shift.go

package binutil

// ShiftLeft performs a left bit shift operation on the provided bytes.
// If the bits count is negative, a right bit shift is performed.
func ShiftLeft(data []byte, bits int) {
	n := len(data)
	if bits < 0 {
		bits = -bits
		for i := n - 1; i > 0; i-- {
			data[i] = data[i-1]<<(8-bits) | data[i]>>bits
		}
		data[0] >>= bits
	} else {
		for i := 0; i < n-1; i++ {
			data[i] = data[i]<<bits | data[i+1]>>(8-bits)
		}
		data[n-1] <<= bits
	}
}