/* *****************************************************************************
 * libg1m/bcd.h -- BCD-encoded numbers manipulation.
 * Copyright (C) 2017 Thomas "Cakeisalie5" Touhey <thomas@touhey.fr>
 *
 * This file is part of libg1m.
 * libg1m is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 3.0 of the License,
 * or (at your option) any later version.
 *
 * libg1m is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with libg1m; if not, see <http://www.gnu.org/licenses/>.
 *
 * 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.
 *
 * Before applying these operations, you should check the most significant bit
 * of the upper nibble of the first binary-coded digit of the exponent.
 * If it is 1, then the number has a complex part. Anyway, always set this
 * bit to zero before interpreting the exponent.
 *
 * The other 15 digits are the mantissa. So the number is: (M ** (E + 1))
 * ************************************************************************** */
#ifndef LIBG1M_BCD_H
# define LIBG1M_BCD_H
# ifdef __cplusplus
extern "C" {
# endif

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

	/* some 4-bytes alignment stuff */
	unsigned char _align[3];
} g1m_bcd_t;

/* ************************************************************************** */
/*  BCD utilities                                                             */
/* ************************************************************************** */
/* Arithmetic */
int g1m_bcd_is_nonzero(g1m_bcd_t *bcd);

/* String/BCD */
char *g1m_bcdtoa(g1m_bcd_t *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(g1m_bcd_t *bcd)
{
	return (bcd->BCDval[0] >= 0x50);
}

/**
 *	g1m_bcd_high_bit:
 *	Quick check.
 *
 *	@arg	bcd		pointer to the BCD number.
 *	@return			a boolean.
 */

static inline int g1m_bcd_high_bit(g1m_bcd_t *bcd)
{
	return (bcd->BCDval[0] & 0x80);
}

/* macros */
# define g1m_bcd_is_positive(B) (!g1m_bcd_is_negative(B))
# define g1m_bcd_is_zero(B) (!g1m_bcd_is_nonzero(B))
# define g1m_bcd_has_complex(B) (g1m_bcd_high_bit(B))

# ifdef __cplusplus
}
# endif
#endif /* LIBG1M_BCD_H */