The labels record holds value labels and variable labels. Unlike the other records, it is not meant to be read directly and sequentially. Instead, this record must be interpreted one piece at a time, by following pointers from the variables record.
The value_label_start, value_label_end, and
var_label_ofs fields in a variable record are all offsets
relative to the beginning of the labels record, with an additional
7-byte offset. That is, if the labels record starts at byte offset
labels_ofs and a variable has a given var_label_ofs,
then the variable label begins at byte offset labels_ofs
+ var_label_ofs + 7 in the file.
A variable label, starting at the offset indicated by
var_label_ofs, consists of a one-byte length followed by the
specified number of bytes of the variable label string, like this:
uint8 length; char s[length];
A set of value labels, extending from value_label_start to
value_label_end (exclusive), consists of a numeric or string
value followed by a string in the format just described. String
values are padded on the right with spaces to fill the 8-byte field,
like this:
union {
flt64 f;
char s[8];
} value;
uint8 length;
char s[length];
The labels record begins with a pair of uint32 values. The first of these is always 3. The second is between 8 and 16 less than the number of bytes in the record. Neither value is important for interpreting the file.