136 lines
5.0 KiB
C
136 lines
5.0 KiB
C
/* *****************************************************************************
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* libg1m/bcd.h -- BCD-encoded numbers manipulation.
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* Copyright (C) 2017 Thomas "Cakeisalie5" Touhey <thomas@touhey.fr>
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*
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* This file is part of libg1m.
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* libg1m is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 3.0 of the License,
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* or (at your option) any later version.
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*
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* libg1m is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with libg1m; if not, see <http://www.gnu.org/licenses/>.
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*
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* BCD are the main number format CASIO uses in its calculators.
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* This format has the huge advantage to make 0.1 + 0.2 and 0.3 equal.
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*
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* There are several raw BCD formats, libg1m offers conversion to its own
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* format, easier to read and write (but not optimized for storing).
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* ************************************************************************** */
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#ifndef LIBG1M_BCD_H
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# define LIBG1M_BCD_H
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# ifdef __cplusplus
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extern "C" {
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# endif
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# define G1M_BCD_MANTISSA_SIZE 16
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# define G1M_BCD_EXPMIN -99
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# define G1M_BCD_EXPMAX 99
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/* String constants; here are some examples:
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* - 1.23456789ABCDEFe99
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* - -0.0000123456789ABCDEF
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* - 123456789ABCDEF0000000 */
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# define G1M_BCD_GOODBUFSIZE \
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(2 + G1M_BCD_MANTISSA_SIZE + 4 + 2 + 1)
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/* ************************************************************************** */
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/* Main type */
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/* ************************************************************************** */
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/* libg1m type definition
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* This is the "unzipped" BCD format. There are several, this is the one libg1m
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* will always convert to.
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*
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* `flags` is the flags (negative, special, precision) of the BCD.
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* `exp` is the 10-exponent, between -99 and 99.
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* `mant` is the mantissa: unpacked BCD digits (one digit per byte).
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*
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* The first digit of the mantissa is the integer part, the others are
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* the decimal part.
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*
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* To interact the flags or the exponent, it is advised to use the g1m_bcd_*
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* macros, as some of them could change. */
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# define g1m_bcdflag_spe 0x80
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# define g1m_bcdflag_neg 0x40
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# define g1m_bcdmask_pre 0x3F
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# define g1m_bcd_has_special(B) ((B)->flags & g1m_bcdflag_spe)
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# define g1m_bcd_is_negative(B) ((B)->flags & g1m_bcdflag_neg)
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# define g1m_bcd_precision(B) ((B)->flags & g1m_bcdmask_pre)
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# define g1m_bcd_exponent(B) ((B)->exp)
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# define g1m_make_bcdflags(SPE, NEG, PREC) \
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(((SPE) << 7) | ((NEG) << 6) | (PREC))
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typedef struct g1m_bcd_s {
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unsigned char flags; char exp;
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char mant[G1M_BCD_MANTISSA_SIZE];
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} g1m_bcd_t;
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/* ************************************************************************** */
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/* Raw formats */
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/* ************************************************************************** */
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/* CAS BCD -- the old BCD format.
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*
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* First two nibbles are the integer part, the fourteen that follow are
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* the decimal part. They are followed by the sign info byte, then with a
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* BCD exponent (two nibbles).
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*
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* The sign info byte is basically the flags of the number.
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* The negative is two bits/flags (I don't know why).
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* `g1m_casbcd_pow_neg`, if there, means the power is negative. */
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# define g1m_casbcd_special 0x80
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# define g1m_casbcd_negative 0x50
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# define g1m_casbcd_pow_neg 0x01
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typedef struct {
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unsigned char mantissa[8];
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unsigned char signinfo;
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unsigned char exponent;
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} cas_bcd_t;
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/* MCS BCD -- the most recent BCD format.
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* Only the first 9 bytes are significant.
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*
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* The highest bit of the first byte isn't to be considered as part of the
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* first nibble, it means something else (generally "the number has a complex
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* part").
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*
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* The first three nibbles are the exponent. If it is more than 500, the
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* number is negative. Its offset is -99.
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* The other values (from the fourth nibble) are the packed BCD mantissa.
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* It starts at 10^0. */
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typedef struct bcd {
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unsigned char BCDval[9];
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unsigned char _align[3];
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} mcs_bcd_t;
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/* ************************************************************************** */
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/* Conversion utilities */
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/* ************************************************************************** */
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/* From and to MCS BCD. */
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int g1m_bcd_frommcs(const mcs_bcd_t *raw, g1m_bcd_t *bcd);
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void g1m_bcd_tomcs(const g1m_bcd_t *bcd, mcs_bcd_t *raw);
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/* From and to CAS BCD. */
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int g1m_bcd_fromcas(const cas_bcd_t *raw, g1m_bcd_t *bcd);
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void g1m_bcd_tocas(const g1m_bcd_t *bcd, cas_bcd_t *raw);
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/* From and to C-double */
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void g1m_bcd_fromdouble(double dbl, g1m_bcd_t *bcd);
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double g1m_bcd_todouble(const g1m_bcd_t *bcd);
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/* Make a string out of a BCD */
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size_t g1m_bcdtoa(const g1m_bcd_t *bcd, char *buf, size_t len);
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# ifdef __cplusplus
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}
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# endif
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#endif /* LIBG1M_BCD_H */
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