Feature: Create new array with length

vm/array.go

@@ -74,20 +74,35 @@ func (a *Array) At(index uint16) ([]byte, error) {
 	return result, err
 }
 
+// Insert sets an element at a certain index of the array
 func (a *Array) Insert(index uint16, element []byte) error {
+	// First remove the current element at the index
 	err := a.Remove(index)
 	if err != nil {
 		return err
 	}
 
-	var f action = func(array *Array, i uint16, s uint16) ([]byte, error) {
-		tmp := Array{}
-		tmp = append(tmp, (*a)[:i]...)
-		tmp.Append(element)
-		*a = append(tmp, (*a)[i:]...)
-		return []byte{}, nil
+	arraySize, err := a.GetSize()
+
+	if err != nil {
+		return err
 	}
-	_, err = a.goToIndex(index, f)
+
+	// The last element can directly be appended
+	if arraySize == index {
+		err = a.Append(element)
+
+	} else {
+		var f action = func(array *Array, i uint16, s uint16) ([]byte, error) {
+			tmp := Array{}
+			tmp = append(tmp, (*a)[:i]...)
+			err := tmp.Append(element)
+			*a = append(tmp, (*a)[i:]...)
+			return []byte{}, err
+		}
+		_, err = a.goToIndex(index, f)
+	}
+
 	return err
 }
 
@@ -104,7 +119,9 @@ func (a *Array) Append(ba []byte) error {
 	return err
 }
 
+// Remove removes the element with the given index from the array
 func (a *Array) Remove(index uint16) error {
+	// This function actually removes the element at the given index from the array
 	var f action = func(array *Array, k uint16, s uint16) ([]byte, error) {
 		tmp := Array{}
 		tmp = append(tmp, (*a)[:k]...)

vm/struct.go

@@ -47,15 +47,5 @@ func (s *Struct) storeField(index uint16, element []byte) error {
 	if index >= size {
 		return errors.New("index out of bounds")
 	}
-
-	// Array insert does not work for an array with size = 1
-	if size == index+1 {
-		err := array.Remove(index)
-		if err != nil {
-			return err
-		}
-		err = array.Append(element)
-		return err
-	}
 	return array.Insert(index, element)
 }

vm/vm.go

@@ -1031,9 +1031,28 @@ func (vm *VM) Exec(trace bool) bool {
 			}
 
 		case NewArr:
+			length, err := vm.PopUnsignedBigInt(opCode)
+
+			if err != nil {
+				_ = vm.evaluationStack.Push([]byte(opCode.Name + ": " + err.Error()))
+				return false
+			}
+
 			a := NewArray()
-			vm.evaluationStack.Push(a)
 
+			for i := big.NewInt(0); i.Cmp(&length) == -1; i.Add(i, big.NewInt(1)) {
+				err := a.Append([]byte{0})
+				if err != nil {
+					_ = vm.evaluationStack.Push([]byte(opCode.Name + ": " + err.Error()))
+					return false
+				}
+			}
+
+			err = vm.evaluationStack.Push(a)
+			if err != nil {
+				_ = vm.evaluationStack.Push([]byte(opCode.Name + ": " + err.Error()))
+				return false
+			}
 		case ArrAppend:
 			a, aerr := vm.PopBytes(opCode)
 			v, verr := vm.PopBytes(opCode)

vm/vm_test.go

@@ -1872,6 +1872,7 @@ func TestVM_Exec_MapRemove(t *testing.T) {
 
 func TestVM_Exec_NewArr(t *testing.T) {
 	code := []byte{
+		PushInt, 1, 0, 1,
 		NewArr,
 		Halt,
 	}
@@ -1890,16 +1891,37 @@ func TestVM_Exec_NewArr(t *testing.T) {
 	if err != nil {
 		t.Errorf("%v", err)
 	}
-	expectedSize := []byte{0x00, 0x00}
+	expectedSize := []byte{0x00, 0x01}
 	actualSize := arr[1:3]
 	if !bytes.Equal(expectedSize, actualSize) {
 		t.Errorf("invalid size, Expected %v but was '%v'", expectedSize, actualSize)
 	}
 }
 
+func TestVM_Exec_NewArrWithoutInitialization(t *testing.T) {
+	code := []byte{
+		PushInt, 1, 0, 2,
+		NewArr,
+		ArrLen,
+		Halt,
+	}
+
+	vm, isSuccess := execCode(code)
+	assert.Assert(t, isSuccess)
+
+	lengthBytes, _ := vm.evaluationStack.Pop()
+
+	length, _ := ByteArrayToUI16(lengthBytes)
+
+	if length != 2 {
+		t.Errorf("Array length should be 2 but is %v", length)
+	}
+}
+
 func TestVM_Exec_ArrAppend(t *testing.T) {
 	code := []byte{
 		Push, 2, 0xFF, 0x00,
+		PushInt, 1, 0, 0,
 		NewArr,
 		ArrAppend,
 		Halt,
@@ -1909,6 +1931,7 @@ func TestVM_Exec_ArrAppend(t *testing.T) {
 	mc := NewMockContext(code)
 	vm.context = mc
 	exec := vm.Exec(false)
+	mc.PersistChanges()
 	if !exec {
 		errorMessage, _ := vm.evaluationStack.Pop()
 		t.Errorf("VM.Exec terminated with Error: %v", string(errorMessage))
@@ -1933,6 +1956,7 @@ func TestVM_Exec_ArrInsert(t *testing.T) {
 
