implement transfers as logs

internal/ethapi/api.go

@@ -1199,7 +1199,6 @@ type blockResult struct {
 type callResult struct {
 	ReturnValue hexutil.Bytes  `json:"return"`
 	Logs        []*types.Log   `json:"logs"`
-	Transfers   []transfer     `json:"transfers,omitempty"`
 	GasUsed     hexutil.Uint64 `json:"gasUsed"`
 	Status      hexutil.Uint64 `json:"status"`
 	Error       string         `json:"error,omitempty"`
@@ -1278,12 +1277,9 @@ func (s *BlockChainAPI) MulticallV1(ctx context.Context, opts multicallOpts, blo
 		}
 		gasUsed := uint64(0)
 		for i, call := range block.Calls {
-			// Hack to get logs from statedb which stores logs by txhash.
-			txhash := common.BigToHash(big.NewInt(int64(i)))
-			state.SetTxContext(txhash, i)
-			vmConfig := &vm.Config{NoBaseFee: true}
-			if opts.TraceTransfers {
-				vmConfig.Tracer = newTracer()
+			vmConfig := &vm.Config{
+				NoBaseFee: true,
+				Tracer:    newTracer(opts.TraceTransfers, blockContext.BlockNumber.Uint64(), hash, common.Hash{}, uint(i)),
 			}
 			result, err := doCall(ctx, s.b, call, state, header, timeout, gp, &blockContext, vmConfig, precompiles, opts.Validation)
 			if err != nil {
@@ -1294,16 +1290,8 @@ func (s *BlockChainAPI) MulticallV1(ctx context.Context, opts multicallOpts, blo
 			if len(result.Revert()) > 0 {
 				result.Err = newRevertError(result)
 			}
-			logs := state.GetLogs(txhash, blockContext.BlockNumber.Uint64(), common.Hash{})
-			// Clear the garbage txhash that was filled in.
-			for _, l := range logs {
-				l.TxHash = common.Hash{}
-			}
-			var transfers []transfer
-			if opts.TraceTransfers {
-				transfers = vmConfig.Tracer.(*tracer).Transfers()
-			}
-			callRes := callResult{ReturnValue: result.Return(), Logs: logs, Transfers: transfers, GasUsed: hexutil.Uint64(result.UsedGas)}
+			logs := vmConfig.Tracer.(*tracer).Logs()
+			callRes := callResult{ReturnValue: result.Return(), Logs: logs, GasUsed: hexutil.Uint64(result.UsedGas)}
 			if result.Failed() {
 				callRes.Status = hexutil.Uint64(types.ReceiptStatusFailed)
 				callRes.Error = result.Err.Error()

internal/ethapi/api_test.go

@@ -712,7 +712,6 @@ func TestMulticallV1(t *testing.T) {
 		Logs        []types.Log
 		GasUsed     string
 		Status      string
-		Transfers   []transfer
 	}
 	type blockRes struct {
 		Number string
@@ -1010,6 +1009,7 @@ func TestMulticallV1(t *testing.T) {
 						Topics:      []common.Hash{common.HexToHash("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")},
 						BlockNumber: 11,
 						Data:        []byte{},
+						BlockHash:   hex2Hash(n11hash),
 					}},
 					GasUsed: "0x5508",
 					Status:  "0x1",
@@ -1175,18 +1175,28 @@ func TestMulticallV1(t *testing.T) {
 				Calls: []callRes{{
 					ReturnValue: "0x",
 					GasUsed:     "0xd984",
-					Transfers: []transfer{
-						{
-							From:  accounts[0].addr,
-							To:    randomAccounts[0].addr,
-							Value: big.NewInt(50),
+					Logs: []types.Log{{
+						Address: common.Address{},
+						Topics: []common.Hash{
+							transferTopic,
+							accounts[0].addr.Hash(),
+							randomAccounts[0].addr.Hash(),
+						},
+						Data:        common.BigToHash(big.NewInt(50)).Bytes(),
+						BlockNumber: 11,
+						BlockHash:   hex2Hash(n11hash),
 					}, {
-							From:  randomAccounts[0].addr,
-							To:    randomAccounts[1].addr,
-							Value: big.NewInt(100),
+						Address: common.Address{},
+						Topics: []common.Hash{
+							transferTopic,
+							randomAccounts[0].addr.Hash(),
+							randomAccounts[1].addr.Hash(),
 						},
-					},
-					Logs:   []types.Log{},
+						Data:        common.BigToHash(big.NewInt(100)).Bytes(),
+						BlockNumber: 11,
+						BlockHash:   hex2Hash(n11hash),
+						Index:       1,
+					}},
 					Status: "0x1",
 				}},
 			}},
@@ -1532,3 +1542,7 @@ func TestRPCMarshalBlock(t *testing.T) {
 		}
 	}
 }
+
+func hex2Hash(s string) common.Hash {
+	return common.BytesToHash(common.FromHex(s))
+}

internal/ethapi/transfertracer.go

@@ -17,38 +17,57 @@
 package ethapi
 
 import (
+	"fmt"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 )
 
-type callLog struct {
-	Address common.Address `json:"address"`
-	Topics  []common.Hash  `json:"topics"`
-	Data    hexutil.Bytes  `json:"data"`
-}
+// keccak256("Transfer(address,address,uint256)")
+var transferTopic = common.HexToHash("ddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef")
 
