265 lines
6.4 KiB
C
265 lines
6.4 KiB
C
/* BFD library -- caching of file descriptors.
|
||
Copyright (C) 1990-1991 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., 675 Mass Ave, Cambridge, MA 02139, USA. */
|
||
|
||
/*doc*
|
||
@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 @code{cache.c} maintains a least recently used list of
|
||
@code{BFD_CACHE_MAX_OPEN} files, and exports the name
|
||
@code{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.
|
||
|
||
*/
|
||
|
||
|
||
|
||
/* $Id$ */
|
||
#include <sysdep.h>
|
||
#include "bfd.h"
|
||
#include "libbfd.h"
|
||
|
||
|
||
/*proto-internal* BFD_CACHE_MAX_OPEN
|
||
The maxiumum number of files which the cache will keep open at one
|
||
time.
|
||
*+
|
||
#define BFD_CACHE_MAX_OPEN 10
|
||
*-
|
||
|
||
*/
|
||
|
||
|
||
static int open_files;
|
||
|
||
static bfd *cache_sentinel; /* Chain of BFDs with active fds we've
|
||
opened */
|
||
|
||
/*proto-internal* bfd_last_cache
|
||
Zero, or a pointer to the topmost BFD on the chain. This is used by
|
||
the @code{bfd_cache_lookup} macro in @file{libbfd.h} to determine when
|
||
it can avoid a function call.
|
||
*+
|
||
extern bfd *bfd_last_cache;
|
||
*-
|
||
|
||
*/
|
||
|
||
bfd *bfd_last_cache;
|
||
|
||
/*proto-internal* bfd_cache_lookup
|
||
Checks to see if the required BFD is the same as the last one looked
|
||
up. If so then it can use the iostream 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))
|
||
|
||
*-
|
||
|
||
*/
|
||
|
||
static void bfd_cache_delete();
|
||
|
||
|
||
static void
|
||
DEFUN_VOID(close_one)
|
||
{
|
||
bfd *kill = cache_sentinel;
|
||
if (kill == 0) /* Nothing in the cache */
|
||
return ;
|
||
|
||
/* We can only close files that want to play this game. */
|
||
while (!kill->cacheable) {
|
||
kill = kill->lru_prev;
|
||
if (kill == cache_sentinel) /* Nobody wants to play */
|
||
return ;
|
||
}
|
||
|
||
kill->where = ftell((FILE *)(kill->iostream));
|
||
bfd_cache_delete(kill);
|
||
}
|
||
|
||
/* Cuts the BFD abfd out of the chain in the cache */
|
||
static void
|
||
DEFUN(snip,(abfd),
|
||
bfd *abfd)
|
||
{
|
||
abfd->lru_prev->lru_next = abfd->lru_next;
|
||
abfd->lru_next->lru_prev = abfd->lru_prev;
|
||
if (cache_sentinel == abfd) cache_sentinel = (bfd *)NULL;
|
||
}
|
||
|
||
static void
|
||
DEFUN(bfd_cache_delete,(abfd),
|
||
bfd *abfd)
|
||
{
|
||
fclose ((FILE *)(abfd->iostream));
|
||
snip (abfd);
|
||
abfd->iostream = NULL;
|
||
open_files--;
|
||
bfd_last_cache = 0;
|
||
}
|
||
|
||
static bfd *
|
||
DEFUN(insert,(x,y),
|
||
bfd *x AND
|
||
bfd *y)
|
||
{
|
||
if (y) {
|
||
x->lru_next = y;
|
||
x->lru_prev = y->lru_prev;
|
||
y->lru_prev->lru_next = x;
|
||
y->lru_prev = x;
|
||
|
||
}
|
||
else {
|
||
x->lru_prev = x;
|
||
x->lru_next = x;
|
||
}
|
||
return x;
|
||
}
|
||
|
||
|
||
/*proto-internal*
|
||
*i bfd_cache_init
|
||
Initialize a BFD by putting it on the cache LRU.
