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.
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
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 `libbfd.h' to
determine when it can avoid a function call.
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))
bfd_cache_init
Synopsis
boolean bfd_cache_init (bfd *abfd);
Description
Add a newly opened BFD to the cache.
bfd_cache_close
Synopsis
boolean bfd_cache_close (bfd *abfd);
Description
Remove the BFD 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_open_file
Synopsis
FILE* bfd_open_file(bfd *abfd);
Description
Call the OS to open a file for 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.
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 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.
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