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blockchain_go
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noahsalvadordenjo 2021-06-26 18:27:13 +07:00 committed by GitHub
parent 54b6c07b6c e17722eb18
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7 changed files with 371 additions and 61 deletions
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6
README.md
View File

@ -2,5 +2,7 @@
A blockchain implementation in Go, as described in these articles:
1. [Basic Prototype](https://jeiwan.cc/posts/building-blockchain-in-go-part-1/)
2. [Proof-of-Work](https://jeiwan.cc/posts/building-blockchain-in-go-part-2/)
1. [Basic Prototype](https://jeiwan.net/posts/building-blockchain-in-go-part-1/)
2. [Proof-of-Work](https://jeiwan.net/posts/building-blockchain-in-go-part-2/)
2. [Persistence and CLI](https://jeiwan.net/posts/building-blockchain-in-go-part-3/)
3. [Transactions 1](https://jeiwan.net/posts/building-blockchain-in-go-part-4/)

24
block.go
View File

@ -2,6 +2,7 @@ package main
import (
"bytes"
"crypto/sha256"
"encoding/gob"
"log"
"time"
@ -10,7 +11,7 @@ import (
// Block keeps block headers
type Block struct {
Timestamp int64
Data []byte
Transactions []*Transaction
PrevBlockHash []byte
Hash []byte
Nonce int
@ -29,9 +30,22 @@ func (b *Block) Serialize() []byte {
return result.Bytes()
}
// HashTransactions returns a hash of the transactions in the block
func (b *Block) HashTransactions() []byte {
var txHashes [][]byte
var txHash [32]byte
for _, tx := range b.Transactions {
txHashes = append(txHashes, tx.ID)
}
txHash = sha256.Sum256(bytes.Join(txHashes, []byte{}))
return txHash[:]
}
// 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 +56,8 @@ 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

