| /* BFD library -- caching of file descriptors. |
| Copyright 1990, 1991, 1992, 1993, 1994, 1996, 2000, 2001, 2002, 2003 |
| 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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" |
| |
| static bfd_boolean bfd_cache_delete (bfd *); |
| |
| /* |
| 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 |
| |
| */ |
| |
| /* The number of BFD files we have open. */ |
| |
| static int open_files; |
| |
| /* |
| 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)) |
| |
| */ |
| |
| /* Insert a BFD into the cache. */ |
| |
| static void |
| insert (bfd *abfd) |
| { |
| if (bfd_last_cache == NULL) |
| { |
| abfd->lru_next = abfd; |
| abfd->lru_prev = abfd; |
| } |
| else |
| { |
| abfd->lru_next = bfd_last_cache; |
| abfd->lru_prev = bfd_last_cache->lru_prev; |
| abfd->lru_prev->lru_next = abfd; |
| abfd->lru_next->lru_prev = abfd; |
| } |
| bfd_last_cache = abfd; |
| } |
| |
| /* Remove a BFD from the cache. */ |
| |
| static void |
| snip (bfd *abfd) |
| { |
| abfd->lru_prev->lru_next = abfd->lru_next; |
| abfd->lru_next->lru_prev = abfd->lru_prev; |
| if (abfd == bfd_last_cache) |
| { |
| bfd_last_cache = abfd->lru_next; |
| if (abfd == bfd_last_cache) |
| bfd_last_cache = NULL; |
| } |
| } |
| |
| /* We need to open a new file, and the cache is full. Find the least |
| recently used cacheable BFD and close it. */ |
| |
| static bfd_boolean |
| close_one (void) |
| { |
| register bfd *kill; |
| |
| if (bfd_last_cache == NULL) |
| kill = NULL; |
| else |
| { |
| for (kill = bfd_last_cache->lru_prev; |
| ! kill->cacheable; |
| kill = kill->lru_prev) |
| { |
| if (kill == bfd_last_cache) |
| { |
| kill = NULL; |
| break; |
| } |
| } |
| } |
| |
| if (kill == NULL) |
| { |
| /* There are no open cacheable BFD's. */ |
| return TRUE; |
| } |
| |
| kill->where = ftell ((FILE *) kill->iostream); |
| |
| return bfd_cache_delete (kill); |
| } |
| |
| /* Close a BFD and remove it from the cache. */ |
| |
| static bfd_boolean |
| bfd_cache_delete (bfd *abfd) |
| { |
| bfd_boolean ret; |
| |
| if (fclose ((FILE *) abfd->iostream) == 0) |
| ret = TRUE; |
| else |
| { |
| ret = FALSE; |
| bfd_set_error (bfd_error_system_call); |
| } |
| |
| snip (abfd); |
| |
| abfd->iostream = NULL; |
| --open_files; |
| |
| return ret; |
| } |
| |
| /* |
| INTERNAL_FUNCTION |
| bfd_cache_init |
| |
| SYNOPSIS |
| bfd_boolean bfd_cache_init (bfd *abfd); |
| |
| DESCRIPTION |
| Add a newly opened BFD to the cache. |
| */ |
| |
| bfd_boolean |
| bfd_cache_init (bfd *abfd) |
| { |
| BFD_ASSERT (abfd->iostream != NULL); |
| if (open_files >= BFD_CACHE_MAX_OPEN) |
| { |
| if (! close_one ()) |
| return FALSE; |
| } |
| insert (abfd); |
| ++open_files; |
| return TRUE; |
| } |
| |
| /* |
| INTERNAL_FUNCTION |
| bfd_cache_close |
| |
| SYNOPSIS |
| bfd_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. |
| */ |
| |
| bfd_boolean |
| bfd_cache_close (bfd *abfd) |
| { |
| if (abfd->iostream == NULL |
| || (abfd->flags & BFD_IN_MEMORY) != 0) |
| return TRUE; |
| |
| return bfd_cache_delete (abfd); |
| } |
| |
| /* |
| 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 * |
| bfd_open_file (bfd *abfd) |
| { |
| abfd->cacheable = TRUE; /* Allow it to be closed later. */ |
| |
| if (open_files >= BFD_CACHE_MAX_OPEN) |
| { |
| if (! close_one ()) |
| return NULL; |
| } |
| |
| switch (abfd->direction) |
| { |
| case read_direction: |
| case no_direction: |
| abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_RB); |
| break; |
| case both_direction: |
| case write_direction: |
| if (abfd->opened_once) |
| { |
| abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_RUB); |
| if (abfd->iostream == NULL) |
| abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_WUB); |
| } |
| else |
| { |
| /* Create the file. |
| |
| Some operating systems won't let us overwrite a running |
| binary. For them, we want to unlink the file first. |
| |
| However, gcc 2.95 will create temporary files using |
| O_EXCL and tight permissions to prevent other users from |
| substituting other .o files during the compilation. gcc |
| will then tell the assembler to use the newly created |
| file as an output file. If we unlink the file here, we |
| open a brief window when another user could still |
| substitute a file. |
| |
| So we unlink the output file if and only if it has |
| non-zero size. */ |
| #ifndef __MSDOS__ |
| /* Don't do this for MSDOS: it doesn't care about overwriting |
| a running binary, but if this file is already open by |
| another BFD, we will be in deep trouble if we delete an |
| open file. In fact, objdump does just that if invoked with |
| the --info option. */ |
| struct stat s; |
| |
| if (stat (abfd->filename, &s) == 0 && s.st_size != 0) |
| unlink (abfd->filename); |
| #endif |
| abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_WUB); |
| abfd->opened_once = TRUE; |
| } |
| break; |
| } |
| |
| if (abfd->iostream != NULL) |
| { |
| if (! bfd_cache_init (abfd)) |
| return NULL; |
| } |
| |
| 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 * |
| bfd_cache_lookup_worker (bfd *abfd) |
| { |
| if ((abfd->flags & BFD_IN_MEMORY) != 0) |
| abort (); |
| |
| if (abfd->my_archive) |
| abfd = abfd->my_archive; |
| |
| if (abfd->iostream != NULL) |
| { |
| /* Move the file to the start of the cache. */ |
| if (abfd != bfd_last_cache) |
| { |
| snip (abfd); |
| insert (abfd); |
| } |
| } |
| else |
| { |
| if (bfd_open_file (abfd) == NULL) |
| return NULL; |
| if (abfd->where != (unsigned long) abfd->where) |
| return NULL; |
| if (fseek ((FILE *) abfd->iostream, (long) abfd->where, SEEK_SET) != 0) |
| return NULL; |
| } |
| |
| return (FILE *) abfd->iostream; |
| } |