aboutsummaryrefslogtreecommitdiff
path: root/libiberty/objalloc.c
blob: d7e9ad03ccfa61f7a9ecf1a1ff31ca382e6680b0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
/* objalloc.c -- routines to allocate memory for objects
   Copyright (C) 1997-2017 Free Software Foundation, Inc.
   Written by Ian Lance Taylor, Cygnus Solutions.

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, 51 Franklin Street - Fifth Floor,
Boston, MA 02110-1301, USA.  */

#include "config.h"
#include "ansidecl.h"

#include "objalloc.h"

/* Get a definition for NULL.  */
#include <stdio.h>

#if VMS
#include <stdlib.h>
#include <unixlib.h>
#else

/* Get a definition for size_t.  */
#include <stddef.h>

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#else
/* For systems with larger pointers than ints, this must be declared.  */
extern PTR malloc (size_t);
extern void free (PTR);
#endif

#endif

/* These routines allocate space for an object.  Freeing allocated
   space may or may not free all more recently allocated space.

   We handle large and small allocation requests differently.  If we
   don't have enough space in the current block, and the allocation
   request is for more than 512 bytes, we simply pass it through to
   malloc.  */

/* The objalloc structure is defined in objalloc.h.  */

/* This structure appears at the start of each chunk.  */

struct objalloc_chunk
{
  /* Next chunk.  */
  struct objalloc_chunk *next;
  /* If this chunk contains large objects, this is the value of
     current_ptr when this chunk was allocated.  If this chunk
     contains small objects, this is NULL.  */
  char *current_ptr;
};

/* The aligned size of objalloc_chunk.  */

#define CHUNK_HEADER_SIZE					\
  ((sizeof (struct objalloc_chunk) + OBJALLOC_ALIGN - 1)	\
   &~ (OBJALLOC_ALIGN - 1))

/* We ask for this much memory each time we create a chunk which is to
   hold small objects.  */

#define CHUNK_SIZE (4096 - 32)

/* A request for this amount or more is just passed through to malloc.  */

#define BIG_REQUEST (512)

/* Create an objalloc structure.  */

struct objalloc *
objalloc_create (void)
{
  struct objalloc *ret;
  struct objalloc_chunk *chunk;

  ret = (struct objalloc *) malloc (sizeof *ret);
  if (ret == NULL)
    return NULL;

  ret->chunks = (PTR) malloc (CHUNK_SIZE);
  if (ret->chunks == NULL)
    {
      free (ret);
      return NULL;
    }

  chunk = (struct objalloc_chunk *) ret->chunks;
  chunk->next = NULL;
  chunk->current_ptr = NULL;

  ret->current_ptr = (char *) chunk + CHUNK_HEADER_SIZE;
  ret->current_space = CHUNK_SIZE - CHUNK_HEADER_SIZE;

  return ret;
}

/* Allocate space from an objalloc structure.  */

PTR
_objalloc_alloc (struct objalloc *o, unsigned long original_len)
{
  unsigned long len = original_len;

  /* We avoid confusion from zero sized objects by always allocating
     at least 1 byte.  */
  if (len == 0)
    len = 1;

  len = (len + OBJALLOC_ALIGN - 1) &~ (OBJALLOC_ALIGN - 1);

  /* Check for overflow in the alignment operation above and the
     malloc argument below. */
  if (len + CHUNK_HEADER_SIZE < original_len)
    return NULL;

  if (len <= o->current_space)
    {
      o->current_ptr += len;
      o->current_space -= len;
      return (PTR) (o->current_ptr - len);
    }

  if (len >= BIG_REQUEST)
    {
      char *ret;
      struct objalloc_chunk *chunk;

      ret = (char *) malloc (CHUNK_HEADER_SIZE + len);
      if (ret == NULL)
	return NULL;

      chunk = (struct objalloc_chunk *) ret;
      chunk->next = (struct objalloc_chunk *) o->chunks;
      chunk->current_ptr = o->current_ptr;

      o->chunks = (PTR) chunk;

      return (PTR) (ret + CHUNK_HEADER_SIZE);
    }
  else
    {
      struct objalloc_chunk *chunk;

      chunk = (struct objalloc_chunk *) malloc (CHUNK_SIZE);
      if (chunk == NULL)
	return NULL;
      chunk->next = (struct objalloc_chunk *) o->chunks;
      chunk->current_ptr = NULL;

      o->current_ptr = (char *) chunk + CHUNK_HEADER_SIZE;
      o->current_space = CHUNK_SIZE - CHUNK_HEADER_SIZE;

      o->chunks = (PTR) chunk;

      return objalloc_alloc (o, len);
    }
}

/* Free an entire objalloc structure.  */

void
objalloc_free (struct objalloc *o)
{
  struct objalloc_chunk *l;

  l = (struct objalloc_chunk *) o->chunks;
  while (l != NULL)
    {
      struct objalloc_chunk *next;

      next = l->next;
      free (l);
      l = next;
    }

  free (o);
}

/* Free a block from an objalloc structure.  This also frees all more
   recently allocated blocks.  */

void
objalloc_free_block (struct objalloc *o, PTR block)
{
  struct objalloc_chunk *p, *small;
  char *b = (char *) block;

  /* First set P to the chunk which contains the block we are freeing,
     and set Q to the last small object chunk we see before P.  */
  small = NULL;
  for (p = (struct objalloc_chunk *) o->chunks; p != NULL; p = p->next)
    {
      if (p->current_ptr == NULL)
	{
	  if (b > (char *) p && b < (char *) p + CHUNK_SIZE)
	    break;
	  small = p;
	}
      else
	{
	  if (b == (char *) p + CHUNK_HEADER_SIZE)
	    break;
	}
    }

  /* If we can't find the chunk, the caller has made a mistake.  */
  if (p == NULL)
    abort ();

  if (p->current_ptr == NULL)
    {
      struct objalloc_chunk *q;
      struct objalloc_chunk *first;

      /* The block is in a chunk containing small objects.  We can
	 free every chunk through SMALL, because they have certainly
	 been allocated more recently.  After SMALL, we will not see
	 any chunks containing small objects; we can free any big
	 chunk if the current_ptr is greater than or equal to B.  We
	 can then reset the new current_ptr to B.  */

      first = NULL;
      q = (struct objalloc_chunk *) o->chunks;
      while (q != p)
	{
	  struct objalloc_chunk *next;

	  next = q->next;
	  if (small != NULL)
	    {
	      if (small == q)
		small = NULL;
	      free (q);
	    }
	  else if (q->current_ptr > b)
	    free (q);
	  else if (first == NULL)
	    first = q;

	  q = next;
	}

      if (first == NULL)
	first = p;
      o->chunks = (PTR) first;

      /* Now start allocating from this small block again.  */
      o->current_ptr = b;
      o->current_space = ((char *) p + CHUNK_SIZE) - b;
    }
  else
    {
      struct objalloc_chunk *q;
      char *current_ptr;

      /* This block is in a large chunk by itself.  We can free
         everything on the list up to and including this block.  We
         then start allocating from the next chunk containing small
         objects, setting current_ptr from the value stored with the
         large chunk we are freeing.  */

      current_ptr = p->current_ptr;
      p = p->next;

      q = (struct objalloc_chunk *) o->chunks;
      while (q != p)
	{
	  struct objalloc_chunk *next;

	  next = q->next;
	  free (q);
	  q = next;
	}

      o->chunks = (PTR) p;

      while (p->current_ptr != NULL)
	p = p->next;

      o->current_ptr = current_ptr;
      o->current_space = ((char *) p + CHUNK_SIZE) - current_ptr;
    }
}