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Cache

Cache — paths and tags (UUID/LABEL) caching

Synopsis

struct              libmnt_cache;
struct libmnt_cache * mnt_new_cache                     (void);
void                mnt_free_cache                      (struct libmnt_cache *cache);
void                mnt_ref_cache                       (struct libmnt_cache *cache);
void                mnt_unref_cache                     (struct libmnt_cache *cache);
int                 mnt_cache_device_has_tag            (struct libmnt_cache *cache,
                                                         const char *devname,
                                                         const char *token,
                                                         const char *value);
char *              mnt_cache_find_tag_value            (struct libmnt_cache *cache,
                                                         const char *devname,
                                                         const char *token);
int                 mnt_cache_read_tags                 (struct libmnt_cache *cache,
                                                         const char *devname);
char *              mnt_get_fstype                      (const char *devname,
                                                         int *ambi,
                                                         struct libmnt_cache *cache);
char *              mnt_pretty_path                     (const char *path,
                                                         struct libmnt_cache *cache);
char *              mnt_resolve_path                    (const char *path,
                                                         struct libmnt_cache *cache);
char *              mnt_resolve_spec                    (const char *spec,
                                                         struct libmnt_cache *cache);
char *              mnt_resolve_tag                     (const char *token,
                                                         const char *value,
                                                         struct libmnt_cache *cache);

Description

The cache is a very simple API for working with tags (LABEL, UUID, ...) and paths. The cache uses libblkid as a backend for TAGs resolution.

All returned paths are always canonicalized.

Details

struct libmnt_cache

struct libmnt_cache;

Stores canonicalized paths and evaluated tags

mnt_new_cache ()

struct libmnt_cache * mnt_new_cache                     (void);

Returns :

new struct libmnt_cache instance or NULL in case of ENOMEM error.

mnt_free_cache ()

void                mnt_free_cache                      (struct libmnt_cache *cache);

Deallocates the cache. This function does not care about reference count. Don't use this function directly -- it's better to use use mnt_unref_cache().

cache :

pointer to struct libmnt_cache instance

mnt_ref_cache ()

void                mnt_ref_cache                       (struct libmnt_cache *cache);

Increments reference counter.

cache :

cache pointer

mnt_unref_cache ()

void                mnt_unref_cache                     (struct libmnt_cache *cache);

De-increments reference counter, on zero the cache is automatically deallocated by mnt_free_cache().

cache :

cache pointer

mnt_cache_device_has_tag ()

int                 mnt_cache_device_has_tag            (struct libmnt_cache *cache,
                                                         const char *devname,
                                                         const char *token,
                                                         const char *value);

Look up cache to check if tag+value are associated with devname.

`cache` :	paths cache
`devname` :	path to the device
`token` :	tag name (e.g "LABEL")
`value` :	tag value
Returns :	1 on success or 0.

mnt_cache_find_tag_value ()

char *              mnt_cache_find_tag_value            (struct libmnt_cache *cache,
                                                         const char *devname,
                                                         const char *token);

`cache` :	cache for results
`devname` :	device name
`token` :	tag name ("LABEL" or "UUID")
Returns :	LABEL or UUID for the `devname` or NULL in case of error.

mnt_cache_read_tags ()

int                 mnt_cache_read_tags                 (struct libmnt_cache *cache,
                                                         const char *devname);

Reads devname LABEL and UUID to the cache.

`cache` :	pointer to struct libmnt_cache instance
`devname` :	path device
Returns :	0 if at least one tag was added, 1 if no tag was added or negative number in case of error.

mnt_get_fstype ()

char *              mnt_get_fstype                      (const char *devname,
                                                         int *ambi,
                                                         struct libmnt_cache *cache);

`devname` :	device name
`ambi` :	returns TRUE if probing result is ambivalent (optional argument)
`cache` :	cache for results or NULL
Returns :	filesystem type or NULL in case of error. The result has to be deallocated by `free()` if `cache` is NULL.

mnt_pretty_path ()

char *              mnt_pretty_path                     (const char *path,
                                                         struct libmnt_cache *cache);

Converts path:

to the absolute path
/dev/dm-N to /dev/mapper/name
/dev/loopN to the loop backing filename
empty path (NULL) to 'none'

`path` :	any path
`cache` :	NULL or pointer to the cache
Returns :	newly allocated string with path, result always has to be deallocated by `free()`.

mnt_resolve_path ()

char *              mnt_resolve_path                    (const char *path,
                                                         struct libmnt_cache *cache);

Converts path:

to the absolute path
/dev/dm-N to /dev/mapper/name

`path` :	"native" path
`cache` :	cache for results or NULL
Returns :	absolute path or NULL in case of error. The result has to be deallocated by `free()` if `cache` is NULL.

mnt_resolve_spec ()

char *              mnt_resolve_spec                    (const char *spec,
                                                         struct libmnt_cache *cache);

`spec` :	path or tag
`cache` :	paths cache
Returns :	canonicalized path or NULL. The result has to be deallocated by `free()` if `cache` is NULL.

mnt_resolve_tag ()

char *              mnt_resolve_tag                     (const char *token,
                                                         const char *value,
                                                         struct libmnt_cache *cache);

`token` :	tag name
`value` :	tag value
`cache` :	for results or NULL
Returns :	device name or NULL in case of error. The result has to be deallocated by `free()` if `cache` is NULL.

			libmount Reference Manual
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