mmalloc/mfree.c

   1 /* Free a block of memory allocated by `mmalloc'.
   2    Copyright 1990, 1991, 1992 Free Software Foundation
   3
   4    Written May 1989 by Mike Haertel.
   5    Heavily modified Mar 1992 by Fred Fish.  (fnf@cygnus.com)
   6
   7 The GNU C Library is free software; you can redistribute it and/or
   8 modify it under the terms of the GNU Library General Public License as
   9 published by the Free Software Foundation; either version 2 of the
  10 License, or (at your option) any later version.
  11
  12 The GNU C Library is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 Library General Public License for more details.
  16
  17 You should have received a copy of the GNU Library General Public
  18 License along with the GNU C Library; see the file COPYING.LIB.  If
  19 not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  20 Boston, MA 02111-1307, USA.
  21
  22    The author may be reached (Email) at the address mike@ai.mit.edu,
  23    or (US mail) as Mike Haertel c/o Free Software Foundation. */
  24
  25 #include "mmprivate.h"
  26
  27 /* Return memory to the heap.
  28    Like `mfree' but don't call a mfree_hook if there is one.  */
  29
  30 void
  31 __mmalloc_free (mdp, ptr)
  32   struct mdesc *mdp;
  33   PTR ptr;
  34 {
  35   int type;
  36   size_t block, blocks;
  37   register size_t i;
  38   struct list *prev, *next;
  39
  40   block = BLOCK (ptr);
  41
  42   type = mdp -> heapinfo[block].busy.type;
  43   switch (type)
  44     {
  45     case 0:
  46       /* Get as many statistics as early as we can.  */
  47       mdp -> heapstats.chunks_used--;
  48       mdp -> heapstats.bytes_used -=
  49           mdp -> heapinfo[block].busy.info.size * BLOCKSIZE;
  50       mdp -> heapstats.bytes_free +=
  51           mdp -> heapinfo[block].busy.info.size * BLOCKSIZE;
  52
  53       /* Find the free cluster previous to this one in the free list.
  54          Start searching at the last block referenced; this may benefit
  55          programs with locality of allocation.  */
  56       i = mdp -> heapindex;
  57       if (i > block)
  58         {
  59           while (i > block)
  60             {
  61               i = mdp -> heapinfo[i].free.prev;
  62             }
  63         }
  64       else
  65         {
  66           do
  67             {
  68               i = mdp -> heapinfo[i].free.next;
  69             }
  70           while ((i != 0) && (i < block));
  71           i = mdp -> heapinfo[i].free.prev;
  72         }
  73
  74       /* Determine how to link this block into the free list.  */
  75       if (block == i + mdp -> heapinfo[i].free.size)
  76         {
  77           /* Coalesce this block with its predecessor.  */
  78           mdp -> heapinfo[i].free.size +=
  79             mdp -> heapinfo[block].busy.info.size;
  80           block = i;
  81         }
  82       else
  83         {
  84           /* Really link this block back into the free list.  */
  85           mdp -> heapinfo[block].free.size =
  86             mdp -> heapinfo[block].busy.info.size;
  87           mdp -> heapinfo[block].free.next = mdp -> heapinfo[i].free.next;
  88           mdp -> heapinfo[block].free.prev = i;
  89           mdp -> heapinfo[i].free.next = block;
  90           mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.prev = block;
  91           mdp -> heapstats.chunks_free++;
  92         }
  93
  94       /* Now that the block is linked in, see if we can coalesce it
  95          with its successor (by deleting its successor from the list
  96          and adding in its size).  */
  97       if (block + mdp -> heapinfo[block].free.size ==
  98           mdp -> heapinfo[block].free.next)
  99         {
 100           mdp -> heapinfo[block].free.size
 101             += mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.size;
 102           mdp -> heapinfo[block].free.next
 103             = mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.next;
 104           mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.prev = block;
 105           mdp -> heapstats.chunks_free--;
 106         }
 107
 108       /* Now see if we can return stuff to the system.  */
 109       blocks = mdp -> heapinfo[block].free.size;
 110       if (blocks >= FINAL_FREE_BLOCKS && block + blocks == mdp -> heaplimit
 111           && mdp -> morecore (mdp, 0) == ADDRESS (block + blocks))
 112         {
 113           register size_t bytes = blocks * BLOCKSIZE;
 114           mdp -> heaplimit -= blocks;
 115           mdp -> morecore (mdp, -bytes);
 116           mdp -> heapinfo[mdp -> heapinfo[block].free.prev].free.next
