312 lines
7.0 KiB
C
312 lines
7.0 KiB
C
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/* BFD library -- caching of file descriptors.
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Copyright 1990, 1991, 1992 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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/*
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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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static boolean
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bfd_cache_delete PARAMS ((bfd *));
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/* Number of bfds on the chain. All such bfds have their file open;
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if it closed, they get snipd()d from the chain. */
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static int open_files;
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static bfd *cache_sentinel; /* Chain of BFDs with active fds we've
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opened */
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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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*
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* DESCRIPTION
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* Checks 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 iostream 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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*
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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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*
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*/
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static void
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DEFUN_VOID(close_one)
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{
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bfd *kill = cache_sentinel;
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if (kill == 0) /* Nothing in the cache */
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return ;
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/* We can only close files that want to play this game. */
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while (!kill->cacheable) {
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kill = kill->lru_prev;
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if (kill == cache_sentinel) /* Nobody wants to play */
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return ;
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}
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kill->where = ftell((FILE *)(kill->iostream));
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(void) bfd_cache_delete(kill);
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}
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/* Cuts the BFD abfd out of the chain in the cache */
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static void
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DEFUN(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 (cache_sentinel == abfd) cache_sentinel = (bfd *)NULL;
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}
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static boolean
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DEFUN(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_error = system_call_error;
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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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bfd_last_cache = 0;
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return ret;
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}
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static bfd *
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DEFUN(insert,(x,y),
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bfd *x AND
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bfd *y)
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{
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if (y) {
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x->lru_next = y;
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x->lru_prev = y->lru_prev;
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y->lru_prev->lru_next = x;
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y->lru_prev = x;
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}
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else {
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x->lru_prev = x;
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x->lru_next = x;
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}
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return x;
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}
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/* Initialize a BFD by putting it on the cache LRU. */
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void
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DEFUN(bfd_cache_init,(abfd),
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bfd *abfd)
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{
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if (open_files >= BFD_CACHE_MAX_OPEN)
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close_one ();
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cache_sentinel = insert(abfd, cache_sentinel);
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++open_files;
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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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DESCRIPTION
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Remove the BFD from the cache. If the attached file is open,
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then close it too.
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SYNOPSIS
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boolean bfd_cache_close (bfd *);
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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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DEFUN(bfd_cache_close,(abfd),
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bfd *abfd)
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{
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/* If this file is open then remove from the chain */
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if (abfd->iostream)
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{
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return bfd_cache_delete(abfd);
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}
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else
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{
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return true;
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}
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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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DESCRIPTION
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Call the OS to open a file for this BFD. Returns the FILE *
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(possibly null) that results from this operation. Sets 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 there is 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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SYNOPSIS
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FILE* bfd_open_file(bfd *);
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*/
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FILE *
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DEFUN(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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close_one();
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}
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switch (abfd->direction) {
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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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abfd->iostream = (char *) fopen(abfd->filename, FOPEN_RUB);
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if (!abfd->iostream) {
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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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/*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) {
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bfd_cache_init (abfd);
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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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DESCRIPTION
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Called when the macro <<bfd_cache_lookup>> fails to find a
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quick answer. Finds a file descriptor for this BFD. 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 trys to close one first, to
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avoid running out of file descriptors.
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SYNOPSIS
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FILE *bfd_cache_lookup_worker(bfd *);
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*/
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FILE *
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DEFUN(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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{
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abfd = abfd->my_archive;
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}
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/* Is this file already open .. if so then quick exit */
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if (abfd->iostream)
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{
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if (abfd != cache_sentinel) {
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/* Place onto head of lru chain */
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snip (abfd);
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cache_sentinel = insert(abfd, cache_sentinel);
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}
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}
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/* This is a BFD without a stream -
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so it must have been closed or never opened.
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find an empty cache entry and use it. */
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else
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{
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if (open_files >= BFD_CACHE_MAX_OPEN)
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{
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close_one();
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}
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BFD_ASSERT(bfd_open_file (abfd) != (FILE *)NULL) ;
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fseek((FILE *)(abfd->iostream), abfd->where, false);
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}
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bfd_last_cache = abfd;
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return (FILE *)(abfd->iostream);
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}
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