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Diffstat (limited to 'mmalloc/mfree.c')
| -rw-r--r-- | mmalloc/mfree.c | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/mmalloc/mfree.c b/mmalloc/mfree.c new file mode 100644 index 0000000..163d31e --- /dev/null +++ b/mmalloc/mfree.c @@ -0,0 +1,249 @@ +/* Free a block of memory allocated by `mmalloc'. + Copyright 1990, 1991, 1992 Free Software Foundation + + Written May 1989 by Mike Haertel. + Heavily modified Mar 1992 by Fred Fish. (fnf@cygnus.com) + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +The GNU C Library 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. + + The author may be reached (Email) at the address mike@ai.mit.edu, + or (US mail) as Mike Haertel c/o Free Software Foundation. */ + +#include "mmalloc.h" + +/* Return memory to the heap. + Like `mfree' but don't call a mfree_hook if there is one. */ + +void +__mmalloc_free (mdp, ptr) + struct mdesc *mdp; + PTR ptr; +{ + int type; + size_t block, blocks; + register size_t i; + struct list *prev, *next; + + block = BLOCK (ptr); + + type = mdp -> heapinfo[block].busy.type; + switch (type) + { + case 0: + /* Get as many statistics as early as we can. */ + mdp -> heapstats.chunks_used--; + mdp -> heapstats.bytes_used -= + mdp -> heapinfo[block].busy.info.size * BLOCKSIZE; + mdp -> heapstats.bytes_free += + mdp -> heapinfo[block].busy.info.size * BLOCKSIZE; + + /* Find the free cluster previous to this one in the free list. + Start searching at the last block referenced; this may benefit + programs with locality of allocation. */ + i = mdp -> heapindex; + if (i > block) + { + while (i > block) + { + i = mdp -> heapinfo[i].free.prev; + } + } + else + { + do + { + i = mdp -> heapinfo[i].free.next; + } + while (i > 0 && i < block); + i = mdp -> heapinfo[i].free.prev; + } + + /* Determine how to link this block into the free list. */ + if (block == i + mdp -> heapinfo[i].free.size) + { + /* Coalesce this block with its predecessor. */ + mdp -> heapinfo[i].free.size += + mdp -> heapinfo[block].busy.info.size; + block = i; + } + else + { + /* Really link this block back into the free list. */ + mdp -> heapinfo[block].free.size = + mdp -> heapinfo[block].busy.info.size; + mdp -> heapinfo[block].free.next = mdp -> heapinfo[i].free.next; + mdp -> heapinfo[block].free.prev = i; + mdp -> heapinfo[i].free.next = block; + mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.prev = block; + mdp -> heapstats.chunks_free++; + } + + /* Now that the block is linked in, see if we can coalesce it + with its successor (by deleting its successor from the list + and adding in its size). */ + if (block + mdp -> heapinfo[block].free.size == + mdp -> heapinfo[block].free.next) + { + mdp -> heapinfo[block].free.size + += mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.size; + mdp -> heapinfo[block].free.next + = mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.next; + mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.prev = block; + mdp -> heapstats.chunks_free--; + } + + /* Now see if we can return stuff to the system. */ + blocks = mdp -> heapinfo[block].free.size; + if (blocks >= FINAL_FREE_BLOCKS && block + blocks == mdp -> heaplimit + && mdp -> morecore (mdp, 0) == ADDRESS (block + blocks)) + { + register size_t bytes = blocks * BLOCKSIZE; + mdp -> heaplimit -= blocks; + mdp -> morecore (mdp, -bytes); + mdp -> heapinfo[mdp -> heapinfo[block].free.prev].free.next + = mdp -> heapinfo[block].free.next; + mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.prev + = mdp -> heapinfo[block].free.prev; + block = mdp -> heapinfo[block].free.prev; + mdp -> heapstats.chunks_free--; + mdp -> heapstats.bytes_free -= bytes; + } + + /* Set the next search to begin at this block. */ + mdp -> heapindex = block; + break; + + default: + /* Do some of the statistics. */ + mdp -> heapstats.chunks_used--; + mdp -> heapstats.bytes_used -= 1 << type; + mdp -> heapstats.chunks_free++; + mdp -> heapstats.bytes_free += 1 << type; + + /* Get the address of the first free fragment in this block. */ + prev = (struct list *) + ((char *) ADDRESS(block) + + (mdp -> heapinfo[block].busy.info.frag.first << type)); + + if (mdp -> heapinfo[block].busy.info.frag.nfree == + (BLOCKSIZE >> type) - 1) + { + /* If all fragments of this block are free, remove them + from the fragment list and free the whole block. */ + next = prev; + for (i = 1; i < (size_t) (BLOCKSIZE >> type); ++i) + { + next = next -> next; + } + prev -> prev -> next = next; + if (next != NULL) + { + next -> prev = prev -> prev; + } + mdp -> heapinfo[block].busy.type = 0; + mdp -> heapinfo[block].busy.info.size = 1; + + /* Keep the statistics accurate. */ + mdp -> heapstats.chunks_used++; + mdp -> heapstats.bytes_used += BLOCKSIZE; + mdp -> heapstats.chunks_free -= BLOCKSIZE >> type; + mdp -> heapstats.bytes_free -= BLOCKSIZE; + + mfree (mdp, ADDRESS(block)); + } + else if (mdp -> heapinfo[block].busy.info.frag.nfree != 0) + { + /* If some fragments of this block are free, link this + fragment into the fragment list after the first free + fragment of this block. */ + next = (struct list *) ptr; + next -> next = prev -> next; + next -> prev = prev; + prev -> next = next; + if (next -> next != NULL) + { + next -> next -> prev = next; + } + ++mdp -> heapinfo[block].busy.info.frag.nfree; + } + else + { + /* No fragments of this block are free, so link this + fragment into the fragment list and announce that + it is the first free fragment of this block. */ + prev = (struct list *) ptr; + mdp -> heapinfo[block].busy.info.frag.nfree = 1; + mdp -> heapinfo[block].busy.info.frag.first = + RESIDUAL (ptr, BLOCKSIZE) >> type; + prev -> next = mdp -> fraghead[type].next; + prev -> prev = &mdp -> fraghead[type]; + prev -> prev -> next = prev; + if (prev -> next != NULL) + { + prev -> next -> prev = prev; + } + } + break; + } +} + +/* Return memory to the heap. */ + +void +mfree (md, ptr) + PTR md; + PTR ptr; +{ + struct mdesc *mdp; + register struct alignlist *l; + + if (ptr != NULL) + { + mdp = MD_TO_MDP (md); + for (l = mdp -> aligned_blocks; l != NULL; l = l -> next) + { + if (l -> aligned == ptr) + { + l -> aligned = NULL; /* Mark the slot in the list as free. */ + ptr = l -> exact; + break; + } + } + if (mdp -> mfree_hook != NULL) + { + (*mdp -> mfree_hook) (md, ptr); + } + else + { + __mmalloc_free (mdp, ptr); + } + } +} + +/* When using this package, provide a version of malloc/realloc/free built + on top of it, so that if we use the default sbrk() region we will not + collide with another malloc package trying to do the same thing, if + the application contains any "hidden" calls to malloc/realloc/free (such + as inside a system library). + + NOTE: Defining our own copy of this breaks ANSI conformance. */ + +void +free (ptr) + PTR ptr; +{ + mfree ((void *) NULL, ptr); +} |