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c906108c SS |
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., 59 Temple Place - Suite 330, | |
18 | Boston, MA 02111-1307, 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 <string.h> /* Prototypes for memcpy, memmove, memset, etc */ | |
24 | ||
25 | #include "mmprivate.h" | |
26 | ||
27 | /* Resize the given region to the new size, returning a pointer | |
28 | to the (possibly moved) region. This is optimized for speed; | |
29 | some benchmarks seem to indicate that greater compactness is | |
30 | achieved by unconditionally allocating and copying to a | |
31 | new region. This module has incestuous knowledge of the | |
32 | internals of both mfree and mmalloc. */ | |
33 | ||
34 | PTR | |
35 | mrealloc (md, ptr, size) | |
36 | PTR md; | |
37 | PTR ptr; | |
38 | size_t size; | |
39 | { | |
40 | struct mdesc *mdp; | |
41 | PTR result; | |
42 | int type; | |
43 | size_t block, blocks, oldlimit; | |
44 | ||
45 | if (size == 0) | |
46 | { | |
47 | mfree (md, ptr); | |
48 | return (mmalloc (md, 0)); | |
49 | } | |
50 | else if (ptr == NULL) | |
51 | { | |
52 | return (mmalloc (md, size)); | |
53 | } | |
54 | ||
55 | mdp = MD_TO_MDP (md); | |
56 | ||
57 | if (mdp -> mrealloc_hook != NULL) | |
58 | { | |
59 | return ((*mdp -> mrealloc_hook) (md, ptr, size)); | |
60 | } | |
61 | ||
62 | block = BLOCK (ptr); | |
63 | ||
64 | type = mdp -> heapinfo[block].busy.type; | |
65 | switch (type) | |
66 | { | |
67 | case 0: | |
68 | /* Maybe reallocate a large block to a small fragment. */ | |
69 | if (size <= BLOCKSIZE / 2) | |
70 | { | |
71 | result = mmalloc (md, size); | |
72 | if (result != NULL) | |
73 | { | |
74 | memcpy (result, ptr, size); | |
75 | mfree (md, ptr); | |
76 | return (result); | |
77 | } | |
78 | } | |
79 | ||
80 | /* The new size is a large allocation as well; | |
81 | see if we can hold it in place. */ | |
82 | blocks = BLOCKIFY (size); | |
83 | if (blocks < mdp -> heapinfo[block].busy.info.size) | |
84 | { | |
85 | /* The new size is smaller; return excess memory to the free list. */ | |
86 | mdp -> heapinfo[block + blocks].busy.type = 0; | |
87 | mdp -> heapinfo[block + blocks].busy.info.size | |
88 | = mdp -> heapinfo[block].busy.info.size - blocks; | |
89 | mdp -> heapinfo[block].busy.info.size = blocks; | |
90 | mfree (md, ADDRESS (block + blocks)); | |
91 | result = ptr; | |
92 | } | |
93 | else if (blocks == mdp -> heapinfo[block].busy.info.size) | |
94 | { | |
95 | /* No size change necessary. */ | |
96 | result = ptr; | |
97 | } | |
98 | else | |
99 | { | |
100 | /* Won't fit, so allocate a new region that will. | |
101 | Free the old region first in case there is sufficient | |
102 | adjacent free space to grow without moving. */ | |
103 | blocks = mdp -> heapinfo[block].busy.info.size; | |
104 | /* Prevent free from actually returning memory to the system. */ | |
105 | oldlimit = mdp -> heaplimit; | |
106 | mdp -> heaplimit = 0; | |
107 | mfree (md, ptr); | |
108 | mdp -> heaplimit = oldlimit; | |
109 | result = mmalloc (md, size); | |
110 | if (result == NULL) | |
111 | { | |
112 | mmalloc (md, blocks * BLOCKSIZE); | |
113 | return (NULL); | |
114 | } | |
115 | if (ptr != result) | |
116 | { | |
117 | memmove (result, ptr, blocks * BLOCKSIZE); | |
118 | } | |
119 | } | |
120 | break; | |
121 | ||
122 | default: | |
123 | /* Old size is a fragment; type is logarithm | |
124 | to base two of the fragment size. */ | |
125 | if (size > (size_t) (1 << (type - 1)) && size <= (size_t) (1 << type)) | |
126 | { | |
127 | /* The new size is the same kind of fragment. */ | |
128 | result = ptr; | |
129 | } | |
130 | else | |
131 | { | |
132 | /* The new size is different; allocate a new space, | |
133 | and copy the lesser of the new size and the old. */ | |
134 | result = mmalloc (md, size); | |
135 | if (result == NULL) | |
136 | { | |
137 | return (NULL); | |
138 | } | |
139 | memcpy (result, ptr, MIN (size, (size_t) 1 << type)); | |
140 | mfree (md, ptr); | |
141 | } | |
142 | break; | |
143 | } | |
144 | ||
145 | return (result); | |
146 | } | |
147 | ||
148 | /* When using this package, provide a version of malloc/realloc/free built | |
149 | on top of it, so that if we use the default sbrk() region we will not | |
150 | collide with another malloc package trying to do the same thing, if | |
151 | the application contains any "hidden" calls to malloc/realloc/free (such | |
152 | as inside a system library). */ | |
153 | ||
154 | PTR | |
155 | realloc (ptr, size) | |
156 | PTR ptr; | |
157 | size_t size; | |
158 | { | |
159 | PTR result; | |
160 | ||
161 | result = mrealloc ((PTR) NULL, ptr, size); | |
162 | return (result); | |
163 | } |