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comparison libiberty/objalloc.c @ 0:a06113de4d67

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author kent <kent@cr.ie.u-ryukyu.ac.jp>
date Fri, 17 Jul 2009 14:47:48 +0900
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children 04ced10e8804
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-1:000000000000 0:a06113de4d67
1 /* objalloc.c -- routines to allocate memory for objects
2 Copyright 1997 Free Software Foundation, Inc.
3 Written by Ian Lance Taylor, Cygnus Solutions.
4
5 This program is free software; you can redistribute it and/or modify it
6 under the terms of the GNU General Public License as published by the
7 Free Software Foundation; either version 2, or (at your option) any
8 later version.
9
10 This program 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
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software
17 Foundation, 51 Franklin Street - Fifth Floor,
18 Boston, MA 02110-1301, USA. */
19
20 #include "config.h"
21 #include "ansidecl.h"
22
23 #include "objalloc.h"
24
25 /* Get a definition for NULL. */
26 #include <stdio.h>
27
28 #if VMS
29 #include <stdlib.h>
30 #include <unixlib.h>
31 #else
32
33 /* Get a definition for size_t. */
34 #include <stddef.h>
35
36 #ifdef HAVE_STDLIB_H
37 #include <stdlib.h>
38 #else
39 /* For systems with larger pointers than ints, this must be declared. */
40 extern PTR malloc (size_t);
41 extern void free (PTR);
42 #endif
43
44 #endif
45
46 /* These routines allocate space for an object. Freeing allocated
47 space may or may not free all more recently allocated space.
48
49 We handle large and small allocation requests differently. If we
50 don't have enough space in the current block, and the allocation
51 request is for more than 512 bytes, we simply pass it through to
52 malloc. */
53
54 /* The objalloc structure is defined in objalloc.h. */
55
56 /* This structure appears at the start of each chunk. */
57
58 struct objalloc_chunk
59 {
60 /* Next chunk. */
61 struct objalloc_chunk *next;
62 /* If this chunk contains large objects, this is the value of
63 current_ptr when this chunk was allocated. If this chunk
64 contains small objects, this is NULL. */
65 char *current_ptr;
66 };
67
68 /* The aligned size of objalloc_chunk. */
69
70 #define CHUNK_HEADER_SIZE \
71 ((sizeof (struct objalloc_chunk) + OBJALLOC_ALIGN - 1) \
72 &~ (OBJALLOC_ALIGN - 1))
73
74 /* We ask for this much memory each time we create a chunk which is to
75 hold small objects. */
76
77 #define CHUNK_SIZE (4096 - 32)
78
79 /* A request for this amount or more is just passed through to malloc. */
80
81 #define BIG_REQUEST (512)
82
83 /* Create an objalloc structure. */
84
85 struct objalloc *
86 objalloc_create (void)
87 {
88 struct objalloc *ret;
89 struct objalloc_chunk *chunk;
90
91 ret = (struct objalloc *) malloc (sizeof *ret);
92 if (ret == NULL)
93 return NULL;
94
95 ret->chunks = (PTR) malloc (CHUNK_SIZE);
96 if (ret->chunks == NULL)
97 {
98 free (ret);
99 return NULL;
100 }
101
102 chunk = (struct objalloc_chunk *) ret->chunks;
103 chunk->next = NULL;
104 chunk->current_ptr = NULL;
105
106 ret->current_ptr = (char *) chunk + CHUNK_HEADER_SIZE;
107 ret->current_space = CHUNK_SIZE - CHUNK_HEADER_SIZE;
108
109 return ret;
110 }
111
112 /* Allocate space from an objalloc structure. */
113
114 PTR
115 _objalloc_alloc (struct objalloc *o, unsigned long len)
116 {
117 /* We avoid confusion from zero sized objects by always allocating
118 at least 1 byte. */
119 if (len == 0)
120 len = 1;
121
122 len = (len + OBJALLOC_ALIGN - 1) &~ (OBJALLOC_ALIGN - 1);
123
124 if (len <= o->current_space)
125 {
126 o->current_ptr += len;
127 o->current_space -= len;
128 return (PTR) (o->current_ptr - len);
129 }
130
131 if (len >= BIG_REQUEST)
