1. 交易的签名
  2. 理解收据receipt
  3. 理解区块
  4. 理解交易
  5. blockchain核心
  6. forkId 解读
  7. oracle 原理和实现
  8. 布隆过滤器原理
  9. TxList 解读
  10. 交易池分析
  11. MPT树
  12. 区块同步
  13. geth源码学习——介绍
  14. How Geth starts its server

核心结构

收据主要包括交易类型、交易是否成功的状态码、交易是否成功的编码、直到这笔交易区块消耗的 gas、和布隆过滤器。为了方便处理交易，也添加了交易的信息，包括交易哈希、合约地址和消耗的 gas。为了检查交易和收据是否匹配，提供了区块哈希、区块高度和交易在区块中的索引。

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// Receipt represents the results of a transaction.
type Receipt struct {
   // Consensus fields: These fields are defined by the Yellow Paper
   Type      uint8  `json:"type,omitempty"` //交易类型
   PostState []byte `json:"root"`           //交易成功/失败时的 RLP 编码
   Status    uint64 `json:"status"`         //交易成功/失败的状态码
   //区块中直到这一笔交易累积使用的 gas
   CumulativeGasUsed uint64 `json:"cumulativeGasUsed" gencodec:"required"`
   //布隆过滤q
   Bloom Bloom `json:"logsBloom"         gencodec:"required"`
   //合约的日志列表
   Logs []*Log `json:"logs"              gencodec:"required"`

   //处理交易时的字段

   // Implementation fields: These fields are added by geth when processing a transaction.
   // They are stored in the chain database.
   TxHash          common.Hash    `json:"transactionHash" gencodec:"required"`
   ContractAddress common.Address `json:"contractAddress"`
   GasUsed         uint64         `json:"gasUsed" gencodec:"required"`

   //记录区块信息和交易索引，用于叫检查交易与对应收据的兼容性
   // Inclusion information: These fields provide information about the inclusion of the
   // transaction corresponding to this receipt.
   BlockHash        common.Hash `json:"blockHash,omitempty"`
   BlockNumber      *big.Int    `json:"blockNumber,omitempty"`
   TransactionIndex uint        `json:"transactionIndex"`
}

收据的部分字段需要编码后永久存储，因此提供了编码时的中间结构和永久存储的结构

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//收据 RLP 编码时的中间结构

// receiptRLP is the consensus encoding of a receipt.
type receiptRLP struct {
	PostStateOrStatus []byte
	CumulativeGasUsed uint64
	Bloom             Bloom
	Logs              []*Log
}

//将会永久存储的部分

// storedReceiptRLP is the storage encoding of a receipt.
type storedReceiptRLP struct {
	PostStateOrStatus []byte
	CumulativeGasUsed uint64
	Logs              []*LogForStorage
}

为了写入数据库时分析收据的内容，为了避免层层嵌套，就直接设置了如下的结构。可见以太坊采用的数据库其实也是不断升级的。

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//封装收据，避免嵌套封装，用于分析收据的内容

// v4StoredReceiptRLP is the storage encoding of a receipt used in database version 4.
type v4StoredReceiptRLP struct {
	PostStateOrStatus []byte
	CumulativeGasUsed uint64
	TxHash            common.Hash
	ContractAddress   common.Address
	Logs              []*LogForStorage
	GasUsed           uint64
}

// v3StoredReceiptRLP is the original storage encoding of a receipt including some unnecessary fields.
type v3StoredReceiptRLP struct {
	PostStateOrStatus []byte
	CumulativeGasUsed uint64
	Bloom             Bloom
	TxHash            common.Hash
	ContractAddress   common.Address
	Logs              []*LogForStorage
	GasUsed           uint64
}

状态标记

首先设置了收据成功/失败时的 RLP 默认编码，以及交易是否成功的状态码

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var (
   receiptStatusFailedRLP     = []byte{}     //收据状态为失败的 RLP 编码
   receiptStatusSuccessfulRLP = []byte{0x01} //收据状态为成功的 RLP 编码
)

