| 1 | #include "pyconfig.h"
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| 2 |
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| 3 | /* comp.sources.misc strtod(), as posted in comp.lang.tcl,
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| 4 | with bugfix for "123000.0" and acceptance of space after 'e' sign nuked.
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| 5 |
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| 6 | ************************************************************
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| 7 | * YOU MUST EDIT THE MACHINE-DEPENDENT DEFINITIONS BELOW!!! *
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| 8 | ************************************************************
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| 9 | */
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| 10 |
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| 11 | /* File : stdtod.c (Modified version of str2dbl.c)
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| 12 | Author : Richard A. O'Keefe @ Quintus Computer Systems, Inc.
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| 13 | Updated: Tuesday August 2nd, 1988
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| 14 | Defines: double strtod (char *str, char**ptr)
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| 15 | */
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| 16 |
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| 17 | /* This is an implementation of the strtod() function described in the
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| 18 | System V manuals, with a different name to avoid linker problems.
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| 19 | All that str2dbl() does itself is check that the argument is well-formed
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| 20 | and is in range. It leaves the work of conversion to atof(), which is
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| 21 | assumed to exist and deliver correct results (if they can be represented).
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| 22 |
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| 23 | There are two reasons why this should be provided to the net:
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| 24 | (a) some UNIX systems do not yet have strtod(), or do not have it
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| 25 | available in the BSD "universe" (but they do have atof()).
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| 26 | (b) some of the UNIX systems that *do* have it get it wrong.
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| 27 | (some crash with large arguments, some assign the wrong *ptr value).
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| 28 | There is a reason why *we* are providing it: we need a correct version
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| 29 | of strtod(), and if we give this one away maybe someone will look for
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| 30 | mistakes in it and fix them for us (:-).
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| 31 | */
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| 32 |
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| 33 | /* The following constants are machine-specific. MD{MIN,MAX}EXPT are
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| 34 | integers and MD{MIN,MAX}FRAC are strings such that
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| 35 | 0.${MDMAXFRAC}e${MDMAXEXPT} is the largest representable double,
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| 36 | 0.${MDMINFRAC}e${MDMINEXPT} is the smallest representable +ve double
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| 37 | MD{MIN,MAX}FRAC must not have any trailing zeros.
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| 38 | The values here are for IEEE-754 64-bit floats.
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| 39 | It is not perfectly clear to me whether an IEEE infinity should be
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| 40 | returned for overflow, nor what a portable way of writing one is,
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| 41 | so HUGE is just 0.MAXFRAC*10**MAXEXPT (this seems still to be the
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| 42 | UNIX convention).
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| 43 |
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| 44 | I do know about <values.h>, but the whole point of this file is that
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| 45 | we can't always trust that stuff to be there or to be correct.
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| 46 | */
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| 47 | static int MDMINEXPT = {-323};
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| 48 | static char MDMINFRAC[] = "494065645841246544";
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| 49 | static double ZERO = 0.0;
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| 50 |
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| 51 | static int MDMAXEXPT = { 309};
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| 52 | static char MDMAXFRAC[] = "17976931348623157";
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| 53 | static double HUGE = 1.7976931348623157e308;
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| 54 |
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| 55 | extern double atof(const char *); /* Only called when result known to be ok */
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| 56 |
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| 57 | #ifdef HAVE_ERRNO_H
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| 58 | #include <errno.h>
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| 59 | #endif
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| 60 | extern int errno;
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| 61 |
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| 62 | double strtod(char *str, char **ptr)
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| 63 | {
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| 64 | int sign, scale, dotseen;
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| 65 | int esign, expt;
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| 66 | char *save;
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| 67 | register char *sp, *dp;
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| 68 | register int c;
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| 69 | char *buforg, *buflim;
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| 70 | char buffer[64]; /* 45-digit significant + */
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| 71 | /* 13-digit exponent */
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| 72 | sp = str;
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| 73 | while (*sp == ' ') sp++;
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| 74 | sign = 1;
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| 75 | if (*sp == '-') sign -= 2, sp++;
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| 76 | dotseen = 0, scale = 0;
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| 77 | dp = buffer;
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| 78 | *dp++ = '0'; *dp++ = '.';
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| 79 | buforg = dp, buflim = buffer+48;
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| 80 | for (save = sp; c = *sp; sp++)
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| 81 | if (c == '.') {
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| 82 | if (dotseen) break;
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| 83 | dotseen++;
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| 84 | } else
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| 85 | if ((unsigned)(c-'0') > (unsigned)('9'-'0')) {
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| 86 | break;
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| 87 | } else
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| 88 | if (c == '0') {
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| 89 | if (dp != buforg) {
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| 90 | /* This is not the first digit, so we want to keep it */
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| 91 | if (dp < buflim) *dp++ = c;
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| 92 | if (!dotseen) scale++;
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| 93 | } else {
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| 94 | /* No non-zero digits seen yet */
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| 95 | /* If a . has been seen, scale must be adjusted */
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| 96 | if (dotseen) scale--;
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| 97 | }
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| 98 | } else {
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| 99 | /* This is a nonzero digit, so we want to keep it */
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| 100 | if (dp < buflim) *dp++ = c;
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| 101 | /* If it precedes a ., scale must be adjusted */
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| 102 | if (!dotseen) scale++;
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| 103 | }
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| 104 | if (sp == save) {
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| 105 | if (ptr) *ptr = str;
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| 106 | errno = EDOM; /* what should this be? */
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| 107 | return ZERO;
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| 108 | }
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| 109 |
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| 110 | while (dp > buforg && dp[-1] == '0') --dp;
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| 111 | if (dp == buforg) *dp++ = '0';
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