| 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). |
| 4 | |
| 5 | This file is part of BFD, the Binary File Descriptor library. |
| 6 | |
| 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. |
| 11 | |
| 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. |
| 16 | |
| 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. */ |
| 20 | |
| 21 | /* |
| 22 | SECTION |
| 23 | File Caching |
| 24 | |
| 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 |
| 34 | handle. |
| 35 | |
| 36 | */ |
| 37 | |
| 38 | #include "bfd.h" |
| 39 | #include "sysdep.h" |
| 40 | #include "libbfd.h" |
| 41 | |
| 42 | /* |
| 43 | INTERNAL_FUNCTION |
| 44 | BFD_CACHE_MAX_OPEN macro |
| 45 | |
| 46 | DESCRIPTION |
| 47 | The maximum number of files which the cache will keep open at |
| 48 | one time. |
| 49 | |
| 50 | .#define BFD_CACHE_MAX_OPEN 10 |
| 51 | |
| 52 | */ |
| 53 | |
| 54 | |
| 55 | static int open_files; |
| 56 | |
| 57 | static bfd *cache_sentinel; /* Chain of BFDs with active fds we've |
| 58 | opened */ |
| 59 | |
| 60 | /* |
| 61 | INTERNAL_FUNCTION |
| 62 | bfd_last_cache |
| 63 | |
| 64 | SYNOPSIS |
| 65 | extern bfd *bfd_last_cache; |
| 66 | |
| 67 | DESCRIPTION |
| 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. |
| 71 | */ |
| 72 | |
| 73 | bfd *bfd_last_cache; |
| 74 | |
| 75 | /* |
| 76 | * INTERNAL_FUNCTION |
| 77 | * bfd_cache_lookup |
| 78 | * |
| 79 | * DESCRIPTION |
| 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 |
| 84 | * |
| 85 | * .#define bfd_cache_lookup(x) \ |
| 86 | * . ((x)==bfd_last_cache? \ |
| 87 | * . (FILE*)(bfd_last_cache->iostream): \ |
| 88 | * . bfd_cache_lookup_worker(x)) |
| 89 | * |
| 90 | * |
| 91 | */ |
| 92 | |
| 93 | static boolean EXFUN(bfd_cache_delete,(bfd *)); |
| 94 | |
| 95 | |
| 96 | static void |
| 97 | DEFUN_VOID(close_one) |
| 98 | { |
| 99 | bfd *kill = cache_sentinel; |
| 100 | if (kill == 0) /* Nothing in the cache */ |
| 101 | return ; |
| 102 | |
| 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 */ |
| 107 | return ; |
| 108 | } |
| 109 | |
| 110 | kill->where = ftell((FILE *)(kill->iostream)); |
| 111 | (void) bfd_cache_delete(kill); |
| 112 | } |
| 113 | |
| 114 | /* Cuts the BFD abfd out of the chain in the cache */ |
| 115 | static void |
| 116 | DEFUN(snip,(abfd), |
| 117 | bfd *abfd) |
| 118 | { |
| 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; |
| 122 | } |
| 123 | |
| 124 | static boolean |
| 125 | DEFUN(bfd_cache_delete,(abfd), |
| 126 | bfd *abfd) |
| 127 | { |
| 128 | boolean ret; |
| 129 | |
| 130 | if (fclose ((FILE *)(abfd->iostream)) == 0) |
| 131 | ret = true; |
| 132 | else |
| 133 | { |
| 134 | ret = false; |
| 135 | bfd_error = system_call_error; |
| 136 | } |
| 137 | snip (abfd); |
| 138 | abfd->iostream = NULL; |
| 139 | open_files--; |
| 140 | bfd_last_cache = 0; |
| 141 | return ret; |
| 142 | } |
| 143 | |
| 144 | static bfd * |
| 145 | DEFUN(insert,(x,y), |
| 146 | bfd *x AND |
| 147 | bfd *y) |
| 148 | { |
| 149 | if (y) { |
| 150 | x->lru_next = y; |
| 151 | x->lru_prev = y->lru_prev; |
| 152 | y->lru_prev->lru_next = x; |
| 153 | y->lru_prev = x; |
| 154 | |
| 155 | } |
| 156 | else { |
| 157 | x->lru_prev = x; |
| 158 | x->lru_next = x; |
| 159 | } |
| 160 | return x; |
| 161 | } |
| 162 | \f |
| 163 | |
| 164 | /* |
| 165 | INTERNAL_FUNCTION |
| 166 | bfd_cache_init |
| 167 | |
| 168 | SYNOPSIS |
| 169 | void bfd_cache_init (bfd *); |
