344 lines
7.2 KiB
C
344 lines
7.2 KiB
C
/* BFD library -- caching of file descriptors.
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Copyright 1990, 1991, 1992, 1994 Free Software Foundation, Inc.
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Hacked by Steve Chamberlain of Cygnus Support (steve@cygnus.com).
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This file is part of BFD, the Binary File Descriptor library.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
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/*
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SECTION
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File caching
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The file caching mechanism is embedded within BFD and allows
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the application to open as many BFDs as it wants without
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regard to the underlying operating system's file descriptor
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limit (often as low as 20 open files). The module in
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<<cache.c>> maintains a least recently used list of
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<<BFD_CACHE_MAX_OPEN>> files, and exports the name
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<<bfd_cache_lookup>>, which runs around and makes sure that
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the required BFD is open. If not, then it chooses a file to
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close, closes it and opens the one wanted, returning its file
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handle.
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*/
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#include "bfd.h"
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#include "sysdep.h"
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#include "libbfd.h"
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static void insert PARAMS ((bfd *));
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static void snip PARAMS ((bfd *));
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static boolean close_one PARAMS ((void));
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static boolean bfd_cache_delete PARAMS ((bfd *));
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/*
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INTERNAL_FUNCTION
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BFD_CACHE_MAX_OPEN macro
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DESCRIPTION
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The maximum number of files which the cache will keep open at
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one time.
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.#define BFD_CACHE_MAX_OPEN 10
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*/
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/* The number of BFD files we have open. */
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static int open_files;
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/*
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INTERNAL_FUNCTION
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bfd_last_cache
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SYNOPSIS
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extern bfd *bfd_last_cache;
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DESCRIPTION
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Zero, or a pointer to the topmost BFD on the chain. This is
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used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
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determine when it can avoid a function call.
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*/
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bfd *bfd_last_cache;
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/*
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INTERNAL_FUNCTION
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bfd_cache_lookup
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DESCRIPTION
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Check to see if the required BFD is the same as the last one
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looked up. If so, then it can use the stream in the BFD with
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impunity, since it can't have changed since the last lookup;
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otherwise, it has to perform the complicated lookup function.
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.#define bfd_cache_lookup(x) \
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. ((x)==bfd_last_cache? \
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. (FILE*)(bfd_last_cache->iostream): \
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. bfd_cache_lookup_worker(x))
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*/
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/* Insert a BFD into the cache. */
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static INLINE void
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insert (abfd)
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bfd *abfd;
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{
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if (bfd_last_cache == NULL)
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{
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abfd->lru_next = abfd;
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abfd->lru_prev = abfd;
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}
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else
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{
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abfd->lru_next = bfd_last_cache;
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abfd->lru_prev = bfd_last_cache->lru_prev;
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abfd->lru_prev->lru_next = abfd;
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abfd->lru_next->lru_prev = abfd;
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}
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bfd_last_cache = abfd;
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}
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/* Remove a BFD from the cache. */
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static INLINE void
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snip (abfd)
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bfd *abfd;
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{
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abfd->lru_prev->lru_next = abfd->lru_next;
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abfd->lru_next->lru_prev = abfd->lru_prev;
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if (abfd == bfd_last_cache)
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{
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bfd_last_cache = abfd->lru_next;
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if (abfd == bfd_last_cache)
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bfd_last_cache = NULL;
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}
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}
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/* We need to open a new file, and the cache is full. Find the least
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recently used cacheable BFD and close it. */
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static boolean
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close_one ()
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{
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register bfd *kill;
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if (bfd_last_cache == NULL)
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kill = NULL;
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else
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{
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for (kill = bfd_last_cache->lru_prev;
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! kill->cacheable;
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kill = kill->lru_prev)
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{
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if (kill == bfd_last_cache)
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{
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kill = NULL;
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break;
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}
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}
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}
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if (kill == NULL)
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{
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/* There are no open cacheable BFD's. */
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return true;
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}
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kill->where = ftell ((FILE *) kill->iostream);
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return bfd_cache_delete (kill);
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}
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/* Close a BFD and remove it from the cache. */
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static boolean
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bfd_cache_delete (abfd)
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bfd *abfd;
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{
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boolean ret;
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if (fclose ((FILE *) abfd->iostream) == 0)
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ret = true;
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else
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{
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ret = false;
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bfd_set_error (bfd_error_system_call);
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}
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snip (abfd);
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abfd->iostream = NULL;
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--open_files;
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return ret;
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}
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/*
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INTERNAL_FUNCTION
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bfd_cache_init
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SYNOPSIS
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boolean bfd_cache_init (bfd *abfd);
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DESCRIPTION
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Add a newly opened BFD to the cache.
