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338 lines
13 KiB
C
338 lines
13 KiB
C
/* Decimal 128-bit format module from the decNumber C Library.
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Copyright (C) 2005 Free Software Foundation, Inc.
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Contributed by IBM Corporation. Author Mike Cowlishaw.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 2, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING. If not, write to the Free
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Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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02111-1307, USA. */
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/* ------------------------------------------------------------------ */
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/* This module comprises the routines for decimal128 format numbers. */
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/* Conversions are supplied to and from decNumber and String. */
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/* */
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/* No arithmetic routines are included; decNumber provides these. */
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/* */
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/* Error handling is the same as decNumber (qv.). */
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/* ------------------------------------------------------------------ */
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#include <string.h> /* [for memset/memcpy] */
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#include <stdio.h> /* [for printf] */
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#define DECNUMDIGITS 34 /* we need decNumbers with space for 34 */
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#include "decNumber.h" /* base number library */
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#include "decNumberLocal.h" /* decNumber local types, etc. */
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#include "decimal128.h" /* our primary include */
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#include "decUtility.h" /* utility routines */
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#if DECTRACE || DECCHECK
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void decimal128Show (decimal128 *); /* for debug */
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void decNumberShow (decNumber *); /* .. */
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#endif
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/* Useful macro */
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/* Clear a structure (e.g., a decNumber) */
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#define DEC_clear(d) memset(d, 0, sizeof(*d))
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/* ------------------------------------------------------------------ */
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/* decimal128FromNumber -- convert decNumber to decimal128 */
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/* */
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/* ds is the target decimal128 */
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/* dn is the source number (assumed valid) */
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/* set is the context, used only for reporting errors */
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/* */
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/* The set argument is used only for status reporting and for the */
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/* rounding mode (used if the coefficient is more than DECIMAL128_Pmax*/
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/* digits or an overflow is detected). If the exponent is out of the */
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/* valid range then Overflow or Underflow will be raised. */
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/* After Underflow a subnormal result is possible. */
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/* */
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/* DEC_Clamped is set if the number has to be 'folded down' to fit, */
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/* by reducing its exponent and multiplying the coefficient by a */
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/* power of ten, or if the exponent on a zero had to be clamped. */
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/* ------------------------------------------------------------------ */
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decimal128 *
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decimal128FromNumber (decimal128 * d128, decNumber * dn, decContext * set)
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{
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uInt status = 0; /* status accumulator */
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Int pad = 0; /* coefficient pad digits */
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decNumber dw; /* work */
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decContext dc; /* .. */
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uByte isneg = dn->bits & DECNEG; /* non-0 if original sign set */
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uInt comb, exp; /* work */
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/* If the number is finite, and has too many digits, or the exponent */
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/* could be out of range then we reduce the number under the */
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/* appropriate constraints */
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if (!(dn->bits & DECSPECIAL))
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{ /* not a special value */
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Int ae = dn->exponent + dn->digits - 1; /* adjusted exponent */
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if (dn->digits > DECIMAL128_Pmax /* too many digits */
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|| ae > DECIMAL128_Emax /* likely overflow */
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|| ae < DECIMAL128_Emin)
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{ /* likely underflow */
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decContextDefault (&dc, DEC_INIT_DECIMAL128); /* [no traps] */
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dc.round = set->round; /* use supplied rounding */
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decNumberPlus (&dw, dn, &dc); /* (round and check) */
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/* [this changes -0 to 0, but it will be restored below] */
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status |= dc.status; /* save status */
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dn = &dw; /* use the work number */
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}
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/* [this could have pushed number to Infinity or zero, so this */
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/* rounding must be done before we generate the decimal128] */
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}
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DEC_clear (d128); /* clean the target */
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if (dn->bits & DECSPECIAL)
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{ /* a special value */
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uByte top; /* work */
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if (dn->bits & DECINF)
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top = DECIMAL_Inf;
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else
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{ /* sNaN or qNaN */
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if ((*dn->lsu != 0 || dn->digits > 1) /* non-zero coefficient */
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&& (dn->digits < DECIMAL128_Pmax))
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{ /* coefficient fits */
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decDensePackCoeff (dn, d128->bytes, sizeof (d128->bytes), 0);
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}
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if (dn->bits & DECNAN)
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top = DECIMAL_NaN;
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else