150
blockchain.go
View File

@ -1,16 +1,19 @@
package main
import (
"encoding/hex"
"fmt"
"log"
"os"
"github.com/boltdb/bolt"
)
const dbFile = "blockchain.db"
const blocksBucket = "blocks"
const genesisCoinbaseData = "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks"
// Blockchain keeps a sequence of Blocks
// Blockchain implements interactions with a DB
type Blockchain struct {
tip []byte
db *bolt.DB
@ -22,8 +25,8 @@ type BlockchainIterator struct {
db *bolt.DB
}
// AddBlock saves provided data as a block in the blockchain
func (bc *Blockchain) AddBlock(data string) {
// MineBlock mines a new block with the provided transactions
func (bc *Blockchain) MineBlock(transactions []*Transaction) {
var lastHash []byte
err := bc.db.View(func(tx *bolt.Tx) error {
@ -37,7 +40,7 @@ func (bc *Blockchain) AddBlock(data string) {
log.Panic(err)
}
newBlock := NewBlock(data, lastHash)
newBlock := NewBlock(transactions, lastHash)
err = bc.db.Update(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(blocksBucket))
@ -57,7 +60,94 @@ func (bc *Blockchain) AddBlock(data string) {
})
}
// Iterator ...
// FindUnspentTransactions returns a list of transactions containing unspent outputs
func (bc *Blockchain) FindUnspentTransactions(address string) []Transaction {
var unspentTXs []Transaction
spentTXOs := make(map[string][]int)
bci := bc.Iterator()
for {
block := bci.Next()
for _, tx := range block.Transactions {
txID := hex.EncodeToString(tx.ID)
Outputs:
for outIdx, out := range tx.Vout {
// Was the output spent?
if spentTXOs[txID] != nil {
for _, spentOut := range spentTXOs[txID] {
if spentOut == outIdx {
continue Outputs
}
}
}
if out.CanBeUnlockedWith(address) {
unspentTXs = append(unspentTXs, *tx)
}
}
if tx.IsCoinbase() == false {
for _, in := range tx.Vin {
if in.CanUnlockOutputWith(address) {
inTxID := hex.EncodeToString(in.Txid)
spentTXOs[inTxID] = append(spentTXOs[inTxID], in.Vout)
}
}
}
}
if len(block.PrevBlockHash) == 0 {
break
}
}
return unspentTXs
}
// FindUTXO finds and returns all unspent transaction outputs
func (bc *Blockchain) FindUTXO(address string) []TXOutput {
var UTXOs []TXOutput
unspentTransactions := bc.FindUnspentTransactions(address)
for _, tx := range unspentTransactions {
for _, out := range tx.Vout {
if out.CanBeUnlockedWith(address) {
UTXOs = append(UTXOs, out)
}
}
}
return UTXOs
}
// FindSpendableOutputs finds and returns unspent outputs to reference in inputs
func (bc *Blockchain) FindSpendableOutputs(address string, amount int) (int, map[string][]int) {
unspentOutputs := make(map[string][]int)
unspentTXs := bc.FindUnspentTransactions(address)
accumulated := 0
Work:
for _, tx := range unspentTXs {
txID := hex.EncodeToString(tx.ID)
for outIdx, out := range tx.Vout {
if out.CanBeUnlockedWith(address) && accumulated < amount {
accumulated += out.Value
unspentOutputs[txID] = append(unspentOutputs[txID], outIdx)
if accumulated >= amount {
break Work
}
}
}
}
return accumulated, unspentOutputs
}
// Iterator returns a BlockchainIterat
func (bc *Blockchain) Iterator() *BlockchainIterator {
bci := &BlockchainIterator{bc.tip, bc.db}
@ -85,8 +175,21 @@ func (i *BlockchainIterator) Next() *Block {
return block
}
func dbExists() bool {
if _, err := os.Stat(dbFile); os.IsNotExist(err) {
return false
}
return true
}
// NewBlockchain creates a new Blockchain with genesis Block
func NewBlockchain() *Blockchain {
func NewBlockchain(address string) *Blockchain {
if dbExists() == false {
fmt.Println("No existing blockchain found. Create one first.")
os.Exit(1)
}
var tip []byte
db, err := bolt.Open(dbFile, 0600, nil)
if err != nil {
@ -95,10 +198,36 @@ func NewBlockchain() *Blockchain {
err = db.Update(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(blocksBucket))
tip = b.Get([]byte("l"))
if b == nil {
fmt.Println("No existing blockchain found. Creating a new one...")
genesis := NewGenesisBlock()
return nil
})
if err != nil {
log.Panic(err)
}
bc := Blockchain{tip, db}
return &bc
}
// CreateBlockchain creates a new blockchain DB
func CreateBlockchain(address string) *Blockchain {
if dbExists() {
fmt.Println("Blockchain already exists.")
os.Exit(1)
}
var tip []byte
db, err := bolt.Open(dbFile, 0600, nil)
if err != nil {
log.Panic(err)
}
err = db.Update(func(tx *bolt.Tx) error {
cbtx := NewCoinbaseTX(address, genesisCoinbaseData)
genesis := NewGenesisBlock(cbtx)
b, err := tx.CreateBucket([]byte(blocksBucket))
if err != nil {
@ -115,9 +244,6 @@ func NewBlockchain() *Blockchain {
log.Panic(err)
}
tip = genesis.Hash
} else {
tip = b.Get([]byte("l"))
}
return nil
})

