/
blockchain.go
258 lines (201 loc) · 5.05 KB
/
blockchain.go
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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 implements interactions with a DB
type Blockchain struct {
tip []byte
db *bolt.DB
}
// BlockchainIterator is used to iterate over blockchain blocks
type BlockchainIterator struct {
currentHash []byte
db *bolt.DB
}
// 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 {
b := tx.Bucket([]byte(blocksBucket))
lastHash = b.Get([]byte("l"))
return nil
})
if err != nil {
log.Panic(err)
}
newBlock := NewBlock(transactions, lastHash)
err = bc.db.Update(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(blocksBucket))
err := b.Put(newBlock.Hash, newBlock.Serialize())
if err != nil {
log.Panic(err)
}
err = b.Put([]byte("l"), newBlock.Hash)
if err != nil {
log.Panic(err)
}
bc.tip = newBlock.Hash
return nil
})
}
// 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}
return bci
}
// Next returns next block starting from the tip
func (i *BlockchainIterator) Next() *Block {
var block *Block
err := i.db.View(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(blocksBucket))
encodedBlock := b.Get(i.currentHash)
block = DeserializeBlock(encodedBlock)
return nil
})
if err != nil {
log.Panic(err)
}
i.currentHash = block.PrevBlockHash
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(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 {
log.Panic(err)
}
err = db.Update(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(blocksBucket))
tip = b.Get([]byte("l"))
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 {
log.Panic(err)
}
err = b.Put(genesis.Hash, genesis.Serialize())
if err != nil {
log.Panic(err)
}
err = b.Put([]byte("l"), genesis.Hash)
if err != nil {
log.Panic(err)
}
tip = genesis.Hash
return nil
})
if err != nil {
log.Panic(err)
}
bc := Blockchain{tip, db}
return &bc
}