atof-generic.c

早期freebsd实现

/* atof_generic.c - turn a string of digits into a Flonum
   Copyright (C) 1987 Free Software Foundation, Inc.

This file is part of GAS, the GNU Assembler.

GAS is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 1, or (at your option)
any later version.

GAS 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with GAS; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include <ctype.h>
#include "flonum.h"
#ifdef __GNUC__
#define alloca __builtin_alloca
#else
#ifdef sparc
#include <alloca.h>
#endif
#endif

#ifdef USG
#define bzero(s,n) memset(s,0,n)
#define index strchr
#endif

#define	FALSE (0)
#define TRUE  (1)

char *index();

/***********************************************************************\
*									*
*	Given a string of decimal digits , with optional decimal	*
*	mark and optional decimal exponent (place value) of the		*
*	lowest_order decimal digit: produce a floating point		*
*	number. The number is 'generic' floating point: our		*
*	caller will encode it for a specific machine architecture.	*
*									*
*	Assumptions							*
*		uses base (radix) 2					*
*		this machine uses 2's complement binary integers	*
*		target flonums use "      "         "       "		*
*		target flonums exponents fit in a long int		*
*									*
\***********************************************************************/

/*

			Syntax:

<flonum>		::=	<optional-sign> <decimal-number> <optional-exponent>
<optional-sign>		::=	'+' | '-' | {empty}
<decimal-number>	::=	  <integer>
				| <integer> <radix-character> 
				| <integer> <radix-character> <integer> 
				|	    <radix-character> <integer>
<optional-exponent>	::=	{empty} | <exponent-character> <optional-sign> <integer> 
<integer>		::=	<digit> | <digit> <integer>
<digit>			::=	'0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
<exponent-character>	::=	{one character from "string_of_decimal_exponent_marks"}
<radix-character>	::=	{one character from "string_of_decimal_marks"}

*/

int				/* 0 if OK */

atof_generic (
	address_of_string_pointer, /* return pointer to just AFTER number we read. */
	string_of_decimal_marks, /* At most one per number. */
	string_of_decimal_exponent_marks,
	address_of_generic_floating_point_number)

     char * *		address_of_string_pointer;
     const char *	string_of_decimal_marks;
     const char *	string_of_decimal_exponent_marks;
     FLONUM_TYPE *	address_of_generic_floating_point_number;

{

  int			return_value; /* 0 means OK. */
  char *		first_digit;
  /* char *		last_digit; JF unused */
  int			number_of_digits_before_decimal;
  int			number_of_digits_after_decimal;
  long int		decimal_exponent;
  int			number_of_digits_available;
  char			digits_sign_char;

  {
    /*
     * Scan the input string, abstracting (1)digits (2)decimal mark (3) exponent.
     * It would be simpler to modify the string, but we don't; just to be nice
     * to caller.
     * We need to know how many digits we have, so we can allocate space for
     * the digits' value.
     */

    char *		p;
    char		c;
    int			seen_significant_digit;

    first_digit = * address_of_string_pointer;
    c= *first_digit;
    if (c=='-' || c=='+')
      {
	digits_sign_char = c;
        first_digit ++;
      }
    else
	digits_sign_char = '+';

    if(   (first_digit[0]=='n' || first_digit[0]=='N')
       && (first_digit[1]=='a' || first_digit[1]=='A')
       && (first_digit[2]=='n' || first_digit[2]=='N')) {
      address_of_generic_floating_point_number->sign=0;
      address_of_generic_floating_point_number->exponent=0;
      address_of_generic_floating_point_number->leader=address_of_generic_floating_point_number->low;
      (*address_of_string_pointer)=first_digit+3;
      return 0;
    }
    if(   (first_digit[0]=='i' || first_digit[0]=='I') 
       && (first_digit[1]=='n' || first_digit[1]=='N')
       && (first_digit[2]=='f' || first_digit[2]=='F')) {
      address_of_generic_floating_point_number->sign= digits_sign_char=='+' ? 'P' : 'N';
      address_of_generic_floating_point_number->exponent=0;
      address_of_generic_floating_point_number->leader=address_of_generic_floating_point_number->low;
      if(   (first_digit[3]=='i' || first_digit[3]=='I')
         && (first_digit[4]=='n' || first_digit[4]=='N')
	 && (first_digit[5]=='i' || first_digit[5]=='I')
	 && (first_digit[6]=='t' || first_digit[6]=='T')
	 && (first_digit[7]=='y' || first_digit[7]=='Y'))
	  (*address_of_string_pointer)=first_digit+8;
      else
	  (*address_of_string_pointer)=first_digit+3;
      return 0;
    }

