usr/src/lib/libc/hp300/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 are permitted
 * provided that: (1) source distributions retain this entire copyright
 * notice and comment, and (2) distributions including binaries display
 * the following acknowledgement:  ``This product includes software
 * developed by the University of California, Berkeley and its contributors''
 * in the documentation or other materials provided with the distribution
 * and in all advertising materials mentioning features or use of this
 * software. 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)atof.c      5.1 (Berkeley) 5/12/90";
#endif /* LIBC_SCCS and not lint */

#include <ctype.h>

double _twoemax =
#ifdef IEEE
        9007199254740992.;      /*2^53*/
#else
        72057594037927936.;     /*2^56*/
#endif

#ifdef hp300
/* attempt to be as exact as possible */
struct {
        long d_high;
        long d_low;
} _exp5[] = {
        { 0x40140000, 0x00000000 },     /* 5 */
        { 0x40390000, 0x00000000 },     /* 25 */
        { 0x40838800, 0x00000000 },     /* 625 */
        { 0x4117d784, 0x00000000 },     /* 390625 */
        { 0x4241c379, 0x37e08000 },     /* 152587890625 */
        { 0x4493b8b5, 0xb5056e17 },     /* 2.3283064365387e+022 */
        { 0x49384f03, 0xe93ff9f6 },     /* 5.42101086242753e+044 */
        { 0x52827748, 0xf9301d33 },     /* 2.93873587705572e+089 */
        { 0x65154fdd, 0x7f73bf3f }      /* 8.63616855509445e+178 */
};
#else
double  _exp5[] = {
        5.,
        25.,
        625.,
        390625.,
        152587890625.,
        23283064365386962890625.,
#ifdef IEEE
        5.4210108624275231e+044,
        2.9387358770557196e+089,
        8.6361685550944492e+178,
#endif
};
#endif

double
atof(p)
register char *p;
{
        extern double ldexp();
        register c, exp = 0, eexp = 0;
        double fl = 0, flexp = 1.0;
        int bexp, neg = 1, negexp = 1;

        while((c = *p++) == ' ');
        if (c == '-') neg = -1; else if (c == '+'); 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++) == '+'); else if (c=='-') negexp = -1; 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; c < sizeof(_exp5)/sizeof(_exp5[0]); c++)
        {
#ifdef hp300
                if (exp & 01) flexp *= *(double *)&_exp5[c];
#else
                if (exp & 01) flexp *= _exp5[c];
#endif
                exp >>= 1; if (exp == 0) break;
        }

        if (bexp < 0) fl /= flexp; else fl *= flexp;
        fl = ldexp(fl, bexp);
        if (neg < 0) return(-fl); else return(fl);
}