577 lines
17 KiB
C
577 lines
17 KiB
C
/* atof_generic.c - turn a string of digits into a Flonum
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Copyright (C) 1987, 1990, 1991, 1992 Free Software Foundation, Inc.
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This file is part of GAS, the GNU Assembler.
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GAS is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GAS is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GAS; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
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#include <ctype.h>
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#include <string.h>
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#include "as.h"
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#ifdef __GNUC__
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#define alloca __builtin_alloca
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#else
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#ifdef sparc
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#include <alloca.h>
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#endif
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#endif
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#ifndef FALSE
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#define FALSE (0)
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#endif
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#ifndef TRUE
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#define TRUE (1)
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#endif
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/***********************************************************************\
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* *
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* Given a string of decimal digits , with optional decimal *
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* mark and optional decimal exponent (place value) of the *
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* lowest_order decimal digit: produce a floating point *
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* number. The number is 'generic' floating point: our *
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* caller will encode it for a specific machine architecture. *
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* *
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* Assumptions *
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* uses base (radix) 2 *
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* this machine uses 2's complement binary integers *
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* target flonums use " " " " *
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* target flonums exponents fit in a long *
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* *
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\***********************************************************************/
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/*
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Syntax:
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<flonum> ::= <optional-sign> <decimal-number> <optional-exponent>
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<optional-sign> ::= '+' | '-' | {empty}
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<decimal-number> ::= <integer>
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| <integer> <radix-character>
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| <integer> <radix-character> <integer>
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| <radix-character> <integer>
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<optional-exponent> ::= {empty}
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| <exponent-character> <optional-sign> <integer>
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<integer> ::= <digit> | <digit> <integer>
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<digit> ::= '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
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<exponent-character> ::= {one character from "string_of_decimal_exponent_marks"}
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<radix-character> ::= {one character from "string_of_decimal_marks"}
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*/
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int
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atof_generic (address_of_string_pointer,
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string_of_decimal_marks,
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string_of_decimal_exponent_marks,
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address_of_generic_floating_point_number)
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/* return pointer to just AFTER number we read. */
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char **address_of_string_pointer;
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/* At most one per number. */
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const char *string_of_decimal_marks;
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const char *string_of_decimal_exponent_marks;
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FLONUM_TYPE *address_of_generic_floating_point_number;
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{
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int return_value; /* 0 means OK. */
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char *first_digit;
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/* char *last_digit; JF unused */
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int number_of_digits_before_decimal;
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int number_of_digits_after_decimal;
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long decimal_exponent;
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int number_of_digits_available;
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char digits_sign_char;
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/*
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* Scan the input string, abstracting (1)digits (2)decimal mark (3) exponent.
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* It would be simpler to modify the string, but we don't; just to be nice
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* to caller.
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* We need to know how many digits we have, so we can allocate space for
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* the digits' value.
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*/
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char *p;
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char c;
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int seen_significant_digit;
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first_digit = *address_of_string_pointer;
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c = *first_digit;
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if (c == '-' || c == '+')
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{
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digits_sign_char = c;
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first_digit++;
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}
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else
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digits_sign_char = '+';
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if ((first_digit[0] == 'n' || first_digit[0] == 'N')
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&& (first_digit[1] == 'a' || first_digit[1] == 'A')
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&& (first_digit[2] == 'n' || first_digit[2] == 'N'))
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{
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address_of_generic_floating_point_number->sign = 0;
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address_of_generic_floating_point_number->exponent = 0;
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address_of_generic_floating_point_number->leader =
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address_of_generic_floating_point_number->low;
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*address_of_string_pointer = first_digit + 3;
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return 0;
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}
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if ((first_digit[0] == 'i' || first_digit[0] == 'I')
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&& (first_digit[1] == 'n' || first_digit[1] == 'N')
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&& (first_digit[2] == 'f' || first_digit[2] == 'F'))
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{
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address_of_generic_floating_point_number->sign =
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digits_sign_char == '+' ? 'P' : 'N';
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address_of_generic_floating_point_number->exponent = 0;
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address_of_generic_floating_point_number->leader =
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address_of_generic_floating_point_number->low;
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if ((first_digit[3] == 'i'
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|| first_digit[3] == 'I')
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&& (first_digit[4] == 'n'
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|| first_digit[4] == 'N')
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&& (first_digit[5] == 'i'
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|| first_digit[5] == 'I')
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&& (first_digit[6] == 't'
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|| first_digit[6] == 'T')
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&& (first_digit[7] == 'y'
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|| first_digit[7] == 'Y'))
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{
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*address_of_string_pointer = first_digit + 8;
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}
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else
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{
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*address_of_string_pointer = first_digit + 3;
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}
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return 0;
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}
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number_of_digits_before_decimal = 0;
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number_of_digits_after_decimal = 0;
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decimal_exponent = 0;
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seen_significant_digit = 0;
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for (p = first_digit;
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(((c = *p) != '\0')
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&& (!c || !strchr (string_of_decimal_marks, c))
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&& (!c || !strchr (string_of_decimal_exponent_marks, c)));
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p++)
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{
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if (isdigit (c))
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{
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if (seen_significant_digit || c > '0')
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{
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++number_of_digits_before_decimal;
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seen_significant_digit = 1;
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}
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else
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{
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first_digit++;
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}
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}
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else
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{
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break; /* p -> char after pre-decimal digits. */
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}
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} /* For each digit before decimal mark. */
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#ifndef OLD_FLOAT_READS
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/* Ignore trailing 0's after the decimal point. The original code here
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* (ifdef'd out) does not do this, and numbers like
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* 4.29496729600000000000e+09 (2**31)
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* come out inexact for some reason related to length of the digit
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* string.
