Create a new action signature with default user and now timestamp.
Create a copy of an existing signature. All internal strings are also duplicated.
Free an existing signature.
Create a new signature by parsing the given buffer, which is expected to be in the format "Real Name <email> timestamp tzoffset", where timestamp is the number of seconds since the Unix epoch and tzoffset is the timezone offset in hhmm format (note the lack of a colon separator).
Create a new action signature.
Create a new action signature with a timestamp of 'now'.