From 0023c4f1f68c1c423d8d3563bccff8ce92a64d9d Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Sun, 5 Apr 2020 17:34:14 +0300
Subject: [PATCH] vm: use truncated division in MOD

Mimic C#'s `%` behavior.
Related 4b44190 (#773).
---
 pkg/vm/vm.go      |  2 +-
 pkg/vm/vm_test.go | 24 ++++++++++++++++--------
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/pkg/vm/vm.go b/pkg/vm/vm.go
index 13ac42441..555deb8ce 100644
--- a/pkg/vm/vm.go
+++ b/pkg/vm/vm.go
@@ -794,7 +794,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 		a := v.estack.Pop().BigInt()
 		v.checkBigIntSize(a)
 
-		v.estack.PushVal(new(big.Int).Mod(a, b))
+		v.estack.PushVal(new(big.Int).Rem(a, b))
 
 	case opcode.SHL, opcode.SHR:
 		b := v.estack.Pop().BigInt().Int64()
diff --git a/pkg/vm/vm_test.go b/pkg/vm/vm_test.go
index e0b13920b..26cebd624 100644
--- a/pkg/vm/vm_test.go
+++ b/pkg/vm/vm_test.go
@@ -844,11 +844,10 @@ func TestMULBigResult(t *testing.T) {
 	checkVMFailed(t, vm)
 }
 
-func TestDiv(t *testing.T) {
-	prog := makeProgram(opcode.DIV)
-	runCase := func(p, q, result int64) func(t *testing.T) {
+func TestDivMod(t *testing.T) {
+	runCase := func(op opcode.Opcode, p, q, result int64) func(t *testing.T) {
 		return func(t *testing.T) {
-			vm := load(prog)
+			vm := load(makeProgram(op))
 			vm.estack.PushVal(p)
 			vm.estack.PushVal(q)
 			runVM(t, vm)
@@ -856,10 +855,19 @@ func TestDiv(t *testing.T) {
 		}
 	}
 
-	t.Run("positive/positive", runCase(5, 2, 2))
-	t.Run("positive/negative", runCase(5, -2, -2))
-	t.Run("negative/positive", runCase(-5, 2, -2))
-	t.Run("negative/negative", runCase(-5, -2, 2))
+	t.Run("DIV", func(t *testing.T) {
+		t.Run("positive/positive", runCase(opcode.DIV, 5, 2, 2))
+		t.Run("positive/negative", runCase(opcode.DIV, 5, -2, -2))
+		t.Run("negative/positive", runCase(opcode.DIV, -5, 2, -2))
+		t.Run("negative/negative", runCase(opcode.DIV, -5, -2, 2))
+	})
+
+	t.Run("MOD", func(t *testing.T) {
+		t.Run("positive/positive", runCase(opcode.MOD, 5, 2, 1))
+		t.Run("positive/negative", runCase(opcode.MOD, 5, -2, 1))
+		t.Run("negative/positive", runCase(opcode.MOD, -5, 2, -1))
+		t.Run("negative/negative", runCase(opcode.MOD, -5, -2, -1))
+	})
 
 }