the GAsyncResult that was provided to the callback.
length
a numeric to get the length of the data read in.
.errwarn
Whether to issue a warning on error or fail silently
Value
A list containing the following elements:
retval[char] a string with the data that was read before encountering
any of the stop characters. Set length to a numeric to get the length
of the string. This function will return NULL on an error.