Implemented MIN, MAX WITHIN opcode

pkg/vm/stack/Int.go

@@ -111,3 +111,29 @@ func (i *Int) Abs() (*Int, error) {
 
 	return b, nil
 }
+
+// Min returns the mininum between two integers.
+func Min(a *Int, b *Int) *Int {
+	if a.Value().Cmp(b.Value()) == -1 {
+		return a
+	}
+	return b
+
+}
+
+// Max returns the maximun between two integers.
+func Max(a *Int, b *Int) *Int {
+	if a.Value().Cmp(b.Value()) == 1 {
+		return a
+	}
+	return b
+}
+
+// Within returns a bool whose value is true
+// iff the value of the integer i is within the specified
+// range [a,b) (left-inclusive).
+func (i *Int) Within(a *Int, b *Int) bool {
+	// i >= a && i < b
+	return !(i.Value().Cmp(a.Value()) == -1) && i.Value().Cmp(b.Value()) == -1
+
+}

pkg/vm/vm_ops.go

@@ -5,6 +5,9 @@ import "github.com/CityOfZion/neo-go/pkg/vm/stack"
 type stackInfo func(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation, rstack *stack.RandomAccess) (Vmstate, error)
 
 var opFunc = map[stack.Instruction]stackInfo{
+	stack.MIN:         Min,
+	stack.MAX:         Max,
+	stack.WITHIN:      Within,
 	stack.SHR:         Shr,
 	stack.SHL:         Shl,
 	stack.INC:         Inc,

pkg/vm/vm_ops_maths.go

@@ -173,6 +173,54 @@ func Mul(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation, rst
 	return NONE, nil
 }
 
+// Min pops two integers, a and b, off of the stack and pushes an integer to the stack
+// whose value is is the minum between a and b's value.
+// Returns an error if either items cannot be casted to an integer
+func Min(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation, rstack *stack.RandomAccess) (Vmstate, error) {
+
+	operandA, operandB, err := popTwoIntegers(ctx)
+	if err != nil {
+		return FAULT, err
+	}
+	res := stack.Min(operandA, operandB)
+
+	ctx.Estack.Push(res)
+
+	return NONE, nil
+}
+
+// Max pops two integers, a and b, off of the stack and pushes an integer to the stack
+// whose value is is the maximum between a and b's value.
+// Returns an error if either items cannot be casted to an integer
+func Max(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation, rstack *stack.RandomAccess) (Vmstate, error) {
+
+	operandA, operandB, err := popTwoIntegers(ctx)
+	if err != nil {
+		return FAULT, err
+	}
+	res := stack.Max(operandA, operandB)
+
+	ctx.Estack.Push(res)
+
+	return NONE, nil
+}
+
+// Within pops three integers, a, b, and c off of the stack and pushes a boolean to the stack
+// whose value is true iff c's value is within b's value (include) and a's value.
+// Returns an error if at least one item cannot be casted to an boolean.
+func Within(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation, rstack *stack.RandomAccess) (Vmstate, error) {
+
+	a, b, c, err := popThreeIntegers(ctx)
+	if err != nil {
+		return FAULT, err
+	}
+	res := stack.NewBoolean(c.Within(b, a))
+
+	ctx.Estack.Push(res)
+
+	return NONE, nil
+}
+
 // Abs pops an integer off of the stack and pushes its absolute value onto the stack.
 // Returns an error if the popped value is not an integer or if the absolute value cannot be taken
 func Abs(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation, rstack *stack.RandomAccess) (Vmstate, error) {
@@ -247,19 +295,6 @@ func Negate(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation,
 	return NONE, nil
 }
 
