| 1 | /* BFD library -- caching of file descriptors. |
| 2 | Copyright 1990, 1991, 1992, 1993, 1994, 1996, 2000, 2001 |
| 3 | Free Software Foundation, Inc. |
| 4 | Hacked by Steve Chamberlain of Cygnus Support (steve@cygnus.com). |
| 5 | |
| 6 | This file is part of BFD, the Binary File Descriptor library. |
| 7 | |
| 8 | This program is free software; you can redistribute it and/or modify |
| 9 | it under the terms of the GNU General Public License as published by |
| 10 | the Free Software Foundation; either version 2 of the License, or |
| 11 | (at your option) any later version. |
| 12 | |
| 13 | This program is distributed in the hope that it will be useful, |
| 14 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | GNU General Public License for more details. |
| 17 | |
| 18 | You should have received a copy of the GNU General Public License |
| 19 | along with this program; if not, write to the Free Software |
| 20 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ |
| 21 | |
| 22 | /* |
| 23 | SECTION |
| 24 | File caching |
| 25 | |
| 26 | The file caching mechanism is embedded within BFD and allows |
| 27 | the application to open as many BFDs as it wants without |
| 28 | regard to the underlying operating system's file descriptor |
| 29 | limit (often as low as 20 open files). The module in |
| 30 | <<cache.c>> maintains a least recently used list of |
| 31 | <<BFD_CACHE_MAX_OPEN>> files, and exports the name |
| 32 | <<bfd_cache_lookup>>, which runs around and makes sure that |
| 33 | the required BFD is open. If not, then it chooses a file to |
| 34 | close, closes it and opens the one wanted, returning its file |
| 35 | handle. |
| 36 | |
| 37 | */ |
| 38 | |
| 39 | #include "bfd.h" |
| 40 | #include "sysdep.h" |
| 41 | #include "libbfd.h" |
| 42 | |
| 43 | static void insert PARAMS ((bfd *)); |
| 44 | static void snip PARAMS ((bfd *)); |
| 45 | static boolean close_one PARAMS ((void)); |
| 46 | static boolean bfd_cache_delete PARAMS ((bfd *)); |
| 47 | |
| 48 | /* |
| 49 | INTERNAL_FUNCTION |
| 50 | BFD_CACHE_MAX_OPEN macro |
| 51 | |
| 52 | DESCRIPTION |
| 53 | The maximum number of files which the cache will keep open at |
| 54 | one time. |
| 55 | |
| 56 | .#define BFD_CACHE_MAX_OPEN 10 |
| 57 | |
| 58 | */ |
| 59 | |
| 60 | /* The number of BFD files we have open. */ |
| 61 | |
| 62 | static int open_files; |
| 63 | |
| 64 | /* |
| 65 | INTERNAL_FUNCTION |
| 66 | bfd_last_cache |
| 67 | |
| 68 | SYNOPSIS |
| 69 | extern bfd *bfd_last_cache; |
| 70 | |
| 71 | DESCRIPTION |
| 72 | Zero, or a pointer to the topmost BFD on the chain. This is |
| 73 | used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to |
| 74 | determine when it can avoid a function call. |
| 75 | */ |
| 76 | |
| 77 | bfd *bfd_last_cache; |
| 78 | |
| 79 | /* |
| 80 | INTERNAL_FUNCTION |
| 81 | bfd_cache_lookup |
| 82 | |
| 83 | DESCRIPTION |
| 84 | Check to see if the required BFD is the same as the last one |
| 85 | looked up. If so, then it can use the stream in the BFD with |
| 86 | impunity, since it can't have changed since the last lookup; |
| 87 | otherwise, it has to perform the complicated lookup function. |
| 88 | |
| 89 | .#define bfd_cache_lookup(x) \ |
| 90 | . ((x)==bfd_last_cache? \ |
| 91 | . (FILE*) (bfd_last_cache->iostream): \ |
| 92 | . bfd_cache_lookup_worker(x)) |
| 93 | |
| 94 | */ |
| 95 | |
| 96 | /* Insert a BFD into the cache. */ |
| 97 | |
| 98 | static INLINE void |
| 99 | insert (abfd) |
| 100 | bfd *abfd; |
| 101 | { |
| 102 | if (bfd_last_cache == NULL) |
| 103 | { |
| 104 | abfd->lru_next = abfd; |
| 105 | abfd->lru_prev = abfd; |
| 106 | } |
| 107 | else |
| 108 | { |
| 109 | abfd->lru_next = bfd_last_cache; |
| 110 | abfd->lru_prev = bfd_last_cache->lru_prev; |
