[#1] Add left and right shift operations for byte array

Closes #1

bit_methods.go → bit_operations.go

@@ -1,5 +1,11 @@
 package gobits
 
+const (
+	byteLength = 8
+	lsb        = 0
+	msb        = byteLength - 1
+)
+
 // ContainsBit test if a bit is contains in the data
 func ContainsBit(data byte, bit uint8) bool {
 	return ContainsBits(data, SetBit(0x00, bit))

bits_operations.go

@@ -0,0 +1,21 @@
+package gobits
+
+// ContainsBits test if some bits is contains in a data
+func ContainsBits(data, bits byte) bool {
+	return data&bits == bits
+}
+
+// SetBits affect the bits to a data
+func SetBits(data, bits byte) byte {
+	return data | bits
+}
+
+// UnsetBits unaffect the bits to a data
+func UnsetBits(data, bits byte) byte {
+	return data &^ bits
+}
+
+// ExtractBits get a byte as subset of another byte
+func ExtractBits(data byte, lsbPosition, msbPosition uint8) byte {
+	return data << (msb - msbPosition) >> (msb + lsbPosition - msbPosition)
+}

bits_methods_test.go → bits_operations_test.go

@@ -26,7 +26,7 @@ func TestUnsetBits(t *testing.T) {
 }
 
 func TestExtractBits(t *testing.T) {
-	var result = ExtractBits(0xDA, 4, 3)
+	var result = ExtractBits(0xDA, 3, 4)
 	if result != 0x03 {
 		t.Errorf("ExtractBits don't work: %08b", result)
 	}

bytearray_operations.go

@@ -0,0 +1,27 @@
+package gobits
+
+// RightShift apply right shift operation to byte array data
+func RightShift(data []byte, shift uint8) []byte {
+	var dataLength = len(data)
+	result := make([]byte, dataLength)
+	for i := dataLength - 1; i >= 0; i-- {
+		if i > 0 {
+			result[i-1] = data[i] >> (byteLength - shift)
+		}
+		result[i] = result[i] | (data[i] << shift)
+	}
+	return result
+}
+
+// LeftShift apply left shift operation to byte array data
+func LeftShift(data []byte, shift uint8) []byte {
+	var dataLength = len(data)
+	result := make([]byte, dataLength)
+	for i := 0; i < dataLength; i++ {
+		if i < dataLength-1 {
+			result[i+1] = data[i] << (byteLength - shift)
+		}
+		result[i] = result[i] | (data[i] >> shift)
+	}
+	return result
+}

bytearray_operations_test.go

@@ -0,0 +1,20 @@
+package gobits
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestRightShift(t *testing.T) {
+	var result = RightShift([]byte{0x99, 0xBA}, 1)
+	if !reflect.DeepEqual(result, []byte{0x33, 0x74}) {
+		t.Errorf("RightShift don't work: %x", result)
+	}
+}
+
+func TestLeftShift(t *testing.T) {
+	var result = LeftShift([]byte{0x99, 0xBA}, 1)
+	if !reflect.DeepEqual(result, []byte{0x4C, 0xDD}) {
+		t.Errorf("LeftShift don't work: %x", result)
+	}
+}