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_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.
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.
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systemd 233 SD_BUS_PATH_ENCODE(3)