From 9402540c3a3ca471bfd6a301d6764f872cf18cc0 Mon Sep 17 00:00:00 2001
From: dauTT <30392990+dauTT@users.noreply.github.com>
Date: Fri, 29 Mar 2019 20:35:16 +0100
Subject: [PATCH] Implemented LT, GT opcode (#259)

* Implemented LT, GT opcode
---
 pkg/vm/stack/Int.go         | 14 +++++++++
 pkg/vm/vm_ops.go            |  3 ++
 pkg/vm/vm_ops_maths.go      | 32 ++++++++++++++++++++
 pkg/vm/vm_ops_maths_test.go | 58 +++++++++++++++++++++++++++++++++++++
 4 files changed, 107 insertions(+)

diff --git a/pkg/vm/stack/Int.go b/pkg/vm/stack/Int.go
index 52e6240d4..3226904ee 100644
--- a/pkg/vm/stack/Int.go
+++ b/pkg/vm/stack/Int.go
@@ -111,3 +111,17 @@ func (i *Int) Abs() (*Int, error) {
 
 	return b, nil
 }
+
+// Lt returns a bool value from the comparison of two integers, a and b.
+// value is true if a < b.
+// value is false if a >= b.
+func (i *Int) Lt(s *Int) bool {
+	return i.Value().Cmp(s.Value()) == -1
+}
+
+// Gt returns a bool value from the comparison of two integers, a and b.
+// value is true if a > b.
+// value is false if a <= b.
+func (i *Int) Gt(s *Int) bool {
+	return i.Value().Cmp(s.Value()) == 1
+}
diff --git a/pkg/vm/vm_ops.go b/pkg/vm/vm_ops.go
index cef46a199..1854b1634 100644
--- a/pkg/vm/vm_ops.go
+++ b/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.LT:          Lt,
+	stack.GT:          Gt,
 	stack.SHR:         Shr,
 	stack.SHL:         Shl,
 	stack.INC:         Inc,
diff --git a/pkg/vm/vm_ops_maths.go b/pkg/vm/vm_ops_maths.go
index 5cbe0552a..7abd73b9f 100644
--- a/pkg/vm/vm_ops_maths.go
+++ b/pkg/vm/vm_ops_maths.go
@@ -300,6 +300,38 @@ func Shr(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation, rst
 	return NONE, nil
 }
 
+// Lt pops two integers, a and b, off of the stack and pushes a boolean the stack
+// whose value is true if a's value is less than b's value.
+// Returns an error if either items cannot be casted to an integer
+func Lt(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 := operandB.Lt(operandA)
+
+	ctx.Estack.Push(stack.NewBoolean(res))
+
+	return NONE, nil
+}
+
+// Gt pops two integers, a and b, off of the stack and pushes a boolean the stack
+// whose value is true if a's value is greated than b's value.
+// Returns an error if either items cannot be casted to an integer
+func Gt(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 := operandB.Gt(operandA)
+
+	ctx.Estack.Push(stack.NewBoolean(res))
+
+	return NONE, 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()
diff --git a/pkg/vm/vm_ops_maths_test.go b/pkg/vm/vm_ops_maths_test.go
index b703751be..29d843999 100644
--- a/pkg/vm/vm_ops_maths_test.go
+++ b/pkg/vm/vm_ops_maths_test.go
@@ -394,3 +394,61 @@ func TestShrOp(t *testing.T) {
 
 	assert.Equal(t, int64(2), item.Value().Int64())
 }
+
+func TestLtOp(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)
+
+	// b is the first item pop.
+	// a is the second item pop.
+	// we perform a < b and place
+	// the result on top of the evaluation
+	// stack
+	v.executeOp(stack.LT, 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, false, item.Value())
+}
+
+func TestGtOp(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)
+
+	// b is the first item pop.
+	// a is the second item pop.
+	// we perform a > b and place
+	// the result on top of the evaluation
+	// stack
+	v.executeOp(stack.GT, 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())
+}