Catch situations where currentframe() returns None. See SF patch #1447410, this is...
[python.git] / Python / strtod.c
blob7911a945908a0ce871e60134535b8edf5d739f1c
1 #include "pyconfig.h"
3 /* comp.sources.misc strtod(), as posted in comp.lang.tcl,
4 with bugfix for "123000.0" and acceptance of space after 'e' sign nuked.
6 ************************************************************
7 * YOU MUST EDIT THE MACHINE-DEPENDENT DEFINITIONS BELOW!!! *
8 ************************************************************
9 */
11 /* File : stdtod.c (Modified version of str2dbl.c)
12 Author : Richard A. O'Keefe @ Quintus Computer Systems, Inc.
13 Updated: Tuesday August 2nd, 1988
14 Defines: double strtod (char *str, char**ptr)
17 /* This is an implementation of the strtod() function described in the
18 System V manuals, with a different name to avoid linker problems.
19 All that str2dbl() does itself is check that the argument is well-formed
20 and is in range. It leaves the work of conversion to atof(), which is
21 assumed to exist and deliver correct results (if they can be represented).
23 There are two reasons why this should be provided to the net:
24 (a) some UNIX systems do not yet have strtod(), or do not have it
25 available in the BSD "universe" (but they do have atof()).
26 (b) some of the UNIX systems that *do* have it get it wrong.
27 (some crash with large arguments, some assign the wrong *ptr value).
28 There is a reason why *we* are providing it: we need a correct version
29 of strtod(), and if we give this one away maybe someone will look for
30 mistakes in it and fix them for us (:-).
33 /* The following constants are machine-specific. MD{MIN,MAX}EXPT are
34 integers and MD{MIN,MAX}FRAC are strings such that
35 0.${MDMAXFRAC}e${MDMAXEXPT} is the largest representable double,
36 0.${MDMINFRAC}e${MDMINEXPT} is the smallest representable +ve double
37 MD{MIN,MAX}FRAC must not have any trailing zeros.
38 The values here are for IEEE-754 64-bit floats.
39 It is not perfectly clear to me whether an IEEE infinity should be
40 returned for overflow, nor what a portable way of writing one is,
41 so HUGE is just 0.MAXFRAC*10**MAXEXPT (this seems still to be the
42 UNIX convention).
44 I do know about <values.h>, but the whole point of this file is that
45 we can't always trust that stuff to be there or to be correct.
47 static int MDMINEXPT = {-323};
48 static char MDMINFRAC[] = "494065645841246544";
49 static double ZERO = 0.0;
51 static int MDMAXEXPT = { 309};
52 static char MDMAXFRAC[] = "17976931348623157";
53 static double HUGE = 1.7976931348623157e308;
55 extern double atof(const char *); /* Only called when result known to be ok */
57 #ifndef DONT_HAVE_ERRNO_H
58 #include <errno.h>
59 #endif
60 extern int errno;
62 double strtod(char *str, char **ptr)
64 int sign, scale, dotseen;
65 int esign, expt;
66 char *save;
67 register char *sp, *dp;
68 register int c;
69 char *buforg, *buflim;
70 char buffer[64]; /* 45-digit significant + */
71 /* 13-digit exponent */
72 sp = str;
73 while (*sp == ' ') sp++;
74 sign = 1;
75 if (*sp == '-') sign -= 2, sp++;
76 dotseen = 0, scale = 0;
77 dp = buffer;
78 *dp++ = '0'; *dp++ = '.';
79 buforg = dp, buflim = buffer+48;
80 for (save = sp; c = *sp; sp++)
81 if (c == '.') {
82 if (dotseen) break;
83 dotseen++;
84 } else
85 if ((unsigned)(c-'0') > (unsigned)('9'-'0')) {
86 break;
87 } else
88 if (c == '0') {
89 if (dp != buforg) {
90 /* This is not the first digit, so we want to keep it */
91 if (dp < buflim) *dp++ = c;
92 if (!dotseen) scale++;
93 } else {
94 /* No non-zero digits seen yet */
95 /* If a . has been seen, scale must be adjusted */
96 if (dotseen) scale--;
98 } else {
99 /* This is a nonzero digit, so we want to keep it */
100 if (dp < buflim) *dp++ = c;
101 /* If it precedes a ., scale must be adjusted */
102 if (!dotseen) scale++;
104 if (sp == save) {
105 if (ptr) *ptr = str;
106 errno = EDOM; /* what should this be? */
107 return ZERO;
110 while (dp > buforg && dp[-1] == '0') --dp;
111 if (dp == buforg) *dp++ = '0';
112 *dp = '\0';
113 /* Now the contents of buffer are
114 +--+--------+-+--------+
115 |0.|fraction|\|leftover|
116 +--+--------+-+--------+
117 ^dp points here
118 where fraction begins with 0 iff it is "0", and has at most
119 45 digits in it, and leftover is at least 16 characters.
121 save = sp, expt = 0, esign = 1;
122 do {
123 c = *sp++;
124 if (c != 'e' && c != 'E') break;
125 c = *sp++;
126 if (c == '-') esign -= 2, c = *sp++; else
127 if (c == '+' /* || c == ' ' */ ) c = *sp++;
128 if ((unsigned)(c-'0') > (unsigned)('9'-'0')) break;
129 while (c == '0') c = *sp++;
130 for (; (unsigned)(c-'0') <= (unsigned)('9'-'0'); c = *sp++)
131 expt = expt*10 + c-'0';
132 if (esign < 0) expt = -expt;
133 save = sp-1;
134 } while (0);
135 if (ptr) *ptr = save;
136 expt += scale;
137 /* Now the number is sign*0.fraction*10**expt */
138 errno = ERANGE;
139 if (expt > MDMAXEXPT) {
140 return HUGE*sign;
141 } else
142 if (expt == MDMAXEXPT) {
143 if (strcmp(buforg, MDMAXFRAC) > 0) return HUGE*sign;
144 } else
145 if (expt < MDMINEXPT) {
146 return ZERO*sign;
147 } else
148 if (expt == MDMINEXPT) {
149 if (strcmp(buforg, MDMINFRAC) < 0) return ZERO*sign;
151 /* We have now established that the number can be */
152 /* represented without overflow or underflow */
153 (void) sprintf(dp, "E%d", expt);
154 errno = 0;
155 return atof(buffer)*sign;