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*/
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if (c && strchr (string_of_decimal_marks, c))
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{
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int zeros = 0; /* Length of current string of zeros */
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for (p++; (c = *p) && isdigit (c); p++)
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{
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if (c == '0')
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{
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zeros++;
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}
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else
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{
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number_of_digits_after_decimal += 1 + zeros;
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zeros = 0;
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}
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}
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}
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#else
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if (c && strchr (string_of_decimal_marks, c))
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{
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for (p++;
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(((c = *p) != '\0')
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&& (!c || !strchr (string_of_decimal_exponent_marks, c)));
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p++)
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{
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if (isdigit (c))
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{
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/* This may be retracted below. */
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number_of_digits_after_decimal++;
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if ( /* seen_significant_digit || */ c > '0')
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{
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seen_significant_digit = TRUE;
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}
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}
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else
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{
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if (!seen_significant_digit)
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{
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number_of_digits_after_decimal = 0;
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}
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break;
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}
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} /* For each digit after decimal mark. */
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}
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while (number_of_digits_after_decimal
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&& first_digit[number_of_digits_before_decimal
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+ number_of_digits_after_decimal] == '0')
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--number_of_digits_after_decimal;
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#endif
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if (c && strchr (string_of_decimal_exponent_marks, c))
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{
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char digits_exponent_sign_char;
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c = *++p;
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if (c && strchr ("+-", c))
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{
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digits_exponent_sign_char = c;
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c = *++p;
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}
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else
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{
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digits_exponent_sign_char = '+';
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}
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for (; (c); c = *++p)
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{
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if (isdigit (c))
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{
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decimal_exponent = decimal_exponent * 10 + c - '0';
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/*
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* BUG! If we overflow here, we lose!
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*/
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}
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else
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{
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break;
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}
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}
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if (digits_exponent_sign_char == '-')
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{
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decimal_exponent = -decimal_exponent;
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}
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}
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*address_of_string_pointer = p;
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number_of_digits_available =
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number_of_digits_before_decimal + number_of_digits_after_decimal;
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return_value = 0;
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if (number_of_digits_available == 0)
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{
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address_of_generic_floating_point_number->exponent = 0; /* Not strictly necessary */
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address_of_generic_floating_point_number->leader
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= -1 + address_of_generic_floating_point_number->low;
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address_of_generic_floating_point_number->sign = digits_sign_char;
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/* We have just concocted (+/-)0.0E0 */
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}
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else
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{
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int count; /* Number of useful digits left to scan. */
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LITTLENUM_TYPE *digits_binary_low;
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unsigned int precision;
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unsigned int maximum_useful_digits;
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unsigned int number_of_digits_to_use;
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unsigned int more_than_enough_bits_for_digits;
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unsigned int more_than_enough_littlenums_for_digits;
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unsigned int size_of_digits_in_littlenums;
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unsigned int size_of_digits_in_chars;
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FLONUM_TYPE power_of_10_flonum;
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FLONUM_TYPE digits_flonum;
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precision = (address_of_generic_floating_point_number->high
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- address_of_generic_floating_point_number->low
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+ 1); /* Number of destination littlenums. */
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/* Includes guard bits (two littlenums worth) */
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maximum_useful_digits = (((double) (precision - 2))
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* ((double) (LITTLENUM_NUMBER_OF_BITS))
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/ (LOG_TO_BASE_2_OF_10))
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+ 2; /* 2 :: guard digits. */
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if (number_of_digits_available > maximum_useful_digits)
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{
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number_of_digits_to_use = maximum_useful_digits;
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}
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else
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{
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number_of_digits_to_use = number_of_digits_available;
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}
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/* Cast these to SIGNED LONG first, otherwise, on systems with
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LONG wider than INT (such as Alpha OSF/1), unsignedness may
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cause unexpected results. */
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decimal_exponent += ((long) number_of_digits_before_decimal
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- (long) number_of_digits_to_use);
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more_than_enough_bits_for_digits
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= ((((double) number_of_digits_to_use) * LOG_TO_BASE_2_OF_10) + 1);
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more_than_enough_littlenums_for_digits
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= (more_than_enough_bits_for_digits
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/ LITTLENUM_NUMBER_OF_BITS)
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+ 2;
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/* Compute (digits) part. In "12.34E56" this is the "1234" part.
