C++ Tutorial/Data Types/shift
Содержание
Demonstrate bitwise left shift
<source lang="cpp">#include <iostream> using std::cout; using std::cin; using std::endl;
- include <iomanip>
using std::setw; void displayBits( unsigned ); // prototype int main() {
unsigned number1 = 960; cout << "The result of left shifting\n"; displayBits( number1 ); cout << "8 bit positions using the left-shift operator is\n"; displayBits( number1 << 8 ); return 0;
} //Quote from //C++ How to Program (5th Edition) (How to Program) (Paperback) //by Harvey & Paul) Deitel & Associates //Publisher: Prentice Hall; 5 edition (January 5, 2005) //Language: English //ISBN-10: 0131857576 //ISBN-13: 978-0131857575 void displayBits( unsigned value ) {
const int SHIFT = 8 * sizeof( unsigned ) - 1;
const unsigned MASK = 1 << SHIFT;
cout << setw( 10 ) << value << " = ";
for ( unsigned i = 1; i <= SHIFT + 1; i++ )
{
cout << ( value & MASK ? "1" : "0" );
value <<= 1;
if ( i 8 == 0 )
cout << " ";
}
cout << endl;
}</source>
The result of left shifting
960 = 00000000 00000000 00000011 11000000
8 bit positions using the left-shift operator is
245760 = 00000000 00000011 11000000 00000000
Demonstrate bitwise right shift
<source lang="cpp">#include <iostream> using std::cout; using std::cin; using std::endl;
- include <iomanip>
using std::setw; void displayBits( unsigned ); // prototype int main() {
unsigned number1 = 960; cout << "\nThe result of right shifting\n"; displayBits( number1 ); cout << "8 bit positions using the right-shift operator is\n"; displayBits( number1 >> 8 );
return 0;
} //Quote from //C++ How to Program (5th Edition) (How to Program) (Paperback) //by Harvey & Paul) Deitel & Associates //Publisher: Prentice Hall; 5 edition (January 5, 2005) //Language: English //ISBN-10: 0131857576 //ISBN-13: 978-0131857575 void displayBits( unsigned value ) {
const int SHIFT = 8 * sizeof( unsigned ) - 1;
const unsigned MASK = 1 << SHIFT;
cout << setw( 10 ) << value << " = ";
for ( unsigned i = 1; i <= SHIFT + 1; i++ )
{
cout << ( value & MASK ? "1" : "0" );
value <<= 1;
if ( i 8 == 0 )
cout << " ";
}
cout << endl;
}</source>
The result of right shifting
960 = 00000000 00000000 00000011 11000000
8 bit positions using the right-shift operator is
3 = 00000000 00000000 00000000 00000011
Left rotate functions for byte values
<source lang="cpp">/* Quote from: C++: A Beginner"s Guide, Second Edition
- Publisher: McGraw-Hill Osborne Media; 2 edition (December 3, 2003)
- Language: English
- ISBN-10: 0072232153
- ISBN-13: 978-0072232158
- /
- include <iostream>
using namespace std;
unsigned char lrotate(unsigned char val, int n); void show_binary(unsigned int u);
int main() {
char ch = "A";
cout << "Original value in binary:\n";
show_binary(ch);
cout << "Rotating left 8 times:\n";
for(int i=0; i < 8; i++) {
ch = lrotate(ch, 1);
show_binary(ch);
}
return 0;
}
unsigned char lrotate(unsigned char val, int n) {
unsigned int t;
t = val;
for(int i=0; i < n; i++) {
t = t << 1;
/* If a bit shifts out, it will be in bit 8
of the integer t. If this is the case,
put that bit on the right side. */
if(t & 256)
t = t | 1; // put a 1 on the right end
}
return t; // return the lower 8 bits.
}
// Display the bits within a byte. void show_binary(unsigned int u) {
int t; for(t=128; t>0; t = t/2) if(u & t) cout << "1 "; else cout << "0 "; cout << "\n";
}</source>
Original value in binary: 0 1 0 0 0 0 0 1 Rotating left 8 times: 1 0 0 0 0 0 1 0 0 0 0 0 0 1 0 1 0 0 0 0 1 0 1 0 0 0 0 1 0 1 0 0 0 0 1 0 1 0 0 0 0 1 0 1 0 0 0 0 1 0 1 0 0 0 0 0 0 1 0 0 0 0 0 1
Right rotate functions for byte values
<source lang="cpp">/* Quote from: C++: A Beginner"s Guide, Second Edition
- Publisher: McGraw-Hill Osborne Media; 2 edition (December 3, 2003)
- Language: English
- ISBN-10: 0072232153
- ISBN-13: 978-0072232158
- /
- include <iostream>
using namespace std;
unsigned char rrotate(unsigned char val, int n); void show_binary(unsigned int u);
int main() {
char ch = "T";
cout << "Original value in binary:\n";
show_binary(ch);
cout << "Rotating right 8 times:\n";
for(int i=0; i < 8; i++) {
ch = rrotate(ch, 1);
show_binary(ch);
}
return 0;
}
// Right-rotate a byte n places. unsigned char rrotate(unsigned char val, int n) {
unsigned int t;
t = val;
// First, move the value 8 bits higher.
t = t << 8;
for(int i=0; i < n; i++) {
t = t >> 1;
/* If a bit shifts out, it will be in bit 7
of the integer t. If this is the case,
put that bit on the left side. */
if(t & 128)
t = t | 32768; // put a 1 on left end
}
/* Finally, move the result back to the
lower 8 bits of t. */
t = t >> 8;
return t;
}
// Display the bits within a byte. void show_binary(unsigned int u) {
int t; for(t=128; t>0; t = t/2) if(u & t) cout << "1 "; else cout << "0 "; cout << "\n";
}</source>
Original value in binary: 0 1 0 1 0 1 0 0 Rotating right 8 times: 0 0 1 0 1 0 1 0 0 0 0 1 0 1 0 1 1 0 0 0 1 0 1 0 0 1 0 0 0 1 0 1 1 0 1 0 0 0 1 0 0 1 0 1 0 0 0 1 1 0 1 0 1 0 0 0 0 1 0 1 0 1 0 0
Shift left
<source lang="cpp">#include <iostream> using namespace std; void show_binary(unsigned int u); int main() {
int i=1, t;
for(t=0; t < 8; t++) {
show_binary(i);
i = i << 1 ;
}
return 0;
} // Display the bits within a byte. void show_binary(unsigned int u) {
int t; for(t=128; t>0; t=t/2) if(u & t) cout << "1 "; else cout << "0 "; cout << "\n";
}</source>
0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0
Shift right
<source lang="cpp">#include <iostream> using namespace std;
void show_binary(unsigned int u);
int main() {
int i=1, t;
for(t=0; t < 8; t++) {
i = i >> 1;
show_binary(i);
}
return 0;
} // Display the bits within a byte. void show_binary(unsigned int u) {
int t; for(t=128; t>0; t=t/2) if(u & t) cout << "1 "; else cout << "0 "; cout << "\n";
}</source>
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
