// CS 350, Illinois Inst Tech, J. Sasaki
// Lecture 8, Spring 2012
//
// Bit shifting examples in C
//
#include <stdio.h>

// Instructions: Compile with LENGTH of 0, 1, or 2 to run the
// examples on characters, short integers, or regular integers.
//
#define LENGTH 0

#if LENGTH == 2
#define TYPE int
#define TYPENAME "int"
#define MAX_POS 0x7fffffff
#define MAX_NEG 0x80000000
#define NEG_ONE 0xffffffff

// For printing:
// %2d means >= 2 chars signed decimal (including possible '-'
//     sign), blank-filled
// %#010x means leading 0x, zero-filled, >= 10 chars hex
// %...X means upper case hex (A-F instead of a-f)
//
#define FORMAT1 "1 << %2d = %#010x = %d\n"
#define FORMAT2 "%08x << %2d = %08x = %d\n"
#define FORMAT3 "%08X >> %2d = %08X = %d\n"

#elif LENGTH == 1
#define TYPE short int
#define TYPENAME "short int"
#define MAX_POS 0x7fff
#define MAX_NEG 0x8000
#define NEG_ONE 0xffff

// For printing:
// %...h means the value is a short int
// %...hh means the value is a char
//
#define FORMAT1 "1 << %2d = %#06hx = %d\n"
#define FORMAT2 "%04hx << %2d = %04hx = %d\n"
#define FORMAT3 "%04hX >> %2d = %04hX = %d\n"

#elif LENGTH == 0
#define TYPE char
#define TYPENAME "char"
#define MAX_POS 0x7f
#define MAX_NEG 0x80
#define NEG_ONE 0xff

#define FORMAT1 "1 << %d = %#04hhx = %d\n"
#define FORMAT2 "%02hhx << %d = %02hhx = %d\n"
#define FORMAT3 "%02hhX >> %d = %02hhX = %d\n"

#endif

int main(void) {
	printf("Bit-shifting on %s values:\n\n", TYPENAME);

	TYPE value, n, power;

	// 1 << i is 1 shifted left i bits (equals 2 to the i power).
	// The loop runs a couple times more than the width (in bits)
	// of the type: sizeof( a type name ) = # bytes for that type.
	//
	int i;
	for (i = 0; i < sizeof(TYPE)*8+2; i++) {
		power = 1 << i;
		printf(FORMAT1, i, power, power);
	}
	printf("\n");

	n = NEG_ONE;
	for (i = 0; i < sizeof(TYPE)*8+2; i++) {
		value = n << i;
		printf(FORMAT2, n, i, value, value);
	}
	printf("\n");

	// n >> i = n shifted right i bits, either 0 or sign-bit filled.
	// (The standard leaves this choice up to the implementation.)
	//
	n = MAX_POS;
	for (i = 0; i < sizeof(TYPE)*8+2; i++) {
		value = n >> i;
		printf(FORMAT3, n, i, value, value);
	}
	printf("\n");

	// Try shifting maximum negative value right
	//
	n = MAX_NEG;
	for (i = 0; i < sizeof(TYPE)*8+2; i++) {
		value = n >> i;
		printf(FORMAT3, n, i, value, value);
	}
	printf("\n");

	return 0;
}