The document record, if present, has the following format:
int32 rec_type; int32 n_lines; char lines[][80];
int32 rec_type;Record type. Always set to 6.
int32 n_lines;Number of lines of documents present.  This should be greater than
zero, but ReadStats writes system files with zero n_lines.
char lines[][80];Document lines.  The number of elements is defined by n_lines.
Lines shorter than 80 characters are padded on the right with spaces.