| 1 | /* Change the size of a block allocated by `mmalloc'. |
| 2 | Copyright 1990, 1991 Free Software Foundation |
| 3 | Written May 1989 by Mike Haertel. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Library General Public License as |
| 7 | published by the Free Software Foundation; either version 2 of the |
| 8 | License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Library General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Library General Public |
| 16 | License along with the GNU C Library; see the file COPYING.LIB. If |
| 17 | not, write to the Free Software Foundation, Inc., 675 Mass Ave, |
| 18 | Cambridge, MA 02139, USA. |
| 19 | |
| 20 | The author may be reached (Email) at the address mike@ai.mit.edu, |
| 21 | or (US mail) as Mike Haertel c/o Free Software Foundation. */ |
| 22 | |
| 23 | #include "mmalloc.h" |
| 24 | |
| 25 | /* Resize the given region to the new size, returning a pointer |
| 26 | to the (possibly moved) region. This is optimized for speed; |
| 27 | some benchmarks seem to indicate that greater compactness is |
| 28 | achieved by unconditionally allocating and copying to a |
| 29 | new region. This module has incestuous knowledge of the |
| 30 | internals of both mfree and mmalloc. */ |
| 31 | |
| 32 | PTR |
| 33 | mrealloc (md, ptr, size) |
| 34 | PTR md; |
| 35 | PTR ptr; |
| 36 | size_t size; |
| 37 | { |
| 38 | struct mdesc *mdp; |
| 39 | PTR result; |
| 40 | int type; |
| 41 | size_t block, blocks, oldlimit; |
| 42 | |
| 43 | if (size == 0) |
| 44 | { |
| 45 | mfree (md, ptr); |
| 46 | return (mmalloc (md, 0)); |
| 47 | } |
| 48 | else if (ptr == NULL) |
| 49 | return (mmalloc (md, size)); |
| 50 | |
| 51 | mdp = MD_TO_MDP (md); |
| 52 | |
| 53 | if (mdp -> mrealloc_hook != NULL) |
| 54 | { |
| 55 | return ((*mdp -> mrealloc_hook) (md, ptr, size)); |
| 56 | } |
| 57 | |
| 58 | block = BLOCK(ptr); |
| 59 | |
| 60 | type = mdp -> heapinfo[block].busy.type; |
| 61 | switch (type) |
| 62 | { |
| 63 | case 0: |
| 64 | /* Maybe reallocate a large block to a small fragment. */ |
| 65 | if (size <= BLOCKSIZE / 2) |
| 66 | { |
| 67 | result = mmalloc (md, size); |
| 68 | if (result != NULL) |
| 69 | { |
| 70 | memcpy (result, ptr, size); |
| 71 | mfree (md, ptr); |
| 72 | return (result); |
| 73 | } |
| 74 | } |
| 75 | |
| 76 | /* The new size is a large allocation as well; |
| 77 | see if we can hold it in place. */ |
| 78 | blocks = BLOCKIFY(size); |
| 79 | if (blocks < mdp -> heapinfo[block].busy.info.size) |
| 80 | { |
| 81 | /* The new size is smaller; return |
| 82 | excess memory to the free list. */ |
| 83 | mdp -> heapinfo[block + blocks].busy.type = 0; |
| 84 | mdp -> heapinfo[block + blocks].busy.info.size |
| 85 | = mdp -> heapinfo[block].busy.info.size - blocks; |
| 86 | mdp -> heapinfo[block].busy.info.size = blocks; |
| 87 | mfree (md, ADDRESS(block + blocks)); |
| 88 | result = ptr; |
| 89 | } |
| 90 | else if (blocks == mdp -> heapinfo[block].busy.info.size) |
| 91 | /* No size change necessary. */ |
| 92 | result = ptr; |
| 93 | else |
| 94 | { |
| 95 | /* Won't fit, so allocate a new region that will. |
| 96 | Free the old region first in case there is sufficient |
| 97 | adjacent free space to grow without moving. */ |
| 98 | blocks = mdp -> heapinfo[block].busy.info.size; |
| 99 | /* Prevent free from actually returning memory to the system. */ |
| 100 | oldlimit = mdp -> heaplimit; |
| 101 | mdp -> heaplimit = 0; |
| 102 | mfree (md, ptr); |
| 103 | mdp -> heaplimit = oldlimit; |
| 104 | result = mmalloc (md, size); |
| 105 | if (result == NULL) |
| 106 | { |
| 107 | (void) mmalloc (md, blocks * BLOCKSIZE); |
| 108 | return NULL; |
| 109 | } |
| 110 | if (ptr != result) |
| 111 | memmove (result, ptr, blocks * BLOCKSIZE); |
| 112 | } |
| 113 | break; |
| 114 | |
| 115 | default: |
| 116 | /* Old size is a fragment; type is logarithm |
| 117 | to base two of the fragment size. */ |
| 118 | if (size > (size_t) (1 << (type - 1)) && size <= (size_t) (1 << type)) |
| 119 | /* The new size is the same kind of fragment. */ |
| 120 | result = ptr; |
| 121 | else |
| 122 | { |
| 123 | /* The new size is different; allocate a new space, |
| 124 | and copy the lesser of the new size and the old. */ |
| 125 | result = mmalloc (md, size); |
| 126 | if (result == NULL) |
| 127 | return (NULL); |
| 128 | memcpy (result, ptr, MIN(size, (size_t) 1 << type)); |
| 129 | mfree (md, ptr); |
| 130 | } |
| 131 | break; |
| 132 | } |
| 133 | |
| 134 | return (result); |
| 135 | } |
| 136 | |
| 137 | /* When using this package, provide a version of malloc/realloc/free built |
| 138 | on top of it, so that if we use the default sbrk() region we will not |
| 139 | collide with another malloc package trying to do the same thing, if |
| 140 | the application contains any "hidden" calls to malloc/realloc/free (such |
| 141 | as inside a system library). |
| 142 | |
| 143 | NOTE: Defining our own copy of this breaks ANSI conformance. */ |
| 144 | |
| 145 | PTR |
| 146 | realloc (ptr, size) |
| 147 | PTR ptr; |
| 148 | size_t size; |
| 149 | { |
| 150 | return (mrealloc ((void *) NULL, ptr, size)); |
| 151 | } |