gas/flonum.h

   1 /* flonum.h - Floating point package
   2    Copyright (C) 1987-2019 Free Software Foundation, Inc.
   3
   4    This file is part of GAS, the GNU Assembler.
   5
   6    GAS is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    GAS is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with GAS; see the file COPYING.  If not, write to the Free
  18    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  19    02110-1301, USA.  */
  20
  21 /***********************************************************************\
  22  *                                                                      *
  23  *      Arbitrary-precision floating point arithmetic.                  *
  24  *                                                                      *
  25  *                                                                      *
  26  *      Notation: a floating point number is expressed as               *
  27  *      MANTISSA * (2 ** EXPONENT).                                     *
  28  *                                                                      *
  29  *      If this offends more traditional mathematicians, then           *
  30  *      please tell me your nomenclature for flonums!                   *
  31  *                                                                      *
  32  \***********************************************************************/
  33
  34 #include "bignum.h"
  35
  36 /***********************************************************************\
  37  *                                                                      *
  38  *      Variable precision floating point numbers.                      *
  39  *                                                                      *
  40  *      Exponent is the place value of the low littlenum. E.g.:         *
  41  *      If  0:  low points to the units             littlenum.          *
  42  *      If  1:  low points to the LITTLENUM_RADIX   littlenum.          *
  43  *      If -1:  low points to the 1/LITTLENUM_RADIX littlenum.          *
  44  *                                                                      *
  45  \***********************************************************************/
  46
  47 /* JF:  A sign value of 0 means we have been asked to assemble NaN
  48    A sign value of 'P' means we've been asked to assemble +Inf
  49    A sign value of 'N' means we've been asked to assemble -Inf
  50    */
  51 struct FLONUM_STRUCT {
  52   LITTLENUM_TYPE *low;          /* low order littlenum of a bignum */
  53   LITTLENUM_TYPE *high;         /* high order littlenum of a bignum */
  54   LITTLENUM_TYPE *leader;       /* -> 1st non-zero littlenum */
  55   /* If flonum is 0.0, leader==low-1 */
  56   long exponent;                /* base LITTLENUM_RADIX */
  57   char sign;                    /* '+' or '-' */
  58 };
  59
  60 typedef struct FLONUM_STRUCT FLONUM_TYPE;
  61
  62 /***********************************************************************\
  63  *                                                                      *
  64  *      Since we can (& do) meet with exponents like 10^5000, it        *
  65  *      is silly to make a table of ~ 10,000 entries, one for each      *
  66  *      power of 10. We keep a table where item [n] is a struct         *
  67  *      FLONUM_FLOATING_POINT representing 10^(2^n). We then            *
  68  *      multiply appropriate entries from this table to get any         *
  69  *      particular power of 10. For the example of 10^5000, a table     *
  70  *      of just 25 entries suffices: 10^(2^-12)...10^(2^+12).           *
  71  *                                                                      *
  72  \***********************************************************************/
  73
  74 extern const FLONUM_TYPE flonum_positive_powers_of_ten[];
  75 extern const FLONUM_TYPE flonum_negative_powers_of_ten[];
  76 extern const int table_size_of_flonum_powers_of_ten;
  77 /* Flonum_XXX_powers_of_ten[] table has legal indices from 0 to
  78    + this number inclusive.  */
  79
  80 /***********************************************************************\
  81  *                                                                      *
  82  *      Declare worker functions.                                       *
  83  *                                                                      *
  84  \***********************************************************************/
  85
  86 int atof_generic (char **address_of_string_pointer,
  87                   const char *string_of_decimal_marks,
  88                   const char *string_of_decimal_exponent_marks,
  89                   FLONUM_TYPE * address_of_generic_floating_point_number);
  90
  91 void flonum_copy (FLONUM_TYPE * in, FLONUM_TYPE * out);
  92 void flonum_multip (const FLONUM_TYPE * a, const FLONUM_TYPE * b,
  93                     FLONUM_TYPE * product);
  94
  95 /***********************************************************************\
  96  *                                                                      *
  97  *      Declare error codes.                                            *
  98  *                                                                      *
  99  \***********************************************************************/
 100
 101 #define ERROR_EXPONENT_OVERFLOW (2)