path: root/core/types/log.go

// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package types

import (
    "io"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/common/hexutil"
    "github.com/ethereum/go-ethereum/rlp"
)

//go:generate gencodec -type Log -field-override logMarshaling -out gen_log_json.go

// Log represents a contract log event. These events are generated by the LOG opcode and
// stored/indexed by the node.
type Log struct {
    // Consensus fields:
    // address of the contract that generated the event
    Address common.Address `json:"address" gencodec:"required"`
    // list of topics provided by the contract.
    Topics []common.Hash `json:"topics" gencodec:"required"`
    // supplied by the contract, usually ABI-encoded
    Data []byte `json:"data" gencodec:"required"`

    // Derived fields. These fields are filled in by the node
    // but not secured by consensus.
    // block in which the transaction was included
    BlockNumber uint64 `json:"blockNumber"`
    // hash of the transaction
    TxHash common.Hash `json:"transactionHash" gencodec:"required"`
    // index of the transaction in the block
    TxIndex uint `json:"transactionIndex" gencodec:"required"`
    // hash of the block in which the transaction was included
    BlockHash common.Hash `json:"blockHash"`
    // index of the log in the block
    Index uint `json:"logIndex" gencodec:"required"`

    // The Removed field is true if this log was reverted due to a chain reorganisation.
    // You must pay attention to this field if you receive logs through a filter query.
    Removed bool `json:"removed"`
}

type logMarshaling struct {
    Data        hexutil.Bytes
    BlockNumber hexutil.Uint64
    TxIndex     hexutil.Uint
    Index       hexutil.Uint
}

type rlpLog struct {
    Address common.Address
    Topics  []common.Hash
    Data    []byte
}

// rlpStorageLog is the storage encoding of a log.
type rlpStorageLog rlpLog

// legacyRlpStorageLog is the previous storage encoding of a log including some redundant fields.
type legacyRlpStorageLog struct {
    Address     common.Address
    Topics      []common.Hash
    Data        []byte
    BlockNumber uint64
    TxHash      common.Hash
    TxIndex     uint
    BlockHash   common.Hash
    Index       uint
}

// EncodeRLP implements rlp.Encoder.
func (l *Log) EncodeRLP(w io.Writer) error {
    return rlp.Encode(w, rlpLog{Address: l.Address, Topics: l.Topics, Data: l.Data})
}

// DecodeRLP implements rlp.Decoder.
func (l *Log) DecodeRLP(s *rlp.Stream) error {
    var dec rlpLog
    err := s.Decode(&dec)
    if err == nil {
        l.Address, l.Topics, l.Data = dec.Address, dec.Topics, dec.Data
    }
    return err
}

// LogForStorage is a wrapper around a Log that flattens and parses the entire content of
// a log including non-consensus fields.
type LogForStorage Log

// EncodeRLP implements rlp.Encoder.
func (l *LogForStorage) EncodeRLP(w io.Writer) error {
    return rlp.Encode(w, rlpStorageLog{
        Address: l.Address,
        Topics:  l.Topics,
        Data:    l.Data,
    })
}

// DecodeRLP implements rlp.Decoder.
//
// Note some redundant fields(e.g. block number, tx hash etc) will be assembled later.
func (l *LogForStorage) DecodeRLP(s *rlp.Stream) error {
    blob, err := s.Raw()
    if err != nil {
        return err
    }
    var dec rlpStorageLog
    err = rlp.DecodeBytes(blob, &dec)
    if err == nil {
        *l = LogForStorage{
            Address: dec.Address,
            Topics:  dec.Topics,
            Data:    dec.Data,
        }
    } else {
        // Try to decode log with previous definition.
        var dec legacyRlpStorageLog
        err = rlp.DecodeBytes(blob, &dec)
        if err == nil {
            *l = LogForStorage{
                Address: dec.Address,
                Topics:  dec.Topics,
                Data:    dec.Data,
            }
        }
    }
    return err
}