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/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
+}