// This error is returned when a typed receipt is decoded, but the string is empty.
var errEmptyTypedReceipt = errors.New("empty typed receipt bytes")

const (
   // ReceiptStatusFailed is the status code of a transaction if execution failed.
   ReceiptStatusFailed = uint64(0)

   // ReceiptStatusSuccessful is the status code of a transaction if execution succeeded.
   ReceiptStatusSuccessful = uint64(1)
)

编码

以太坊的数据都是编码后以字典树的形式存储，依靠哈希索引寻找值。因此，对于会写入数据库的内容，总是需要对应的编码和解码。编码和解码又分成了死否写入传入的接口还是直接返回编码的字节。由于交易的内容会逐渐拓展（如类型、新的编码方式），编码会越来越复杂。此处不做详细介绍，当需要研究编码时再回头看。

共识检查时的编码和解码

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// EncodeRLP implements rlp.Encoder, and flattens the consensus fields of a receipt
// into an RLP stream. If no post state is present, byzantium fork is assumed.
func (r *Receipt) EncodeRLP(w io.Writer) error {
	data := &receiptRLP{r.statusEncoding(), r.CumulativeGasUsed, r.Bloom, r.Logs}
	if r.Type == LegacyTxType {
		return rlp.Encode(w, data)
	}
	buf := encodeBufferPool.Get().(*bytes.Buffer)
	defer encodeBufferPool.Put(buf)
	buf.Reset()
	if err := r.encodeTyped(data, buf); err != nil {
		return err
	}
	return rlp.Encode(w, buf.Bytes())
}

// encodeTyped writes the canonical encoding of a typed receipt to w.
func (r *Receipt) encodeTyped(data *receiptRLP, w *bytes.Buffer) error {
	w.WriteByte(r.Type)
	return rlp.Encode(w, data)
}

// MarshalBinary returns the consensus encoding of the receipt.
func (r *Receipt) MarshalBinary() ([]byte, error) {
	if r.Type == LegacyTxType {
		return rlp.EncodeToBytes(r)
	}
	data := &receiptRLP{r.statusEncoding(), r.CumulativeGasUsed, r.Bloom, r.Logs}
	var buf bytes.Buffer
	err := r.encodeTyped(data, &buf)
	return buf.Bytes(), err
}

// DecodeRLP implements rlp.Decoder, and loads the consensus fields of a receipt
// from an RLP stream.
func (r *Receipt) DecodeRLP(s *rlp.Stream) error {
	kind, _, err := s.Kind()
	switch {
	case err != nil:
		return err
	case kind == rlp.List:
		// It's a legacy receipt.
		var dec receiptRLP
		if err := s.Decode(&dec); err != nil {
			return err
		}
		r.Type = LegacyTxType
		return r.setFromRLP(dec)
	case kind == rlp.String:
		// It's an EIP-2718 typed tx receipt.
		b, err := s.Bytes()
		if err != nil {
			return err
		}
		if len(b) == 0 {
			return errEmptyTypedReceipt
		}
		r.Type = b[0]
		if r.Type == AccessListTxType || r.Type == DynamicFeeTxType {
			var dec receiptRLP
			if err := rlp.DecodeBytes(b[1:], &dec); err != nil {
				return err
			}
			return r.setFromRLP(dec)
		}
		return ErrTxTypeNotSupported
	default:
		return rlp.ErrExpectedList
	}
}

// UnmarshalBinary decodes the consensus encoding of receipts.
// It supports legacy RLP receipts and EIP-2718 typed receipts.
func (r *Receipt) UnmarshalBinary(b []byte) error {
	if len(b) > 0 && b[0] > 0x7f {
		// It's a legacy receipt decode the RLP
		var data receiptRLP
		err := rlp.DecodeBytes(b, &data)
		if err != nil {
			return err
		}
		r.Type = LegacyTxType
		return r.setFromRLP(data)
	}
	// It's an EIP2718 typed transaction envelope.
	return r.decodeTyped(b)
}

