mdp -> heapstats.chunks_used++;
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mdp -> heapstats.bytes_used += blocks * BLOCKSIZE;
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mdp -> heapstats.bytes_free -= blocks * BLOCKSIZE;
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}
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return (result);
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}
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/* When using this package, provide a version of malloc/realloc/free built
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on top of it, so that if we use the default sbrk() region we will not
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collide with another malloc package trying to do the same thing, if
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the application contains any "hidden" calls to malloc/realloc/free (such
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as inside a system library). */
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PTR
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malloc (size)
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size_t size;
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{
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return (mmalloc ((void *) NULL, size));
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}
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