adding GNU dc ("desk calculator")

[unix-history] / lib / libc / i386 / stdlib / atof.c

/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* the Systems Programming Group of the University of Utah Computer
* Science Department.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*      This product includes software developed by the University of
*      California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* PATCHES MAGIC                LEVEL   PATCH THAT GOT US HERE
* --------------------         -----   ----------------------
* CURRENT PATCH LEVEL:         2       00108
* --------------------         -----   ----------------------
*
* 27 Feb 93    Joerg Wunsch    Implement strtod, fix atof.
* 28 Mar 93    Jordan Hubbard  Fix stdtod bug with endp, remove warnings.
*
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)atof.c      5.2 (Berkeley) 4/12/91";
#endif /* LIBC_SCCS and not lint */

/*
* simple atof() for IEEE 754 architectures
*/

#include <machine/endian.h>
#include <stdlib.h>
#include <math.h>
#include <ctype.h>
#include <errno.h>
#include <stdio.h>

static double twoemax = 9007199254740992.;      /*2^53*/

/* attempt to be as exact as possible */
static struct {
       long low_word;
       long high_word;
} exp5[] = {
#if     BYTE_ORDER == BIG_ENDIAN
       { 0x40140000, 0x00000000 },     /* 5 */
       { 0x40390000, 0x00000000 },     /* 25 */
       { 0x40838800, 0x00000000 },     /* 625 */
       { 0x4117d784, 0x00000000 },     /* 390625 */
       { 0x4241c379, 0x37e08000 },     /* 152587890625 */
       { 0x4493b8b5, 0xb5056e17 },     /* 2.3283064365387e+022 */
       { 0x49384f03, 0xe93ff9f5 },     /* 5.42101086242753e+044 */
       { 0x52827748, 0xf9301d32 },     /* 2.93873587705572e+089 */
       { 0x65154fdd, 0x7f73bf3b }      /* 8.63616855509445e+178 */
#else   /* BYTE_ORDER == LITTLE_ENDIAN */
       { 0x00000000, 0x40140000 },     /* 5 */
       { 0x00000000, 0x40390000 },     /* 25 */
       { 0x00000000, 0x40838800 },     /* 625 */
       { 0x00000000, 0x4117d784 },     /* 390625 */
       { 0x37e08000, 0x4241c379 },     /* 152587890625 */
       { 0xb5056e17, 0x4493b8b5 },     /* 2.3283064365387e+022 */
       { 0xe93ff9f5, 0x49384f03 },     /* 5.42101086242753e+044 */
       { 0xf9301d32, 0x52827748 },     /* 2.93873587705572e+089 */
       { 0x7f73bf3b, 0x65154fdd }      /* 8.63616855509445e+178 */
#endif
};

double
strtod(p, endp)
       register const char *p;
       char **endp;
{
       register int c;
       register int exp = 0;
       register int eexp = 0;
       double fl = 0;
       double flexp = 1.0;
       int bexp;
       int neg = 1;
       int negexp = 1;
       const char *oldp = p;

       while (isspace(*p))
               ++p;

       if ((c = *p++) == '-')
               neg = -1;
       else if (c == '+')
               /* skip it */;
       else
               --p;

       while ((c = *p++) && isdigit(c))
               if (fl < twoemax)
                       fl = 10 * fl + (c-'0');
               else
                       ++exp;

       if (c == '.')
               while ((c = *p++) && isdigit(c))
                       if (fl < twoemax) {
                               fl = 10 * fl + (c-'0');
                               --exp;
                       }

       if (c == 'E' || c == 'e') {
               if ((c = *p++) == '-')
                       negexp = -1;
               else if (c == '+')
                       /* skip it */;
               else
                       --p;
               while ((c = *p++) && isdigit(c))
                       eexp = 10 * eexp + (c-'0');
               if (negexp < 0)
                       eexp = -eexp;
               exp += eexp;
       }

       bexp = exp;
       if (exp < 0)
               exp = -exp;

       for (c = 0; exp && c < sizeof exp5 / sizeof exp5[0]; ++c) {
               if (exp & 1)
                       flexp *= *(double *)&exp5[c];
               exp >>= 1;
       }

       /* according to ANSI, check for over-/underflow */
       if(exp > 0) {
               if(endp)
                       *endp = (char *)oldp;
               errno = ERANGE;
               return neg < 0? -HUGE_VAL: HUGE_VAL;
       }

       if (bexp < 0)
               fl /= flexp;
       else
               fl *= flexp;

       fl = ldexp(fl, bexp);

       if(endp)
               *endp = (char *)(p - 1);
       return neg < 0 ? -fl : fl;
}


double
atof(p)
       const char *p;
{
       return strtod(p, (char **)NULL);
}