core: added a new RemovedLogEvent

When a chain reorganisation occurs we collect the logs that were deleted
during the chain reorganisation. The removed logs are posted to the
event mux indicating that those were deleted during the reorg.

core/blockchain_test.go

@@ -963,3 +963,46 @@ func TestChainTxReorgs(t *testing.T) {
 		}
 	}
 }
+
+func TestLogReorgs(t *testing.T) {
+	params.MinGasLimit = big.NewInt(125000)      // Minimum the gas limit may ever be.
+	params.GenesisGasLimit = big.NewInt(3141592) // Gas limit of the Genesis block.
+
+	var (
+		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
+		db, _   = ethdb.NewMemDatabase()
+		// this code generates a log
+		code = common.Hex2Bytes("60606040525b7f24ec1d3ff24c2f6ff210738839dbc339cd45a5294d85c79361016243157aae7b60405180905060405180910390a15b600a8060416000396000f360606040526008565b00")
+	)
+	genesis := WriteGenesisBlockForTesting(db,
+		GenesisAccount{addr1, big.NewInt(10000000000000)},
+	)
+
+	evmux := &event.TypeMux{}
+	blockchain, _ := NewBlockChain(db, FakePow{}, evmux)
+
+	subs := evmux.Subscribe(RemovedLogEvent{})
+	chain, _ := GenerateChain(genesis, db, 2, func(i int, gen *BlockGen) {
+		if i == 1 {
+			tx, err := types.NewContractCreation(gen.TxNonce(addr1), new(big.Int), big.NewInt(1000000), new(big.Int), code).SignECDSA(key1)
+			if err != nil {
+				t.Fatalf("failed to create tx: %v", err)
+			}
+			gen.AddTx(tx)
+		}
+	})
+	if _, err := blockchain.InsertChain(chain); err != nil {
+		t.Fatalf("failed to insert chain: %v", err)
+	}
+
+	chain, _ = GenerateChain(genesis, db, 3, func(i int, gen *BlockGen) {})
+	if _, err := blockchain.InsertChain(chain); err != nil {
+		t.Fatalf("failed to insert forked chain: %v", err)
+	}
+
+	ev := <-subs.Chan()
+	if len(ev.Data.(RemovedLogEvent).Logs) == 0 {
+		t.Error("expected logs")
+	}
+}