// decodeTyped decodes a typed receipt from the canonical format.
func (r *Receipt) decodeTyped(b []byte) error {
	if len(b) == 0 {
		return errEmptyTypedReceipt
	}
	switch b[0] {
	case DynamicFeeTxType, AccessListTxType:
		var data receiptRLP
		err := rlp.DecodeBytes(b[1:], &data)
		if err != nil {
			return err
		}
		r.Type = b[0]
		return r.setFromRLP(data)
	default:
		return ErrTxTypeNotSupported
	}
}

func (r *Receipt) setFromRLP(data receiptRLP) error {
	r.CumulativeGasUsed, r.Bloom, r.Logs = data.CumulativeGasUsed, data.Bloom, data.Logs
	return r.setStatus(data.PostStateOrStatus)
}

写入存储的编码和解码

区别在于这里写入了 log。首先为了区分上面提到的编码和接下来提到的编码，设置了不同的别名。

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// ReceiptForStorage is a wrapper around a Receipt that flattens and parses the
// entire content of a receipt, as opposed to only the consensus fields originally.
type ReceiptForStorage Receipt

接下来，也是一堆的编码和解码函数

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// EncodeRLP implements rlp.Encoder, and flattens all content fields of a receipt
// into an RLP stream.
func (r *ReceiptForStorage) EncodeRLP(w io.Writer) error {
	enc := &storedReceiptRLP{
		PostStateOrStatus: (*Receipt)(r).statusEncoding(),
		CumulativeGasUsed: r.CumulativeGasUsed,
		Logs:              make([]*LogForStorage, len(r.Logs)),
	}
	for i, log := range r.Logs {
		enc.Logs[i] = (*LogForStorage)(log)
	}
	return rlp.Encode(w, enc)
}

// DecodeRLP implements rlp.Decoder, and loads both consensus and implementation
// fields of a receipt from an RLP stream.
func (r *ReceiptForStorage) DecodeRLP(s *rlp.Stream) error {
	// Retrieve the entire receipt blob as we need to try multiple decoders
	blob, err := s.Raw()
	if err != nil {
		return err
	}
	// Try decoding from the newest format for future proofness, then the older one
	// for old nodes that just upgraded. V4 was an intermediate unreleased format so
	// we do need to decode it, but it's not common (try last).
	if err := decodeStoredReceiptRLP(r, blob); err == nil {
		return nil
	}
	if err := decodeV3StoredReceiptRLP(r, blob); err == nil {
		return nil
	}
	return decodeV4StoredReceiptRLP(r, blob)
}

func decodeStoredReceiptRLP(r *ReceiptForStorage, blob []byte) error {
	var stored storedReceiptRLP
	if err := rlp.DecodeBytes(blob, &stored); err != nil {
		return err
	}
	if err := (*Receipt)(r).setStatus(stored.PostStateOrStatus); err != nil {
		return err
	}
	r.CumulativeGasUsed = stored.CumulativeGasUsed
	r.Logs = make([]*Log, len(stored.Logs))
	for i, log := range stored.Logs {
		r.Logs[i] = (*Log)(log)
	}
	r.Bloom = CreateBloom(Receipts{(*Receipt)(r)})

	return nil
}

func decodeV4StoredReceiptRLP(r *ReceiptForStorage, blob []byte) error {
	var stored v4StoredReceiptRLP
	if err := rlp.DecodeBytes(blob, &stored); err != nil {
		return err
	}
	if err := (*Receipt)(r).setStatus(stored.PostStateOrStatus); err != nil {
		return err
	}
	r.CumulativeGasUsed = stored.CumulativeGasUsed
	r.TxHash = stored.TxHash
	r.ContractAddress = stored.ContractAddress
	r.GasUsed = stored.GasUsed
	r.Logs = make([]*Log, len(stored.Logs))
	for i, log := range stored.Logs {
		r.Logs[i] = (*Log)(log)
	}
	r.Bloom = CreateBloom(Receipts{(*Receipt)(r)})

