/*
 * Here is the code for the bit field functions as
 * discussed in class.
 */

/*
 * Author:  Paul J. Drongowski
 * Address: Computer Science Department
 *          Tufts University
 *          Medford, MA
 *
 * Copyright (c) 2005 Paul J. Drongowski
 */

#include <iostream>
#include <iomanip>
using namespace std ;

unsigned long int mask[] =
  {
    0x00000001UL, 0x00000003UL, 0x00000007UL, 0x0000000FUL,
    0x0000001FUL, 0x0000003FUL, 0x0000007FUL, 0x000000FFUL,
    0x000001FFUL, 0x000003FFUL, 0x000007FFUL, 0x00000FFFUL,
    0x00001FFFUL, 0x00003FFFUL, 0x00007FFFUL, 0x0000FFFFUL,
    0x0001FFFFUL, 0x0003FFFFUL, 0x0007FFFFUL, 0x000FFFFFUL,
    0x001FFFFFUL, 0x003FFFFFUL, 0x007FFFFFUL, 0x00FFFFFFUL,
    0x01FFFFFFUL, 0x03FFFFFFUL, 0x07FFFFFFUL, 0x0FFFFFFFUL,
    0x1FFFFFFFUL, 0x3FFFFFFFUL, 0x7FFFFFFFUL, 0xFFFFFFFFUL
  } ;

// Function: extract
// Purpose: Extract bit field with specified position and width
// Parameters:
//   position: Position of field's low order bit
//   width: Number of bits in bit field

int extract(int value, int position, int width)
{
  return( (value >> position) & mask[width-1] ) ;
}

int clear(int value, int position, int width)
{
  return( (value & ~(mask[width-1] << position)) ) ;
}

int set(int value, int position, int width, int field)
{
  int v ;
  v = clear(value, position, width) ;
  v = v | (field << position) ;
  return( v ) ;
}

void print_sizes()
{
  char c ;
  short int s ;
  int i ;
  long int l ;
  float f ;
  double d ;

  cout << "Size of char:   " << dec << sizeof(c) << endl ;
  cout << "Size of short:  " << sizeof(s) << endl ;
  cout << "Size of int:    " << sizeof(i) << endl ;
  cout << "Size of long:   " << sizeof(l) << endl ;
  cout << "Size of float:  " << sizeof(f) << endl ;
  cout << "Size of double: " << sizeof(d) << endl ;
}

main(int argc, char *argv[])
{
  int a, b, r, i ;

  a = 0x76543210 ;
  b = 0x33221100 ;

  /*
  for (i = 0 ; i < 32 ; i += 4) {
    cout << extract(a, i, 4) << showbase << hex << endl ;
  }

  for (i = 0 ; i < 32 ; i += 4) {
    cout << extract(b, i, 4) << showbase << hex << endl ;
  }
  */

  a = 0xFFFFFFFF ;
  a = clear(a, 12, 4) ;
  cout << showbase << hex << a << endl ;

  a = clear(a, 4, 4) ;
  cout << showbase << hex << a << endl ;

  a = set(a, 12, 4, 1) ;
  a = set(a, 4, 4, 2) ;
  cout << showbase << hex << a << endl ;
}