145 lines
4.4 KiB
C
145 lines
4.4 KiB
C
/*-
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* Copyright (c) 2004-2008 David Schultz <das@FreeBSD.ORG>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <float.h>
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#include <limits.h>
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#include <math.h>
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#include "../stdio/floatio.h"
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#include "fpmath.h"
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#include "gdtoaimp.h"
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/* Strings values used by dtoa() */
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#define INFSTR "Infinity"
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#define NANSTR "NaN"
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#define DBL_ADJ (DBL_MAX_EXP - 2)
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#define SIGFIGS ((DBL_MANT_DIG + 3) / 4 + 1)
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static const float one[] = { 1.0f, -1.0f };
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/*
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* This procedure converts a double-precision number in IEEE format
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* into a string of hexadecimal digits and an exponent of 2. Its
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* behavior is bug-for-bug compatible with dtoa() in mode 2, with the
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* following exceptions:
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*
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* - An ndigits < 0 causes it to use as many digits as necessary to
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* represent the number exactly.
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* - The additional xdigs argument should point to either the string
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* "0123456789ABCDEF" or the string "0123456789abcdef", depending on
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* which case is desired.
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* - This routine does not repeat dtoa's mistake of setting decpt
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* to 9999 in the case of an infinity or NaN. INT_MAX is used
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* for this purpose instead.
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*
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* Note that the C99 standard does not specify what the leading digit
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* should be for non-zero numbers. For instance, 0x1.3p3 is the same
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* as 0x2.6p2 is the same as 0x4.cp3. This implementation always makes
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* the leading digit a 1. This ensures that the exponent printed is the
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* actual base-2 exponent, i.e., ilogb(d).
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*
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* Inputs: d, xdigs, ndigits
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* Outputs: decpt, sign, rve
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*/
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char *
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__hdtoa(double d, const char *xdigs, int ndigits, int *decpt, int *sign,
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char **rve)
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{
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union IEEEd2bits u;
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char *s, *s0;
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int bufsize;
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uint32_t manh, manl;
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u.d = d;
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*sign = u.bits.sign;
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switch (fpclassify(d)) {
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case FP_NORMAL:
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*decpt = u.bits.exp - DBL_ADJ;
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break;
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case FP_ZERO:
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*decpt = 1;
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return (nrv_alloc("0", rve, 1));
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case FP_SUBNORMAL:
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u.d *= 0x1p514;
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*decpt = u.bits.exp - (514 + DBL_ADJ);
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break;
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case FP_INFINITE:
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*decpt = INT_MAX;
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return (nrv_alloc(INFSTR, rve, sizeof(INFSTR) - 1));
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default: /* FP_NAN or unrecognized */
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*decpt = INT_MAX;
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return (nrv_alloc(NANSTR, rve, sizeof(NANSTR) - 1));
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}
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/* FP_NORMAL or FP_SUBNORMAL */
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if (ndigits == 0) /* dtoa() compatibility */
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ndigits = 1;
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/*
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* If ndigits < 0, we are expected to auto-size, so we allocate
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* enough space for all the digits.
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*/
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bufsize = (ndigits > 0) ? ndigits : SIGFIGS;
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s0 = rv_alloc(bufsize);
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/* Round to the desired number of digits. */
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if (SIGFIGS > ndigits && ndigits > 0) {
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float redux = one[u.bits.sign];
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int offset = 4 * ndigits + DBL_MAX_EXP - 4 - DBL_MANT_DIG;
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u.bits.exp = offset;
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u.d += redux;
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u.d -= redux;
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*decpt += u.bits.exp - offset;
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}
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manh = u.bits.manh;
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manl = u.bits.manl;
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*s0 = '1';
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for (s = s0 + 1; s < s0 + bufsize; s++) {
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*s = xdigs[(manh >> (DBL_MANH_SIZE - 4)) & 0xf];
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manh = (manh << 4) | (manl >> (DBL_MANL_SIZE - 4));
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manl <<= 4;
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}
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/* If ndigits < 0, we are expected to auto-size the precision. */
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if (ndigits < 0) {
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for (ndigits = SIGFIGS; s0[ndigits - 1] == '0'; ndigits--)
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;
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}
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s = s0 + ndigits;
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*s = '\0';
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if (rve != NULL)
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*rve = s;
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return (s0);
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}
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