libg1m/include/libg1m/bcd.h

/* ************************************************************************** */
/*                                       _____           _                    */
/*  libg1m/bcd.h                        |_   _|__  _   _| |__   ___ _   _     */
/*  | Project: libg1m                     | |/ _ \| | | | '_ \ / _ \ | | |    */
/*                                        | | (_) | |_| | | | |  __/ |_| |    */
/*  By: thomas <thomas@touhey.fr>         |_|\___/ \__,_|_| |_|\___|\__, |.fr */
/*  Last updated: 2016/11/21 09:23:44                               |___/     */
/*                                                                            */
/* ************************************************************************** */
#ifndef LIBG1M_BCD_H
# define LIBG1M_BCD_H

/* ************************************************************************** */
/*  Type definition                                                           */
/* ************************************************************************** */
/*	BCD are the main number format CASIO uses in its calculators.
 *	Each semi-byte is a digit going from 0 to 9 (0xA to 0xF aren't used).
 *	This format has the huge advantage to make 0.1 + 0.2 and 0.3 equal.
 *
 *	The first three digits are the exponent.
 *	If the exponent is more than 500, then remove 500, and that means the
 *	number is negative.
 *	Then you have to remove 100 to have the real exponent.
 *
 *	The other 15 digits are the mantissa. So the number is: (0,M ** E) */

struct bcd {
	/* the BCD value itself */
	unsigned char BCDval[9];

	/* some 4-bytes alignment stuff */
	unsigned char _align[3];
};

/* ************************************************************************** */
/*  BCD utilities                                                             */
/* ************************************************************************** */
/* Arithmetic */
int g1m_bcd_is_nonzero(struct bcd *bcd);

/* String/BCD */
char *g1m_bcdtoa(struct bcd *bcd);

/* ************************************************************************** */
/*  Inline BCD utilities                                                      */
/* ************************************************************************** */
/**
 *	g1m_bcd_is_negative:
 *	Quick check.
 *
 *	@arg	bcd		pointer to the BCD number.
 *	@return			a boolean.
 */

static inline int g1m_bcd_is_negative(struct bcd *bcd)
{
	return (bcd->BCDval[0] >= 0x50);
}

/* macros */
# define g1m_bcd_is_positive(B) (!g1m_bcd_is_negative(B))
# define g1m_bcd_is_zero(B) (!g1m_bcd_is_nonzero(B))

#endif /* LIBG1M_BCD_H */