преобразование внешнего идентификатора в путь к объекту и обратно (convert an external identifier into an object path and back)
Имя (Name)
sd_bus_path_encode, sd_bus_path_encode_many, sd_bus_path_decode,
sd_bus_path_decode_many - Convert an external identifier into an
object path and back
Синопсис (Synopsis)
#include <systemd/sd-bus.h>
int sd_bus_path_encode(const char *prefix,
const char *external_id, char **ret_path);
int sd_bus_path_encode_many(char **out,
const char *path_template, ...);
int sd_bus_path_decode(const char *path, const char *prefix,
char **ret_external_id);
int sd_bus_path_decode_many(const char *path,
const char *path_template, ...);
Описание (Description)
sd_bus_path_encode() and sd_bus_path_decode() convert external
identifier strings into object paths and back. These functions
are useful to map application-specific string identifiers of any
kind into bus object paths in a simple, reversible and safe way.
sd_bus_path_encode() takes a bus path prefix and an external
identifier string as arguments, plus a place to store the
returned bus path string. The bus path prefix must be a valid bus
path, starting with a slash "/", and not ending in one. The
external identifier string may be in any format, may be the empty
string, and has no restrictions on the charset — however, it must
always be NUL-terminated. The returned string will be the
concatenation of the bus path prefix plus an escaped version of
the external identifier string. This operation may be reversed
with sd_bus_path_decode(). It is recommended to only use external
identifiers that generally require little escaping to be turned
into valid bus path identifiers (for example, by sticking to a
7-bit ASCII character set), in order to ensure the resulting bus
path is still short and easily processed.
sd_bus_path_decode() reverses the operation of
sd_bus_path_encode() and thus regenerates an external identifier
string from a bus path. It takes a bus path and a prefix string,
plus a place to store the returned external identifier string. If
the bus path does not start with the specified prefix, 0 is
returned and the returned string is set to NULL. Otherwise, the
string following the prefix is unescaped and returned in the
external identifier string.
The escaping used will replace all characters which are invalid
in a bus object path by "_", followed by a hexadecimal value. As
a special case, the empty string will be replaced by a lone "_".
sd_bus_path_encode_many() works like its counterpart
sd_bus_path_encode(), but takes a path template as argument and
encodes multiple labels according to its embedded directives. For
each "%" character found in the template, the caller must provide
a string via varargs, which will be encoded and embedded at the
position of the "%" character. Any other character in the
template is copied verbatim into the encoded path.
sd_bus_path_decode_many() does the reverse of
sd_bus_path_encode_many(). It decodes the passed object path
according to the given path template. For each "%" character in
the template, the caller must provide an output storage ("char
**") via varargs. The decoded label will be stored there. Each
"%" character will only match the current label. It will never
match across labels. Furthermore, only a single directive is
allowed per label. If NULL is passed as output storage, the label
is verified but not returned to the caller.
Возвращаемое значение (Return value)
On success, sd_bus_path_encode() returns positive or 0, and a
valid bus path in the return argument. On success,
sd_bus_path_decode() returns a positive value if the prefixed
matched, or 0 if it did not. If the prefix matched, the external
identifier is returned in the return parameter. If it did not
match, NULL is returned in the return parameter. On failure, a
negative errno-style error number is returned by either function.
The returned strings must be free(3)'d by the caller.
Примечание (Note)
These APIs are implemented as a shared library, which can be
compiled and linked to with the libsystemd pkg-config(1) file.
Смотри также (See also)
systemd(1), sd-bus(3), free(3)
