cb9de2289f
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3439 42af7a65-404d-4744-a932-0658087f49c3
228 lines
5.5 KiB
C
Executable File
228 lines
5.5 KiB
C
Executable File
/****************************************************************************
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* lib/string/lib_strtod.c
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* Convert string to double
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*
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* Copyright (C) 2002 Michael Ringgaard. All rights reserved.
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* Copyright (C) 2006-2007 H. Peter Anvin.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the project nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <stdlib.h>
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#include <ctype.h>
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#include <errno.h>
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/****************************************************************************
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* Pre-processor definitions
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****************************************************************************/
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/* These are predefined with GCC, but could be issues for other compilers. If
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* not defined, an arbitrary big number is put in for now. These should be
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* added to nuttx/compiler for your compiler.
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*/
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#if !defined(__DBL_MIN_EXP__) || !defined(__DBL_MAX_EXP__)
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# ifdef CONFIG_CPP_HAVE_WARNING
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# warning "Size of exponent is unknown"
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# endif
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# undef __DBL_MIN_EXP__
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# define __DBL_MIN_EXP__ (-1021)
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# undef __DBL_MAX_EXP__
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# define __DBL_MAX_EXP__ (1024)
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#endif
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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static inline int is_real(double x)
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{
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const double_t infinite = 1.0/0.0;
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return (x < infinite) && (x >= -infinite);
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/***************************************************(************************
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* Name: strtod
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*
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* Description:
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* Convert a string to a double value
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*
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****************************************************************************/
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double_t strtod(const char *str, char **endptr)
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{
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double_t number;
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int exponent;
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int negative;
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char *p = (char *) str;
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double p10;
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int n;
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int num_digits;
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int num_decimals;
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const double_t infinite = 1.0/0.0;
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/* Skip leading whitespace */
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while (isspace(*p))
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{
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p++;
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}
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/* Handle optional sign */
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negative = 0;
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switch (*p)
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{
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case '-':
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negative = 1; /* Fall through to increment position */
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case '+':
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p++;
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}
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number = 0.;
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exponent = 0;
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num_digits = 0;
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num_decimals = 0;
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/* Process string of digits */
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while (isdigit(*p))
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{
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number = number * 10. + (*p - '0');
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p++;
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num_digits++;
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}
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/* Process decimal part */
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if (*p == '.')
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{
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p++;
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while (isdigit(*p))
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{
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number = number * 10. + (*p - '0');
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p++;
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num_digits++;
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num_decimals++;
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}
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exponent -= num_decimals;
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}
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if (num_digits == 0)
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{
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errno = ERANGE;
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return 0.0;
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}
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/* Correct for sign */
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if (negative)
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{
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number = -number;
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}
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/* Process an exponent string */
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if (*p == 'e' || *p == 'E')
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{
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/* Handle optional sign */
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negative = 0;
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switch(*++p)
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{
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case '-':
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negative = 1; /* Fall through to increment pos */
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case '+':
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p++;
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}
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/* Process string of digits */
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n = 0;
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while (isdigit(*p))
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{
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n = n * 10 + (*p - '0');
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p++;
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}
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if (negative)
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{
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exponent -= n;
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}
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else
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{
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exponent += n;
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}
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}
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if (exponent < __DBL_MIN_EXP__ ||
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exponent > __DBL_MAX_EXP__)
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{
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errno = ERANGE;
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return infinite;
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}
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/* Scale the result */
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p10 = 10.;
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n = exponent;
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if (n < 0) n = -n;
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while (n)
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{
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if (n & 1)
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{
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if (exponent < 0)
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{
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number /= p10;
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}
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else
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{
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number *= p10;
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}
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}
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n >>= 1;
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p10 *= p10;
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}
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if (!is_real(number)) errno = ERANGE;
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if (endptr) *endptr = p;
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return number;
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}
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