1 /* BFD library -- caching of file descriptors.
2 Copyright 1990, 1991, 1992 Free Software Foundation, Inc.
3 Hacked by Steve Chamberlain of Cygnus Support (steve@cygnus.com).
5 This file is part of BFD, the Binary File Descriptor library.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
25 The file caching mechanism is embedded within BFD and allows
26 the application to open as many BFDs as it wants without
27 regard to the underlying operating system's file descriptor
28 limit (often as low as 20 open files). The module in
29 <<cache.c>> maintains a least recently used list of
30 <<BFD_CACHE_MAX_OPEN>> files, and exports the name
31 <<bfd_cache_lookup>> which runs around and makes sure that
32 the required BFD is open. If not, then it chooses a file to
33 close, closes it and opens the one wanted, returning its file
44 BFD_CACHE_MAX_OPEN macro
47 The maximum number of files which the cache will keep open at
50 .#define BFD_CACHE_MAX_OPEN 10
55 static int open_files
;
57 static bfd
*cache_sentinel
; /* Chain of BFDs with active fds we've
65 extern bfd *bfd_last_cache;
68 Zero, or a pointer to the topmost BFD on the chain. This is
69 used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
70 determine when it can avoid a function call.
80 * Checks to see if the required BFD is the same as the last one
81 * looked up. If so then it can use the iostream in the BFD with
82 * impunity, since it can't have changed since the last lookup,
83 * otherwise it has to perform the complicated lookup function
85 * .#define bfd_cache_lookup(x) \
86 * . ((x)==bfd_last_cache? \
87 * . (FILE*)(bfd_last_cache->iostream): \
88 * . bfd_cache_lookup_worker(x))
93 static boolean
EXFUN(bfd_cache_delete
,(bfd
*));
99 bfd
*kill
= cache_sentinel
;
100 if (kill
== 0) /* Nothing in the cache */
103 /* We can only close files that want to play this game. */
104 while (!kill
->cacheable
) {
105 kill
= kill
->lru_prev
;
106 if (kill
== cache_sentinel
) /* Nobody wants to play */
110 kill
->where
= ftell((FILE *)(kill
->iostream
));
111 (void) bfd_cache_delete(kill
);
114 /* Cuts the BFD abfd out of the chain in the cache */
119 abfd
->lru_prev
->lru_next
= abfd
->lru_next
;
120 abfd
->lru_next
->lru_prev
= abfd
->lru_prev
;
121 if (cache_sentinel
== abfd
) cache_sentinel
= (bfd
*)NULL
;
125 DEFUN(bfd_cache_delete
,(abfd
),
130 if (fclose ((FILE *)(abfd
->iostream
)) == 0)
135 bfd_error
= system_call_error
;
138 abfd
->iostream
= NULL
;
151 x
->lru_prev
= y
->lru_prev
;
152 y
->lru_prev
->lru_next
= x
;
169 void bfd_cache_init (bfd *);
172 Initialize a BFD by putting it on the cache LRU.
176 DEFUN(bfd_cache_init
,(abfd
),
179 cache_sentinel
= insert(abfd
, cache_sentinel
);
188 Remove the BFD from the cache. If the attached file is open,
192 boolean bfd_cache_close (bfd *);
195 <<false>> is returned if closing the file fails, <<true>> is
196 returned if all is well.
199 DEFUN(bfd_cache_close
,(abfd
),
202 /* If this file is open then remove from the chain */
205 return bfd_cache_delete(abfd
);
218 Call the OS to open a file for this BFD. Returns the FILE *
219 (possibly null) that results from this operation. Sets up the
220 BFD so that future accesses know the file is open. If the FILE
221 * returned is null, then there is won't have been put in the
222 cache, so it won't have to be removed from it.
225 FILE* bfd_open_file(bfd *);
229 DEFUN(bfd_open_file
, (abfd
),
232 abfd
->cacheable
= true; /* Allow it to be closed later. */
234 if(open_files
>= BFD_CACHE_MAX_OPEN
) {
238 switch (abfd
->direction
) {
241 abfd
->iostream
= (char *) fopen(abfd
->filename
, FOPEN_RB
);
244 case write_direction
:
245 if (abfd
->opened_once
== true) {
246 abfd
->iostream
= (char *) fopen(abfd
->filename
, FOPEN_RUB
);
247 if (!abfd
->iostream
) {
248 abfd
->iostream
= (char *) fopen(abfd
->filename
, FOPEN_WUB
);
252 abfd
->iostream
= (char *) fopen(abfd
->filename
, FOPEN_WB
);
253 abfd
->opened_once
= true;
258 if (abfd
->iostream
) {
260 bfd_cache_init (abfd
);
263 return (FILE *)(abfd
->iostream
);
268 bfd_cache_lookup_worker
271 Called when the macro <<bfd_cache_lookup>> fails to find a
272 quick answer. Finds a file descriptor for this BFD. If
273 necessary, it open it. If there are already more than
274 BFD_CACHE_MAX_OPEN files open, it trys to close one first, to
275 avoid running out of file descriptors.
278 FILE *bfd_cache_lookup_worker(bfd *);
283 DEFUN(bfd_cache_lookup_worker
,(abfd
),
286 if (abfd
->my_archive
)
288 abfd
= abfd
->my_archive
;
290 /* Is this file already open .. if so then quick exit */
293 if (abfd
!= cache_sentinel
) {
294 /* Place onto head of lru chain */
296 cache_sentinel
= insert(abfd
, cache_sentinel
);
299 /* This is a BFD without a stream -
300 so it must have been closed or never opened.
301 find an empty cache entry and use it. */
305 if (open_files
>= BFD_CACHE_MAX_OPEN
)
310 BFD_ASSERT(bfd_open_file (abfd
) != (FILE *)NULL
) ;
311 fseek((FILE *)(abfd
->iostream
), abfd
->where
, false);
313 bfd_last_cache
= abfd
;
314 return (FILE *)(abfd
->iostream
);
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