98
cli.go
View File

@ -9,14 +9,34 @@ import (
)
// CLI responsible for processing command line arguments
type CLI struct {
bc *Blockchain
type CLI struct{}
func (cli *CLI) createBlockchain(address string) {
bc := CreateBlockchain(address)
bc.db.Close()
fmt.Println("Done!")
}
func (cli *CLI) getBalance(address string) {
bc := NewBlockchain(address)
defer bc.db.Close()
balance := 0
UTXOs := bc.FindUTXO(address)
for _, out := range UTXOs {
balance += out.Value
}
fmt.Printf("Balance of '%s': %d\n", address, balance)
}
func (cli *CLI) printUsage() {
fmt.Println("Usage:")
fmt.Println(" addblock -data BLOCK_DATA - add a block to the blockchain")
fmt.Println(" printchain - print all the blocks of the blockchain")
fmt.Println(" getbalance -address ADDRESS - Get balance of ADDRESS")
fmt.Println(" createblockchain -address ADDRESS - Create a blockchain and send genesis block reward to ADDRESS")
fmt.Println(" printchain - Print all the blocks of the blockchain")
fmt.Println(" send -from FROM -to TO -amount AMOUNT - Send AMOUNT of coins from FROM address to TO")
}
func (cli *CLI) validateArgs() {
@ -26,19 +46,17 @@ func (cli *CLI) validateArgs() {
}
}
func (cli *CLI) addBlock(data string) {
cli.bc.AddBlock(data)
fmt.Println("Success!")
}
func (cli *CLI) printChain() {
bci := cli.bc.Iterator()
// TODO: Fix this
bc := NewBlockchain("")
defer bc.db.Close()
bci := bc.Iterator()
for {
block := bci.Next()
fmt.Printf("Prev. hash: %x\n", block.PrevBlockHash)
fmt.Printf("Data: %s\n", block.Data)
fmt.Printf("Hash: %x\n", block.Hash)
pow := NewProofOfWork(block)
fmt.Printf("PoW: %s\n", strconv.FormatBool(pow.Validate()))
@ -50,18 +68,38 @@ func (cli *CLI) printChain() {
}
}
func (cli *CLI) send(from, to string, amount int) {
bc := NewBlockchain(from)
defer bc.db.Close()
tx := NewUTXOTransaction(from, to, amount, bc)
bc.MineBlock([]*Transaction{tx})
fmt.Println("Success!")
}
// Run parses command line arguments and processes commands
func (cli *CLI) Run() {
cli.validateArgs()
addBlockCmd := flag.NewFlagSet("addblock", flag.ExitOnError)
getBalanceCmd := flag.NewFlagSet("getbalance", flag.ExitOnError)
createBlockchainCmd := flag.NewFlagSet("createblockchain", flag.ExitOnError)
sendCmd := flag.NewFlagSet("send", flag.ExitOnError)
printChainCmd := flag.NewFlagSet("printchain", flag.ExitOnError)
addBlockData := addBlockCmd.String("data", "", "Block data")
getBalanceAddress := getBalanceCmd.String("address", "", "The address to get balance for")
createBlockchainAddress := createBlockchainCmd.String("address", "", "The address to send genesis block reward to")
sendFrom := sendCmd.String("from", "", "Source wallet address")
sendTo := sendCmd.String("to", "", "Destination wallet address")
sendAmount := sendCmd.Int("amount", 0, "Amount to send")
switch os.Args[1] {
case "addblock":
err := addBlockCmd.Parse(os.Args[2:])
case "getbalance":
err := getBalanceCmd.Parse(os.Args[2:])
if err != nil {
log.Panic(err)
}
case "createblockchain":
err := createBlockchainCmd.Parse(os.Args[2:])
if err != nil {
log.Panic(err)
}
@ -70,20 +108,42 @@ func (cli *CLI) Run() {
if err != nil {
log.Panic(err)
}
case "send":
err := sendCmd.Parse(os.Args[2:])
if err != nil {
log.Panic(err)
}
default:
cli.printUsage()
os.Exit(1)
}
if addBlockCmd.Parsed() {
if *addBlockData == "" {
addBlockCmd.Usage()
if getBalanceCmd.Parsed() {
if *getBalanceAddress == "" {
getBalanceCmd.Usage()
os.Exit(1)
}
cli.addBlock(*addBlockData)
cli.getBalance(*getBalanceAddress)
}
if createBlockchainCmd.Parsed() {
if *createBlockchainAddress == "" {
createBlockchainCmd.Usage()
os.Exit(1)
}
cli.createBlockchain(*createBlockchainAddress)
}
if printChainCmd.Parsed() {
cli.printChain()
}
if sendCmd.Parsed() {
if *sendFrom == "" || *sendTo == "" || *sendAmount <= 0 {
sendCmd.Usage()
os.Exit(1)
}
cli.send(*sendFrom, *sendTo, *sendAmount)
}
}