-type transfer struct {
-	From  common.Address `json:"from"`
-	To    common.Address `json:"to"`
-	Value *big.Int       `json:"value"`
-}
-
-// tracer is a simple tracer that records all ether transfers.
-// This includes tx value, call value, and self destructs.
+// tracer is a simple tracer that records all logs and
+// ether transfers. Transfers are recorded as if they
+// were logs. Transfer events include:
+// - tx value
+// - call value
+// - self destructs
+//
+// The log format for a transfer is:
+// - address: 0x0000000000000000000000000000000000000000
+// - data: Value
+// - topics:
+//   - Transfer(address,address,uint256)
+//   - Sender address
+//   - Recipient address
+//
+// TODO: embed noopTracer
 type tracer struct {
-	transfers []transfer
+	logs           []*types.Log
+	traceTransfers bool
+	// TODO: replace with tracers.Context once extended tracer PR is merged.
+	blockNumber uint64
+	blockHash   common.Hash
+	txHash      common.Hash
+	txIdx       uint
 }
 
-func newTracer() *tracer {
-	return &tracer{transfers: make([]transfer, 0)}
+func newTracer(traceTransfers bool, blockNumber uint64, blockHash, txHash common.Hash, txIdx uint) *tracer {
+	return &tracer{
+		logs:           make([]*types.Log, 0),
+		traceTransfers: traceTransfers,
+		blockNumber:    blockNumber,
+		blockHash:      blockHash,
+		txHash:         txHash,
+		txIdx:          txIdx,
+	}
 }
 
 func (t *tracer) CaptureStart(env *vm.EVM, from common.Address, to common.Address, create bool, input []byte, gas uint64, value *big.Int) {
 	if value.Cmp(common.Big0) > 0 {
-		t.transfers = append(t.transfers, transfer{From: from, To: to, Value: value})
+		t.captureTransfer(from, to, value)
 	}
 }
 
@@ -56,6 +75,34 @@ func (t *tracer) CaptureEnd(output []byte, gasUsed uint64, err error) {
 }
 
 func (t *tracer) CaptureState(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, rData []byte, depth int, err error) {
+	// skip if the previous op caused an error
+	if err != nil {
+		return
+	}
+	// TODO: Use OnLog instead of CaptureState once extended tracer PR is merged.
+	switch op {
+	case vm.LOG0, vm.LOG1, vm.LOG2, vm.LOG3, vm.LOG4:
+		size := int(op - vm.LOG0)
+
+		stack := scope.Stack
+		stackData := stack.Data()
+
+		// Don't modify the stack
+		mStart := stackData[len(stackData)-1]
+		mSize := stackData[len(stackData)-2]
+		topics := make([]common.Hash, size)
+		for i := 0; i < size; i++ {
+			topic := stackData[len(stackData)-2-(i+1)]
+			topics[i] = common.Hash(topic.Bytes32())
+		}
+
+		data, err := getMemoryCopyPadded(scope.Memory, int64(mStart.Uint64()), int64(mSize.Uint64()))
+		if err != nil {
+			// mSize was unrealistically large
+			return
+		}
+		t.captureLog(scope.Contract.Address(), topics, data)
+	}
 }
 
 func (t *tracer) CaptureFault(pc uint64, op vm.OpCode, gas, cost uint64, scope *vm.ScopeContext, depth int, err error) {
@@ -63,8 +110,8 @@ func (t *tracer) CaptureFault(pc uint64, op vm.OpCode, gas, cost uint64, scope *
 
 func (t *tracer) CaptureEnter(typ vm.OpCode, from common.Address, to common.Address, input []byte, gas uint64, value *big.Int) {
 	toCopy := to
-	if value.Cmp(common.Big0) > 0 {
-		t.transfers = append(t.transfers, transfer{From: from, To: toCopy, Value: value})
+	if value != nil && value.Cmp(common.Big0) > 0 {
+		t.captureTransfer(from, toCopy, value)
 	}
 }
 
@@ -76,6 +123,50 @@ func (t *tracer) CaptureTxStart(gasLimit uint64) {}
 
 func (t *tracer) CaptureTxEnd(restGas uint64) {}
 
-func (t *tracer) Transfers() []transfer {
-	return t.transfers
+func (t *tracer) captureLog(address common.Address, topics []common.Hash, data []byte) {
+	t.logs = append(t.logs, &types.Log{
+		Address:     address,
+		Topics:      topics,
+		Data:        data,
+		BlockNumber: t.blockNumber,
+		BlockHash:   t.blockHash,
+		TxHash:      t.txHash,
+		TxIndex:     t.txIdx,
+		Index:       uint(len(t.logs)),
+	})
+}
+
+func (t *tracer) captureTransfer(from, to common.Address, value *big.Int) {
+	if !t.traceTransfers {
+		return
+	}
+	topics := []common.Hash{
+		transferTopic,
+		common.BytesToHash(from.Bytes()),
+		common.BytesToHash(to.Bytes()),
+	}
+	t.captureLog(common.Address{}, topics, common.BigToHash(value).Bytes())
+}
+
+func (t *tracer) Logs() []*types.Log {
+	return t.logs
+}
+
+// TODO: remove once extended tracer PR is merged.
+func getMemoryCopyPadded(m *vm.Memory, offset, size int64) ([]byte, error) {
+	if offset < 0 || size < 0 {
+		return nil, fmt.Errorf("offset or size must not be negative")
+	}
+	if int(offset+size) < m.Len() { // slice fully inside memory
+		return m.GetCopy(offset, size), nil
+	}
+	paddingNeeded := int(offset+size) - m.Len()
+	if paddingNeeded > 1024*1024 {
+		return nil, fmt.Errorf("reached limit for padding memory slice: %d", paddingNeeded)
+	}
+	cpy := make([]byte, size)
+	if overlap := int64(m.Len()) - offset; overlap > 0 {
+		copy(cpy, m.GetPtr(offset, overlap))
+	}
+	return cpy, nil
 }