Add blockchain multi store implementation. Close #73

blockchain/Multi.go

@@ -0,0 +1,194 @@
+/*
+File Name:  Multi.go
+Copyright:  2021 Peernet s.r.o.
+Author:     Peter Kleissner
+
+Multi-blockchain store implementation.
+
+Keys used in the key-value store:
+1. Key: Public key compressed, Value: Header
+2. Key: Public key compressed + version + block number, Value: Block
+
+*/
+
+package blockchain
+
+import (
+	"encoding/binary"
+	"errors"
+	"time"
+
+	"github.com/PeernetOfficial/core/btcec"
+	"github.com/PeernetOfficial/core/store"
+)
+
+const (
+	MultiStatusOK              = 0 // Success.
+	MultiStatusErrorReadHeader = 1 // Error reading header for blockchain.
+	MultiStatusHeaderNA        = 2 // Header not available. This indicates nothing is stored for the blockchain.
+	MultiStatusInvalidRemote   = 3 // Invalid remote reported blockchain version and height. (local cache is "newer" which should not happen)
+	MultiStatusEqual           = 4 // Remote blockchain and local cache are equal.
+	MultiStatusNewVersion      = 5 // Local cache is out of date. A new version of the blockchain is available.
+	MultiStatusNewBlocks       = 6 // Local cache is out of date. Additional blocks are available.
+)
+
+// MultiStore stores multiple blockchains.
+type MultiStore struct {
+	path     string      // Path of the blockchain on disk. Depends on key-value store whether a filename or folder.
+	Database store.Store // The database storing the blockchain.
+}
+
+func InitMultiStore(path string) (multi *MultiStore, err error) {
+	multi = &MultiStore{path: path}
+
+	// open existing blockchain file or create new one
+	if multi.Database, err = store.NewPogrebStore(path); err != nil {
+		return nil, err
+	}
+
+	return multi, nil
+}
+
+/*
+Header for blockchains:
+
+Offset  Size   Info
+0       8      Version of the blockchain
+8       8      Height of the blockchain
+16      8      Count of blocks
+24      8      Date first block added
+32      8      Date last block added
+40      8 * n  List of block numbers that are stored
+
+*/
+
+// This is a header for a single blockchain stored in a multi store.
+type MultiBlockchainHeader struct {
+	Height              uint64    // Height is exchanged as uint32 in the protocol, but stored as uint64.
+	Version             uint64    // Version is always uint64.
+	DateFirstBlockAdded time.Time // Date the first block was added
+	DateLastBlockAdded  time.Time // Date the last block was added
+	ListBlocks          []uint64  // List of block numbers that are stored
+}
+
+// Reads a blockchains header if available.
+func (multi *MultiStore) ReadBlockchainHeader(publicKey *btcec.PublicKey) (header *MultiBlockchainHeader, found bool, err error) {
+	buffer, found := multi.Database.Get(publicKey.SerializeCompressed())
+	if !found {
+		return nil, false, nil
+	} else if len(buffer) < 40 {
+		return nil, false, errors.New("header length too small")
+	}
+
+	header = &MultiBlockchainHeader{}
+	header.Version = binary.LittleEndian.Uint64(buffer[0:8])
+	header.Height = binary.LittleEndian.Uint64(buffer[8:16])
+	countBlocks := binary.LittleEndian.Uint64(buffer[16:24])
+	header.DateFirstBlockAdded = time.Unix(int64(binary.LittleEndian.Uint64(buffer[24:32])), 0)
+	header.DateLastBlockAdded = time.Unix(int64(binary.LittleEndian.Uint64(buffer[32:40])), 0)
+
+	if uint64(len(buffer)) < 40+8*countBlocks {
+		return nil, false, errors.New("header length too small")
+	}
+
+	index := 40
+
+	for n := uint64(0); n < countBlocks; n++ {
+		blockN := binary.LittleEndian.Uint64(buffer[index : index+8])
+		header.ListBlocks = append(header.ListBlocks, blockN)
+		index += 8
+	}
+
+	return header, true, nil
+}
+
+// WriteBlockchainHeader writes a blockchain header. If one exists, it will be overwritten.