132 {
133 char *ret;
134 struct objalloc_chunk *chunk;
135
136 ret = (char *) malloc (CHUNK_HEADER_SIZE + len);
137 if (ret == NULL)
138 return NULL;
139
140 chunk = (struct objalloc_chunk *) ret;
141 chunk->next = (struct objalloc_chunk *) o->chunks;
142 chunk->current_ptr = o->current_ptr;
143
144 o->chunks = (PTR) chunk;
145
146 return (PTR) (ret + CHUNK_HEADER_SIZE);
147 }
148 else
149 {
150 struct objalloc_chunk *chunk;
151
152 chunk = (struct objalloc_chunk *) malloc (CHUNK_SIZE);
153 if (chunk == NULL)
154 return NULL;
155 chunk->next = (struct objalloc_chunk *) o->chunks;
156 chunk->current_ptr = NULL;
157
158 o->current_ptr = (char *) chunk + CHUNK_HEADER_SIZE;
159 o->current_space = CHUNK_SIZE - CHUNK_HEADER_SIZE;
160
161 o->chunks = (PTR) chunk;
162
163 return objalloc_alloc (o, len);
164 }
165 }
166
167 /* Free an entire objalloc structure. */
168
169 void
170 objalloc_free (struct objalloc *o)
171 {
172 struct objalloc_chunk *l;
173
174 l = (struct objalloc_chunk *) o->chunks;
175 while (l != NULL)
176 {
177 struct objalloc_chunk *next;
178
179 next = l->next;
180 free (l);
181 l = next;
182 }
183
184 free (o);
185 }
186
187 /* Free a block from an objalloc structure. This also frees all more
188 recently allocated blocks. */
189
190 void
191 objalloc_free_block (struct objalloc *o, PTR block)
192 {
193 struct objalloc_chunk *p, *small;
194 char *b = (char *) block;
195
196 /* First set P to the chunk which contains the block we are freeing,
197 and set Q to the last small object chunk we see before P. */
198 small = NULL;
199 for (p = (struct objalloc_chunk *) o->chunks; p != NULL; p = p->next)
200 {
201 if (p->current_ptr == NULL)
202 {
203 if (b > (char *) p && b < (char *) p + CHUNK_SIZE)
204 break;
205 small = p;
206 }
207 else
208 {
209 if (b == (char *) p + CHUNK_HEADER_SIZE)
210 break;
211 }
212 }
213
214 /* If we can't find the chunk, the caller has made a mistake. */
215 if (p == NULL)
216 abort ();
217
218 if (p->current_ptr == NULL)
219 {
220 struct objalloc_chunk *q;
221 struct objalloc_chunk *first;
222
223 /* The block is in a chunk containing small objects. We can
224 free every chunk through SMALL, because they have certainly
225 been allocated more recently. After SMALL, we will not see
226 any chunks containing small objects; we can free any big
227 chunk if the current_ptr is greater than or equal to B. We
228 can then reset the new current_ptr to B. */
229
230 first = NULL;
231 q = (struct objalloc_chunk *) o->chunks;
232 while (q != p)
233 {
234 struct objalloc_chunk *next;
235
236 next = q->next;
237 if (small != NULL)
238 {
239 if (small == q)
240 small = NULL;
241 free (q);
242 }
243 else if (q->current_ptr > b)
244 free (q);
245 else if (first == NULL)
246 first = q;
247
248 q = next;
249 }
250
251 if (first == NULL)
252 first = p;
253 o->chunks = (PTR) first;
254
255 /* Now start allocating from this small block again. */
256 o->current_ptr = b;
257 o->current_space = ((char *) p + CHUNK_SIZE) - b;
258 }
259 else
260 {
261 struct objalloc_chunk *q;
262 char *current_ptr;
263
264 /* This block is in a large chunk by itself. We can free
265 everything on the list up to and including this block. We
266 then start allocating from the next chunk containing small
267 objects, setting current_ptr from the value stored with the
268 large chunk we are freeing. */
269
270 current_ptr = p->current_ptr;
271 p = p->next;
272
273 q = (struct objalloc_chunk *) o->chunks;
274 while (q != p)
275 {
276 struct objalloc_chunk *next;
277
278 next = q->next;
279 free (q);
280 q = next;
281 }
282
283 o->chunks = (PTR) p;
284
285 while (p->current_ptr != NULL)
286 p = p->next;
287
288 o->current_ptr = current_ptr;
289 o->current_space = ((char *) p + CHUNK_SIZE) - current_ptr;
290 }
291 }