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freebsd/gnu/usr.bin/as/atof-generic.c
Peter Wemm 9b7a44a60e $Id$ -> $FreeBSD$
1999-08-27 23:37:10 +00:00

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/* atof_generic.c - turn a string of digits into a Flonum
Copyright (C) 1987, 1990, 1991, 1992 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 2, 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. */
#ifndef lint
static char rcsid[] = "$FreeBSD$";
#endif
#include <ctype.h>
#include <string.h>
#include "as.h"
#ifdef __GNUC__
#define alloca __builtin_alloca
#else
#ifdef sparc
#include <alloca.h>
#endif
#endif
/* #define FALSE (0) */
/* #define TRUE (1) */
/***********************************************************************\
* *
* 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 *
* *
\***********************************************************************/
/*
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 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);
}
/* 99e999 is a "special" token to some older, broken compilers. */
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);
}
if (strncmp(first_digit, "99e999", 6) == 0) {
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;
*address_of_string_pointer = first_digit + 6;
return(0);
}
number_of_digits_before_decimal = 0;
number_of_digits_after_decimal = 0;
decimal_exponent = 0;
seen_significant_digit = 0;
for (p = first_digit; (((c = * p) != '\0')
&& (!c || ! strchr(string_of_decimal_marks, c))
&& (!c || !strchr(string_of_decimal_exponent_marks, c)));
p++) {
if (isdigit(c)) {
if (seen_significant_digit || c > '0') {
++number_of_digits_before_decimal;
seen_significant_digit = 1;
} else {
first_digit++;
}
} else {
break; /* p -> char after pre-decimal digits. */
}
} /* For each digit before decimal mark. */
#ifndef OLD_FLOAT_READS
/* Ignore trailing 0's after the decimal point. The original code here
* (ifdef'd out) does not do this, and numbers like
* 4.29496729600000000000e+09 (2**31)
* come out inexact for some reason related to length of the digit
* string.
*/
if (c && strchr(string_of_decimal_marks, c)) {
int zeros = 0; /* Length of current string of zeros */
for (p++; (c = *p) && isdigit(c); p++) {
if (c == '0') {
zeros++;
} else {
number_of_digits_after_decimal += 1 + zeros;
zeros = 0;
}
}
}
#else
if (c && strchr(string_of_decimal_marks, c)) {
for (p++; (((c = *p) != '\0')
&& (!c || !strchr(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 */
#endif
if (c && strchr(string_of_decimal_exponent_marks, c) ) {
char digits_exponent_sign_char;
c = *++p;
if (c && strchr ("+-",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 {
int count; /* Number of useful digits left to scan. */
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);
memset((char *)digits_binary_low, '\0', 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
*/
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 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 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.
*/
as_fatal("failed sanity check."); /* 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);
memset((char *)power_binary_low, '\0', 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 of atof_generic.c */
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