accounts/abi: generic unpacking of event logs into map[string]interface{} (#18440)

Add methods that allow for the unpacking of event logs into maps (allows for agnostic unpacking of logs)

accounts/abi/abi.go

@@ -72,19 +72,39 @@ func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error) {
 }
 
 // Unpack output in v according to the abi specification
-func (abi ABI) Unpack(v interface{}, name string, output []byte) (err error) {
-	if len(output) == 0 {
+func (abi ABI) Unpack(v interface{}, name string, data []byte) (err error) {
+	if len(data) == 0 {
 		return fmt.Errorf("abi: unmarshalling empty output")
 	}
 	// since there can't be naming collisions with contracts and events,
 	// we need to decide whether we're calling a method or an event
 	if method, ok := abi.Methods[name]; ok {
-		if len(output)%32 != 0 {
-			return fmt.Errorf("abi: improperly formatted output: %s - Bytes: [%+v]", string(output), output)
+		if len(data)%32 != 0 {
+			return fmt.Errorf("abi: improperly formatted output: %s - Bytes: [%+v]", string(data), data)
 		}
-		return method.Outputs.Unpack(v, output)
-	} else if event, ok := abi.Events[name]; ok {
-		return event.Inputs.Unpack(v, output)
+		return method.Outputs.Unpack(v, data)
+	}
+	if event, ok := abi.Events[name]; ok {
+		return event.Inputs.Unpack(v, data)
+	}
+	return fmt.Errorf("abi: could not locate named method or event")
+}
+
+// UnpackIntoMap unpacks a log into the provided map[string]interface{}
+func (abi ABI) UnpackIntoMap(v map[string]interface{}, name string, data []byte) (err error) {
+	if len(data) == 0 {
+		return fmt.Errorf("abi: unmarshalling empty output")
+	}
+	// since there can't be naming collisions with contracts and events,
+	// we need to decide whether we're calling a method or an event
+	if method, ok := abi.Methods[name]; ok {
+		if len(data)%32 != 0 {
+			return fmt.Errorf("abi: improperly formatted output")
+		}
+		return method.Outputs.UnpackIntoMap(v, data)
+	}
+	if event, ok := abi.Events[name]; ok {
+		return event.Inputs.UnpackIntoMap(v, data)
 	}
 	return fmt.Errorf("abi: could not locate named method or event")
 }

accounts/abi/argument.go

@@ -102,6 +102,16 @@ func (arguments Arguments) Unpack(v interface{}, data []byte) error {
 	return arguments.unpackAtomic(v, marshalledValues[0])
 }
 
+// UnpackIntoMap performs the operation hexdata -> mapping of argument name to argument value
+func (arguments Arguments) UnpackIntoMap(v map[string]interface{}, data []byte) error {
+	marshalledValues, err := arguments.UnpackValues(data)
+	if err != nil {
+		return err
+	}
+
+	return arguments.unpackIntoMap(v, marshalledValues)
+}
+
 // unpack sets the unmarshalled value to go format.
 // Note the dst here must be settable.
 func unpack(t *Type, dst interface{}, src interface{}) error {
@@ -160,6 +170,19 @@ func unpack(t *Type, dst interface{}, src interface{}) error {
 	return nil
 }
 
+// unpackIntoMap unpacks marshalledValues into the provided map[string]interface{}
+func (arguments Arguments) unpackIntoMap(v map[string]interface{}, marshalledValues []interface{}) error {
+	// Make sure map is not nil
+	if v == nil {
+		return fmt.Errorf("abi: cannot unpack into a nil map")
+	}
+
+	for i, arg := range arguments.NonIndexed() {
+		v[arg.Name] = marshalledValues[i]
+	}
+	return nil
+}
+
 // unpackAtomic unpacks ( hexdata -> go ) a single value
 func (arguments Arguments) unpackAtomic(v interface{}, marshalledValues interface{}) error {
 	if arguments.LengthNonIndexed() == 0 {

accounts/abi/bind/base.go

@@ -340,6 +340,22 @@ func (c *BoundContract) UnpackLog(out interface{}, event string, log types.Log)
 	return parseTopics(out, indexed, log.Topics[1:])
 }
 
