Subversion Repositories wf3d

//=======================================================================

// Project Monophony

//   Wire-Frame 3D Graphics Accelerator IP Core

//

// File:

//   f22.c

//

// Abstract:

//   22-bit floating point number utility

//

// Author:

//   Kenji Ishimaru (info.info.wf3d@gmail.com)

//

//======================================================================

//

// Copyright (c) 2015, Kenji Ishimaru

// All rights reserved.

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//

//  -Redistributions of source code must retain the above copyright notice,

//   this list of conditions and the following disclaimer.

//  -Redistributions in binary form must reproduce the above copyright notice,

//   this list of conditions and the following disclaimer in the documentation

//   and/or other materials provided with the distribution.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR

// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;

// OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

// OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,

// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

// Revision History

#include <stdio.h>

union {

  unsigned int ui;

  float f;

} uif;

float cnv_f22_to_f32(unsigned int a) {

  // extract sign

  unsigned int tmp_s = (a >> 21) & 1;

  // extract exp

  unsigned int tmp_e = (a >> 16) & 0x1f;

  unsigned int tmp_oe = (a >> 16) & 0x1f;

  // extract fraction(with integer bit)

  unsigned int tmp_m = a  & 0xffff;

  if ((tmp_oe != 0)||(tmp_m != 0)) {

    tmp_e -= 15;

    tmp_e += 127;

  }

  // denormal

  if ((tmp_oe == 0)&&(tmp_m != 0)) {

    while (((tmp_m >> 15)&1) != 1) {

        tmp_m = tmp_m << 1;

        tmp_e--;

    }

  }

  tmp_m = (tmp_m << 1) & 0xfff; // remove integer bit

  unsigned int t =   (tmp_s << 31) | (tmp_e << 23) | (tmp_m << 7);

  uif.ui = t;

  return uif.f;

}

int main() {

  unsigned int x;

  while (1) {

    printf("f22 = ");

    scanf("%x", &x);

    printf("float value = %f\n",cnv_f22_to_f32(x));

  }

}