Utility function to calculate how many bytes are needed to completely deserialize the D-Bus message stored at @blob.
A blob represent a binary D-Bus message.
Number of bytes needed or -1 if @error is set (e.g. if @blob contains invalid data or not enough data is available to determine the size).
GException on failure.
2.26
See Implementation
Utility function to calculate how many bytes are needed to completely deserialize the D-Bus message stored at @blob.