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, 51 Franklin Street - Fifth Floor,
18 Boston, MA 02110-1301, USA. */
25 /* Get a definition for NULL. */
33 /* Get a definition for size_t. */
39 /* For systems with larger pointers than ints, this must be declared. */
40 extern PTR
malloc (size_t);
41 extern void free (PTR
);
46 /* These routines allocate space for an object. Freeing allocated
47 space may or may not free all more recently allocated space.
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
54 /* The objalloc structure is defined in objalloc.h. */
56 /* This structure appears at the start of each 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. */
68 /* The aligned size of objalloc_chunk. */
70 #define CHUNK_HEADER_SIZE \
71 ((sizeof (struct objalloc_chunk) + OBJALLOC_ALIGN - 1) \
72 &~ (OBJALLOC_ALIGN - 1))
74 /* We ask for this much memory each time we create a chunk which is to
75 hold small objects. */
77 #define CHUNK_SIZE (4096 - 32)
79 /* A request for this amount or more is just passed through to malloc. */
81 #define BIG_REQUEST (512)
83 /* Create an objalloc structure. */
86 objalloc_create (void)
89 struct objalloc_chunk
*chunk
;
91 ret
= (struct objalloc
*) malloc (sizeof *ret
);
95 ret
->chunks
= (PTR
) malloc (CHUNK_SIZE
);
96 if (ret
->chunks
== NULL
)
102 chunk
= (struct objalloc_chunk
*) ret
->chunks
;
104 chunk
->current_ptr
= NULL
;
106 ret
->current_ptr
= (char *) chunk
+ CHUNK_HEADER_SIZE
;
107 ret
->current_space
= CHUNK_SIZE
- CHUNK_HEADER_SIZE
;
112 /* Allocate space from an objalloc structure. */
115 _objalloc_alloc (struct objalloc
*o
, unsigned long len
)
117 /* We avoid confusion from zero sized objects by always allocating
122 len
= (len
+ OBJALLOC_ALIGN
- 1) &~ (OBJALLOC_ALIGN
- 1);
124 if (len
<= o
->current_space
)
126 o
->current_ptr
+= len
;
127 o
->current_space
-= len
;
128 return (PTR
) (o
->current_ptr
- len
);
131 if (len
>= BIG_REQUEST
)
134 struct objalloc_chunk
*chunk
;
136 ret
= (char *) malloc (CHUNK_HEADER_SIZE
+ len
);
140 chunk
= (struct objalloc_chunk
*) ret
;
141 chunk
->next
= (struct objalloc_chunk
*) o
->chunks
;
142 chunk
->current_ptr
= o
->current_ptr
;
144 o
->chunks
= (PTR
) chunk
;
146 return (PTR
) (ret
+ CHUNK_HEADER_SIZE
);
150 struct objalloc_chunk
*chunk
;
152 chunk
= (struct objalloc_chunk
*) malloc (CHUNK_SIZE
);
155 chunk
->next
= (struct objalloc_chunk
*) o
->chunks
;
156 chunk
->current_ptr
= NULL
;
158 o
->current_ptr
= (char *) chunk
+ CHUNK_HEADER_SIZE
;
159 o
->current_space
= CHUNK_SIZE
- CHUNK_HEADER_SIZE
;
161 o
->chunks
= (PTR
) chunk
;
163 return objalloc_alloc (o
, len
);
167 /* Free an entire objalloc structure. */
170 objalloc_free (struct objalloc
*o
)
172 struct objalloc_chunk
*l
;
174 l
= (struct objalloc_chunk
*) o
->chunks
;
177 struct objalloc_chunk
*next
;
187 /* Free a block from an objalloc structure. This also frees all more
188 recently allocated blocks. */
191 objalloc_free_block (struct objalloc
*o
, PTR block
)
193 struct objalloc_chunk
*p
, *small
;
194 char *b
= (char *) block
;
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. */
199 for (p
= (struct objalloc_chunk
*) o
->chunks
; p
!= NULL
; p
= p
->next
)
201 if (p
->current_ptr
== NULL
)
203 if (b
> (char *) p
&& b
< (char *) p
+ CHUNK_SIZE
)
209 if (b
== (char *) p
+ CHUNK_HEADER_SIZE
)
214 /* If we can't find the chunk, the caller has made a mistake. */
218 if (p
->current_ptr
== NULL
)
220 struct objalloc_chunk
*q
;
221 struct objalloc_chunk
*first
;
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. */
231 q
= (struct objalloc_chunk
*) o
->chunks
;
234 struct objalloc_chunk
*next
;
243 else if (q
->current_ptr
> b
)
245 else if (first
== NULL
)
253 o
->chunks
= (PTR
) first
;
255 /* Now start allocating from this small block again. */
257 o
->current_space
= ((char *) p
+ CHUNK_SIZE
) - b
;
261 struct objalloc_chunk
*q
;
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. */
270 current_ptr
= p
->current_ptr
;
273 q
= (struct objalloc_chunk
*) o
->chunks
;
276 struct objalloc_chunk
*next
;
285 while (p
->current_ptr
!= NULL
)
288 o
->current_ptr
= current_ptr
;
289 o
->current_space
= ((char *) p
+ CHUNK_SIZE
) - current_ptr
;
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