aboutsummaryrefslogtreecommitdiff
path: root/bfd/cache.c
blob: cefae728f631d4a4fe93d9b42e9b459588224b1c (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
299
300
301
302
303
304
305
306
307
308
309
310
311
/* BFD library -- caching of file descriptors.
   Copyright 1990, 1991, 1992 Free Software Foundation, Inc.
   Hacked by Steve Chamberlain of Cygnus Support (steve@cygnus.com).

This file is part of BFD, the Binary File Descriptor library.

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 of the License, 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, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

/*
SECTION
	File caching

	The file caching mechanism is embedded within BFD and allows
	the application to open as many BFDs as it wants without
	regard to the underlying operating system's file descriptor
	limit (often as low as 20 open files).  The module in
	<<cache.c>> maintains a least recently used list of
	<<BFD_CACHE_MAX_OPEN>> files, and exports the name
	<<bfd_cache_lookup>>, which runs around and makes sure that
	the required BFD is open. If not, then it chooses a file to
	close, closes it and opens the one wanted, returning its file
	handle. 

*/

#include "bfd.h"
#include "sysdep.h"
#include "libbfd.h"

/*
INTERNAL_FUNCTION
	BFD_CACHE_MAX_OPEN macro

DESCRIPTION
	The maximum number of files which the cache will keep open at
	one time.

.#define BFD_CACHE_MAX_OPEN 10

*/


static boolean
bfd_cache_delete PARAMS ((bfd *));

/* Number of bfds on the chain.  All such bfds have their file open;
   if it closed, they get snipd()d from the chain.  */

static int open_files;

static bfd *cache_sentinel;	/* Chain of BFDs with active fds we've
				   opened */

/*
INTERNAL_FUNCTION
	bfd_last_cache

SYNOPSIS
	extern bfd *bfd_last_cache;

DESCRIPTION
	Zero, or a pointer to the topmost BFD on the chain.  This is
	used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
	determine when it can avoid a function call.
*/

bfd *bfd_last_cache;

/*
  INTERNAL_FUNCTION
  	bfd_cache_lookup
 
  DESCRIPTION
 	Check to see if the required BFD is the same as the last one
 	looked up. If so, then it can use the stream in the BFD with
 	impunity, since it can't have changed since the last lookup;
 	otherwise, it has to perform the complicated lookup function.
 
  .#define bfd_cache_lookup(x) \
  .    ((x)==bfd_last_cache? \
  .      (FILE*)(bfd_last_cache->iostream): \
  .       bfd_cache_lookup_worker(x))
 
 
 */

static void
DEFUN_VOID(close_one)
{
    bfd *kill = cache_sentinel;
    if (kill == 0)		/* Nothing in the cache */
	return ;

    /* We can only close files that want to play this game.  */
    while (!kill->cacheable) {
	kill = kill->lru_prev;
	if (kill == cache_sentinel) /* Nobody wants to play */
	   return ;
    }

    kill->where = ftell((FILE *)(kill->iostream));
    (void) bfd_cache_delete(kill);
}

/* Cuts the BFD abfd out of the chain in the cache */
static void 
DEFUN(snip,(abfd),
      bfd *abfd)
{
  abfd->lru_prev->lru_next = abfd->lru_next;
  abfd->lru_next->lru_prev = abfd->lru_prev; 
  if (cache_sentinel == abfd) cache_sentinel = (bfd *)NULL;
}

static boolean
DEFUN(bfd_cache_delete,(abfd),
      bfd *abfd)
{
  boolean ret;

  if (fclose ((FILE *)(abfd->iostream)) == 0)
    ret = true;
  else
    {
      ret = false;
      bfd_error = system_call_error;
    }
  snip (abfd);
  abfd->iostream = NULL;
  open_files--;
  bfd_last_cache = 0;
  return ret;
}
  
static bfd *
DEFUN(insert,(x,y),
      bfd *x AND
      bfd *y)
{
  if (y) {
    x->lru_next = y;
    x->lru_prev = y->lru_prev;
    y->lru_prev->lru_next = x;
    y->lru_prev = x;