|
||
*; PROTO(void, bfd_cache_init, (bfd *));
|
||
*-*/
|
||
|
||
void
|
||
DEFUN(bfd_cache_init,(abfd),
|
||
bfd *abfd)
|
||
{
|
||
cache_sentinel = insert(abfd, cache_sentinel);
|
||
}
|
||
|
||
|
||
/*proto-internal*
|
||
*i bfd_cache_close
|
||
Remove the BFD from the cache. If the attatched file is open, then close it too.
|
||
*; PROTO(void, bfd_cache_close, (bfd *));
|
||
*-*/
|
||
void
|
||
DEFUN(bfd_cache_close,(abfd),
|
||
bfd *abfd)
|
||
{
|
||
/* If this file is open then remove from the chain */
|
||
if (abfd->iostream)
|
||
{
|
||
bfd_cache_delete(abfd);
|
||
}
|
||
}
|
||
|
||
/*proto-internal*
|
||
*i bfd_open_file
|
||
Call the OS to open a file for this BFD. Returns the FILE *
|
||
(possibly null) that results from this operation. Sets up the
|
||
BFD so that future accesses know the file is open. If the FILE *
|
||
returned is null, then there is won't have been put in the cache, so
|
||
it won't have to be removed from it.
|
||
*; PROTO(FILE *, bfd_open_file, (bfd *));
|
||
*-*/
|
||
FILE *
|
||
DEFUN(bfd_open_file, (abfd),
|
||
bfd *abfd)
|
||
{
|
||
abfd->cacheable = true; /* Allow it to be closed later. */
|
||
if(open_files >= BFD_CACHE_MAX_OPEN) {
|
||
close_one();
|
||
}
|
||
switch (abfd->direction) {
|
||
case read_direction:
|
||
case no_direction:
|
||
abfd->iostream = (char *) fopen(abfd->filename, "r");
|
||
break;
|
||
case both_direction:
|
||
case write_direction:
|
||
if (abfd->opened_once == true) {
|
||
abfd->iostream = (char *) fopen(abfd->filename, "r+");
|
||
if (!abfd->iostream) {
|
||
abfd->iostream = (char *) fopen(abfd->filename, "w+");
|
||
}
|
||
} else {
|
||
/*open for creat */
|
||
abfd->iostream = (char *) fopen(abfd->filename, "w");
|
||
abfd->opened_once = true;
|
||
}
|
||
break;
|
||
}
|
||
if (abfd->iostream) {
|
||
open_files++;
|
||
bfd_cache_init (abfd);
|
||
}
|
||
|
||
return (FILE *)(abfd->iostream);
|
||
}
|
||
|
||
/*proto-internal*
|
||
*i bfd_cache_lookup_worker
|
||
Called when the macro @code{bfd_cache_lookup} fails to find a quick
|
||
answer. Finds a file descriptor for this BFD. If necessary, it open it.
|
||
If there are already more than BFD_CACHE_MAX_OPEN files open, it trys to close
|
||
one first, to avoid running out of file descriptors.
|
||
*; PROTO(FILE *, bfd_cache_lookup_worker, (bfd *));
|
||
|
||
*-*/
|
||
|
||
FILE *
|
||
DEFUN(bfd_cache_lookup_worker,(abfd),
|
||
bfd *abfd)
|
||
{
|
||
if (abfd->my_archive)
|
||
{
|
||
abfd = abfd->my_archive;
|
||
}
|
||
/* Is this file already open .. if so then quick exit */
|
||
if (abfd->iostream)
|
||
{
|
||
if (abfd != cache_sentinel) {
|
||
/* Place onto head of lru chain */
|
||
snip (abfd);
|
||
cache_sentinel = insert(abfd, cache_sentinel);
|
||
}
|
||
}
|
||
/* This is a BFD without a stream -
|
||
so it must have been closed or never opened.
|
||
find an empty cache entry and use it. */
|
||
else
|
||
{
|
||
|
||
if (open_files >= BFD_CACHE_MAX_OPEN)
|
||
{
|
||
close_one();
|
||
}
|
||
|
||
BFD_ASSERT(bfd_open_file (abfd) != (FILE *)NULL) ;
|
||
fseek((FILE *)(abfd->iostream), abfd->where, false);
|
||
}
|
||
bfd_last_cache = abfd;
|
||
return (FILE *)(abfd->iostream);
|
||
}
|