vm: make (*VM).GasLimit public

VM is inherently single-threaded and replacing setter/getter methods
with public field simplifies code a bit.

pkg/core/blockchain.go

@@ -566,7 +566,7 @@ func (bc *Blockchain) storeBlock(block *block.Block) error {
 		v.LoadScriptWithFlags(tx.Script, smartcontract.All)
 		v.SetPriceGetter(getPrice)
 		if bc.config.FreeGasLimit > 0 {
-			v.SetGasLimit(bc.config.FreeGasLimit + tx.SystemFee)
+			v.GasLimit = bc.config.FreeGasLimit + tx.SystemFee
 		}
 
 		err := v.Run()

pkg/rpc/server/server.go

@@ -906,7 +906,7 @@ func (s *Server) invokescript(reqParams request.Params) (interface{}, *response.
 // result.
 func (s *Server) runScriptInVM(script []byte, tx *transaction.Transaction) *result.Invoke {
 	vm := s.chain.GetTestVM(tx)
-	vm.SetGasLimit(s.config.MaxGasInvoke)
+	vm.GasLimit = s.config.MaxGasInvoke
 	vm.LoadScriptWithFlags(script, smartcontract.All)
 	_ = vm.Run()
 	result := &result.Invoke{

pkg/vm/vm.go

@@ -78,7 +78,7 @@ type VM struct {
 	refs *refCounter
 
 	gasConsumed util.Fixed8
-	gasLimit    util.Fixed8
+	GasLimit    util.Fixed8
 
 	trigger trigger.Type
 
@@ -134,16 +134,10 @@ func (v *VM) GasConsumed() util.Fixed8 {
 	return v.gasConsumed
 }
 
-// SetGasLimit sets maximum amount of gas which v can spent.
-// If max <= 0, no limit is imposed.
-func (v *VM) SetGasLimit(max util.Fixed8) {
-	v.gasLimit = max
-}
-
 // AddGas consumes specified amount of gas. It returns true iff gas limit wasn't exceeded.
 func (v *VM) AddGas(gas util.Fixed8) bool {
 	v.gasConsumed += gas
-	return v.gasLimit == 0 || v.gasConsumed <= v.gasLimit
+	return v.GasLimit == 0 || v.gasConsumed <= v.GasLimit
 }
 
 // Estack returns the evaluation stack so interop hooks can utilize this.
@@ -520,7 +514,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 
 	if v.getPrice != nil && ctx.ip < len(ctx.prog) {
 		v.gasConsumed += v.getPrice(v, op, parameter)
-		if v.gasLimit > 0 && v.gasConsumed > v.gasLimit {
+		if v.GasLimit > 0 && v.gasConsumed > v.GasLimit {
 			panic("gas limit is exceeded")
 		}
 	}

pkg/vm/vm_test.go

@@ -90,7 +90,7 @@ func TestVM_SetPriceGetter(t *testing.T) {
 
 	t.Run("with sufficient gas limit", func(t *testing.T) {
 		v.Load(prog)
-		v.SetGasLimit(9)
+		v.GasLimit = 9
 		runVM(t, v)
 
 		require.EqualValues(t, 9, v.GasConsumed())
@@ -98,14 +98,14 @@ func TestVM_SetPriceGetter(t *testing.T) {
 
 	t.Run("with small gas limit", func(t *testing.T) {
 		v.Load(prog)
-		v.SetGasLimit(8)
+		v.GasLimit = 8
 		checkVMFailed(t, v)
 	})
 }
 
 func TestAddGas(t *testing.T) {
 	v := New()
-	v.SetGasLimit(10)
+	v.GasLimit = 10
 	require.True(t, v.AddGas(5))
 	require.True(t, v.AddGas(5))
 	require.False(t, v.AddGas(5))