-func popTwoIntegers(ctx *stack.Context) (*stack.Int, *stack.Int, error) {
-	operandA, err := ctx.Estack.PopInt()
-	if err != nil {
-		return nil, nil, err
-	}
-	operandB, err := ctx.Estack.PopInt()
-	if err != nil {
-		return nil, nil, err
-	}
-
-	return operandA, operandB, nil
-}
-
 // Shl pops two integers, a and b, off of the stack and pushes an integer to the stack
 // whose value is the b's value shift to the left by a's value bits.
 // Returns an error if either items cannot be casted to an integer
@@ -300,6 +335,36 @@ func Shr(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation, rst
 	return NONE, nil
 }
 
+func popTwoIntegers(ctx *stack.Context) (*stack.Int, *stack.Int, error) {
+	operandA, err := ctx.Estack.PopInt()
+	if err != nil {
+		return nil, nil, err
+	}
+	operandB, err := ctx.Estack.PopInt()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return operandA, operandB, nil
+}
+
+func popThreeIntegers(ctx *stack.Context) (*stack.Int, *stack.Int, *stack.Int, error) {
+	operandA, err := ctx.Estack.PopInt()
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	operandB, err := ctx.Estack.PopInt()
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	operandC, err := ctx.Estack.PopInt()
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	return operandA, operandB, operandC, nil
+}
+
 func popTwoByteArrays(ctx *stack.Context) (*stack.ByteArray, *stack.ByteArray, error) {
 	// Pop first stack item and cast as byte array
 	ba1, err := ctx.Estack.PopByteArray()

pkg/vm/vm_ops_maths_test.go

@@ -394,3 +394,85 @@ func TestShrOp(t *testing.T) {
 
 	assert.Equal(t, int64(2), item.Value().Int64())
 }
+
+func TestMinOp(t *testing.T) {
+
+	v := VM{}
+
+	a, err := stack.NewInt(big.NewInt(10))
+	assert.NoError(t, err)
+
+	b, err := stack.NewInt(big.NewInt(2))
+	assert.NoError(t, err)
+
+	ctx := stack.NewContext([]byte{})
+	ctx.Estack.Push(a).Push(b)
+
+	v.executeOp(stack.MIN, ctx)
+
+	// Stack should have one item
+	assert.Equal(t, 1, ctx.Estack.Len())
+
+	item, err := ctx.Estack.PopInt()
+	assert.NoError(t, err)
+
+	assert.Equal(t, int64(2), item.Value().Int64())
+}
+
+func TestMaxOp(t *testing.T) {
+
+	v := VM{}
+
+	a, err := stack.NewInt(big.NewInt(10))
+	assert.NoError(t, err)
+
+	b, err := stack.NewInt(big.NewInt(2))
+	assert.NoError(t, err)
+
+	ctx := stack.NewContext([]byte{})
+	ctx.Estack.Push(a).Push(b)
+
+	v.executeOp(stack.MAX, ctx)
+
+	// Stack should have one item
+	assert.Equal(t, 1, ctx.Estack.Len())
+
+	item, err := ctx.Estack.PopInt()
+	assert.NoError(t, err)
+
+	assert.Equal(t, int64(10), item.Value().Int64())
+}
+
+func TestWithinOp(t *testing.T) {
+
+	v := VM{}
+
+	a, err := stack.NewInt(big.NewInt(5))
+	assert.NoError(t, err)
+
+	b, err := stack.NewInt(big.NewInt(2))
+	assert.NoError(t, err)
+
+	c, err := stack.NewInt(big.NewInt(10))
+	assert.NoError(t, err)
+
+	ctx := stack.NewContext([]byte{})
+	ctx.Estack.Push(a).Push(b).Push(c)
+
+	// c is the first item popped.
+	// b is the second item popped.
+	// a is the third item popped.
+	// if a is within [b, c) we place a boolean,
+	// whose value is true, on top of the evaluation
+	// stack. Otherwise we place a boolean with
+	// false value.
+	v.executeOp(stack.WITHIN, ctx)
+
+	// Stack should have one item
+	assert.Equal(t, 1, ctx.Estack.Len())
+
+	item, err := ctx.Estack.PopBoolean()
+	assert.NoError(t, err)
+
+	assert.Equal(t, true, item.Value())
+}