| 170 | |
| 171 | DESCRIPTION |
| 172 | Initialize a BFD by putting it on the cache LRU. |
| 173 | */ |
| 174 | |
| 175 | void |
| 176 | DEFUN(bfd_cache_init,(abfd), |
| 177 | bfd *abfd) |
| 178 | { |
| 179 | cache_sentinel = insert(abfd, cache_sentinel); |
| 180 | } |
| 181 | |
| 182 | |
| 183 | /* |
| 184 | INTERNAL_FUNCTION |
| 185 | bfd_cache_close |
| 186 | |
| 187 | DESCRIPTION |
| 188 | Remove the BFD from the cache. If the attached file is open, |
| 189 | then close it too. |
| 190 | |
| 191 | SYNOPSIS |
| 192 | boolean bfd_cache_close (bfd *); |
| 193 | |
| 194 | RETURNS |
| 195 | <<false>> is returned if closing the file fails, <<true>> is |
| 196 | returned if all is well. |
| 197 | */ |
| 198 | boolean |
| 199 | DEFUN(bfd_cache_close,(abfd), |
| 200 | bfd *abfd) |
| 201 | { |
| 202 | /* If this file is open then remove from the chain */ |
| 203 | if (abfd->iostream) |
| 204 | { |
| 205 | return bfd_cache_delete(abfd); |
| 206 | } |
| 207 | else |
| 208 | { |
| 209 | return true; |
| 210 | } |
| 211 | } |
| 212 | |
| 213 | /* |
| 214 | INTERNAL_FUNCTION |
| 215 | bfd_open_file |
| 216 | |
| 217 | DESCRIPTION |
| 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. |
| 223 | |
| 224 | SYNOPSIS |
| 225 | FILE* bfd_open_file(bfd *); |
| 226 | */ |
| 227 | |
| 228 | FILE * |
| 229 | DEFUN(bfd_open_file, (abfd), |
| 230 | bfd *abfd) |
| 231 | { |
| 232 | abfd->cacheable = true; /* Allow it to be closed later. */ |
| 233 | |
| 234 | if(open_files >= BFD_CACHE_MAX_OPEN) { |
| 235 | close_one(); |
| 236 | } |
| 237 | |
| 238 | switch (abfd->direction) { |
| 239 | case read_direction: |
| 240 | case no_direction: |
| 241 | abfd->iostream = (char *) fopen(abfd->filename, FOPEN_RB); |
| 242 | break; |
| 243 | case both_direction: |
| 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); |
| 249 | } |
| 250 | } else { |
| 251 | /*open for creat */ |
| 252 | abfd->iostream = (char *) fopen(abfd->filename, FOPEN_WB); |
| 253 | abfd->opened_once = true; |
| 254 | } |
| 255 | break; |
| 256 | } |
| 257 | |
| 258 | if (abfd->iostream) { |
| 259 | open_files++; |
| 260 | bfd_cache_init (abfd); |
| 261 | } |
| 262 | |
| 263 | return (FILE *)(abfd->iostream); |
| 264 | } |
| 265 | |
| 266 | /* |
| 267 | INTERNAL_FUNCTION |
| 268 | bfd_cache_lookup_worker |
| 269 | |
| 270 | DESCRIPTION |
| 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. |
| 276 | |
| 277 | SYNOPSIS |
| 278 | FILE *bfd_cache_lookup_worker(bfd *); |
| 279 | |
| 280 | */ |
| 281 | |
| 282 | FILE * |
| 283 | DEFUN(bfd_cache_lookup_worker,(abfd), |
| 284 | bfd *abfd) |
| 285 | { |
| 286 | if (abfd->my_archive) |
| 287 | { |
| 288 | abfd = abfd->my_archive; |
| 289 | } |
| 290 | /* Is this file already open .. if so then quick exit */ |
| 291 | if (abfd->iostream) |
| 292 | { |
| 293 | if (abfd != cache_sentinel) { |
| 294 | /* Place onto head of lru chain */ |
| 295 | snip (abfd); |
| 296 | cache_sentinel = insert(abfd, cache_sentinel); |
| 297 | } |
| 298 | } |
| 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. */ |
| 302 | else |
| 303 | { |
| 304 | |
| 305 | if (open_files >= BFD_CACHE_MAX_OPEN) |
| 306 | { |
| 307 | close_one(); |
| 308 | } |
| 309 | |
| 310 | BFD_ASSERT(bfd_open_file (abfd) != (FILE *)NULL) ; |
| 311 | fseek((FILE *)(abfd->iostream), abfd->where, false); |
| 312 | } |
| 313 | bfd_last_cache = abfd; |
| 314 | return (FILE *)(abfd->iostream); |
| 315 | } |