153 lines
5.1 KiB
C
153 lines
5.1 KiB
C
/* ****************************************************************************
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* libcasio/number.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 libcasio.
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* libcasio 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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* libcasio 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 libcasio; 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, libcasio provides 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 LIBCASIO_NUMBER_H
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# define LIBCASIO_NUMBER_H
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# include "cdefs.h"
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CASIO_BEGIN_NAMESPACE
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# define CASIO_BCD_MANTISSA_SIZE 16
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# define CASIO_BCD_EXPMIN -99
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# define CASIO_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 CASIO_BCD_GOODBUFSIZE \
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(2 + CASIO_BCD_MANTISSA_SIZE + 4 + 2 + 1)
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/* ---
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* Main type.
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* --- */
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/* libcasio type definition.
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* This is the "unzipped" BCD format. There are several, this is the one
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* libcasio 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
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* `casio_bcd_*` macros, as some of them could change. */
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# define casio_bcdflag_spe 0x80
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# define casio_bcdflag_neg 0x40
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# define casio_bcdmask_pre 0x3F
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# define casio_bcd_has_special(B) ((B)->casio_bcd_flags & casio_bcdflag_spe)
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# define casio_bcd_is_negative(B) ((B)->casio_bcd_flags & casio_bcdflag_neg)
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# define casio_bcd_precision(B) ((B)->casio_bcd_flags & casio_bcdmask_pre)
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# define casio_bcd_exponent(B) ((B)->casio_bcd_exp)
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# define casio_make_bcdflags(SPE, NEG, PREC) \
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(((SPE) << 7) | ((NEG) << 6) | (PREC))
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typedef struct casio_bcd_s {
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unsigned char casio_bcd_flags;
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char casio_bcd_exp;
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char casio_bcd_mant[CASIO_BCD_MANTISSA_SIZE];
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} casio_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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* `casio_casbcd_pow_neg`, if there, means the power is negative. */
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# define casio_casbcdflag_special 0x80
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# define casio_casbcdflag_negative 0x50
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# define casio_casbcdflag_pow_neg 0x01
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typedef struct casio_casbcd_s {
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unsigned char casio_casbcd_mant[8];
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unsigned char casio_casbcd_flags;
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unsigned char casio_casbcd_exp;
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} casio_casbcd_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 casio_mcsbcd_s {
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unsigned char casio_mcsbcd_BCDval[9];
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unsigned char casio_mcsbcd__align[3];
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} casio_mcsbcd_t;
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/* ---
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* Conversion utilities.
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* --- */
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CASIO_BEGIN_DECLS
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/* From and to MCS BCD. */
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CASIO_EXTERN int CASIO_EXPORT casio_bcd_frommcs
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OF((casio_bcd_t *casio__bcd, casio_mcsbcd_t const *casio__raw));
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CASIO_EXTERN int CASIO_EXPORT casio_bcd_tomcs
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OF((casio_mcsbcd_t *casio__raw, casio_bcd_t const *casio__bcd));
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/* From and to CAS BCD. */
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CASIO_EXTERN int CASIO_EXPORT casio_bcd_fromcas
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OF((casio_bcd_t *casio__bcd, casio_casbcd_t const *casio__raw));
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CASIO_EXTERN int CASIO_EXPORT casio_bcd_tocas
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OF((casio_casbcd_t *casio__raw, casio_bcd_t const *casio__bcd));
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/* From and to C-double */
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CASIO_EXTERN void CASIO_EXPORT casio_bcd_fromdouble
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OF((casio_bcd_t *casio__bcd, double casio__raw));
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CASIO_EXTERN double CASIO_EXPORT casio_bcd_todouble
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OF((casio_bcd_t const *casio__bcd));
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/* Make a string out of a BCD */
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CASIO_EXTERN size_t CASIO_EXPORT casio_bcdtoa
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OF((char *casio__buf, size_t casio__len, casio_bcd_t const *casio__bcd));
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CASIO_END_DECLS
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CASIO_END_NAMESPACE
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#endif /* LIBCASIO_NUMBER_H */
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