This structure is defined in the file llvs_plane.h.
/* some basic types: */ typedef unsigned char llvs_ubyte; /* unsigned bytes (8-bits) */ typedef long int llvs_integer; /* long integer (32-bits) */ typedef float llvs_single_float; /* 32-bit floating point */ typedef short int llvs_half_integer; /* short integer (16-bits) */ /* primary header record: LLVS Plane files start with this */ typedef struct { llvs_ubyte ptype; /* datatype of plane */ #define LLVS_PLF_BIT 0 /* bit type */ #define LLVS_PLF_BYTE 1 /* unsigned byte type */ #define LLVS_PLF_SHORT 2 /* signed 16 bit type */ #define LLVS_PLF_INT 3 /* integer type */ #define LLVS_PLF_FLOAT 4 /* float type */ llvs_ubyte bsex; /* byte sex (byte order) */ #define LLVS_LOW_BYTE_FIRST 0 /* low byte first (VAX, 80x86) */ #define LLVS_HIGH_BYTE_FIRST 1 /* high byte first (680x0, Spark) */ llvs_ubyte floatfmt; /* floating point format */ #define LLVS_DEC_SINGLE_FLOAT 0 /* DEC 32-bit floating point format (PDP-11, VAX) */ #define LLVS_IEEE_SINGLE_FLOAT 1 /* IEEE 32-bit floating point format (Sun, Sequent, Spark, TI LISPM) */ llvs_ubyte reserved; /* reserved byte - must be ZERO at present */ /* the remaining fields are in the format indicated above */ llvs_integer pl_level; /* plane level */ llvs_integer row_location; /* row offset of plane */ llvs_integer col_location; /* column offset of plane */ union { llvs_integer iback; /* integer background value */ llvs_single_float fback; /* floating point background value */ } background; /* plane background value */ llvs_integer alist_length; /* length of alist record */ llvs_integer data_length; /* length of data + size header */ llvs_integer multi_plane_flag; /* Multi-plane flag - if 0 this is the last/only plane otherwise, additional planes are stored after this one. */ } LLVS_PLANE_FILE_HEADER;
The first three bytes of this header record describe the format of the plane data: its data type, its ``byte sex'' (byte ordering of multi-byte numerical values), and the floating point number format used for floating point numbers.