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top = DECIMAL_sNaN;
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}
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d128->bytes[0] = top;
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}
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else if (decNumberIsZero (dn))
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{ /* a zero */
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/* set and clamp exponent */
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if (dn->exponent < -DECIMAL128_Bias)
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{
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exp = 0;
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status |= DEC_Clamped;
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}
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else
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{
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exp = dn->exponent + DECIMAL128_Bias; /* bias exponent */
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if (exp > DECIMAL128_Ehigh)
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{ /* top clamp */
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exp = DECIMAL128_Ehigh;
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status |= DEC_Clamped;
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}
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}
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comb = (exp >> 9) & 0x18; /* combination field */
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d128->bytes[0] = (uByte) (comb << 2);
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exp &= 0xfff; /* remaining exponent bits */
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decimal128SetExpCon (d128, exp);
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}
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else
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{ /* non-zero finite number */
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uInt msd; /* work */
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/* we have a dn that fits, but it may need to be padded */
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exp = (uInt) (dn->exponent + DECIMAL128_Bias); /* bias exponent */
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if (exp > DECIMAL128_Ehigh)
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{ /* fold-down case */
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pad = exp - DECIMAL128_Ehigh;
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exp = DECIMAL128_Ehigh; /* [to maximum] */
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status |= DEC_Clamped;
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}
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decDensePackCoeff (dn, d128->bytes, sizeof (d128->bytes), pad);
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/* save and clear the top digit */
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msd = ((unsigned) d128->bytes[1] << 2) & 0x0c; /* top 2 bits */
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msd |= ((unsigned) d128->bytes[2] >> 6); /* low 2 bits */
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d128->bytes[1] &= 0xfc;
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d128->bytes[2] &= 0x3f;
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/* create the combination field */
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if (msd >= 8)
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comb = 0x18 | (msd & 0x01) | ((exp >> 11) & 0x06);
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else
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comb = (msd & 0x07) | ((exp >> 9) & 0x18);
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d128->bytes[0] = (uByte) (comb << 2);
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exp &= 0xfff; /* remaining exponent bits */
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decimal128SetExpCon (d128, exp);
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}
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if (isneg)
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decimal128SetSign (d128, 1);
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if (status != 0)
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decContextSetStatus (set, status); /* pass on status */
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/* decimal128Show(d128); */
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return d128;
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}
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/* ------------------------------------------------------------------ */
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/* decimal128ToNumber -- convert decimal128 to decNumber */
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/* d128 is the source decimal128 */
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/* dn is the target number, with appropriate space */
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/* No error is possible. */
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/* ------------------------------------------------------------------ */
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decNumber *
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decimal128ToNumber (decimal128 * d128, decNumber * dn)
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{
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uInt msd; /* coefficient MSD */
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decimal128 wk; /* working copy, if needed */
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uInt top = d128->bytes[0] & 0x7f; /* top byte, less sign bit */
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decNumberZero (dn); /* clean target */
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/* set the sign if negative */
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if (decimal128Sign (d128))
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dn->bits = DECNEG;
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if (top >= 0x78)
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{ /* is a special */
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if ((top & 0x7c) == (DECIMAL_Inf & 0x7c))
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dn->bits |= DECINF;
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else if ((top & 0x7e) == (DECIMAL_NaN & 0x7e))
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dn->bits |= DECNAN;
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else
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dn->bits |= DECSNAN;
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msd = 0; /* no top digit */
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}
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else
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{ /* have a finite number */
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uInt comb = top >> 2; /* combination field */
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uInt exp; /* exponent */
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if (comb >= 0x18)
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{
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msd = 8 + (comb & 0x01);
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exp = (comb & 0x06) << 11; /* MSBs */
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}
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else
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{
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msd = comb & 0x07;
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exp = (comb & 0x18) << 9;
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}
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dn->exponent = exp + decimal128ExpCon (d128) - DECIMAL128_Bias; /* remove bias */
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}
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/* get the coefficient, unless infinite */
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if (!(dn->bits & DECINF))
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{
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Int bunches = DECIMAL128_Pmax / 3; /* coefficient full bunches to convert */
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Int odd = 0; /* assume MSD is 0 (no odd bunch) */
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if (msd != 0)