5
main.go
View File

@ -1,9 +1,6 @@
package main
func main() {
bc := NewBlockchain()
defer bc.db.Close()
cli := CLI{bc}
cli := CLI{}
cli.Run()
}

4
proofofwork.go
View File

@ -34,7 +34,7 @@ func (pow *ProofOfWork) prepareData(nonce int) []byte {
data := bytes.Join(
[][]byte{
pow.block.PrevBlockHash,
pow.block.Data,
pow.block.HashTransactions(),
IntToHex(pow.block.Timestamp),
IntToHex(int64(targetBits)),
IntToHex(int64(nonce)),
@ -51,7 +51,7 @@ func (pow *ProofOfWork) Run() (int, []byte) {
var hash [32]byte
nonce := 0
fmt.Printf("Mining the block containing \"%s\"\n", pow.block.Data)
fmt.Printf("Mining a new block")
for nonce < maxNonce {
data := pow.prepareData(nonce)

111
transaction.go Normal file
View File

@ -0,0 +1,111 @@
package main
import (
"bytes"
"crypto/sha256"
"encoding/gob"
"encoding/hex"
"fmt"
"log"
)
const subsidy = 10
// Transaction represents a Bitcoin transaction
type Transaction struct {
ID []byte
Vin []TXInput
Vout []TXOutput
}
// IsCoinbase checks whether the transaction is coinbase
func (tx Transaction) IsCoinbase() bool {
return len(tx.Vin) == 1 && len(tx.Vin[0].Txid) == 0 && tx.Vin[0].Vout == -1
}
// SetID sets ID of a transaction
func (tx *Transaction) SetID() {
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())
tx.ID = hash[:]
}
// TXInput represents a transaction input
type TXInput struct {
Txid []byte
Vout int
ScriptSig string
}
// TXOutput represents a transaction output
type TXOutput struct {
Value int
ScriptPubKey string
}
// CanUnlockOutputWith checks whether the address initiated the transaction
func (in *TXInput) CanUnlockOutputWith(unlockingData string) bool {
return in.ScriptSig == unlockingData
}
// CanBeUnlockedWith checks if the output can be unlocked with the provided data
func (out *TXOutput) CanBeUnlockedWith(unlockingData string) bool {
return out.ScriptPubKey == unlockingData
}
// NewCoinbaseTX creates a new coinbase transaction
func NewCoinbaseTX(to, data string) *Transaction {
if data == "" {
data = fmt.Sprintf("Reward to '%s'", to)
}
txin := TXInput{[]byte{}, -1, data}
txout := TXOutput{subsidy, to}
tx := Transaction{nil, []TXInput{txin}, []TXOutput{txout}}
tx.SetID()
return &tx
}
// NewUTXOTransaction creates a new transaction
func NewUTXOTransaction(from, to string, amount int, bc *Blockchain) *Transaction {
var inputs []TXInput
var outputs []TXOutput
acc, validOutputs := bc.FindSpendableOutputs(from, amount)
if acc < amount {
log.Panic("ERROR: Not enough funds")
}
// Build a list of inputs
for txid, outs := range validOutputs {
txID, err := hex.DecodeString(txid)
if err != nil {
log.Panic(err)
}
for _, out := range outs {
input := TXInput{txID, out, from}
inputs = append(inputs, input)
}
}
// Build a list of outputs
outputs = append(outputs, TXOutput{amount, to})
if acc > amount {
outputs = append(outputs, TXOutput{acc - amount, from}) // a change
}
tx := Transaction{nil, inputs, outputs}
tx.SetID()
return &tx
}