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129 lines
2.6 KiB
C
129 lines
2.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Sane helper for 'strtod()'.
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*
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* Sad that we even need this, but the C library version has
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* insane locale behavior, and while the Qt "doDouble()" routines
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* are better in that regard, they don't have an end pointer
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* (having replaced it with the completely idiotic "ok" boolean
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* pointer instead).
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*
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* I wonder what drugs people are on sometimes.
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*
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* Right now we support the following flags to limit the
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* parsing some ways:
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*
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* STRTOD_NO_SIGN - don't accept signs
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* STRTOD_NO_DOT - no decimal dots, I'm European
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* STRTOD_NO_COMMA - no comma, please, I'm C locale
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* STRTOD_NO_EXPONENT - no exponent parsing, I'm human
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*
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* The "negative" flags are so that the common case can just
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* use a flag value of 0, and only if you have some special
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* requirements do you need to state those with explicit flags.
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*
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* So if you want the C locale kind of parsing, you'd use the
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* STRTOD_NO_COMMA flag to disallow a decimal comma. But if you
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* want a more relaxed "Hey, Europeans are people too, even if
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* they have locales with commas", just pass in a zero flag.
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*/
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#include <ctype.h>
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#include "subsurface-string.h"
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double strtod_flags(const char *str, const char **ptr, unsigned int flags)
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{
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char c;
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const char *p = str, *ep;
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double val = 0.0;
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double decimal = 1.0;
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int sign = 0, esign = 0;
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int numbers = 0, dot = 0;
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/* skip spaces */
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while (isspace(c = *p++))
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/* */;
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/* optional sign */
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if (!(flags & STRTOD_NO_SIGN)) {
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switch (c) {
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case '-':
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sign = 1;
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/* fallthrough */
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case '+':
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c = *p++;
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}
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}
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/* Mantissa */
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for (;; c = *p++) {
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if ((c == '.' && !(flags & STRTOD_NO_DOT)) ||
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(c == ',' && !(flags & STRTOD_NO_COMMA))) {
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if (dot)
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goto done;
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dot = 1;
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continue;
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}
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if (c >= '0' && c <= '9') {
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numbers++;
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val = (val * 10) + (c - '0');
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if (dot)
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decimal *= 10;
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continue;
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}
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if (c != 'e' && c != 'E')
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goto done;
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if (flags & STRTOD_NO_EXPONENT)
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goto done;
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break;
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}
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if (!numbers)
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goto done;
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/* Exponent */
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ep = p;
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c = *ep++;
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switch (c) {
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case '-':
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esign = 1;
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/* fallthrough */
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case '+':
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c = *ep++;
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}
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if (c >= '0' && c <= '9') {
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p = ep;
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int exponent = c - '0';
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for (;;) {
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c = *p++;
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if (c < '0' || c > '9')
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break;
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exponent *= 10;
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exponent += c - '0';
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}
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/* We're not going to bother playing games */
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if (exponent > 308)
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exponent = 308;
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while (exponent-- > 0) {
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if (esign)
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decimal *= 10;
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else
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decimal /= 10;
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}
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}
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done:
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if (!numbers)
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goto no_conversion;
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if (ptr)
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*ptr = p - 1;
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return (sign ? -val : val) / decimal;
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no_conversion:
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if (ptr)
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*ptr = str;
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return 0.0;
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}
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