Controls output buffer length
The number of characters in each string written out through the sink function will not be greater than the value of this attribute (but may be less). A value of zero (the default) means there is no limit - each string can be of any length.
Note, the default value of zero is unlikely to be appropriate when an XmlChan is used within Fortran code. In this case, XmlLength should usually be set to the size of the CHARACTER variable used to receive the text returned by AST_GETLINE within the sink function. This avoids the possibility of long lines being truncated invisibly within AST_GETLINE.