ETH源码阅读(TxLookupEntry)

1.数据结构

TxLookupEntry：一个交易所对应的区块讯息

// TxLookupEntry is a positional metadata to help looking up the data content of
// a transaction or receipt given only its hash.
type TxLookupEntry struct {
    BlockHash  common.Hash  //区块hash
    BlockIndex uint64          //区块高度
    Index      uint64           //交易在区块中的索引
}

2.源码

TxLookupEntry在db中存储的key:l + hash(交易hash)

//l + hash
// txLookupKey = txLookupPrefix + hash
func txLookupKey(hash common.Hash) []byte {
    return append(txLookupPrefix, hash.Bytes()...)
}

通过交易hash从db读取TxLookupEntry

go-ethereum/core/rawdb/accessors_indexes.go

// ReadTxLookupEntry retrieves the positional metadata associated with a transaction
// hash to allow retrieving the transaction or receipt by hash.
func ReadTxLookupEntry(db DatabaseReader, hash common.Hash) (common.Hash, uint64, uint64) {
    data, _ := db.Get(txLookupKey(hash)) //通过key从db读取出data
    if len(data) == 0 {
        return common.Hash{}, 0, 0
    }
    var entry TxLookupEntry
    if err := rlp.DecodeBytes(data, &entry); err != nil { //将data解析成TxLookupEntry
        log.Error("Invalid transaction lookup entry RLP", "hash", hash, "err", err)
        return common.Hash{}, 0, 0
    }
    return entry.BlockHash, entry.BlockIndex, entry.Index
}