adding the method EventById and its test

accounts/abi/abi.go

@@ -21,6 +21,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+
+	"github.com/ethereum/go-ethereum/common"
 )
 
 // The ABI holds information about a contract's context and available
@@ -145,3 +147,14 @@ func (abi *ABI) MethodById(sigdata []byte) (*Method, error) {
 	}
 	return nil, fmt.Errorf("no method with id: %#x", sigdata[:4])
 }
+
+// EventById looks up a event by the topic hash
+// returns nil if none found
+func (abi *ABI) EventById(topic common.Hash) (*Event, error) {
+	for _, event := range abi.Events {
+		if event.Id() == topic {
+			return &event, nil
+		}
+	}
+	return nil, fmt.Errorf("no event with topic: %#x", topic.Hex())
+}

accounts/abi/abi_test.go

@@ -745,3 +745,30 @@ func TestABI_MethodById(t *testing.T) {
 		t.Errorf("Expected error, nil is short to decode data")
 	}
 }
+
+func TestABI_EventById(t *testing.T) {
+	const abiJSON = `[
+		{"type":"event","name":"received","anonymous":false,"inputs":[
+			{"indexed":false,"name":"sender","type":"address"},
+			{"indexed":false,"name":"amount","type":"uint256"},
+			{"indexed":false,"name":"memo","type":"bytes"}
+			]
+		}]`
+
+	abi, err := JSON(strings.NewReader(abiJSON))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	topic := "received(address,uint256,bytes)"
+	topicID := crypto.Keccak256Hash([]byte(topic))
+
+	event, err := abi.EventById(topicID)
+	if err != nil {
+		t.Fatalf("Failed to look up ABI event: %v", err)
+	}
+
+	if event.Id() != topicID {
+		t.Errorf("topic %v (id %v) not 'findable' by id in ABI", topic, topicID)
+	}
+}