Man page - sd_bus_path_decode(3)

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SD_BUS_PATH_ENCODE

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
NOTES
HISTORY
SEE ALSO

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.

HISTORY

sd_bus_path_encode() and sd_bus_path_decode() were added in version 211.

sd_bus_path_encode_many() and sd_bus_path_decode_many() were added in version 227.