core: calculate a price of System.Storage.Put correctly

It also depends on the item already stored by key.

pkg/core/gas_price.go

@@ -24,7 +24,11 @@ func getPrice(v *vm.VM, op opcode.Opcode, parameter []byte) util.Fixed8 {
 	switch op {
 	case opcode.SYSCALL:
 		interopID := vm.GetInteropID(parameter)
-		return getSyscallPrice(v, interopID)
+		ifunc := v.GetInteropByID(interopID)
+		if ifunc != nil && ifunc.Price > 0 {
+			return toFixed8(int64(ifunc.Price))
+		}
+		return toFixed8(1)
 	default:
 		return toFixed8(1)
 	}
@@ -33,30 +37,3 @@ func getPrice(v *vm.VM, op opcode.Opcode, parameter []byte) util.Fixed8 {
 func toFixed8(n int64) util.Fixed8 {
 	return util.Fixed8(n * interopGasRatio)
 }
-
-// getSyscallPrice returns cost of executing syscall with provided id.
-// Is SYSCALL is not found, cost is 1.
-func getSyscallPrice(v *vm.VM, id uint32) util.Fixed8 {
-	ifunc := v.GetInteropByID(id)
-	if ifunc != nil && ifunc.Price > 0 {
-		return toFixed8(int64(ifunc.Price))
-	}
-
-	const (
-		systemStoragePut   = 0x84183fe6 // System.Storage.Put
-		systemStoragePutEx = 0x3a9be173 // System.Storage.PutEx
-		neoStoragePut      = 0xf541a152 // Neo.Storage.Put
-	)
-
-	estack := v.Estack()
-
-	switch id {
-	case systemStoragePut, systemStoragePutEx, neoStoragePut:
-		// price for storage PUT is 1 GAS per 1 KiB
-		keySize := len(estack.Peek(1).Bytes())
-		valSize := len(estack.Peek(2).Bytes())
-		return util.Fixed8FromInt64(int64((keySize+valSize-1)/1024 + 1))
-	default:
-		return util.Fixed8FromInt64(1)
-	}
-}

pkg/core/gas_price_test.go

@@ -1,54 +0,0 @@
-package core
-
-import (
-	"testing"
-
-	"github.com/nspcc-dev/neo-go/pkg/core/dao"
-	"github.com/nspcc-dev/neo-go/pkg/core/storage"
-	"github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger"
-	"github.com/nspcc-dev/neo-go/pkg/util"
-	"github.com/nspcc-dev/neo-go/pkg/vm"
-	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
-	"github.com/stretchr/testify/require"
-)
-
-// These tests are taken from C# code
-// https://github.com/neo-project/neo/blob/master-2.x/neo.UnitTests/UT_InteropPrices.cs#L245
-func TestGetPrice(t *testing.T) {
-	bc := newTestChain(t)
-	defer bc.Close()
-	sdao := dao.NewSimple(storage.NewMemoryStore())
-	systemInterop := bc.newInteropContext(trigger.Application, sdao, nil, nil)
-
-	v := SpawnVM(systemInterop)
-	v.SetPriceGetter(getPrice)
-
-	t.Run("System.Storage.Put", func(t *testing.T) {
-		// System.Storage.Put: e63f1884 (requires push key and value)
-		v.Load([]byte{byte(opcode.PUSH3), byte(opcode.PUSH3), byte(opcode.PUSH0),
-			byte(opcode.SYSCALL), 0xe6, 0x3f, 0x18, 0x84})
-		require.NoError(t, v.StepInto()) // push 03 (length 1)
-		require.NoError(t, v.StepInto()) // push 03 (length 1)
-		require.NoError(t, v.StepInto()) // push 00
-
-		checkGas(t, util.Fixed8FromInt64(1), v)
-	})
-
-	t.Run("System.Storage.PutEx", func(t *testing.T) {
-		// System.Storage.PutEx: 73e19b3a (requires push key and value)
-		v.Load([]byte{byte(opcode.PUSH3), byte(opcode.PUSH3), byte(opcode.PUSH0),
-			byte(opcode.SYSCALL), 0x73, 0xe1, 0x9b, 0x3a})
-		require.NoError(t, v.StepInto()) // push 03 (length 1)
-		require.NoError(t, v.StepInto()) // push 03 (length 1)
-		require.NoError(t, v.StepInto()) // push 00
-
-		checkGas(t, util.Fixed8FromInt64(1), v)
-	})
-}
-
-func checkGas(t *testing.T, expected util.Fixed8, v *vm.VM) {
-	op, par, err := v.Context().Next()
-
-	require.NoError(t, err)
-	require.Equal(t, expected, getPrice(v, op, par))
-}

pkg/core/interop_neo.go

@@ -26,6 +26,8 @@ const (
 	MaxContractStringLen = 252
 )
 
+var errGasLimitExceeded = errors.New("gas limit exceeded")
+
 // storageFind finds stored key-value pair.
 func storageFind(ic *interop.Context, v *vm.VM) error {
 	stcInterface := v.Estack().Pop().Value()
@@ -71,7 +73,7 @@ func createContractStateFromVM(ic *interop.Context, v *vm.VM) (*state.Contract,
 		return nil, errors.New("manifest is too big")
 	}
 	if !v.AddGas(util.Fixed8(StoragePrice * (len(script) + len(manifestBytes)))) {
-		return nil, errors.New("gas limit exceeded")
+		return nil, errGasLimitExceeded
 	}
 	var m manifest.Manifest
 	r := io.NewBinReaderFromBuf(manifestBytes)

pkg/core/interop_system.go

@@ -332,7 +332,7 @@ func storageGetReadOnlyContext(ic *interop.Context, v *vm.VM) error {
 	return nil
 }
 
-func putWithContextAndFlags(ic *interop.Context, stc *StorageContext, key []byte, value []byte, isConst bool) error {
+func putWithContextAndFlags(ic *interop.Context, v *vm.VM, stc *StorageContext, key []byte, value []byte, isConst bool) error {
 	if len(key) > MaxStorageKeyLen {
 		return errors.New("key is too big")
 	}
@@ -350,6 +350,13 @@ func putWithContextAndFlags(ic *interop.Context, stc *StorageContext, key []byte
 	if si.IsConst {
 		return errors.New("storage item exists and is read-only")
 	}
+	sizeInc := 1
+	if len(value) > len(si.Value) {
+		sizeInc = len(value) - len(si.Value)
+	}
+	if !v.AddGas(util.Fixed8(sizeInc) * StoragePrice) {
+		return errGasLimitExceeded
+	}
 	si.Value = value
 	si.IsConst = isConst
 	return ic.DAO.PutStorageItem(stc.ScriptHash, key, si)
@@ -368,7 +375,7 @@ func storagePutInternal(ic *interop.Context, v *vm.VM, getFlag bool) error {
 	if getFlag {
 		flag = int(v.Estack().Pop().BigInt().Int64())
 	}
-	return putWithContextAndFlags(ic, stc, key, value, flag == 1)
+	return putWithContextAndFlags(ic, v, stc, key, value, flag == 1)
 }
 
 // storagePut puts key-value pair into the storage.