sd_id128_to_string() formats a 128-bit ID as a character string. It
expects the ID and a string array capable of storing 33 characters.
The ID will be formatted as 32 lowercase hexadecimal digits and be
terminated by a NUL byte.
sd_id128_from_string() implements the reverse operation: it takes a
33 character string with 32 hexadecimal digits (either lowercase or
uppercase, terminated by NUL) and parses them back into a 128-bit ID
returned in ret. Alternatively, this call can also parse a
37-character string with a 128-bit ID formatted as RFC UUID. If ret
is passed as NULL the function will validate the passed ID string,
but not actually return it in parsed form.
For more information about the "sd_id128_t" type see sd-id128(3).
Note that these calls operate the same way on all architectures, i.e.
the results do not depend on endianness.
When formatting a 128-bit ID into a string, it is often easier to use
a format string for printf(3). This is easily done using the
SD_ID128_FORMAT_STR and SD_ID128_FORMAT_VAL() macros. For more
information see sd-id128(3).
sd_id128_to_string() always succeeds and returns a pointer to the
string array passed in. sd_id128_from_string returns 0 on success,
in which case ret is filled in, or a negative errno-style error code.
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systemd 231 SD_ID128_TO_STRING(3)