diff options
Diffstat (limited to 'libc/stdlib/strtod.c')
| -rw-r--r-- | libc/stdlib/strtod.c | 312 |
1 files changed, 246 insertions, 66 deletions
diff --git a/libc/stdlib/strtod.c b/libc/stdlib/strtod.c index de3aecbd3..dff5aeb73 100644 --- a/libc/stdlib/strtod.c +++ b/libc/stdlib/strtod.c @@ -1,83 +1,263 @@ /* - * strtod.c - This file is part of the libc-8086 package for ELKS, - * Copyright (C) 1995, 1996 Nat Friedman <ndf@linux.mit.edu>. - * - * This library is free software; you can redistribute it and/or - * modify it under the terms of the GNU Library General Public - * License as published by the Free Software Foundation; either - * version 2 of the License, or (at your option) any later version. + * Copyright (C) 2000 Manuel Novoa III * - * This library is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Library General Public License for more details. + * Notes: * - * You should have received a copy of the GNU Library General Public - * License along with this library; if not, write to the Free - * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + * The primary objective of this implementation was minimal size while + * providing robustness and resonable accuracy. + * + * This implementation depends on IEEE floating point behavior and expects + * to be able to generate +/- infinity as a result. + * + * There are a number of compile-time options below. * */ + +/*****************************************************************************/ +/* OPTIONS */ +/*****************************************************************************/ + +/* Set if we want to scale with a O(log2(exp)) multiplications. */ +#define _STRTOD_LOG_SCALING 1 + +/* Set if we want strtod to set errno appropriately. */ +/* NOTE: Implies all options below and pulls in _zero_or_inf_check. */ +#define _STRTOD_ERRNO 0 + +/* Set if we want support for the endptr arg. */ +/* Implied by _STRTOD_ERRNO. */ +#define _STRTOD_ENDPTR 1 + +/* Set if we want to prevent overflow in accumulating the exponent. */ +#define _STRTOD_RESTRICT_EXP 1 + +/* Set if we want to process mantissa digits more intelligently. */ +/* Implied by _STRTOD_ERRNO. */ +#define _STRTOD_RESTRICT_DIGITS 1 + +/* Set if we want to skip scaling 0 for the exponent. */ +/* Implied by _STRTOD_ERRNO. */ +#define _STRTOD_ZERO_CHECK 0 + +/*****************************************************************************/ +/* Don't change anything that follows. */ +/*****************************************************************************/ + +#if _STRTOD_ERRNO +#undef _STRTOD_ENDPTR +#undef _STRTOD_RESTRICT_EXP +#undef _STRTOD_RESTRICT_DIGITS +#undef _STRTOD_ZERO_CHECK +#define _STRTOD_ENDPTR 1 +#define _STRTOD_RESTRICT_EXP 1 +#define _STRTOD_RESTRICT_DIGITS 1 +#define _STRTOD_ZERO_CHECK 1 +#endif + +/*****************************************************************************/ + #include <stdlib.h> + +#include <float.h> + +#if _STRTOD_RESTRICT_DIGITS +#define MAX_SIG_DIGITS 20 +#define EXP_DENORM_ADJUST MAX_SIG_DIGITS +#define MAX_ALLOWED_EXP (MAX_SIG_DIGITS + EXP_DENORM_ADJUST - DBL_MIN_10_EXP) + +#if DBL_DIG > MAX_SIG_DIGITS +#error need to adjust MAX_SIG_DIGITS +#endif + +#include <limits.h> +#if MAX_ALLOWED_EXP > INT_MAX +#error size assumption violated for MAX_ALLOWED_EXP +#endif +#else +/* We want some excess if we're not restricting mantissa digits. */ +#define MAX_ALLOWED_EXP ((20 - DBL_MIN_10_EXP) * 2) +#endif + #include <ctype.h> +/* Note: For i386 the macro resulted in smaller code than the function call. */ +#if 1 +#undef isdigit +#define isdigit(x) ( (x >= '0') && (x <= '9') ) +#endif + +#if _STRTOD_ERRNO +#include <errno.h> +extern int _zero_or_inf_check(double x); +#endif -float strtod(const char *nptr, char **endptr) +double strtod(const char *str, char **endptr) { - unsigned short negative; - float number; - float fp_part; - int exponent; - unsigned short exp_negative; - - /* advance beyond any leading whitespace */ - while (isspace(*nptr)) - nptr++; - - /* check for optional '+' or '-' */ - negative = 0; - if (*nptr == '-') { - negative = 