/*
 * Definitions for variable data used by Color BASIC
 *
 * Copyright 2013 by John W. Linville <linville@tuxdriver.com>
 */

/*
 * cb_float -- Microsoft Binary Format floating point value
 *
 *	exponent -- 128 + actual signed value of exponent
 *			(zero value of exponent == overall value of 0)
 *
 *	mantissa -- 4-byte normalized value of mantissa
 *			(MSB of offset 0 is assumed to be '1',
 *			 so this bit is instead used to indicate
 *			 the sign -- '0' is positive, '1' is negative)
 */
struct cb_float {
	unsigned char exponent;
	unsigned char mantissa[4];
};

/*
 * cb_str -- string variable descriptor
 *
 *	len           -- length of string in bytes
 *
 *	cbstr_unused1 -- unused byte
 *
 *	location      -- pointer to array of bytes of length len
 *
 *	cbstr_unused2 -- unused byte
 */
struct cb_str {
	unsigned char len;
	unsigned char cbstr_unused1;
	char *location;
	unsigned char cbstr_unused2;
};

/*
 * cb_fac -- unpacked floating point value stored in FAC
 *
 *	cbfloat -- floating point data with MSB of mantissa[0] unpacked
 *
 *	sign    -- MSB represents the MSB of mantissa[0] when packed
 *
 */
struct cb_fac {
	struct cb_float cbfloat;
	unsigned char sign;
};

/*
 * cb_var -- data as passed to USR program when not using VARPTR
 *
 *	cbfac -- Floating Point Accumulator data as passed to USR program
 *
 *	cbstr -- string data as passed to USR program
 */
union cb_var {
	struct cb_fac cbfac;
	struct cb_str cbstr;
};