 		Push, 1, 0xFE, // value [254] at index 1
 		Push, 1, 0xFF, // value [255] at index 0
+		PushInt, 1, 0, 0,
 		NewArr,
 		ArrAppend,
 		ArrAppend,
@@ -1950,6 +1974,8 @@ func TestVM_Exec_ArrInsert(t *testing.T) {
 		t.Errorf("VM.Exec terminated with Error: %v", string(errorMessage))
 	}
 
+	mc.PersistChanges()
+
 	actual, err := vm.evaluationStack.Pop()
 	if err != nil {
 		t.Errorf("%v", err)
@@ -1973,6 +1999,7 @@ func TestVM_Exec_ArrRemove(t *testing.T) {
 		Push, 2, 0xAA, 0x00,
 		Push, 2, 0xFF, 0x00,
 
+		PushInt, 1, 0, 0,
 		NewArr,
 
 		ArrAppend,
@@ -2030,6 +2057,7 @@ func TestVM_Exec_ArrAt(t *testing.T) {
 		Push, 2, 0xAA, 0x00,
 		Push, 2, 0xFF, 0x00,
 
+		PushInt, 1, 0, 0,
 		NewArr,
 
 		ArrAppend,
@@ -2911,8 +2939,9 @@ func TestMultipleReturnValuesDifferentTypes(t *testing.T) {
 	}
 }
 
-func TestArrayLengthEmptyArray(t *testing.T) {
+func TestNewArrayFromLengthOnStack(t *testing.T) {
 	code := []byte{
+		PushInt, 1, 0, 2,
 		NewArr,
 		ArrLen,
 		Halt,
@@ -2921,18 +2950,43 @@ func TestArrayLengthEmptyArray(t *testing.T) {
 	vm, isSuccess := execCode(code)
 	assert.Assert(t, isSuccess)
 
-	length_bytes, _ := vm.evaluationStack.Pop()
+	lengthBytes, _ := vm.evaluationStack.Pop()
 
-	length, _ := ByteArrayToUI16(length_bytes)
+	length, _ := ByteArrayToUI16(lengthBytes)
 
-	if length != 0 {
-		t.Errorf("Array length should be 0 but is %v", length)
+	if length != 2 {
+		t.Errorf("Array length should be 2 but is %v", length)
 	}
 }
 
+func TestArrayInsert(t *testing.T) {
+	code := []byte{
+		PushInt, 1, 0, 2,
+		PushInt, 1, 0, 0,
+		PushInt, 1, 0, 1,
+		NewArr,
+		ArrInsert,
+		Halt,
+	}
+
+	vm, isSuccess := execCode(code)
+	assert.Assert(t, isSuccess)
+
+	arrayBytes, _ := vm.evaluationStack.Pop()
+
+	offset := 3
+	numberOfBytes := 2
+	arrayValue := ByteArrayToInt(arrayBytes[0+offset : 0+offset+numberOfBytes])
+	if arrayValue != 2 {
+		t.Errorf("Expected value at position 0 to be 2 but was %v", arrayValue)
+	}
+
+}
+
 func TestArrayLength(t *testing.T) {
 	code := []byte{
 		PushInt, 1, 0, 2,
+		PushInt, 1, 0, 0,
 		NewArr,
 		ArrAppend,
 		ArrLen,
@@ -2942,9 +2996,9 @@ func TestArrayLength(t *testing.T) {
 	vm, isSuccess := execCode(code)
 	assert.Assert(t, isSuccess)
 
-	length_bytes, _ := vm.evaluationStack.Pop()
+	lengthBytes, _ := vm.evaluationStack.Pop()
 
-	length, _ := ByteArrayToUI16(length_bytes)
+	length, _ := ByteArrayToUI16(lengthBytes)
 
 	if length != 1 {
 		t.Errorf("Array length should be 1 but is %v", length)
@@ -2955,6 +3009,7 @@ func TestArrayLengthMultipleElements(t *testing.T) {
 	code := []byte{
 		PushInt, 1, 0, 2, // will be appended at index 1
 		PushInt, 1, 0, 1, // will be appended at index 0
+		PushInt, 1, 0, 0,
 		NewArr,
 		ArrAppend,
 		ArrAppend,
@@ -2965,9 +3020,9 @@ func TestArrayLengthMultipleElements(t *testing.T) {
 	vm, isSuccess := execCode(code)
 	assert.Assert(t, isSuccess)
 
-	length_bytes, _ := vm.evaluationStack.Pop()
+	lengthBytes, _ := vm.evaluationStack.Pop()
 
-	length, _ := ByteArrayToUI16(length_bytes)
+	length, _ := ByteArrayToUI16(lengthBytes)
 
 	if length != 2 {
 		t.Errorf("Array length should be 2 but is %v", length)