An string matching 'host/plugin-instance/type-instance'. Both instance part are optionals, in which case the '-' should be omitted.
An identifier to fill with the parsed string. If this function returns non-null, the state of identifier should not be relied upon.
null if the parsing succeeded, else a string representing the error.
Parse a string and returns the corresponding Identifier
If the string passed is not a valid identifier, this function will return the reason why, else it returns null.
This function is useful to get an identifier out of Collectd, or from any Collectd-formatted identifier. To construct an identifier with known values, initializing the fields is enough.