kc3-lang/gnulib/lib/printf-frexp.c

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• Hash : 281b825e
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  Date : 2018-01-01T00:57:25
  

  maint: Run 'make update-copyright'
  

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• lib/printf-frexp.c

• /* Split a double into fraction and mantissa, for hexadecimal printf.
     Copyright (C) 2007, 2009-2018 Free Software Foundation, Inc.
  
     This program 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 3 of the License, or
     (at your option) any later version.
  
     This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.  */
  
  #if ! defined USE_LONG_DOUBLE
  # include <config.h>
  #endif
  
  /* Specification.  */
  #ifdef USE_LONG_DOUBLE
  # include "printf-frexpl.h"
  #else
  # include "printf-frexp.h"
  #endif
  
  #include <float.h>
  #include <math.h>
  #ifdef USE_LONG_DOUBLE
  # include "fpucw.h"
  #endif
  
  /* This file assumes FLT_RADIX = 2.  If FLT_RADIX is a power of 2 greater
     than 2, or not even a power of 2, some rounding errors can occur, so that
     then the returned mantissa is only guaranteed to be <= 2.0, not < 2.0.  */
  
  #ifdef USE_LONG_DOUBLE
  # define FUNC printf_frexpl
  # define DOUBLE long double
  # define MIN_EXP LDBL_MIN_EXP
  # if HAVE_FREXPL_IN_LIBC && HAVE_LDEXPL_IN_LIBC
  #  define USE_FREXP_LDEXP
  #  define FREXP frexpl
  #  define LDEXP ldexpl
  # endif
  # define DECL_ROUNDING DECL_LONG_DOUBLE_ROUNDING
  # define BEGIN_ROUNDING() BEGIN_LONG_DOUBLE_ROUNDING ()
  # define END_ROUNDING() END_LONG_DOUBLE_ROUNDING ()
  # define L_(literal) literal##L
  #else
  # define FUNC printf_frexp
  # define DOUBLE double
  # define MIN_EXP DBL_MIN_EXP
  # if HAVE_FREXP_IN_LIBC && HAVE_LDEXP_IN_LIBC
  #  define USE_FREXP_LDEXP
  #  define FREXP frexp
  #  define LDEXP ldexp
  # endif
  # define DECL_ROUNDING
  # define BEGIN_ROUNDING()
  # define END_ROUNDING()
  # define L_(literal) literal
  #endif
  
  DOUBLE
  FUNC (DOUBLE x, int *expptr)
  {
    int exponent;
    DECL_ROUNDING
  
    BEGIN_ROUNDING ();
  
  #ifdef USE_FREXP_LDEXP
    /* frexp and ldexp are usually faster than the loop below.  */
    x = FREXP (x, &exponent);
  
    x = x + x;
    exponent -= 1;
  
    if (exponent < MIN_EXP - 1)
      {
        x = LDEXP (x, exponent - (MIN_EXP - 1));
        exponent = MIN_EXP - 1;
      }
  #else
    {
      /* Since the exponent is an 'int', it fits in 64 bits.  Therefore the
         loops are executed no more than 64 times.  */
      DOUBLE pow2[64]; /* pow2[i] = 2^2^i */
      DOUBLE powh[64]; /* powh[i] = 2^-2^i */
      int i;
  
      exponent = 0;
      if (x >= L_(1.0))
        {
          /* A nonnegative exponent.  */
          {
            DOUBLE pow2_i; /* = pow2[i] */
            DOUBLE powh_i; /* = powh[i] */
  
            /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
               x * 2^exponent = argument, x >= 1.0.  */
            for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
                 ;
                 i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
              {
                if (x >= pow2_i)
                  {
                    exponent += (1 << i);
                    x *= powh_i;
                  }
                else
                  break;
  
                pow2[i] = pow2_i;
                powh[i] = powh_i;
              }
          }
          /* Here 1.0 <= x < 2^2^i.  */
        }
      else
        {
          /* A negative exponent.  */
          {
            DOUBLE pow2_i; /* = pow2[i] */
            DOUBLE powh_i; /* = powh[i] */
  
            /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
               x * 2^exponent = argument, x < 1.0, exponent >= MIN_EXP - 1.  */
            for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
                 ;
                 i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
              {
                if (exponent - (1 << i) < MIN_EXP - 1)
                  break;
  
                exponent -= (1 << i);
                x *= pow2_i;
                if (x >= L_(1.0))
                  break;
  
                pow2[i] = pow2_i;
                powh[i] = powh_i;
              }
          }
          /* Here either x < 1.0 and exponent - 2^i < MIN_EXP - 1 <= exponent,
             or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1.  */
  
          if (x < L_(1.0))
            /* Invariants: x * 2^exponent = argument, x < 1.0 and
               exponent - 2^i < MIN_EXP - 1 <= exponent.  */
            while (i > 0)
              {
                i--;
                if (exponent - (1 << i) >= MIN_EXP - 1)
                  {
                    exponent -= (1 << i);
                    x *= pow2[i];
                    if (x >= L_(1.0))
                      break;
                  }
              }
  
          /* Here either x < 1.0 and exponent = MIN_EXP - 1,
             or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1.  */
        }
  
      /* Invariants: x * 2^exponent = argument, and
         either x < 1.0 and exponent = MIN_EXP - 1,
         or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1.  */
      while (i > 0)
        {
          i--;
          if (x >= pow2[i])
            {
              exponent += (1 << i);
              x *= powh[i];
            }
        }
      /* Here either x < 1.0 and exponent = MIN_EXP - 1,
         or 1.0 <= x < 2.0 and exponent >= MIN_EXP - 1.  */
    }
  #endif
  
    END_ROUNDING ();
  
    *expptr = exponent;
    return x;
  }
  

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