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{ /* coefficient has leading non-0 digit */
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/* make a copy of the decimal128, with an extra bunch which has */
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/* the top digit ready for conversion */
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wk = *d128; /* take a copy */
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wk.bytes[0] = 0; /* clear all but coecon */
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wk.bytes[1] = 0; /* .. */
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wk.bytes[2] &= 0x3f; /* .. */
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wk.bytes[1] |= (msd >> 2); /* and prefix MSD */
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wk.bytes[2] |= (msd << 6); /* .. */
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odd++; /* indicate the extra */
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d128 = &wk; /* use the work copy */
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}
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decDenseUnpackCoeff (d128->bytes, sizeof (d128->bytes), dn, bunches,
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odd);
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}
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/* decNumberShow(dn); */
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return dn;
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}
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/* ------------------------------------------------------------------ */
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/* to-scientific-string -- conversion to numeric string */
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/* to-engineering-string -- conversion to numeric string */
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/* */
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/* decimal128ToString(d128, string); */
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/* decimal128ToEngString(d128, string); */
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/* */
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/* d128 is the decimal128 format number to convert */
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/* string is the string where the result will be laid out */
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/* */
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/* string must be at least 24 characters */
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/* */
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/* No error is possible, and no status can be set. */
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/* ------------------------------------------------------------------ */
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char *
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decimal128ToString (decimal128 * d128, char *string)
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{
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decNumber dn; /* work */
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decimal128ToNumber (d128, &dn);
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decNumberToString (&dn, string);
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return string;
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}
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char *
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decimal128ToEngString (decimal128 * d128, char *string)
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{
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decNumber dn; /* work */
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decimal128ToNumber (d128, &dn);
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decNumberToEngString (&dn, string);
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return string;
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}
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/* ------------------------------------------------------------------ */
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/* to-number -- conversion from numeric string */
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/* */
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/* decimal128FromString(result, string, set); */
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/* */
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/* result is the decimal128 format number which gets the result of */
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/* the conversion */
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/* *string is the character string which should contain a valid */
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/* number (which may be a special value) */
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/* set is the context */
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/* */
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/* The context is supplied to this routine is used for error handling */
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/* (setting of status and traps) and for the rounding mode, only. */
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/* If an error occurs, the result will be a valid decimal128 NaN. */
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/* ------------------------------------------------------------------ */
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decimal128 *
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decimal128FromString (decimal128 * result, char *string, decContext * set)
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{
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decContext dc; /* work */
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decNumber dn; /* .. */
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decContextDefault (&dc, DEC_INIT_DECIMAL128); /* no traps, please */
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dc.round = set->round; /* use supplied rounding */
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decNumberFromString (&dn, string, &dc); /* will round if needed */
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decimal128FromNumber (result, &dn, &dc);
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if (dc.status != 0)
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{ /* something happened */
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decContextSetStatus (set, dc.status); /* .. pass it on */
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}
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return result;
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}
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#if DECTRACE || DECCHECK
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/* ------------------------------------------------------------------ */
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/* decimal128Show -- display a single in hexadecimal [debug aid] */
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/* d128 -- the number to show */
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/* ------------------------------------------------------------------ */
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/* Also shows sign/cob/expconfields extracted */
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void
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decimal128Show (decimal128 * d128)
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{
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char buf[DECIMAL128_Bytes * 2 + 1];
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Int i, j;
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j = 0;
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for (i = 0; i < DECIMAL128_Bytes; i++)
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{
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sprintf (&buf[j], "%02x", d128->bytes[i]);
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j = j + 2;
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}
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printf (" D128> %s [S:%d Cb:%02x E:%d]\n", buf,
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decimal128Sign (d128), decimal128Comb (d128),
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decimal128ExpCon (d128));
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}
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#endif
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