    number_of_digits_before_decimal = 0;
    number_of_digits_after_decimal = 0;
    decimal_exponent = 0;
    seen_significant_digit = FALSE;
    for (p = first_digit;
	 (c = * p)
	 && (!c || ! index (string_of_decimal_marks,          c) )
	 && (!c || ! index (string_of_decimal_exponent_marks, c) );
	 p ++)
      {
	if (isdigit(c))
	  {
	    if (seen_significant_digit || c > '0')
	      {
		number_of_digits_before_decimal ++;
		seen_significant_digit = TRUE;
	      }
	    else
	      {
	        first_digit++;
	      }
	  }
	else
	  {
	    break;		/* p -> char after pre-decimal digits. */
	  }
      }				/* For each digit before decimal mark. */
    if (c && index (string_of_decimal_marks, c))
      {
	for (p ++;
	     (c = * p)
	     && (!c || ! index (string_of_decimal_exponent_marks, c) );
	     p ++)
	  {
	    if (isdigit(c))
	      {
		number_of_digits_after_decimal ++; /* This may be retracted below. */
		if (/* seen_significant_digit || */ c > '0')
		  {
		    seen_significant_digit = TRUE;
		  }
	      }
	    else
	      {
		if ( ! seen_significant_digit)
		  {
		    number_of_digits_after_decimal = 0;
		  }
		break;
	      }
	  }			/* For each digit after decimal mark. */
      }
      while(number_of_digits_after_decimal && first_digit[number_of_digits_before_decimal+number_of_digits_after_decimal]=='0')
	--number_of_digits_after_decimal;
/*    last_digit = p; JF unused */
    
    if (c && index (string_of_decimal_exponent_marks, c) )
      {
	char		digits_exponent_sign_char;
	
	c = * ++ p;
	if (c && index ("+-",c))
	  {
	    digits_exponent_sign_char = c;
	    c = * ++ p;
	  }
	else
	  {
	    digits_exponent_sign_char = '+';
	  }
	for (;
	     (c);
	     c = * ++ p)
	  {
	    if (isdigit(c))
	      {
		decimal_exponent = decimal_exponent * 10 + c - '0';
		/*
		 * BUG! If we overflow here, we lose!
		 */
	      }
	    else
	      {
		break;
	      }
	  }
	if (digits_exponent_sign_char == '-')
	  {
	    decimal_exponent = - decimal_exponent;
	  }
      }
    * address_of_string_pointer = p;
  }

  number_of_digits_available =
    number_of_digits_before_decimal
      + number_of_digits_after_decimal;
  return_value = 0;
  if (number_of_digits_available == 0)
    {
      address_of_generic_floating_point_number -> exponent = 0;	/* Not strictly necessary */
      address_of_generic_floating_point_number -> leader
	= -1 + address_of_generic_floating_point_number -> low;
      address_of_generic_floating_point_number -> sign = digits_sign_char;
      /* We have just concocted (+/-)0.0E0 */
    }
  else
    {
      LITTLENUM_TYPE *	digits_binary_low;
      int		precision;
      int		maximum_useful_digits;
      int		number_of_digits_to_use;
      int		more_than_enough_bits_for_digits;
      int		more_than_enough_littlenums_for_digits;
      int		size_of_digits_in_littlenums;
      int		size_of_digits_in_chars;
      FLONUM_TYPE	power_of_10_flonum;
      FLONUM_TYPE	digits_flonum;