2000-05-29 Philip Blundell <philb@gnu.org>

[binutils.git] / gas / atof-generic.c

/* atof_generic.c - turn a string of digits into a Flonum
   Copyright (C) 1987, 90, 91, 92, 93, 94, 95, 96, 1998
   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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

#include <ctype.h>
#include <string.h>

#include "as.h"

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

#ifdef TRACE
static void flonum_print PARAMS ((const FLONUM_TYPE *));
#endif

#define ASSUME_DECIMAL_MARK_IS_DOT

/***********************************************************************\
 *                                                                      *
 *      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
atof_generic (address_of_string_pointer,
              string_of_decimal_marks,
              string_of_decimal_exponent_marks,
              address_of_generic_floating_point_number)
     /* return pointer to just AFTER number we read. */
     char **address_of_string_pointer;
     /* At most one per number. */
     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;
  unsigned int number_of_digits_before_decimal;
  unsigned int number_of_digits_after_decimal;
  long decimal_exponent;
  unsigned 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;

#ifdef ASSUME_DECIMAL_MARK_IS_DOT
  assert (string_of_decimal_marks[0] == '.'
          && string_of_decimal_marks[1] == 0);
#define IS_DECIMAL_MARK(c)      ((c) == '.')
#else
#define IS_DECIMAL_MARK(c)      (0 != strchr (string_of_decimal_marks, (c)))
#endif

  first_digit = *address_of_string_pointer;
  c = *first_digit;

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

  switch (first_digit[0])
    {
    case 'n':
    case 'N':
      if (!strncasecmp ("nan", first_digit, 3))
        {
          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;
        }
      break;

    case 'i':
    case 'I':
      if (!strncasecmp ("inf", first_digit, 3))
        {
          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;

          first_digit += 3;
          if (!strncasecmp ("inity", first_digit, 5))
            first_digit += 5;

          *address_of_string_pointer = first_digit;

          return 0;
        }
      break;
    }

  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 || !IS_DECIMAL_MARK (c))
        && (!c || !strchr (string_of_decimal_exponent_marks, c)));
       p++)
    {
      if (isdigit ((unsigned char) 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 && IS_DECIMAL_MARK (c))
    {
      unsigned int zeros = 0;   /* Length of current string of zeros */

      for (p++; (c = *p) && isdigit ((unsigned char) c); p++)
        {
          if (c == '0')
            {
              zeros++;
            }
          else
            {
              number_of_digits_after_decimal += 1 + zeros;
              zeros = 0;
            }
        }
    }
#else
  if (c && IS_DECIMAL_MARK (c))
    {
      for (p++;
           (((c = *p) != '\0')
            && (!c || !strchr (string_of_decimal_exponent_marks, c)));
           p++)
        {
          if (isdigit ((unsigned char) c))
            {
              /* This may be retracted below. */
              number_of_digits_after_decimal++;

              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;
#endif

  if (flag_m68k_mri)
    {
      while (c == '_')
        c = *++p;
    }
  if (c && strchr (string_of_decimal_exponent_marks, c))
    {
      char digits_exponent_sign_char;

      c = *++p;
      if (flag_m68k_mri)
        {
          while (c == '_')
            c = *++p;
        }
      if (c && strchr ("+-", c))
        {
          digits_exponent_sign_char = c;
          c = *++p;
        }
      else
        {
          digits_exponent_sign_char = '+';
        }

      for (; (c); c = *++p)
        {
          if (isdigit ((unsigned char) 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;
      unsigned int precision;
      unsigned int maximum_useful_digits;
      unsigned int number_of_digits_to_use;
      unsigned int more_than_enough_bits_for_digits;
      unsigned int more_than_enough_littlenums_for_digits;
      unsigned int size_of_digits_in_littlenums;
      unsigned 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) */
#if 0 /* The integer version below is very close, and it doesn't
         require floating point support (which is currently buggy on
         the Alpha).  */
      maximum_useful_digits = (((double) (precision - 2))
                               * ((double) (LITTLENUM_NUMBER_OF_BITS))
                               / (LOG_TO_BASE_2_OF_10))
        + 2;                    /* 2 :: guard digits. */
#else
      maximum_useful_digits = (((precision - 2))
                               * ( (LITTLENUM_NUMBER_OF_BITS))
                               * 1000000 / 3321928)
        + 2;                    /* 2 :: guard digits. */
#endif

      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;
        }

      /* Cast these to SIGNED LONG first, otherwise, on systems with
         LONG wider than INT (such as Alpha OSF/1), unsignedness may
         cause unexpected results.  */
      decimal_exponent += ((long) number_of_digits_before_decimal
                           - (long) number_of_digits_to_use);

#if 0
      more_than_enough_bits_for_digits
        = ((((double) number_of_digits_to_use) * LOG_TO_BASE_2_OF_10) + 1);
#else
      more_than_enough_bits_for_digits
        = (number_of_digits_to_use * 3321928 / 1000000 + 1);
#endif

      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 ((unsigned char) 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."));
                }
            }
          else
            {
              ++count;          /* '.' doesn't alter digits used count. */
            }
        }


      /*
       * 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;
        unsigned int size_of_power_in_littlenums;
        unsigned 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 separate. */

        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
#ifdef TRACE
                      printf ("multiplier:\n");
                      flonum_print (multiplicand + place_number);
                      (void) putchar ('\n');
#endif
                      flonum_multip (multiplicand + place_number,
                                     &power_of_10_flonum, &temporary_flonum);
#ifdef TRACE
                      printf ("after multiply:\n");
                      flonum_print (&temporary_flonum);
                      (void) putchar ('\n');
#endif
                      flonum_copy (&temporary_flonum, &power_of_10_flonum);
#ifdef TRACE
                      printf ("after copy:\n");
                      flonum_print (&power_of_10_flonum);
                      (void) putchar ('\n');
#endif
                    } /* 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:\n");
          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;
}

#ifdef TRACE
static void
flonum_print (f)
     const FLONUM_TYPE *f;
{
  LITTLENUM_TYPE *lp;
  char littlenum_format[10];
  sprintf (littlenum_format, " %%0%dx", sizeof (LITTLENUM_TYPE) * 2);
#define print_littlenum(LP)     (printf (littlenum_format, LP))
  printf ("flonum @%p %c e%ld", f, f->sign, f->exponent);
  if (f->low < f->high)
    for (lp = f->high; lp >= f->low; lp--)
      print_littlenum (*lp);
  else
    for (lp = f->low; lp <= f->high; lp++)
      print_littlenum (*lp);
  printf ("\n");
  fflush (stdout);
}
#endif

/* end of atof_generic.c */