add crosslink data structure and leveldb read/write

core/blockchain.go

@@ -1959,6 +1959,26 @@ func (bc *BlockChain) WriteEpochVdfBlockNum(epoch *big.Int, blockNum *big.Int) e
 	return nil
 }
 
+// WriteCrossLinks saves the hashes of crosslinks by shardID and blockNum combination key
+func (bc *BlockChain) WriteCrossLinks(cls []types.CrossLink) error {
+	var err error
+	for _, cl := range cls {
+		err = rawdb.WriteCrossLinkShardBlock(bc.db, cl.ShardID(), cl.BlockNum(), cl.Bytes())
+	}
+	return err
+}
+
+// ReadCrossLink retrieves crosslink hash given shardID and blockNum
+func (bc *BlockChain) ReadCrossLinkHash(shardID uint32, blockNum uint64) (common.Hash, error) {
+	h, err := rawdb.ReadCrossLinkShardBlock(bc.db, shardID, blockNum)
+	if err != nil {
+		return common.Hash{}, err
+	}
+	hash := common.Hash{}
+	hash.SetBytes(h)
+	return hash, nil
+}
+
 // IsSameLeaderAsPreviousBlock retrieves a block from the database by number, caching it
 func (bc *BlockChain) IsSameLeaderAsPreviousBlock(block *types.Block) bool {
 	if block.NumberU64() == 0 {

core/rawdb/accessors_chain.go

@@ -502,3 +502,13 @@ func ReadEpochVdfBlockNum(db DatabaseReader, epoch *big.Int) ([]byte, error) {
 func WriteEpochVdfBlockNum(db DatabaseWriter, epoch *big.Int, data []byte) error {
 	return db.Put(epochVdfBlockNumberKey(epoch), data)
 }
+
+// ReadCrossLinkShardBlock retrieves the blockHash given shardID and blockNum
+func ReadCrossLinkShardBlock(db DatabaseReader, shardID uint32, blockNum uint64) ([]byte, error) {
+	return db.Get(crosslinkKey(shardID, blockNum))
+}
+
+// WriteCrossLinkShardBlock stores the blockHash given shardID and blockNum
+func WriteCrossLinkShardBlock(db DatabaseWriter, shardID uint32, blockNum uint64, data []byte) error {
+	return db.Put(crosslinkKey(shardID, blockNum), data)
+}

core/rawdb/schema.go

@@ -60,6 +60,8 @@ var (
 	preimagePrefix = []byte("secure-key-")      // preimagePrefix + hash -> preimage
 	configPrefix   = []byte("ethereum-config-") // config prefix for the db
 
+	crosslinkPrefix = []byte("crosslink") // prefix for crosslink
+
 	// epochBlockNumberPrefix + epoch (big.Int.Bytes())
 	// -> epoch block number (big.Int.Bytes())
 	epochBlockNumberPrefix = []byte("harmony-epoch-block-number-")
@@ -162,3 +164,11 @@ func epochVrfBlockNumbersKey(epoch *big.Int) []byte {
 func epochVdfBlockNumberKey(epoch *big.Int) []byte {
 	return append(epochVdfBlockNumberPrefix, epoch.Bytes()...)
 }
+
+func crosslinkKey(shardID uint32, blockNum uint64) []byte {
+	sbKey := make([]byte, 12)
+	binary.BigEndian.PutUint32(sbKey, shardID)
+	binary.BigEndian.PutUint64(sbKey[4:], blockNum)
+	key := append(crosslinkPrefix, sbKey...)
+	return key
+}

core/types/block.go

@@ -93,6 +93,7 @@ type Header struct {
 	Vrf                 []byte      `json:"vrf"`
 	Vdf                 []byte      `json:"vdf"`
 	ShardState          []byte      `json:"shardState"`
+	CrossLink           []byte      `json:"crossLink"`
 }
 
 // field type overrides for gencodec

core/types/crosslink.go

@@ -0,0 +1,44 @@
+package types
+
+import (
+	"sort"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// CrossLink is only used on beacon chain to store the hash links from other shards
+type CrossLink struct {
+	shardID  uint32
+	blockNum uint64
+	hash     common.Hash
+}
+
+// ShardID returns shardID
+func (cl CrossLink) ShardID() uint32 {
+	return cl.shardID
+}
+
+// BlockNum returns blockNum
+func (cl CrossLink) BlockNum() uint64 {
+	return cl.blockNum
+}
+
+// Hash returns hash
+func (cl CrossLink) Hash() common.Hash {
+	return cl.hash
+}
+
+// Bytes returns bytes of the hash
+func (cl CrossLink) Bytes() []byte {
+	return cl.hash[:]
+}
+
+// CrossLinks is a collection of cross links
+type CrossLinks []CrossLink
+
+// Sort crosslinks by shardID and then by blockNum
+func (cls CrossLinks) Sort() {
+	sort.Slice(cls, func(i, j int) bool {
+		return cls[i].shardID < cls[j].shardID || (cls[i].shardID == cls[j].shardID && cls[i].blockNum < cls[j].blockNum)
+	})
+}