gas/flonum.h

   1 /* flonum.h - Floating point package
   2    Copyright 1987, 1990, 1991, 1992, 1994, 1996, 2000, 2003, 2007
   3    Free Software Foundation, Inc.
   4
   5    This file is part of GAS, the GNU Assembler.
   6
   7    GAS is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3, or (at your option)
  10    any later version.
  11
  12    GAS is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with GAS; see the file COPYING.  If not, write to the Free
  19    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  20    02110-1301, USA.  */
  21
  22 /***********************************************************************\
  23  *                                                                      *
  24  *      Arbitrary-precision floating point arithmetic.                  *
  25  *                                                                      *
  26  *                                                                      *
  27  *      Notation: a floating point number is expressed as               *
  28  *      MANTISSA * (2 ** EXPONENT).                                     *
  29  *                                                                      *
  30  *      If this offends more traditional mathematicians, then           *
  31  *      please tell me your nomenclature for flonums!                   *
  32  *                                                                      *
  33  \***********************************************************************/
  34
  35 #include "bignum.h"
  36
  37 /***********************************************************************\
  38  *                                                                      *
  39  *      Variable precision floating point numbers.                      *
  40  *                                                                      *
  41  *      Exponent is the place value of the low littlenum. E.g.:         *
  42  *      If  0:  low points to the units             littlenum.          *
  43  *      If  1:  low points to the LITTLENUM_RADIX   littlenum.          *
  44  *      If -1:  low points to the 1/LITTLENUM_RADIX littlenum.          *
  45  *                                                                      *
  46  \***********************************************************************/
  47
  48 /* JF:  A sign value of 0 means we have been asked to assemble NaN
  49    A sign value of 'P' means we've been asked to assemble +Inf
  50    A sign value of 'N' means we've been asked to assemble -Inf
  51    */
  52 struct FLONUM_STRUCT {
  53   LITTLENUM_TYPE *low;          /* low order littlenum of a bignum */
  54   LITTLENUM_TYPE *high;         /* high order littlenum of a bignum */
  55   LITTLENUM_TYPE *leader;       /* -> 1st non-zero littlenum */
  56   /* If flonum is 0.0, leader==low-1 */
  57   long exponent;                /* base LITTLENUM_RADIX */
  58   char sign;                    /* '+' or '-' */
  59 };
  60
  61 typedef struct FLONUM_STRUCT FLONUM_TYPE;
  62
  63 /***********************************************************************\
  64  *                                                                      *
  65  *      Since we can (& do) meet with exponents like 10^5000, it        *
  66  *      is silly to make a table of ~ 10,000 entries, one for each      *
  67  *      power of 10. We keep a table where item [n] is a struct         *
  68  *      FLONUM_FLOATING_POINT representing 10^(2^n). We then            *
  69  *      multiply appropriate entries from this table to get any         *
  70  *      particular power of 10. For the example of 10^5000, a table     *
  71  *      of just 25 entries suffices: 10^(2^-12)...10^(2^+12).           *
  72  *                                                                      *
  73  \***********************************************************************/
  74
  75 extern const FLONUM_TYPE flonum_positive_powers_of_ten[];
  76 extern const FLONUM_TYPE flonum_negative_powers_of_ten[];
  77 extern const int table_size_of_flonum_powers_of_ten;
  78 /* Flonum_XXX_powers_of_ten[] table has legal indices from 0 to
  79    + this number inclusive.  */
  80
  81 /***********************************************************************\
  82  *                                                                      *
  83  *      Declare worker functions.                                       *
  84  *                                                                      *
  85  \***********************************************************************/
  86
  87 int atof_generic (char **address_of_string_pointer,
  88                   const char *string_of_decimal_marks,
  89                   const char *string_of_decimal_exponent_marks,
  90                   FLONUM_TYPE * address_of_generic_floating_point_number);
  91
  92 void flonum_copy (FLONUM_TYPE * in, FLONUM_TYPE * out);
  93 void flonum_multip (const FLONUM_TYPE * a, const FLONUM_TYPE * b,
  94                     FLONUM_TYPE * product);
  95
  96 /***********************************************************************\
  97  *                                                                      *
  98  *      Declare error codes.                                            *
  99  *                                                                      *
 100  \***********************************************************************/
 101
 102 #define ERROR_EXPONENT_OVERFLOW (2)