[DEV-24] changed wire.BlockHeader to have list of previous hashes, instead of only 1

wire/blockheader.go

@@ -12,19 +12,29 @@ import (
 	"github.com/daglabs/btcd/chaincfg/chainhash"
 )
 
-// MaxBlockHeaderPayload is the maximum number of bytes a block header can be.
+// BaseBlockHeaderPayload is the base number of bytes a block header can be,
+// not including the list of previous block headers.
 // Version 4 bytes + Timestamp 4 bytes + Bits 4 bytes + Nonce 4 bytes +
-// PrevBlock and MerkleRoot hashes.
-const MaxBlockHeaderPayload = 16 + (chainhash.HashSize * 2)
+// + NumPrevBlocks 1 byte + MerkleRoot hash.
+// To get total size of block header len(PrevBlocks) * chainhash.HashSize should be
+// added to this value
+const BaseBlockHeaderPayload = 21 + (chainhash.HashSize)
+
+// MaxBlockHeaderPayload is the maximum number of bytes a block header can be.
+// BaseBlockHeaderPayload + up to 255 hashes of previous blocks
+const MaxBlockHeaderPayload = BaseBlockHeaderPayload + (255 * chainhash.HashSize)
 
 // BlockHeader defines information about a block and is used in the bitcoin
-// block (MsgBlock) and headers (MsgHeaders) messages.
+// block (MsgBlock) and headers (MsgHeader ) messages.
 type BlockHeader struct {
 	// Version of the block.  This is not the same as the protocol version.
 	Version int32
 
-	// Hash of the previous block header in the block chain.
-	PrevBlock chainhash.Hash
+	// Number of entries in PrevBlocks
+	NumPrevBlocks byte
+
+	// Hashes of the previous block headers in the blockDAG.
+	PrevBlocks []chainhash.Hash
 
 	// Merkle tree reference to hash of all transactions for the block.
 	MerkleRoot chainhash.Hash
@@ -50,7 +60,7 @@ func (h *BlockHeader) BlockHash() chainhash.Hash {
 	// transactions.  Ignore the error returns since there is no way the
 	// encode could fail except being out of memory which would cause a
 	// run-time panic.
-	buf := bytes.NewBuffer(make([]byte, 0, MaxBlockHeaderPayload))
+	buf := bytes.NewBuffer(make([]byte, 0, BaseBlockHeaderPayload+len(h.PrevBlocks)))
 	_ = writeBlockHeader(buf, 0, h)
 
 	return chainhash.DoubleHashH(buf.Bytes())
@@ -94,19 +104,20 @@ func (h *BlockHeader) Serialize(w io.Writer) error {
 
 // NewBlockHeader returns a new BlockHeader using the provided version, previous
 // block hash, merkle root hash, difficulty bits, and nonce used to generate the
-// block with defaults for the remaining fields.
-func NewBlockHeader(version int32, prevHash, merkleRootHash *chainhash.Hash,
+// block with defaults or calclulated values for the remaining fields.
+func NewBlockHeader(version int32, prevHashes []chainhash.Hash, merkleRootHash *chainhash.Hash,
 	bits uint32, nonce uint32) *BlockHeader {
 
 	// Limit the timestamp to one second precision since the protocol
 	// doesn't support better.
 	return &BlockHeader{
-		Version:    version,
-		PrevBlock:  *prevHash,
-		MerkleRoot: *merkleRootHash,
-		Timestamp:  time.Unix(time.Now().Unix(), 0),
-		Bits:       bits,
-		Nonce:      nonce,
+		Version:       version,
+		NumPrevBlocks: byte(len(prevHashes)),
+		PrevBlocks:    prevHashes,
+		MerkleRoot:    *merkleRootHash,
+		Timestamp:     time.Unix(time.Now().Unix(), 0),
+		Bits:          bits,
+		Nonce:         nonce,
 	}
 }
 
@@ -114,8 +125,20 @@ func NewBlockHeader(version int32, prevHash, merkleRootHash *chainhash.Hash,
 // decoding block headers stored to disk, such as in a database, as opposed to
 // decoding from the wire.
 func readBlockHeader(r io.Reader, pver uint32, bh *BlockHeader) error {
-	return readElements(r, &bh.Version, &bh.PrevBlock, &bh.MerkleRoot,
-		(*uint32Time)(&bh.Timestamp), &bh.Bits, &bh.Nonce)
+	err := readElements(r, &bh.Version, &bh.NumPrevBlocks)
+	if err != nil {
+		return err
+	}
+
+	bh.NumPrevBlocks, err = binarySerializer.Uint8(r)
+	if err != nil {
+		return err
+	}
+	bh.PrevBlocks = make([]chainhash.Hash, bh.NumPrevBlocks)
+	for i := byte(0); i < bh.NumPrevBlocks; i++ {
+		readElement(r, &bh.PrevBlocks[i])
+	}
+	return readElements(r, &bh.MerkleRoot, (*uint32Time)(&bh.Timestamp), &bh.Bits, &bh.Nonce)
 }
 
 // writeBlockHeader writes a bitcoin block header to w.  See Serialize for
@@ -123,6 +146,6 @@ func readBlockHeader(r io.Reader, pver uint32, bh *BlockHeader) error {
 // opposed to encoding for the wire.
 func writeBlockHeader(w io.Writer, pver uint32, bh *BlockHeader) error {
 	sec := uint32(bh.Timestamp.Unix())
-	return writeElements(w, bh.Version, &bh.PrevBlock, &bh.MerkleRoot,
+	return writeElements(w, bh.Version, bh.NumPrevBlocks, &bh.PrevBlocks, &bh.MerkleRoot,
 		sec, bh.Bits, bh.Nonce)
 }