text: /****************************************************************************
   *
   * Copyright 2016 Samsung Electronics All Rights Reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied. See the License for the specific
   * language governing permissions and limitations under the License.
   *
   ****************************************************************************/
  /****************************************************************************
   * libc/stdlib/lib_strtod.c
   * Convert string to double
   *
   *   Copyright (C) 2002 Michael Ringgaard. All rights reserved.
   *   Copyright (C) 2006-2007 H. Peter Anvin.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of the project nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
   * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   ****************************************************************************/
  
  /****************************************************************************
   * Included Files
   ****************************************************************************/
  
  #include <tinyara/config.h>
  #include <tinyara/compiler.h>
  
  #include <stdlib.h>
  #include <ctype.h>
  #include <errno.h>
  
  #ifdef CONFIG_HAVE_DOUBLE
  
  /****************************************************************************
   * Pre-processor definitions
   ****************************************************************************/
  
  /* These are predefined with GCC, but could be issues for other compilers. If
   * not defined, an arbitrary big number is put in for now.  These should be
   * added to tinyara/compiler for your compiler.
   */
  
  #if !defined(__DBL_MIN_EXP__) || !defined(__DBL_MAX_EXP__)
  #ifdef CONFIG_CPP_HAVE_WARNING
  #warning "Size of exponent is unknown"
  #endif
  #undef  __DBL_MIN_EXP__
  #define __DBL_MIN_EXP__ (-1021)
  #undef  __DBL_MAX_EXP__
  #define __DBL_MAX_EXP__ (1024)
  #endif
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  static inline int is_real(double x)
  {
  	const double infinite = 1.0 / 0.0;
  	return (x < infinite) && (x >= -infinite);
  }
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /***************************************************(************************
   * Name: strtod
   *
   * Description:
   *   Convert a string to a double value
   *
   ****************************************************************************/
  
  double strtod(const char *str, char **endptr)
  {
  	double number;
  	int exponent;
  	int negative;
  	FAR char *p = (char *)str;
  	double p10;
  	int n;
  	int num_digits;
  	int num_decimals;
  	const double infinite = 1.0 / 0.0;
  
  	/* Skip leading whitespace */
  
  	while (isspace(*p)) {
  		p++;
  	}
  
  	/* Handle optional sign */
  
  	negative = 0;
  	switch (*p) {
  	case '-':
  		negative = 1;			/* Fall through to increment position */
  	case '+':
  		p++;
  	}
  
  	number = 0.;
  	exponent = 0;
  	num_digits = 0;
  	num_decimals = 0;
  
  	/* Process string of digits */
  
  	while (isdigit(*p)) {
  		number = number * 10. + (*p - '0');
  		p++;
  		num_digits++;
  	}
  
  	/* Process decimal part */
  
  	if (*p == '.') {
  		p++;
  
  		while (isdigit(*p)) {
  			number = number * 10. + (*p - '0');
  			p++;
  			num_digits++;
  			num_decimals++;
  		}
  
  		exponent -= num_decimals;
  	}
  
  	if (num_digits == 0) {
  		set_errno(ERANGE);
  		return 0.0;
  	}
  
  	/* Correct for sign */
  
  	if (negative) {
  		number = -number;
  	}
  
  	/* Process an exponent string */
  
  	if (*p == 'e' || *p == 'E') {
  		/* Handle optional sign */
  
  		negative = 0;
  		switch (*++p) {
  		case '-':
  			negative = 1;		/* Fall through to increment pos */
  		case '+':
  			p++;
  		}
  
  		/* Process string of digits */
  
  		n = 0;
  		while (isdigit(*p)) {
  			n = n * 10 + (*p - '0');
  			p++;
  		}
  
  		if (negative) {
  			exponent -= n;
  		} else {
  			exponent += n;
  		}
  	}
  
  	if (exponent < __DBL_MIN_EXP__ || exponent > __DBL_MAX_EXP__) {
  		set_errno(ERANGE);
  		return infinite;
  	}
  
  	/* Scale the result */
  
  	p10 = 10.;
  	n = exponent;
  	if (n < 0) {
  		n = -n;
  	}
  	while (n) {
  		if (n & 1) {
  			if (exponent < 0) {
  				number /= p10;
  			} else {
  				number *= p10;
  			}
  		}
  		n >>= 1;
  		p10 *= p10;
  	}
  
  	if (!is_real(number)) {
  		set_errno(ERANGE);
  	}
  
  	if (endptr) {
  		*endptr = p;
  	}
  
  	return number;
  }
  
  #endif							/* CONFIG_HAVE_DOUBLE */
  