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- /*
- * edlib v1.1 Copyright 1989 Edwin Hoogerbeets
- * This code is freely redistributable as long as no charge other than
- * reasonable copying fees are levied for it.
- */
-
-
- /* File : strtod.c
- Author : Richard A. O'Keefe @ Quintus Computer Systems, Inc.
- Updated: Saturday March 11, 1989
- Defines: double strtod(char *str, char**ptr)
- */
-
- /* This is an implementation of the strtod() function described in the
- System V manuals, with a different name to avoid linker problems.
- All that str2dbl() does itself is check that the argument is well-formed
- and is in range. It leaves the work of conversion to atof(), which is
- assumed to exist and deliver correct results (if they can be represented).
-
- There are two reasons why this should be provided to the net:
- (a) some UNIX systems do not yet have strtod(), or do not have it
- available in the BSD "universe" (but they do have atof()).
- (b) some of the UNIX systems that *do* have it get it wrong.
- (some crash with large arguments, some assign the wrong *ptr value).
- There is a reason why *we* are providing it: we need a correct version
- of strtod(), and if we give this one away maybe someone will look for
- mistakes in it and fix them for us (:-).
- */
-
- /* The following constants are machine-specific. MD{MIN,MAX}EXPT are
- integers and MD{MIN,MAX}FRAC are strings such that
- 0.${MDMAXFRAC}e${MDMAXEXPT} is the largest representable double,
- 0.${MDMINFRAC}e${MDMINEXPT} is the smallest representable +ve double
- MD{MIN,MAX}FRAC must not have any trailing zeros.
- The values here are for IEEE-754 64-bit floats.
- It is not perfectly clear to me whether an IEEE infinity should be
- returned for overflow, nor what a portable way of writing one is,
- so HUGE is just 0.MAXFRAC*10**MAXEXPT (this seems still to be the
- UNIX convention).
-
- I do know about <values.h>, but the whole point of this file is that
- we can't always trust that stuff to be there or to be correct.
- */
-
- extern double atof(); /* Only called when result known to be ok */
-
- #include "edlib.h"
- #include <ctype.h>
- #include <errno.h>
- extern int errno;
-
- double strtod(str, ptr)
- char *str;
- char **ptr;
- {
- int sign, scale, dotseen;
- int esign, expt;
- char *save;
- register char *sp, *dp;
- register int c;
- char *buforg, *buflim;
- char buffer[64]; /* 45-digit significand + */
- /* 13-digit exponent */
- sp = str;
- while (*sp == ' ')
- sp++;
-
- sign = 1;
-
- if (*sp == '-') {
- sign -= 2;
- sp++;
- }
-
- dotseen = 0;
- scale = 0;
- dp = buffer;
-
- *dp++ = '0';
- *dp++ = '.';
-
- buforg = dp;
- buflim = buffer+48;
-
- for (save = sp; c = *sp; sp++) {
-
- if (c == '.') {
-
- if (dotseen)
- break;
-
- dotseen++;
-
- } else if ( !isdigit(c) ) {
- break;
-
- } else if (c == '0') {
-
- if (dp != buforg) {
-
- /* This is not the first digit, so we want to keep it */
- if (dp < buflim) {
- *dp++ = c;
- scale += 1;
- }
-
- } else {
-
- /* No non-zero digits seen yet */
- /* If a . has been seen, scale must be adjusted */
- if (dotseen)
- scale--;
- }
- } else {
-
- /* This is a nonzero digit, so we want to keep it */
- if (dp < buflim)
- *dp++ = c;
-
- /* If it precedes a ., scale must be adjusted */
- if (!dotseen)
- scale++;
- }
- }
- if (sp == save) {
- if (ptr)
- *ptr = str;
- errno = EDOM; /* what should this be? */
- return ZERO;
- }
-
- while (dp > buforg && dp[-1] == '0')
- --dp;
-
- if (dp == buforg)
- *dp++ = '0';
-
- *dp = '\0';
-
- /* Now the contents of buffer are
- +--+--------+-+--------+
- |0.|fraction|\|leftover|
- +--+--------+-+--------+
- ^dp points here
- where fraction begins with 0 iff it is "0", and has at most
- 45 digits in it, and leftover is at least 16 characters.
- */
-
- save = sp;
- expt = 0;
- esign = 1;
-
- do {
- c = *sp++;
-
- if (c != 'e' && c != 'E')
- break;
-
- c = *sp++;
-
- if ( c == '-' ) {
- esign -= 2;
- c = *sp++;
- } else if (c == '+' || c == ' ') {
- c = *sp++;
- }
-
- if ( !isdigit(c) )
- break;
-
- while (c == '0')
- c = *sp++;
-
- for (; isdigit(c); c = *sp++)
- expt = expt*10 + toint(c);
-
- if (esign < 0)
- expt = -expt;
-
- save = sp-1;
-
- } while (0);
-
- if (ptr)
- *ptr = save;
-
- expt += scale;
-
- /* Now the number is sign*0.fraction*10**expt */
- errno = ERANGE;
-
- if (expt > MDMAXEXPT) {
- return(HUGE*sign);
- } else if (expt == MDMAXEXPT) {
- if (strcmp(buforg, MDMAXFRAC) > 0)
- return(HUGE*sign);
- } else if (expt < MDMINEXPT) {
- return(ZERO*sign);
- } else if (expt == MDMINEXPT) {
- if (strcmp(buforg, MDMINFRAC) < 0)
- return(ZERO*sign);
- }
-
- /* We have now established that the number can be */
- /* represented without overflow or underflow */
- (void) sprintf(dp, "e%d", expt);
- errno = 0;
- return(atof(buffer)*sign);
- }
-
-