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Arithmetic is exact here. If no digits are supplied then this
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part is a 0 valued binary integer. Allocate room to build up
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the binary number as littlenums. We want this memory to
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disappear when we leave this function. Assume no alignment
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problems => (room for n objects) == n * (room for 1
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object). */
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size_of_digits_in_littlenums = more_than_enough_littlenums_for_digits;
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size_of_digits_in_chars = size_of_digits_in_littlenums
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* sizeof (LITTLENUM_TYPE);
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digits_binary_low = (LITTLENUM_TYPE *)
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alloca (size_of_digits_in_chars);
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memset ((char *) digits_binary_low, '\0', size_of_digits_in_chars);
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/* Digits_binary_low[] is allocated and zeroed. */
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/*
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* Parse the decimal digits as if * digits_low was in the units position.
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* Emit a binary number into digits_binary_low[].
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*
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* Use a large-precision version of:
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* (((1st-digit) * 10 + 2nd-digit) * 10 + 3rd-digit ...) * 10 + last-digit
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*/
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for (p = first_digit, count = number_of_digits_to_use; count; p++, --count)
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{
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c = *p;
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if (isdigit (c))
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{
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/*
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* Multiply by 10. Assume can never overflow.
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* Add this digit to digits_binary_low[].
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*/
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long carry;
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LITTLENUM_TYPE *littlenum_pointer;
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LITTLENUM_TYPE *littlenum_limit;
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littlenum_limit = digits_binary_low
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+ more_than_enough_littlenums_for_digits
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- 1;
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carry = c - '0'; /* char -> binary */
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for (littlenum_pointer = digits_binary_low;
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littlenum_pointer <= littlenum_limit;
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littlenum_pointer++)
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{
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long work;
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work = carry + 10 * (long) (*littlenum_pointer);
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*littlenum_pointer = work & LITTLENUM_MASK;
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carry = work >> LITTLENUM_NUMBER_OF_BITS;
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}
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if (carry != 0)
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{
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/*
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* We have a GROSS internal error.
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* This should never happen.
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*/
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as_fatal ("failed sanity check.");
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}
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}
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else
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{
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++count; /* '.' doesn't alter digits used count. */
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}
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}
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/*
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* Digits_binary_low[] properly encodes the value of the digits.
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* Forget about any high-order littlenums that are 0.
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*/
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while (digits_binary_low[size_of_digits_in_littlenums - 1] == 0
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&& size_of_digits_in_littlenums >= 2)
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size_of_digits_in_littlenums--;
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digits_flonum.low = digits_binary_low;
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digits_flonum.high = digits_binary_low + size_of_digits_in_littlenums - 1;
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digits_flonum.leader = digits_flonum.high;
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digits_flonum.exponent = 0;
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/*
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* The value of digits_flonum . sign should not be important.
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* We have already decided the output's sign.
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* We trust that the sign won't influence the other parts of the number!
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* So we give it a value for these reasons:
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* (1) courtesy to humans reading/debugging
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* these numbers so they don't get excited about strange values
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* (2) in future there may be more meaning attached to sign,
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* and what was
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* harmless noise may become disruptive, ill-conditioned (or worse)
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* input.
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*/
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digits_flonum.sign = '+';
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{
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/*
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* Compute the mantssa (& exponent) of the power of 10.
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* If sucessful, then multiply the power of 10 by the digits
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* giving return_binary_mantissa and return_binary_exponent.
