1 /* objalloc.c -- routines to allocate memory for objects
2 Copyright 1997 Free Software Foundation, Inc.
3 Written by Ian Lance Taylor, Cygnus Solutions.
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
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.
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, 675 Mass Ave, Cambridge, MA 02139, USA. */
22 /* Get a definition for NULL. */
30 #ifdef ANSI_PROTOTYPES
31 /* Get a definition for size_t. */
35 /* For systems with larger pointers than ints, this must be declared. */
36 extern PTR malloc PARAMS ((size_t));
37 extern void free PARAMS ((PTR));
40 /* These routines allocate space for an object. Freeing allocated
41 space may or may not free all more recently allocated space.
43 We handle large and small allocation requests differently. If we
44 don't have enough space in the current block, and the allocation
45 request is for more than 512 bytes, we simply pass it through to
48 /* The objalloc structure is defined in objalloc.h. */
50 /* This structure appears at the start of each chunk. */
55 struct objalloc_chunk *next;
56 /* If this chunk contains large objects, this is the value of
57 current_ptr when this chunk was allocated. If this chunk
58 contains small objects, this is NULL. */
62 /* The aligned size of objalloc_chunk. */
64 #define CHUNK_HEADER_SIZE \
65 ((sizeof (struct objalloc_chunk) + OBJALLOC_ALIGN - 1) \
66 &~ (OBJALLOC_ALIGN - 1))
68 /* We ask for this much memory each time we create a chunk which is to
69 hold small objects. */
71 #define CHUNK_SIZE (4096 - 32)
73 /* A request for this amount or more is just passed through to malloc. */
75 #define BIG_REQUEST (512)
77 /* Create an objalloc structure. */
83 struct objalloc_chunk *chunk;
85 ret = (struct objalloc *) malloc (sizeof *ret);
89 ret->chunks = (PTR) malloc (CHUNK_SIZE);
90 if (ret->chunks == NULL)
96 chunk = (struct objalloc_chunk *) ret->chunks;
98 chunk->current_ptr = NULL;
100 ret->current_ptr = (char *) chunk + CHUNK_HEADER_SIZE;
101 ret->current_space = CHUNK_SIZE - CHUNK_HEADER_SIZE;
106 /* Allocate space from an objalloc structure. */
109 _objalloc_alloc (o, len)
113 /* We avoid confusion from zero sized objects by always allocating
118 len = (len + OBJALLOC_ALIGN - 1) &~ (OBJALLOC_ALIGN - 1);
120 if (len <= o->current_space)
122 o->current_ptr += len;
123 o->current_space -= len;
124 return (PTR) (o->current_ptr - len);
127 if (len >= BIG_REQUEST)
130 struct objalloc_chunk *chunk;
132 ret = (char *) malloc (CHUNK_HEADER_SIZE + len);
136 chunk = (struct objalloc_chunk *) ret;
137 chunk->next = (struct objalloc_chunk *) o->chunks;
138 chunk->current_ptr = o->current_ptr;
140 o->chunks = (PTR) chunk;
142 return (PTR) (ret + CHUNK_HEADER_SIZE);
146 struct objalloc_chunk *chunk;
148 chunk = (struct objalloc_chunk *) malloc (CHUNK_SIZE);
151 chunk->next = (struct objalloc_chunk *) o->chunks;
152 chunk->current_ptr = NULL;
154 o->current_ptr = (char *) chunk + CHUNK_HEADER_SIZE;
155 o->current_space = CHUNK_SIZE - CHUNK_HEADER_SIZE;
157 o->chunks = (PTR) chunk;
159 return objalloc_alloc (o, len);
163 /* Free an entire objalloc structure. */
169 struct objalloc_chunk *l;
171 l = (struct objalloc_chunk *) o->chunks;
174 struct objalloc_chunk *next;
184 /* Free a block from an objalloc structure. This also frees all more
185 recently allocated blocks. */
188 objalloc_free_block (o, block)
192 struct objalloc_chunk *p, *small;
193 char *b = (char *) block;
195 /* First set P to the chunk which contains the block we are freeing,
196 and set Q to the last small object chunk we see before P. */
198 for (p = (struct objalloc_chunk *) o->chunks; p != NULL; p = p->next)
200 if (p->current_ptr == NULL)
202 if (b > (char *) p && b < (char *) p + CHUNK_SIZE)
208 if (b == (char *) p + CHUNK_HEADER_SIZE)
213 /* If we can't find the chunk, the caller has made a mistake. */
217 if (p->current_ptr == NULL)
219 struct objalloc_chunk *q;
220 struct objalloc_chunk *first;
222 /* The block is in a chunk containing small objects. We can
223 free every chunk through SMALL, because they have certainly
224 been allocated more recently. After SMALL, we will not see
225 any chunks containing small objects; we can free any big
226 chunk if the current_ptr is greater than or equal to B. We
227 can then reset the new current_ptr to B. */
230 q = (struct objalloc_chunk *) o->chunks;
233 struct objalloc_chunk *next;
242 else if (q->current_ptr > b)
244 else if (first == NULL)
252 o->chunks = (PTR) first;
254 /* Now start allocating from this small block again. */
256 o->current_space = ((char *) p + CHUNK_SIZE) - b;
260 struct objalloc_chunk *q;
263 /* This block is in a large chunk by itself. We can free
264 everything on the list up to and including this block. We
265 then start allocating from the next chunk containing small
266 objects, setting current_ptr from the value stored with the
267 large chunk we are freeing. */
269 current_ptr = p->current_ptr;
272 q = (struct objalloc_chunk *) o->chunks;
275 struct objalloc_chunk *next;
284 while (p->current_ptr != NULL)
287 o->current_ptr = current_ptr;
288 o->current_space = ((char *) p + CHUNK_SIZE) - current_ptr;