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[unix-history] / gnu / usr.bin / as / atof-generic.c
/* 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"}
*/
\f
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;
\f
{
/*
* 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;
}
\f
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;
precision = (address_of_generic_floating_point_number -> high
- address_of_generic_floating_point_number -> low
+ 1
); /* Number of destination littlenums. */
/* Includes guard bits (two littlenums worth) */
maximum_useful_digits = ( ((double) (precision - 2))
* ((double) (LITTLENUM_NUMBER_OF_BITS))
/ (LOG_TO_BASE_2_OF_10)
)
+ 2; /* 2 :: guard digits. */
if (number_of_digits_available > maximum_useful_digits)
{
number_of_digits_to_use = maximum_useful_digits;
}
else
{
number_of_digits_to_use = number_of_digits_available;
}
decimal_exponent += number_of_digits_before_decimal - number_of_digits_to_use;
more_than_enough_bits_for_digits
= ((((double)number_of_digits_to_use) * LOG_TO_BASE_2_OF_10) + 1);
more_than_enough_littlenums_for_digits
= ( more_than_enough_bits_for_digits
/ LITTLENUM_NUMBER_OF_BITS
)
+ 2;
/*
* Compute (digits) part. In "12.34E56" this is the "1234" part.
* Arithmetic is exact here. If no digits are supplied then
* this part is a 0 valued binary integer.
* Allocate room to build up the binary number as littlenums.
* We want this memory to disappear when we leave this function.
* Assume no alignment problems => (room for n objects) ==
* n * (room for 1 object).
*/
size_of_digits_in_littlenums = more_than_enough_littlenums_for_digits;
size_of_digits_in_chars = size_of_digits_in_littlenums
* sizeof( LITTLENUM_TYPE );
digits_binary_low = (LITTLENUM_TYPE *)
alloca (size_of_digits_in_chars);
bzero ((char *)digits_binary_low, size_of_digits_in_chars);
/* Digits_binary_low[] is allocated and zeroed. */
{
/*
* Parse the decimal digits as if * digits_low was in the units position.
* Emit a binary number into digits_binary_low[].
*
* Use a large-precision version of:
* (((1st-digit) * 10 + 2nd-digit) * 10 + 3rd-digit ...) * 10 + last-digit
*/
char * p;
char c;
int count; /* Number of useful digits left to scan. */
for (p = first_digit, count = number_of_digits_to_use;
count;
p ++, -- count)
{
c = * p;
if (isdigit(c))
{
/*
* Multiply by 10. Assume can never overflow.
* Add this digit to digits_binary_low[].
*/
long int carry;
LITTLENUM_TYPE * littlenum_pointer;
LITTLENUM_TYPE * littlenum_limit;
littlenum_limit
= digits_binary_low
+ more_than_enough_littlenums_for_digits
- 1;
carry = c - '0'; /* char -> binary */
for (littlenum_pointer = digits_binary_low;
littlenum_pointer <= littlenum_limit;
littlenum_pointer ++)
{
long int work;
work = carry + 10 * (long)(*littlenum_pointer);
* littlenum_pointer = work & LITTLENUM_MASK;
carry = work >> LITTLENUM_NUMBER_OF_BITS;
}
if (carry != 0)
{
/*
* We have a GROSS internal error.
* This should never happen.
*/
abort(); /* RMS prefers abort() to any message. */
}
}
else
{
++ count; /* '.' doesn't alter digits used count. */
} /* if valid digit */
} /* for each digit */
}
/*
* Digits_binary_low[] properly encodes the value of the digits.
* Forget about any high-order littlenums that are 0.
*/
while (digits_binary_low [size_of_digits_in_littlenums - 1] == 0
&& size_of_digits_in_littlenums >= 2)
size_of_digits_in_littlenums --;
digits_flonum . low = digits_binary_low;
digits_flonum . high = digits_binary_low + size_of_digits_in_littlenums - 1;
digits_flonum . leader = digits_flonum . high;
digits_flonum . exponent = 0;
/*
* The value of digits_flonum . sign should not be important.
* We have already decided the output's sign.
* We trust that the sign won't influence the other parts of the number!
* So we give it a value for these reasons:
* (1) courtesy to humans reading/debugging
* these numbers so they don't get excited about strange values
* (2) in future there may be more meaning attached to sign,
* and what was
* harmless noise may become disruptive, ill-conditioned (or worse)
* input.
*/
digits_flonum . sign = '+';
{
/*
* Compute the mantssa (& exponent) of the power of 10.
* If sucessful, then multiply the power of 10 by the digits
* giving return_binary_mantissa and return_binary_exponent.
*/
LITTLENUM_TYPE *power_binary_low;
int decimal_exponent_is_negative;
/* This refers to the "-56" in "12.34E-56". */
/* FALSE: decimal_exponent is positive (or 0) */
/* TRUE: decimal_exponent is negative */
FLONUM_TYPE temporary_flonum;
LITTLENUM_TYPE *temporary_binary_low;
int size_of_power_in_littlenums;
int size_of_power_in_chars;
size_of_power_in_littlenums = precision;
/* Precision has a built-in fudge factor so we get a few guard bits. */
decimal_exponent_is_negative = decimal_exponent < 0;
if (decimal_exponent_is_negative)
{
decimal_exponent = - decimal_exponent;
}
/* From now on: the decimal exponent is > 0. Its sign is seperate. */
size_of_power_in_chars
= size_of_power_in_littlenums
* sizeof( LITTLENUM_TYPE ) + 2;
power_binary_low = (LITTLENUM_TYPE *) alloca ( size_of_power_in_chars );
temporary_binary_low = (LITTLENUM_TYPE *) alloca ( size_of_power_in_chars );
bzero ((char *)power_binary_low, size_of_power_in_chars);
* power_binary_low = 1;
power_of_10_flonum . exponent = 0;
power_of_10_flonum . low = power_binary_low;
power_of_10_flonum . leader = power_binary_low;
power_of_10_flonum . high = power_binary_low + size_of_power_in_littlenums - 1;
power_of_10_flonum . sign = '+';
temporary_flonum . low = temporary_binary_low;
temporary_flonum . high = temporary_binary_low + size_of_power_in_littlenums - 1;
/*
* (power) == 1.
* Space for temporary_flonum allocated.
*/
/*
* ...
*
* WHILE more bits
* DO find next bit (with place value)
* multiply into power mantissa
* OD
*/
{
int place_number_limit;
/* Any 10^(2^n) whose "n" exceeds this */
/* value will fall off the end of */
/* flonum_XXXX_powers_of_ten[]. */
int place_number;
const FLONUM_TYPE * multiplicand; /* -> 10^(2^n) */
place_number_limit = table_size_of_flonum_powers_of_ten;
multiplicand
= ( decimal_exponent_is_negative
? flonum_negative_powers_of_ten
: flonum_positive_powers_of_ten);
for (place_number = 1; /* Place value of this bit of exponent. */
decimal_exponent; /* Quit when no more 1 bits in exponent. */
decimal_exponent >>= 1
, place_number ++)
{
if (decimal_exponent & 1)
{
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.
*/
return_value = ERROR_EXPONENT_OVERFLOW;
/*
* quit out of loop gracefully
*/
decimal_exponent = 0;
}
else
{
#ifdef TRACE
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;
} /* If we had any significant digits. */
return (return_value);
} /* atof_generic () */
/* end: atof_generic.c */
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.