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*/
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LITTLENUM_TYPE *power_binary_low;
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int decimal_exponent_is_negative;
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/* This refers to the "-56" in "12.34E-56". */
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/* FALSE: decimal_exponent is positive (or 0) */
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/* TRUE: decimal_exponent is negative */
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FLONUM_TYPE temporary_flonum;
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LITTLENUM_TYPE *temporary_binary_low;
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unsigned int size_of_power_in_littlenums;
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unsigned int size_of_power_in_chars;
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size_of_power_in_littlenums = precision;
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/* Precision has a built-in fudge factor so we get a few guard bits. */
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decimal_exponent_is_negative = decimal_exponent < 0;
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if (decimal_exponent_is_negative)
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{
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decimal_exponent = -decimal_exponent;
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}
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/* From now on: the decimal exponent is > 0. Its sign is seperate. */
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size_of_power_in_chars = size_of_power_in_littlenums
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* sizeof (LITTLENUM_TYPE) + 2;
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power_binary_low = (LITTLENUM_TYPE *) alloca (size_of_power_in_chars);
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temporary_binary_low = (LITTLENUM_TYPE *) alloca (size_of_power_in_chars);
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memset ((char *) power_binary_low, '\0', size_of_power_in_chars);
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*power_binary_low = 1;
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power_of_10_flonum.exponent = 0;
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power_of_10_flonum.low = power_binary_low;
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power_of_10_flonum.leader = power_binary_low;
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power_of_10_flonum.high = power_binary_low + size_of_power_in_littlenums - 1;
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power_of_10_flonum.sign = '+';
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temporary_flonum.low = temporary_binary_low;
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temporary_flonum.high = temporary_binary_low + size_of_power_in_littlenums - 1;
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/*
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* (power) == 1.
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* Space for temporary_flonum allocated.
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*/
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/*
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* ...
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*
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* WHILE more bits
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* DO find next bit (with place value)
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* multiply into power mantissa
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* OD
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*/
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{
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int place_number_limit;
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/* Any 10^(2^n) whose "n" exceeds this */
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|
/* value will fall off the end of */
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/* flonum_XXXX_powers_of_ten[]. */
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int place_number;
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const FLONUM_TYPE *multiplicand; /* -> 10^(2^n) */
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|
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place_number_limit = table_size_of_flonum_powers_of_ten;
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|
|
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multiplicand = (decimal_exponent_is_negative
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? flonum_negative_powers_of_ten
|
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: flonum_positive_powers_of_ten);
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|
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for (place_number = 1;/* Place value of this bit of exponent. */
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|
decimal_exponent;/* Quit when no more 1 bits in exponent. */
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|
decimal_exponent >>= 1, place_number++)
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{
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|
if (decimal_exponent & 1)
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|
{
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|
if (place_number > place_number_limit)
|
|
{
|
|
/* The decimal exponent has a magnitude so great
|
|
that our tables can't help us fragment it.
|
|
Although this routine is in error because it
|
|
can't imagine a number that big, signal an
|
|
error as if it is the user's fault for
|
|
presenting such a big number. */
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|
return_value = ERROR_EXPONENT_OVERFLOW;
|
|
/* quit out of loop gracefully */
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|
decimal_exponent = 0;
|
|
}
|
|
else
|
|
{
|
|
#ifdef TRACE
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|
printf ("before multiply, place_number = %d., power_of_10_flonum:\n",
|
|
place_number);
|
|
|
|
flonum_print (&power_of_10_flonum);
|
|
(void) putchar ('\n');
|
|
#endif
|
|
flonum_multip (multiplicand + place_number,
|
|
&power_of_10_flonum, &temporary_flonum);
|
|
flonum_copy (&temporary_flonum, &power_of_10_flonum);
|
|
} /* If this bit of decimal_exponent was computable.*/
|
|
} /* If this bit of decimal_exponent was set. */
|
|
} /* For each bit of binary representation of exponent */
|
|
#ifdef TRACE
|
|
printf (" after computing power_of_10_flonum: ");
|
|
flonum_print (&power_of_10_flonum);
|
|
(void) putchar ('\n');
|
|
#endif
|
|
}
|
|
|
|
}
|
|
|
|
/*
|
|
* power_of_10_flonum is power of ten in binary (mantissa) , (exponent).
|
|
* It may be the number 1, in which case we don't NEED to multiply.
|
|
*
|
|
* Multiply (decimal digits) by power_of_10_flonum.
|
|
*/
|
|
|
|
flonum_multip (&power_of_10_flonum, &digits_flonum, address_of_generic_floating_point_number);
|
|
/* Assert sign of the number we made is '+'. */
|
|
address_of_generic_floating_point_number->sign = digits_sign_char;
|
|
|
|
}
|
|
return return_value;
|
|
}
|
|
|
|
/* end of atof_generic.c */
|