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*/
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boolean
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bfd_cache_init (abfd)
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bfd *abfd;
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{
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BFD_ASSERT (abfd->iostream != NULL);
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if (open_files >= BFD_CACHE_MAX_OPEN)
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{
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if (! close_one ())
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return false;
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}
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insert (abfd);
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++open_files;
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return true;
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}
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/*
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INTERNAL_FUNCTION
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bfd_cache_close
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SYNOPSIS
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boolean bfd_cache_close (bfd *abfd);
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DESCRIPTION
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Remove the BFD @var{abfd} from the cache. If the attached file is open,
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then close it too.
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RETURNS
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<<false>> is returned if closing the file fails, <<true>> is
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returned if all is well.
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*/
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boolean
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bfd_cache_close (abfd)
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bfd *abfd;
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{
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if (abfd->iostream == NULL)
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return true;
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return bfd_cache_delete (abfd);
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}
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/*
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INTERNAL_FUNCTION
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bfd_open_file
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SYNOPSIS
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FILE* bfd_open_file(bfd *abfd);
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DESCRIPTION
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Call the OS to open a file for @var{abfd}. Return the <<FILE *>>
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(possibly <<NULL>>) that results from this operation. Set up the
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BFD so that future accesses know the file is open. If the <<FILE *>>
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returned is <<NULL>>, then it won't have been put in the
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cache, so it won't have to be removed from it.
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*/
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FILE *
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bfd_open_file (abfd)
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bfd *abfd;
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{
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abfd->cacheable = true; /* Allow it to be closed later. */
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if (open_files >= BFD_CACHE_MAX_OPEN)
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{
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if (! close_one ())
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return NULL;
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}
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switch (abfd->direction)
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{
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case read_direction:
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case no_direction:
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abfd->iostream = (char *) fopen (abfd->filename, FOPEN_RB);
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break;
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case both_direction:
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case write_direction:
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if (abfd->opened_once == true)
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{
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abfd->iostream = (char *) fopen (abfd->filename, FOPEN_RUB);
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if (abfd->iostream == NULL)
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abfd->iostream = (char *) fopen (abfd->filename, FOPEN_WUB);
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}
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else
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{
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/*open for creat */
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abfd->iostream = (char *) fopen (abfd->filename, FOPEN_WB);
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abfd->opened_once = true;
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}
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break;
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}
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if (abfd->iostream != NULL)
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{
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if (! bfd_cache_init (abfd))
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return NULL;
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}
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return (FILE *) abfd->iostream;
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}
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/*
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INTERNAL_FUNCTION
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bfd_cache_lookup_worker
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SYNOPSIS
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FILE *bfd_cache_lookup_worker(bfd *abfd);
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DESCRIPTION
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Called when the macro <<bfd_cache_lookup>> fails to find a
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quick answer. Find a file descriptor for @var{abfd}. If
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necessary, it open it. If there are already more than
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<<BFD_CACHE_MAX_OPEN>> files open, it tries to close one first, to
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avoid running out of file descriptors.
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*/
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FILE *
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bfd_cache_lookup_worker (abfd)
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bfd *abfd;
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{
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if (abfd->my_archive)
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abfd = abfd->my_archive;
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if (abfd->iostream != NULL)
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{
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/* Move the file to the start of the cache. */
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if (abfd != bfd_last_cache)
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{
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snip (abfd);
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insert (abfd);
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}
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}
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else
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{
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if (bfd_open_file (abfd) == NULL)
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return NULL;
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if (fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0)
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return NULL;
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}
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return (FILE *) abfd->iostream;
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}
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