+// UnpackLogIntoMap unpacks a retrieved log into the provided map.
+func (c *BoundContract) UnpackLogIntoMap(out map[string]interface{}, event string, log types.Log) error {
+	if len(log.Data) > 0 {
+		if err := c.abi.UnpackIntoMap(out, event, log.Data); err != nil {
+			return err
+		}
+	}
+	var indexed abi.Arguments
+	for _, arg := range c.abi.Events[event].Inputs {
+		if arg.Indexed {
+			indexed = append(indexed, arg)
+		}
+	}
+	return parseTopicsIntoMap(out, indexed, log.Topics[1:])
+}
+
 // ensureContext is a helper method to ensure a context is not nil, even if the
 // user specified it as such.
 func ensureContext(ctx context.Context) context.Context {

accounts/abi/bind/topics.go

@@ -17,6 +17,7 @@
 package bind
 
 import (
+	"encoding/binary"
 	"errors"
 	"fmt"
 	"math/big"
@@ -191,3 +192,50 @@ func parseTopics(out interface{}, fields abi.Arguments, topics []common.Hash) er
 	}
 	return nil
 }
+
+// parseTopicsIntoMap converts the indexed topic field-value pairs into map key-value pairs
+func parseTopicsIntoMap(out map[string]interface{}, fields abi.Arguments, topics []common.Hash) error {
+	// Sanity check that the fields and topics match up
+	if len(fields) != len(topics) {
+		return errors.New("topic/field count mismatch")
+	}
+	// Iterate over all the fields and reconstruct them from topics
+	for _, arg := range fields {
+		if !arg.Indexed {
+			return errors.New("non-indexed field in topic reconstruction")
+		}
+
+		switch arg.Type.T {
+		case abi.BoolTy:
+			out[arg.Name] = topics[0][common.HashLength-1] == 1
+		case abi.IntTy, abi.UintTy:
+			num := new(big.Int).SetBytes(topics[0][:])
+			out[arg.Name] = num
+		case abi.AddressTy:
+			var addr common.Address
+			copy(addr[:], topics[0][common.HashLength-common.AddressLength:])
+			out[arg.Name] = addr
+		case abi.HashTy:
+			out[arg.Name] = topics[0]
+		case abi.FixedBytesTy:
+			out[arg.Name] = topics[0][:]
+		case abi.StringTy, abi.BytesTy, abi.SliceTy, abi.ArrayTy:
+			// Array types (including strings and bytes) have their keccak256 hashes stored in the topic- not a hash
+			// whose bytes can be decoded to the actual value- so the best we can do is retrieve that hash
+			out[arg.Name] = topics[0]
+		case abi.FunctionTy:
+			if garbage := binary.BigEndian.Uint64(topics[0][0:8]); garbage != 0 {
+				return fmt.Errorf("bind: got improperly encoded function type, got %v", topics[0].Bytes())
+			}
+			var tmp [24]byte
+			copy(tmp[:], topics[0][8:32])
+			out[arg.Name] = tmp
+		default: // Not handling tuples
+			return fmt.Errorf("unsupported indexed type: %v", arg.Type)
+		}
+
+		topics = topics[1:]
+	}
+
+	return nil
+}

accounts/abi/unpack.go

@@ -269,7 +269,7 @@ func lengthPrefixPointsTo(index int, output []byte) (start int, length int, err
 	totalSize.Add(totalSize, bigOffsetEnd)
 	totalSize.Add(totalSize, lengthBig)
 	if totalSize.BitLen() > 63 {
-		return 0, 0, fmt.Errorf("abi length larger than int64: %v", totalSize)
+		return 0, 0, fmt.Errorf("abi: length larger than int64: %v", totalSize)
 	}
 
 	if totalSize.Cmp(outputLength) > 0 {