Encode and Decode uint64 values for sending them over the network or similar use cases. Fast (30 ns per number for both functions)

uint64encode.go

// Converts a number to a little-endian byte array
func lengthToBytes(l uint64) [8]byte {
	var sizebuf [8]byte

	var i int = 7
	for ; i >= 0; i-- {
		// The commented implementation is 5 times slower but equivalent
		/*
			var divisor uint64 = 1 << (uint(i) * 8)
			sizebuf[i] = uint8(l / divisor)
			l = l - ((l / divisor) * divisor)
		*/
		var shift uint = uint(i * 8)
		sizebuf[i] = uint8((l & (255 << shift)) >> shift)
	}

	return sizebuf
}

// Gets the value from an encoded size number (lengthToBytes())
func sizebufToLength(b [8]byte) uint64 {
	var size uint64 = 0

	var i int = 7

	for ; i >= 0; i-- {
		var multiplier uint64 = 1 << (8 * uint(i))
		size += multiplier * uint64(b[i])

		// Bitshift is not faster
		/*
			var shift uint = 8 * uint(i)
			size |= uint64(b[i]) << shift
		*/
	}
	return size
}