| 111 | abfd->lru_prev->lru_next = abfd; |
| 112 | abfd->lru_next->lru_prev = abfd; |
| 113 | } |
| 114 | bfd_last_cache = abfd; |
| 115 | } |
| 116 | |
| 117 | /* Remove a BFD from the cache. */ |
| 118 | |
| 119 | static INLINE void |
| 120 | snip (abfd) |
| 121 | bfd *abfd; |
| 122 | { |
| 123 | abfd->lru_prev->lru_next = abfd->lru_next; |
| 124 | abfd->lru_next->lru_prev = abfd->lru_prev; |
| 125 | if (abfd == bfd_last_cache) |
| 126 | { |
| 127 | bfd_last_cache = abfd->lru_next; |
| 128 | if (abfd == bfd_last_cache) |
| 129 | bfd_last_cache = NULL; |
| 130 | } |
| 131 | } |
| 132 | |
| 133 | /* We need to open a new file, and the cache is full. Find the least |
| 134 | recently used cacheable BFD and close it. */ |
| 135 | |
| 136 | static boolean |
| 137 | close_one () |
| 138 | { |
| 139 | register bfd *kill; |
| 140 | |
| 141 | if (bfd_last_cache == NULL) |
| 142 | kill = NULL; |
| 143 | else |
| 144 | { |
| 145 | for (kill = bfd_last_cache->lru_prev; |
| 146 | ! kill->cacheable; |
| 147 | kill = kill->lru_prev) |
| 148 | { |
| 149 | if (kill == bfd_last_cache) |
| 150 | { |
| 151 | kill = NULL; |
| 152 | break; |
| 153 | } |
| 154 | } |
| 155 | } |
| 156 | |
| 157 | if (kill == NULL) |
| 158 | { |
| 159 | /* There are no open cacheable BFD's. */ |
| 160 | return true; |
| 161 | } |
| 162 | |
| 163 | kill->where = ftell ((FILE *) kill->iostream); |
| 164 | |
| 165 | return bfd_cache_delete (kill); |
| 166 | } |
| 167 | |
| 168 | /* Close a BFD and remove it from the cache. */ |
| 169 | |
| 170 | static boolean |
| 171 | bfd_cache_delete (abfd) |
| 172 | bfd *abfd; |
| 173 | { |
| 174 | boolean ret; |
| 175 | |
| 176 | if (fclose ((FILE *) abfd->iostream) == 0) |
| 177 | ret = true; |
| 178 | else |
| 179 | { |
| 180 | ret = false; |
| 181 | bfd_set_error (bfd_error_system_call); |
| 182 | } |
| 183 | |
| 184 | snip (abfd); |
| 185 | |
| 186 | abfd->iostream = NULL; |
| 187 | --open_files; |
| 188 | |
| 189 | return ret; |
| 190 | } |
| 191 | |
| 192 | /* |
| 193 | INTERNAL_FUNCTION |
| 194 | bfd_cache_init |
| 195 | |
| 196 | SYNOPSIS |
| 197 | boolean bfd_cache_init (bfd *abfd); |
| 198 | |
| 199 | DESCRIPTION |
| 200 | Add a newly opened BFD to the cache. |
| 201 | */ |
| 202 | |
| 203 | boolean |
| 204 | bfd_cache_init (abfd) |
| 205 | bfd *abfd; |
| 206 | { |
| 207 | BFD_ASSERT (abfd->iostream != NULL); |
| 208 | if (open_files >= BFD_CACHE_MAX_OPEN) |
| 209 | { |
| 210 | if (! close_one ()) |
| 211 | return false; |
| 212 | } |
| 213 | insert (abfd); |
| 214 | ++open_files; |
| 215 | return true; |
| 216 | } |
| 217 | |
| 218 | /* |
| 219 | INTERNAL_FUNCTION |
| 220 | bfd_cache_close |
| 221 | |
| 222 | SYNOPSIS |
| 223 | boolean bfd_cache_close (bfd *abfd); |
| 224 | |
| 225 | DESCRIPTION |
| 226 | Remove the BFD @var{abfd} from the cache. If the attached file is open, |
| 227 | then close it too. |
| 228 | |
| 229 | RETURNS |
| 230 | <<false>> is returned if closing the file fails, <<true>> is |
| 231 | returned if all is well. |
| 232 | */ |
| 233 | |
| 234 | boolean |
| 235 | bfd_cache_close (abfd) |
| 236 | bfd *abfd; |
| 237 | { |
| 238 | if (abfd->iostream == NULL |
| 239 | || (abfd->flags & BFD_IN_MEMORY) != 0) |
| 240 | return true; |
| 241 | |
| 242 | return bfd_cache_delete (abfd); |
| 243 | } |
| 244 | |
| 245 | /* |
| 246 | INTERNAL_FUNCTION |
| 247 | bfd_open_file |
| 248 | |
| 249 | SYNOPSIS |
| 250 | FILE* bfd_open_file(bfd *abfd); |
| 251 | |
| 252 | DESCRIPTION |
| 253 | Call the OS to open a file for @var{abfd}. Return the <<FILE *>> |
| 254 | (possibly <<NULL>>) that results from this operation. Set up the |
| 255 | BFD so that future accesses know the file is open. If the <<FILE *>> |
| 256 | returned is <<NULL>>, then it won't have been put in the |