+func (multi *MultiStore) WriteBlockchainHeader(publicKey *btcec.PublicKey, header *MultiBlockchainHeader) (err error) {
+	raw := make([]byte, 40+8*len(header.ListBlocks))
+
+	binary.LittleEndian.PutUint64(raw[0:8], header.Version)
+	binary.LittleEndian.PutUint64(raw[8:16], header.Height)
+	binary.LittleEndian.PutUint64(raw[16:24], uint64(len(header.ListBlocks)))
+	binary.LittleEndian.PutUint64(raw[24:32], uint64(header.DateFirstBlockAdded.UTC().Unix()))
+	binary.LittleEndian.PutUint64(raw[32:40], uint64(header.DateLastBlockAdded.UTC().Unix()))
+
+	index := 40
+
+	for _, blockN := range header.ListBlocks {
+		binary.LittleEndian.PutUint64(raw[index:index+8], blockN)
+		index += 8
+	}
+
+	return multi.Database.Set(publicKey.SerializeCompressed(), raw)
+}
+
+func lookupKeyForBlock(publicKey *btcec.PublicKey, version, blockNumber uint64) (key []byte) {
+	var buffer [16]byte
+	binary.LittleEndian.PutUint64(buffer[0:8], version)
+	binary.LittleEndian.PutUint64(buffer[8:16], blockNumber)
+
+	key = append(key, publicKey.SerializeCompressed()...)
+	key = append(key, buffer[:]...)
+
+	return key
+}
+
+// ReadBlock reads a raw block
+func (multi *MultiStore) ReadBlock(publicKey *btcec.PublicKey, version, blockNumber uint64) (raw []byte, found bool) {
+	return multi.Database.Get(lookupKeyForBlock(publicKey, version, blockNumber))
+}
+
+// WriteBlock writes a raw block. It does not update the blockchains header.
+func (multi *MultiStore) WriteBlock(publicKey *btcec.PublicKey, version, blockNumber uint64, raw []byte) (err error) {
+	return multi.Database.Set(lookupKeyForBlock(publicKey, version, blockNumber), raw)
+}
+
+// AssessBlockchainHeader reads the blockchain header, if available, and assesses the status.
+func (multi *MultiStore) AssessBlockchainHeader(publicKey *btcec.PublicKey, version, height uint64) (header *MultiBlockchainHeader, status int, err error) {
+	// check if there is an existing header for the blockchain
+	header, found, err := multi.ReadBlockchainHeader(publicKey)
+	if err != nil {
+		return nil, MultiStatusErrorReadHeader, err
+	} else if !found {
+		return nil, MultiStatusHeaderNA, nil
+	}
+
+	if header.Version == version && header.Height == height {
+		return header, MultiStatusEqual, nil
+	}
+
+	// Check if existing version is newer than reported - indicates illegal behavior by the remote peer.
+	// Improper refactoring could happen if the local blockchain folder is deleted and automatically recreated.
+	if header.Version > version || (header.Version == version && header.Height > height) {
+		return header, MultiStatusInvalidRemote, nil
+	}
+
+	if version > header.Version {
+		return header, MultiStatusNewVersion, nil
+	}
+
+	return header, MultiStatusNewBlocks, nil
+}
+
+// Deletes a blockchain
+func (multi *MultiStore) DeleteBlockchain(publicKey *btcec.PublicKey, header *MultiBlockchainHeader) {
+	// first delete all blocks
+	for _, blockN := range header.ListBlocks {
+		multi.Database.Delete(lookupKeyForBlock(publicKey, header.Version, blockN))
+	}
+
+	// delete the header
+	multi.Database.Delete(publicKey.SerializeCompressed())
+}
+
+func (multi *MultiStore) NewBlockchainHeader(publicKey *btcec.PublicKey, version, height uint64) (header *MultiBlockchainHeader, err error) {
+	timeN := time.Now().UTC()
+	header = &MultiBlockchainHeader{
+		Height:              height,
+		Version:             version,
+		DateFirstBlockAdded: timeN,
+		DateLastBlockAdded:  timeN,
+	}
+
+	return header, multi.WriteBlockchainHeader(publicKey, header)
+}