Is there a built-in function to reverse bit order

Question

I\'ve come up with several manual ways of doing this, but i keep wondering if there is something built-in .NET that does this.

Basically, i want to reverse the bit o

Answer 1

You can find bit twiddling algorithms in the fxtbook. Chapter 1.14 gives these bit swapping algorithms:

    static uint bitSwap1(uint x) {
        uint m = 0x55555555;
        return ((x & m) << 1) | ((x & (~m)) >> 1);
    }
    static uint bitSwap2(uint x) {
        uint m = 0x33333333;
        return ((x & m) << 2) | ((x & (~m)) >> 2);
    }
    static uint bitSwap4(uint x) {
        uint m = 0x0f0f0f0f;
        return ((x & m) << 4) | ((x & (~m)) >> 4);
    }

Which makes your byte value bit reversal:

    public static byte swapBits(byte value) {
        return (byte)(bitSwap4(bitSwap2(bitSwap1(value))));
    }

The x86 JIT compiler doesn't do a great job optimizing this code. If speed matters then you could use it to initialize a byte[] to make it a fast lookup instead.