151 lines
4.4 KiB
C
151 lines
4.4 KiB
C
/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* the Systems Programming Group of the University of Utah Computer
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* Science Department.
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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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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#if defined(LIBC_SCCS) && !defined(lint)
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/*static char sccsid[] = "from: @(#)atof.c 5.2 (Berkeley) 4/12/91";*/
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static char rcsid[] = "$Id: atof.c,v 1.2 1993/08/01 18:41:45 mycroft Exp $";
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#endif /* LIBC_SCCS and not lint */
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/*
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* simple atof() for IEEE 754 architectures
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*/
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#include <machine/endian.h>
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#include <stdlib.h>
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#include <math.h>
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#include <ctype.h>
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static double twoemax = 9007199254740992.; /*2^53*/
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/* attempt to be as exact as possible */
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static struct {
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long low_word;
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long high_word;
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} exp5[] = {
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#if BYTE_ORDER == BIG_ENDIAN
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{ 0x40140000, 0x00000000 }, /* 5 */
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{ 0x40390000, 0x00000000 }, /* 25 */
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{ 0x40838800, 0x00000000 }, /* 625 */
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{ 0x4117d784, 0x00000000 }, /* 390625 */
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{ 0x4241c379, 0x37e08000 }, /* 152587890625 */
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{ 0x4493b8b5, 0xb5056e17 }, /* 2.3283064365387e+022 */
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{ 0x49384f03, 0xe93ff9f6 }, /* 5.42101086242753e+044 */
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{ 0x52827748, 0xf9301d33 }, /* 2.93873587705572e+089 */
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{ 0x65154fdd, 0x7f73bf3f } /* 8.63616855509445e+178 */
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#else /* BYTE_ORDER == LITTLE_ENDIAN */
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{ 0x00000000, 0x40140000 }, /* 5 */
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{ 0x00000000, 0x40390000 }, /* 25 */
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{ 0x00000000, 0x40838800 }, /* 625 */
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{ 0x00000000, 0x4117d784 }, /* 390625 */
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{ 0x37e08000, 0x4241c379 }, /* 152587890625 */
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{ 0xb5056e17, 0x4493b8b5 }, /* 2.3283064365387e+022 */
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{ 0xe93ff9f6, 0x49384f03 }, /* 5.42101086242753e+044 */
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{ 0xf9301d33, 0x52827748 }, /* 2.93873587705572e+089 */
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{ 0x7f73bf3f, 0x65154fdd } /* 8.63616855509445e+178 */
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#endif
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};
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double
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atof(p)
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register const char *p;
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{
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register int c;
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register int exp = 0;
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register int eexp = 0;
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double fl = 0;
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double flexp = 1.0;
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int bexp;
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int neg = 1;
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int negexp = 1;
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while (isspace(*p))
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++p;
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if ((c = *p++) == '-')
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neg = -1;
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else if (c == '+')
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/* skip it */;
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else
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--p;
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while ((c = *p++) && isdigit(c))
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if (fl < twoemax)
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fl = 10 * fl + (c-'0');
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else
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++exp;
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if (c == '.')
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while ((c = *p++) && isdigit(c))
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if (fl < twoemax) {
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fl = 10 * fl + (c-'0');
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--exp;
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}
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if (c == 'E' || c == 'e') {
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if ((c = *p++) == '-')
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negexp = -1;
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else if (c == '+')
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/* skip it */;
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else
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--p;
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while ((c = *p++) && isdigit(c))
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eexp = 10 * eexp + (c-'0');
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if (negexp < 0)
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eexp = -eexp;
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exp += eexp;
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}
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bexp = exp;
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if (exp < 0)
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exp = -exp;
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for (c = 0; exp && c < sizeof exp5 / sizeof exp5[0]; ++c) {
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if (exp & 1)
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flexp *= *(double *)&exp5[c];
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exp >>= 1;
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}
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if (bexp < 0)
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fl /= flexp;
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else
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fl *= flexp;
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fl = ldexp(fl, bexp);
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return neg < 0 ? -fl : fl;
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}
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