Bit Masking

bit_masking.cs

void Main()
{
	/* use XOR to toggle bits */
	var value = 0x11; 			// 00010001
	var mask = 0xFF; 			// 11111111 (flip everything; make a mirror)
	var result = value ^ mask;	// 11101110
	OutputAsBinary(result); 
	
	/* use OR to set bits (to true) */
	value = 0x11; 			// 00010001
	mask = 0x2; 			// 00000010
	result = value | mask;	// 00010011	
	OutputAsBinary(result); // 00010011
	
	/* use AND with NOT to unset a bit (set to false) */
	value = 0x11;			// 00010001
	mask = 0x1;				// 00000001 (unset the first bit)
	result = value & ~mask; // 00010000
	OutputAsBinary(result);	
	
	/* use AND to check a bit  */
	value = 0x11; 	// 00010001
	mask = 0x10; 	// 00010000 (requires fifth bit = true)
	var hasBits = (value & mask) == mask; // if the bit(s) are present, then the result will be equal to the mask
	Console.WriteLine(hasBits);
	
	// check if multiple bits are present (same thing)
	value = 0x39; 	// 00111001
	mask = 0x18; 	// 00110000 (requires 4th and fifth bits = true)	
	var hasFlags = (value & mask) == mask;
	Console.WriteLine(hasFlags);
	
	/* Extract pieces of a larger word */
	value = 0x3F2C; 				// 0011 1111 0010 1100
	mask = 0xFF; 					// 0000 0000 1111 1111 (one byte mask. Everything to the left is 'dont care')
	var firstByte = value >> 8;		// 0000 0000 0011 1111 (move it into byte 1 position and mask out everything else)
	var secondByte = value & mask;	// 0000 0000 0010 1100 (already in byte 1 position)
	Console.WriteLine("\r\nSmall word word extraction example: ");
	OutputAsBinary(value);
	OutputAsBinary(firstByte);
	OutputAsBinary(secondByte);	
	
	/* larger extraction example */
	Console.WriteLine("\r\nLarge word extraction example: ");
	value = 0x32E2CD1D; 				// 0011 0010 1110 0010 1100 1101 0001 1101 (32 bit integer)
	mask = 0xFF;						// 0000 0000 1111 1111
	var first = value >> 24; 			// 0011 0010
	var second = (value >> 16) & mask;	// 1110 0010
	var third =  (value >> 8) & mask;	// 1100 1101
	var fourth = value & mask;			// 0001 1101
	OutputAsBinary(value);
	OutputAsBinary(first);
	OutputAsBinary(second);
	OutputAsBinary(third);
	OutputAsBinary(fourth);
}

public static void OutputAsBinary(int input)
{
	var asHex = input.ToString("X2");
	var asBinary = Convert.ToString(input, 2).PadLeft(8, '0');
	Console.WriteLine($"{asBinary} (0x{asHex})");		
}