  }
  else {
    x->lru_prev = x;
    x->lru_next = x;
  }
  return x;
}


/* Initialize a BFD by putting it on the cache LRU.  */

void
DEFUN(bfd_cache_init,(abfd),
      bfd *abfd)
{
  if (open_files >= BFD_CACHE_MAX_OPEN)
    close_one ();
  cache_sentinel = insert(abfd, cache_sentinel);
  ++open_files;
}


/*
INTERNAL_FUNCTION
	bfd_cache_close

SYNOPSIS
	boolean bfd_cache_close (bfd *abfd);

DESCRIPTION
	Remove the BFD @var{abfd} from the cache. If the attached file is open,
	then close it too.

RETURNS
	<<false>> is returned if closing the file fails, <<true>> is
	returned if all is well.
*/
boolean
DEFUN(bfd_cache_close,(abfd),
      bfd *abfd)
{
  /* If this file is open then remove from the chain */
  if (abfd->iostream) 
    {
      return bfd_cache_delete(abfd);
    }
  else
    {
      return true;
    }
}

/*
INTERNAL_FUNCTION
	bfd_open_file

SYNOPSIS
	FILE* bfd_open_file(bfd *abfd);

DESCRIPTION
	Call the OS to open a file for @var{abfd}.  Return the <<FILE *>>
	(possibly NULL) that results from this operation.  Set up the
	BFD so that future accesses know the file is open. If the <<FILE *>>
	returned is NULL, then it won't have been put in the
	cache, so it won't have to be removed from it.
*/

FILE *
DEFUN(bfd_open_file, (abfd),
      bfd *abfd)
{
  abfd->cacheable = true;	/* Allow it to be closed later. */

  if(open_files >= BFD_CACHE_MAX_OPEN) {
    close_one();
  }

  switch (abfd->direction) {
  case read_direction:
  case no_direction:
    abfd->iostream = (char *) fopen(abfd->filename, FOPEN_RB);
    break;
  case both_direction:
  case write_direction:
    if (abfd->opened_once == true) {
      abfd->iostream = (char *) fopen(abfd->filename, FOPEN_RUB);
      if (!abfd->iostream) {
	abfd->iostream = (char *) fopen(abfd->filename, FOPEN_WUB);
      }
    } else {
      /*open for creat */
      abfd->iostream = (char *) fopen(abfd->filename, FOPEN_WB);
      abfd->opened_once = true;
    }
    break;
  }

  if (abfd->iostream) {
    bfd_cache_init (abfd);
  }

  return (FILE *)(abfd->iostream);
}

/*
INTERNAL_FUNCTION
	bfd_cache_lookup_worker

SYNOPSIS
	FILE *bfd_cache_lookup_worker(bfd *abfd);

DESCRIPTION
	Called when the macro <<bfd_cache_lookup>> fails to find a
	quick answer.  Find a file descriptor for @var{abfd}.  If
	necessary, it open it.  If there are already more than
	<<BFD_CACHE_MAX_OPEN>> files open, it tries to close one first, to
	avoid running out of file descriptors.  

*/

FILE *
DEFUN(bfd_cache_lookup_worker,(abfd),
      bfd *abfd)
{
  if (abfd->my_archive) 
      {
	abfd = abfd->my_archive;
      }
  /* Is this file already open .. if so then quick exit */
  if (abfd->iostream) 
      {
	if (abfd != cache_sentinel) {
	  /* Place onto head of lru chain */
	  snip (abfd);
	  cache_sentinel = insert(abfd, cache_sentinel);
	}
      }
  /* This is a BFD without a stream -
     so it must have been closed or never opened.
     find an empty cache entry and use it.  */
  else 
      {

	if (open_files >= BFD_CACHE_MAX_OPEN) 
	    {
	      close_one();
	    }

	BFD_ASSERT(bfd_open_file (abfd) != (FILE *)NULL) ;
	fseek((FILE *)(abfd->iostream), abfd->where, false);
      }
  bfd_last_cache = abfd;
  return (FILE *)(abfd->iostream);
}