af_crkey, af_open, af_close, af_rm, af_establish, af_restore - AtFS
file system operations
int af_crkey (char *syspath, char *name, char *type, Af_key *aso)
FILE *af_open (Af_key *aso, char *mode)
int af_close (FILE *stream)
int af_rm (Af_key *aso)
int af_establish (Af_key *aso, char *filename)
int af_restore (Af_key *aso, Af_key *restoredAso)
af_crkey creates an object key for a regular UNIX file identified by
name, type and system path. syspath is an either absolute or relative
directory name. An empty syspath refers to the current directory. By
convention, AtFS interprets the filename suffix of a UNIX file as type
and the filename without suffix as name attribute. To give an example,
the path name
/usr/andy/foo.c is split up in /usr/andy (syspath) foo (name) c (type)
A period as first character in the filename is always considered as
part of the name. Hence .cshrc has a name but no type. "." and ".." are
recognized as names too. If the named UNIX file does not exist,
af_crkey creates an empty file. The created key remains accessible
until it is explicitly given up by af_dropkey (manual page
af_open opens the contents of the ASO pointed to by aso and associates
a stream with it. A pointer to the FILE structure associated with the
stream is returned. Mode is a character string that is either "r[+]",
"w[+]" or "a[+]". See fopen(3) for further details. Upon error, af_open
returns a NULL pointer. Non-busy ASOs can only be opened with mode
"r". If a non-busy ASO is opened, it’s contents will be placed in a
temporary UNIX file due to storage of versions as deltas.
af_close closes a stream previously opened by af_open (see fclose(3)).
Temporary files created by af_open, holding the contents of a saved
versions are unlinked right after being opened so that they will
automatically disappear on closing.
af_rm removes the specified ASO. The application has to have a lock
(see af_lock(3)) set on the ASO that shall be deleted by af_rm. ASOs
with the state attribute set to accessed or frozen cannot be removed.
If you keep multiple keys of one object (perhaps in different sets)
af_rm invalidates all keys of the removed object. As AtFS does not
support multiple links to saved ASOs, af_rm on a saved version always
does a physical removal.
af_establish establishes the contents of the saved version, pointed to
by aso in a file named filename. The resulting file gets the version’s
modification and access date.
af_restore is used to restore formerly saved derived ASOs into their
old file location. It also restores the file modification and access
date. This function cannot be applied to source objects. af_restore
returns the key of the restored version in the buffer restoredAso.
fopen(3), fclose(3), af_retrieve(3), af_lock(3)
Upon error, -1 or a nil pointer (depending on the return type) is
returned and af_errno is set to the corresponding error number.