19990502 sourceware importbinu_ss_19990502

1 files changed, 350 insertions, 0 deletions

diff --git a/bfd/cache.c b/bfd/cache.c
new file mode 100644
index 0000000..b28de4b
--- /dev/null
+++ b/bfd/cache.c
@@ -0,0 +1,350 @@
+/* BFD library -- caching of file descriptors.
+   Copyright 1990, 91, 92, 93, 94, 95, 1996 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 void insert PARAMS ((bfd *));
+static void snip PARAMS ((bfd *));
+static boolean close_one PARAMS ((void));
+static boolean bfd_cache_delete PARAMS ((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 INLINE void
+insert (abfd)
+     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 INLINE void
+snip (abfd)
+     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 boolean
+close_one ()
+{
+  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 boolean
+bfd_cache_delete (abfd)
+     bfd *abfd;
+{
+  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
+	boolean bfd_cache_init (bfd *abfd);
+
+DESCRIPTION
+	Add a newly opened BFD to the cache.
+*/
+
+boolean
+bfd_cache_init (abfd)
+     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
+	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.
+*/
+
+boolean
+bfd_cache_close (abfd)
+     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 (abfd)
+     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 == true)
+	{
+	  abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_RUB);
+	  if (abfd->iostream == NULL)
+	    abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_WUB);
+	}
+      else
+	{
+	  /* Create the file.  Unlink it first, for the convenience of
+             operating systems which worry about overwriting running
+             binaries.  */
+	  unlink (abfd->filename);
+	  abfd->iostream = (PTR) fopen (abfd->filename, FOPEN_WB);
+	  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 (abfd)
+     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 (fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0)
+	return NULL;
+    }
+
+  return (FILE *) abfd->iostream;
+}