This section defines the file format of serialized
The tables format allows for one or more sets of tables to be specified, where each set corresponds to a given scanner. Scanners are indexed by name, as described below. The file format is as follows:
TABLE SET 1 +-------------------------------+ Header | uint32 th_magic; | | uint32 th_hsize; | | uint32 th_ssize; | | uint16 th_flags; | | char th_version; | | char th_name; | | uint8 th_pad64; | +-------------------------------+ Table 1 | uint16 td_id; | | uint16 td_flags; | | uint32 td_hilen; | | uint32 td_lolen; | | void td_data; | | uint8 td_pad64; | +-------------------------------+ Table 2 | | . . . . . . . . . . . . Table n | | +-------------------------------+ TABLE SET 2 . . . TABLE SET N
The above diagram shows that a complete set of tables consists of a header followed by multiple individual tables. Furthermore, multiple complete sets may be present in the same file, each set with its own header and tables. The sets are contiguous in the file. The only way to know if another set follows is to check the next four bytes for the magic number (or check for EOF). The header and tables sections are padded to 64-bit boundaries. Below we describe each field in detail. This format does not specify how the scanner will expand the given data, i.e., data may be serialized as int8, but expanded to an int32 array at runtime. This is to reduce the size of the serialized data where possible. Remember, all integer values are in network byte order.
Fields of a table header:
Magic number, always 0xF13C57B1.
Size of this entire header, in bytes, including all fields plus any padding.
Size of this entire set, in bytes, including the header, all tables, plus any padding.
Bit flags for this table set. Currently unused.
Flex version in NULL-terminated string format. e.g., ‘2.5.13a’. This is the version of flex that was used to create the serialized tables.
Contains the name of this table set. The default is ‘yytables’, and is prefixed accordingly, e.g., ‘footables’. Must be NULL-terminated.
Zero or more NULL bytes, padding the entire header to the next 64-bit boundary as calculated from the beginning of the header.
Fields of a table:
Specifies the table identifier. Possible values are:
yy_nxt. This array may be two dimensional. See the
yy_start_state_list. This array is handled specially because it is an
array of pointers to structs. See the
td_flags field below.
yy_transition. This array is handled specially because it is an array of
structs. See the
td_lolen field below.
Bit flags describing how to interpret the data in
The data arrays are one-dimensional by default, but may be
two dimensional as specified in the
The data is serialized as an array of type int8.
The data is serialized as an array of type int16.
The data is serialized as an array of type int32.
The data is a list of indexes of entries in the expanded
array. Each index should be expanded to a pointer to the corresponding entry
yy_transition array. We count on the fact that the
yy_transition array has already been seen.
The data is a list of yy_trans_info structs, each of which consists of
two integers. There is no padding between struct elements or between structs.
The type of each member is determined by the
td_hilen is non-zero, then the data is a two-dimensional array.
Otherwise, the data is a one-dimensional array.
td_hilen contains the
number of elements in the higher dimensional array, and
the number of elements in the lowest dimension.
td_data is either
sometype td_data[td_lolen], or
sometype td_data[td_hilen][td_lolen], where
sometype is specified
td_flags field. It is possible for both
td_hilen to be zero, in which case
td_data is a zero length
array, and no data is loaded, i.e., this table is simply skipped. Flex does not
currently generate tables of zero length.
Specifies the number of elements in the lowest dimension array. If this is
a one-dimensional array, then it is simply the number of elements in this array.
The element size is determined by the
The table data. This array may be a one- or two-dimensional array, of type
struct yy_trans_info, or
struct yy_trans_info*, depending upon the values in the
Zero or more NULL bytes, padding the entire table to the next 64-bit boundary as calculated from the beginning of this table.