	return nil
}

func decodeV3StoredReceiptRLP(r *ReceiptForStorage, blob []byte) error {
	var stored v3StoredReceiptRLP
	if err := rlp.DecodeBytes(blob, &stored); err != nil {
		return err
	}
	if err := (*Receipt)(r).setStatus(stored.PostStateOrStatus); err != nil {
		return err
	}
	r.CumulativeGasUsed = stored.CumulativeGasUsed
	r.Bloom = stored.Bloom
	r.TxHash = stored.TxHash
	r.ContractAddress = stored.ContractAddress
	r.GasUsed = stored.GasUsed
	r.Logs = make([]*Log, len(stored.Logs))
	for i, log := range stored.Logs {
		r.Logs[i] = (*Log)(log)
	}
	return nil
}

批量处理

为了批量处理收据，设置了收据列表和配套的方法。

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// Receipts implements DerivableList for receipts.
type Receipts []*Receipt

方法包括：获取收据的数量、编码特定索引的收据和封装区块信息。

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// Len returns the number of receipts in this list.
func (rs Receipts) Len() int { return len(rs) }

// EncodeIndex encodes the i'th receipt to w.
func (rs Receipts) EncodeIndex(i int, w *bytes.Buffer) {
	r := rs[i]
	data := &receiptRLP{r.statusEncoding(), r.CumulativeGasUsed, r.Bloom, r.Logs}
	switch r.Type {
	case LegacyTxType:
		rlp.Encode(w, data)
	case AccessListTxType:
		w.WriteByte(AccessListTxType)
		rlp.Encode(w, data)
	case DynamicFeeTxType:
		w.WriteByte(DynamicFeeTxType)
		rlp.Encode(w, data)
	default:
		// For unsupported types, write nothing. Since this is for
		// DeriveSha, the error will be caught matching the derived hash
		// to the block.
	}
}

// DeriveFields fills the receipts with their computed fields based on consensus
// data and contextual infos like containing block and transactions.
func (rs Receipts) DeriveFields(config *params.ChainConfig, hash common.Hash, number uint64, txs Transactions) error {
	signer := MakeSigner(config, new(big.Int).SetUint64(number))

	logIndex := uint(0)
	if len(txs) != len(rs) {
		return errors.New("transaction and receipt count mismatch")
	}
	for i := 0; i < len(rs); i++ {
		// The transaction type and hash can be retrieved from the transaction itself
		rs[i].Type = txs[i].Type()
		rs[i].TxHash = txs[i].Hash()

		// block location fields
		rs[i].BlockHash = hash
		rs[i].BlockNumber = new(big.Int).SetUint64(number)
		rs[i].TransactionIndex = uint(i)

		// The contract address can be derived from the transaction itself
		if txs[i].To() == nil {
			// Deriving the signer is expensive, only do if it's actually needed
			from, _ := Sender(signer, txs[i])
			rs[i].ContractAddress = crypto.CreateAddress(from, txs[i].Nonce())
		}
		// The used gas can be calculated based on previous r
		if i == 0 {
			rs[i].GasUsed = rs[i].CumulativeGasUsed
		} else {
			rs[i].GasUsed = rs[i].CumulativeGasUsed - rs[i-1].CumulativeGasUsed
		}
		// The derived log fields can simply be set from the block and transaction
		for j := 0; j < len(rs[i].Logs); j++ {
			rs[i].Logs[j].BlockNumber = number
			rs[i].Logs[j].BlockHash = hash
			rs[i].Logs[j].TxHash = rs[i].TxHash
			rs[i].Logs[j].TxIndex = uint(i)
			rs[i].Logs[j].Index = logIndex
			logIndex++
		}
	}
	return nil
}