Integrate transactions into the blockchain

block.go

@@ -10,7 +10,7 @@ import (
 // Block keeps block headers
 type Block struct {
 	Timestamp     int64
-	Data          []byte
+	Transactions  []*Transaction
 	PrevBlockHash []byte
 	Hash          []byte
 	Nonce         int
@@ -30,8 +30,8 @@ func (b *Block) Serialize() []byte {
 }
 
 // NewBlock creates and returns Block
-func NewBlock(data string, prevBlockHash []byte) *Block {
-	block := &Block{time.Now().Unix(), []byte(data), prevBlockHash, []byte{}, 0}
+func NewBlock(transactions []*Transaction, prevBlockHash []byte) *Block {
+	block := &Block{time.Now().Unix(), transactions, prevBlockHash, []byte{}, 0}
 	pow := NewProofOfWork(block)
 	nonce, hash := pow.Run()
 
@@ -42,8 +42,8 @@ func NewBlock(data string, prevBlockHash []byte) *Block {
 }
 
 // NewGenesisBlock creates and returns genesis Block
-func NewGenesisBlock() *Block {
-	return NewBlock("Genesis Block", []byte{})
+func NewGenesisBlock(coinbase *Transaction) *Block {
+	return NewBlock([]*Transaction{coinbase}, []byte{})
 }
 
 // DeserializeBlock deserializes a block

blockchain.go

@@ -9,6 +9,7 @@ import (
 
 const dbFile = "blockchain.db"
 const blocksBucket = "blocks"
+const genesisCoinbase = "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks"
 
 // Blockchain keeps a sequence of Blocks
 type Blockchain struct {
@@ -86,7 +87,7 @@ func (i *BlockchainIterator) Next() *Block {
 }
 
 // NewBlockchain creates a new Blockchain with genesis Block
-func NewBlockchain() *Blockchain {
+func NewBlockchain(address string) *Blockchain {
 	var tip []byte
 	db, err := bolt.Open(dbFile, 0600, nil)
 	if err != nil {
@@ -98,7 +99,8 @@ func NewBlockchain() *Blockchain {
 
 		if b == nil {
 			fmt.Println("No existing blockchain found. Creating a new one...")
-			genesis := NewGenesisBlock()
+			cbtx := NewCoinbaseTX(address, genesisCoinbase)
+			genesis := NewGenesisBlock(cbtx)
 
 			b, err := tx.CreateBucket([]byte(blocksBucket))
 			if err != nil {

proofofwork.go

@@ -31,10 +31,18 @@ func NewProofOfWork(b *Block) *ProofOfWork {
 }
 
 func (pow *ProofOfWork) prepareData(nonce int) []byte {
+	var txHashes [][]byte
+	var txHash [32]byte
+
+	for _, tx := range pow.block.Transactions {
+		txHashes = append(txHashes, tx.GetHash())
+	}
+	txHash = sha256.Sum256(bytes.Join(txHashes, []byte{}))
+
 	data := bytes.Join(
 		[][]byte{
 			pow.block.PrevBlockHash,
-			pow.block.Data,
+			txHash[:],
 			IntToHex(pow.block.Timestamp),
 			IntToHex(int64(targetBits)),
 			IntToHex(int64(nonce)),

transaction.go

@@ -1,6 +1,11 @@
 package main
 
-import "log"
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/gob"
+	"log"
+)
 
 const subsidy = 10
 
@@ -15,6 +20,21 @@ func (tx Transaction) IsCoinbase() bool {
 	return len(tx.Vin) == 1 && tx.Vin[0].Txid == -1 && tx.Vin[0].Vout == -1
 }
 
+// GetHash hashes the transaction and returns the hash
+func (tx Transaction) GetHash() []byte {
+	var encoded bytes.Buffer
+	var hash [32]byte
+
+	enc := gob.NewEncoder(&encoded)
+	err := enc.Encode(tx)
+	if err != nil {
+		log.Panic(err)
+	}
+	hash = sha256.Sum256(encoded.Bytes())
+
+	return hash[:]
+}
+
 // TXInput represents a transaction input
 type TXInput struct {
 	Txid      int
@@ -34,8 +54,12 @@ func (out *TXOutput) Unlock(unlockingData string) bool {
 }
 
 // NewCoinbaseTX creates a new coinbase transaction
-func NewCoinbaseTX(to string) *Transaction {
-	txin := TXInput{-1, -1, "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks"}
+func NewCoinbaseTX(to, data string) *Transaction {
+	if data == "" {
+		data = "Coinbase"
+	}
+
+	txin := TXInput{-1, -1, data}
 	txout := TXOutput{subsidy, to}
 	tx := Transaction{[]TXInput{txin}, []TXOutput{txout}}