 117             = mdp -> heapinfo[block].free.next;
 118           mdp -> heapinfo[mdp -> heapinfo[block].free.next].free.prev
 119             = mdp -> heapinfo[block].free.prev;
 120           block = mdp -> heapinfo[block].free.prev;
 121           mdp -> heapstats.chunks_free--;
 122           mdp -> heapstats.bytes_free -= bytes;
 123         }
 124
 125       /* Set the next search to begin at this block.  */
 126       mdp -> heapindex = block;
 127       break;
 128
 129     default:
 130       /* Do some of the statistics.  */
 131       mdp -> heapstats.chunks_used--;
 132       mdp -> heapstats.bytes_used -= 1 << type;
 133       mdp -> heapstats.chunks_free++;
 134       mdp -> heapstats.bytes_free += 1 << type;
 135
 136       /* Get the address of the first free fragment in this block.  */
 137       prev = (struct list *)
 138         ((char *) ADDRESS(block) +
 139          (mdp -> heapinfo[block].busy.info.frag.first << type));
 140
 141       if (mdp -> heapinfo[block].busy.info.frag.nfree ==
 142           (BLOCKSIZE >> type) - 1)
 143         {
 144           /* If all fragments of this block are free, remove them
 145              from the fragment list and free the whole block.  */
 146           next = prev;
 147           for (i = 1; i < (size_t) (BLOCKSIZE >> type); ++i)
 148             {
 149               next = next -> next;
 150             }
 151           prev -> prev -> next = next;
 152           if (next != NULL)
 153             {
 154               next -> prev = prev -> prev;
 155             }
 156           mdp -> heapinfo[block].busy.type = 0;
 157           mdp -> heapinfo[block].busy.info.size = 1;
 158
 159           /* Keep the statistics accurate.  */
 160           mdp -> heapstats.chunks_used++;
 161           mdp -> heapstats.bytes_used += BLOCKSIZE;
 162           mdp -> heapstats.chunks_free -= BLOCKSIZE >> type;
 163           mdp -> heapstats.bytes_free -= BLOCKSIZE;
 164
 165           mfree ((PTR) mdp, (PTR) ADDRESS(block));
 166         }
 167       else if (mdp -> heapinfo[block].busy.info.frag.nfree != 0)
 168         {
 169           /* If some fragments of this block are free, link this
 170              fragment into the fragment list after the first free
 171              fragment of this block. */
 172           next = (struct list *) ptr;
 173           next -> next = prev -> next;
 174           next -> prev = prev;
 175           prev -> next = next;
 176           if (next -> next != NULL)
 177             {
 178               next -> next -> prev = next;
 179             }
 180           ++mdp -> heapinfo[block].busy.info.frag.nfree;
 181         }
 182       else
 183         {
 184           /* No fragments of this block are free, so link this
 185              fragment into the fragment list and announce that
 186              it is the first free fragment of this block. */
 187           prev = (struct list *) ptr;
 188           mdp -> heapinfo[block].busy.info.frag.nfree = 1;
 189           mdp -> heapinfo[block].busy.info.frag.first =
 190             RESIDUAL (ptr, BLOCKSIZE) >> type;
 191           prev -> next = mdp -> fraghead[type].next;
 192           prev -> prev = &mdp -> fraghead[type];
 193           prev -> prev -> next = prev;
 194           if (prev -> next != NULL)
 195             {
 196               prev -> next -> prev = prev;
 197             }
 198         }
 199       break;
 200     }
 201 }
 202
 203 /* Return memory to the heap.  */
 204
 205 void
 206 mfree (md, ptr)
 207   PTR md;
 208   PTR ptr;
 209 {
 210   struct mdesc *mdp;
 211   register struct alignlist *l;
 212
 213   if (ptr != NULL)
 214     {
 215       mdp = MD_TO_MDP (md);
 216       for (l = mdp -> aligned_blocks; l != NULL; l = l -> next)
 217         {
 218           if (l -> aligned == ptr)
 219             {
 220               l -> aligned = NULL;  /* Mark the slot in the list as free. */
 221               ptr = l -> exact;
 222               break;
 223             }
 224         }
 225       if (mdp -> mfree_hook != NULL)
 226         {
 227           (*mdp -> mfree_hook) (md, ptr);
 228         }
 229       else
 230         {
 231           __mmalloc_free (mdp, ptr);
 232         }
 233     }
 234 }
 235
 236 /* When using this package, provide a version of malloc/realloc/free built
 237    on top of it, so that if we use the default sbrk() region we will not
 238    collide with another malloc package trying to do the same thing, if
 239    the application contains any "hidden" calls to malloc/realloc/free (such
 240    as inside a system library). */
 241
 242 void
 243 free (ptr)
 244   PTR ptr;
 245 {
 246   mfree ((PTR) NULL, ptr);
 247 }