| 257 | cache, so it won't have to be removed from it. |
| 258 | */ |
| 259 | |
| 260 | FILE * |
| 261 | bfd_open_file (abfd) |
| 262 | bfd *abfd; |
| 263 | { |
| 264 | abfd->cacheable = true; /* Allow it to be closed later. */ |
| 265 | |
| 266 | if (open_files >= BFD_CACHE_MAX_OPEN) |
| 267 | { |
| 268 | if (! close_one ()) |
| 269 | return NULL; |
| 270 | } |
| 271 | |
| 272 | switch (abfd->direction) |
| 273 | { |
| 274 | case read_direction: |
| 275 | case no_direction: |
| 276 | abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_RB); |
| 277 | break; |
| 278 | case both_direction: |
| 279 | case write_direction: |
| 280 | if (abfd->opened_once == true) |
| 281 | { |
| 282 | abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_RUB); |
| 283 | if (abfd->iostream == NULL) |
| 284 | abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_WUB); |
| 285 | } |
| 286 | else |
| 287 | { |
| 288 | /* Create the file. |
| 289 | |
| 290 | Some operating systems won't let us overwrite a running |
| 291 | binary. For them, we want to unlink the file first. |
| 292 | |
| 293 | However, gcc 2.95 will create temporary files using |
| 294 | O_EXCL and tight permissions to prevent other users from |
| 295 | substituting other .o files during the compilation. gcc |
| 296 | will then tell the assembler to use the newly created |
| 297 | file as an output file. If we unlink the file here, we |
| 298 | open a brief window when another user could still |
| 299 | substitute a file. |
| 300 | |
| 301 | So we unlink the output file if and only if it has |
| 302 | non-zero size. */ |
| 303 | #ifndef __MSDOS__ |
| 304 | /* Don't do this for MSDOS: it doesn't care about overwriting |
| 305 | a running binary, but if this file is already open by |
| 306 | another BFD, we will be in deep trouble if we delete an |
| 307 | open file. In fact, objdump does just that if invoked with |
| 308 | the --info option. */ |
| 309 | struct stat s; |
| 310 | |
| 311 | if (stat (abfd->filename, &s) == 0 && s.st_size != 0) |
| 312 | unlink (abfd->filename); |
| 313 | #endif |
| 314 | abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_WUB); |
| 315 | abfd->opened_once = true; |
| 316 | } |
| 317 | break; |
| 318 | } |
| 319 | |
| 320 | if (abfd->iostream != NULL) |
| 321 | { |
| 322 | if (! bfd_cache_init (abfd)) |
| 323 | return NULL; |
| 324 | } |
| 325 | |
| 326 | return (FILE *) abfd->iostream; |
| 327 | } |
| 328 | |
| 329 | /* |
| 330 | INTERNAL_FUNCTION |
| 331 | bfd_cache_lookup_worker |
| 332 | |
| 333 | SYNOPSIS |
| 334 | FILE *bfd_cache_lookup_worker(bfd *abfd); |
| 335 | |
| 336 | DESCRIPTION |
| 337 | Called when the macro <<bfd_cache_lookup>> fails to find a |
| 338 | quick answer. Find a file descriptor for @var{abfd}. If |
| 339 | necessary, it open it. If there are already more than |
| 340 | <<BFD_CACHE_MAX_OPEN>> files open, it tries to close one first, to |
| 341 | avoid running out of file descriptors. |
| 342 | */ |
| 343 | |
| 344 | FILE * |
| 345 | bfd_cache_lookup_worker (abfd) |
| 346 | bfd *abfd; |
| 347 | { |
| 348 | if ((abfd->flags & BFD_IN_MEMORY) != 0) |
| 349 | abort (); |
| 350 | |
| 351 | if (abfd->my_archive) |
| 352 | abfd = abfd->my_archive; |
| 353 | |
| 354 | if (abfd->iostream != NULL) |
| 355 | { |
| 356 | /* Move the file to the start of the cache. */ |
| 357 | if (abfd != bfd_last_cache) |
| 358 | { |
| 359 | snip (abfd); |
| 360 | insert (abfd); |
| 361 | } |
| 362 | } |
| 363 | else |
| 364 | { |
| 365 | if (bfd_open_file (abfd) == NULL) |
| 366 | return NULL; |
| 367 | if (fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0) |
| 368 | return NULL; |
| 369 | } |
| 370 | |
| 371 | return (FILE *) abfd->iostream; |
| 372 | } |