1; - nptr++; - } else if (*nptr == '+') - nptr++; - - number = 0; - while (isdigit(*nptr)) { - number = number * 10 + (*nptr - '0'); - nptr++; + double number; +#if _STRTOD_LOG_SCALING + double p10; +#endif + char *pos0; +#if _STRTOD_ENDPTR + char *pos1; +#endif + char *pos = (char *) str; + int exponent_power; + int exponent_temp; + int negative; +#if _STRTOD_RESTRICT_DIGITS || _STRTOD_ENDPTR + int num_digits; +#endif + + while (isspace(*pos)) { /* skip leading whitespace */ + ++pos; + } + + negative = 0; + switch(*pos) { /* handle optional sign */ + case '-': negative = 1; /* fall through to increment position */ + case '+': ++pos; + } + + number = 0.; +#if _STRTOD_RESTRICT_DIGITS || _STRTOD_ENDPTR + num_digits = -1; +#endif + exponent_power = 0; + pos0 = NULL; + + LOOP: + while (isdigit(*pos)) { /* process string of digits */ +#if _STRTOD_RESTRICT_DIGITS + if (num_digits < 0) { /* first time through? */ + ++num_digits; /* we've now seen a digit */ + } + if (num_digits || (*pos != '0')) { /* had/have nonzero */ + ++num_digits; + if (num_digits <= MAX_SIG_DIGITS) { /* is digit significant */ + number = number * 10. + (*pos - '0'); + } } +#else +#if _STRTOD_ENDPTR + ++num_digits; +#endif + number = number * 10. + (*pos - '0'); +#endif + ++pos; + } + + if ((*pos == '.') && !pos0) { /* is this the first decimal point? */ + pos0 = ++pos; /* save position of decimal point */ + goto LOOP; /* and process rest of digits */ + } + +#if _STRTOD_ENDPTR + if (num_digits<0) { /* must have at least one digit */ + pos = (char *) str; + goto DONE; + } +#endif + +#if _STRTOD_RESTRICT_DIGITS + if (num_digits > MAX_SIG_DIGITS) { /* adjust exponent for skipped digits */ + exponent_power += num_digits - MAX_SIG_DIGITS; + } +#endif + + if (pos0) { + exponent_power += pos0 - pos; /* adjust exponent for decimal point */ + } + + if (negative) { /* correct for sign */ + number = -number; + negative = 0; /* reset for exponent processing below */ + } - if (*nptr == '.') { - nptr++; - fp_part = 0; - while (isdigit(*nptr)) { - fp_part = fp_part / 10.0 + (*nptr - '0') / 10.0; - nptr++; - } - number += fp_part; + /* process an exponent string */ + if (*pos == 'e' || *pos == 'E') { +#if _STRTOD_ENDPTR + pos1 = pos; +#endif + switch(*++pos) { /* handle optional sign */ + case '-': negative = 1; /* fall through to increment pos */ + case '+': ++pos; } - if (*nptr == 'e' || *nptr == 'E') { - nptr++; - exp_negative = 0; - if (*nptr == '-') { - exp_negative = 1; - nptr++; - } else if (*nptr == '+') - nptr++; - - exponent = 0; - while (isdigit(*nptr)) { - exponent = exponent * 10 + (*nptr - '0'); - exponent++; - } + pos0 = pos; + exponent_temp = 0; + while (isdigit(*pos)) { /* process string of digits */ +#if _STRTOD_RESTRICT_EXP + if (exponent_temp < MAX_ALLOWED_EXP) { /* overflow check */ + exponent_temp = exponent_temp * 10 + (*pos - '0'); + } +#else + exponent_temp = exponent_temp * 10 + (*pos - '0'); +#endif + ++pos; } - while (exponent) { - if (exp_negative) - number /= 10; - else - number *= 10; - exponent--; +#if _STRTOD_ENDPTR + if (pos == pos0) { /* were there no digits? */ + pos = pos1; /* back up to e|E */ + } /* else */ +#endif + if (negative) { + exponent_power -= exponent_temp; + } else { + exponent_power += exponent_temp; } - return (negative ? -number : number); + } + +#if _STRTOD_ZERO_CHECK + if (number == 0.) { + goto DONE; + } +#endif + + /* scale the result */ +#if _STRTOD_LOG_SCALING + exponent_temp = exponent_power; + p10 = 10.; + + if (exponent_temp < 0) { + exponent_temp = -exponent_temp; + } + + while (exponent_temp) { + if (exponent_temp & 1) { + if (exponent_power < 0) { + number /= p10; + } else { + number *= p10; + } + } + exponent_temp >>= 1; + p10 *= p10; + } +#else + while (exponent_power) { + if (exponent_power < 0) { + number /= 10.; + exponent_power++; + } else { + number *= 10.; + exponent_power--; + } + } +#endif + +#if _STRTOD_ERRNO + if (_zero_or_inf_check(number)) { + errno=ERANGE; + } +#endif + + DONE: +#if _STRTOD_ENDPTR + if (endptr) { + *endptr = pos; + } +#endif + + return number; } |