x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_BUS_PATH_ENCODE(3) sd_bus_path_encode SD_BUS_PATH_ENCODE(3)
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
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, ...);
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.
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.
NOTES
Functions described here are available as a shared library, which can
be compiled against and linked to with the libsystemd pkg-config(1)
file.
The code described here uses getenv(3), which is declared to be not
multi-thread-safe. This means that the code calling the functions
described here must not call setenv(3) from a parallel thread. It is
recommended to only do calls to setenv() from an early phase of the
program when no other threads have been started.
SEE ALSO
systemd(1), sd-bus(3), free(3)
systemd 254 SD_BUS_PATH_ENCODE(3)
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