Official Go implementation of the Ethereum protocol
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go-ethereum/internal/era/builder.go

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// Copyright 2023 The go-ethereum Authors
// This file is part of go-ethereum.
//
// go-ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// go-ethereum 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
package era
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"math/big"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/internal/era/e2store"
"github.com/ethereum/go-ethereum/rlp"
"github.com/golang/snappy"
)
// Builder is used to create Era1 archives of block data.
//
// Era1 files are themselves e2store files. For more information on this format,
// see https://github.com/status-im/nimbus-eth2/blob/stable/docs/e2store.md.
//
// The overall structure of an Era1 file follows closely the structure of an Era file
// which contains consensus Layer data (and as a byproduct, EL data after the merge).
//
// The structure can be summarized through this definition:
//
// era1 := Version | block-tuple* | other-entries* | Accumulator | BlockIndex
// block-tuple := CompressedHeader | CompressedBody | CompressedReceipts | TotalDifficulty
//
// Each basic element is its own entry:
//
// Version = { type: [0x65, 0x32], data: nil }
// CompressedHeader = { type: [0x03, 0x00], data: snappyFramed(rlp(header)) }
// CompressedBody = { type: [0x04, 0x00], data: snappyFramed(rlp(body)) }
// CompressedReceipts = { type: [0x05, 0x00], data: snappyFramed(rlp(receipts)) }
// TotalDifficulty = { type: [0x06, 0x00], data: uint256(header.total_difficulty) }
// AccumulatorRoot = { type: [0x07, 0x00], data: accumulator-root }
// BlockIndex = { type: [0x32, 0x66], data: block-index }
//
// Accumulator is computed by constructing an SSZ list of header-records of length at most
// 8192 and then calculating the hash_tree_root of that list.
//
// header-record := { block-hash: Bytes32, total-difficulty: Uint256 }
// accumulator := hash_tree_root([]header-record, 8192)
//
// BlockIndex stores relative offsets to each compressed block entry. The
// format is:
//
// block-index := starting-number | index | index | index ... | count
//
// starting-number is the first block number in the archive. Every index is a
// defined relative to beginning of the record. The total number of block
// entries in the file is recorded with count.
//
// Due to the accumulator size limit of 8192, the maximum number of blocks in
// an Era1 batch is also 8192.
type Builder struct {
w *e2store.Writer
startNum *uint64
startTd *big.Int
indexes []uint64
hashes []common.Hash
tds []*big.Int
written int
buf *bytes.Buffer
snappy *snappy.Writer
}
// NewBuilder returns a new Builder instance.
func NewBuilder(w io.Writer) *Builder {
buf := bytes.NewBuffer(nil)
return &Builder{
w: e2store.NewWriter(w),
buf: buf,
snappy: snappy.NewBufferedWriter(buf),
}
}
// Add writes a compressed block entry and compressed receipts entry to the
// underlying e2store file.
func (b *Builder) Add(block *types.Block, receipts types.Receipts, td *big.Int) error {
eh, err := rlp.EncodeToBytes(block.Header())
if err != nil {
return err
}
eb, err := rlp.EncodeToBytes(block.Body())
if err != nil {
return err
}
er, err := rlp.EncodeToBytes(receipts)
if err != nil {
return err
}
return b.AddRLP(eh, eb, er, block.NumberU64(), block.Hash(), td, block.Difficulty())
}
// AddRLP writes a compressed block entry and compressed receipts entry to the
// underlying e2store file.
func (b *Builder) AddRLP(header, body, receipts []byte, number uint64, hash common.Hash, td, difficulty *big.Int) error {
// Write Era1 version entry before first block.
if b.startNum == nil {
n, err := b.w.Write(TypeVersion, nil)
if err != nil {
return err
}
startNum := number
b.startNum = &startNum
b.startTd = new(big.Int).Sub(td, difficulty)
b.written += n
}
if len(b.indexes) >= MaxEra1Size {
return fmt.Errorf("exceeds maximum batch size of %d", MaxEra1Size)
}
b.indexes = append(b.indexes, uint64(b.written))
b.hashes = append(b.hashes, hash)
b.tds = append(b.tds, td)
// Write block data.
if err := b.snappyWrite(TypeCompressedHeader, header); err != nil {
return err
}
if err := b.snappyWrite(TypeCompressedBody, body); err != nil {
return err
}
if err := b.snappyWrite(TypeCompressedReceipts, receipts); err != nil {
return err
}
// Also write total difficulty, but don't snappy encode.
btd := bigToBytes32(td)
n, err := b.w.Write(TypeTotalDifficulty, btd[:])
b.written += n
if err != nil {
return err
}
return nil
}
// Finalize computes the accumulator and block index values, then writes the
// corresponding e2store entries.
func (b *Builder) Finalize() (common.Hash, error) {
if b.startNum == nil {
return common.Hash{}, fmt.Errorf("finalize called on empty builder")
}
// Compute accumulator root and write entry.
root, err := ComputeAccumulator(b.hashes, b.tds)
if err != nil {
return common.Hash{}, fmt.Errorf("error calculating accumulator root: %w", err)
}
n, err := b.w.Write(TypeAccumulator, root[:])
b.written += n
if err != nil {
return common.Hash{}, fmt.Errorf("error writing accumulator: %w", err)
}
// Get beginning of index entry to calculate block relative offset.
base := int64(b.written)
// Construct block index. Detailed format described in Builder
// documentation, but it is essentially encoded as:
// "start | index | index | ... | count"
var (
count = len(b.indexes)
index = make([]byte, 16+count*8)
)
binary.LittleEndian.PutUint64(index, *b.startNum)
// Each offset is relative from the position it is encoded in the
// index. This means that even if the same block was to be included in
// the index twice (this would be invalid anyways), the relative offset
// would be different. The idea with this is that after reading a
// relative offset, the corresponding block can be quickly read by
// performing a seek relative to the current position.
for i, offset := range b.indexes {
relative := int64(offset) - base
binary.LittleEndian.PutUint64(index[8+i*8:], uint64(relative))
}
binary.LittleEndian.PutUint64(index[8+count*8:], uint64(count))
// Finally, write the block index entry.
if _, err := b.w.Write(TypeBlockIndex, index); err != nil {
return common.Hash{}, fmt.Errorf("unable to write block index: %w", err)
}
return root, nil
}
// snappyWrite is a small helper to take care snappy encoding and writing an e2store entry.
func (b *Builder) snappyWrite(typ uint16, in []byte) error {
var (
buf = b.buf
s = b.snappy
)
buf.Reset()
s.Reset(buf)
if _, err := b.snappy.Write(in); err != nil {
return fmt.Errorf("error snappy encoding: %w", err)
}
if err := s.Flush(); err != nil {
return fmt.Errorf("error flushing snappy encoding: %w", err)
}
n, err := b.w.Write(typ, b.buf.Bytes())
b.written += n
if err != nil {
return fmt.Errorf("error writing e2store entry: %w", err)
}
return nil
}