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utxo_set.go
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/
utxo_set.go
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package coin
import (
"encoding/hex"
"log"
"github.com/boltdb/bolt"
)
const utxoBucket = "chainstate"
type UTXOSet struct {
Blockchain *Blockchain
}
// Reindex all UTXOs in the DB
func (u UTXOSet) Reindex() error {
db := u.Blockchain.DB
bucketName := []byte(utxoBucket)
err := db.Update(func(tx *bolt.Tx) error {
err := tx.DeleteBucket(bucketName)
if err != nil && err != bolt.ErrBucketNotFound {
log.Panic(err)
}
_, err = tx.CreateBucket(bucketName)
if err != nil {
return err
}
return nil
})
if err != nil {
return err
}
UTXO := u.Blockchain.FindUTXO()
err = db.Update(func(tx *bolt.Tx) error {
b := tx.Bucket(bucketName)
for txID, outs := range UTXO {
key, err := hex.DecodeString(txID)
if err != nil {
return err
}
err = b.Put(key, outs.Serialize())
if err != nil {
return err
}
}
return nil
})
return err
}
// FindSpendableOutputs finds and returns unspent outputs to reference in inputs
func (u UTXOSet) FindSpendableOutputs(pubkeyHash []byte, amount int) (int, map[string][]int, error) {
unspentOutputs := make(map[string][]int)
accumulated := 0
db := u.Blockchain.DB
err := db.View(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(utxoBucket))
c := b.Cursor()
for k, v := c.First(); k != nil; k, v = c.Next() {
txID := hex.EncodeToString(k)
outs := DeserializeOutputs(v)
for outIdx, out := range outs.Outputs {
if out.IsLockedWithKey(pubkeyHash) && accumulated < amount {
accumulated += out.Value
unspentOutputs[txID] = append(unspentOutputs[txID], outIdx)
}
}
}
return nil
})
return accumulated, unspentOutputs, err
}
// FindUTXO finds UTXO for a public key hash
func (u UTXOSet) FindUTXO(pubKeyHash []byte) ([]TXOutput, error) {
var UTXOs []TXOutput
db := u.Blockchain.DB
err := db.View(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(utxoBucket))
c := b.Cursor()
for k, v := c.First(); k != nil; k, v = c.Next() {
outs := DeserializeOutputs(v)
for _, out := range outs.Outputs {
if out.IsLockedWithKey(pubKeyHash) {
UTXOs = append(UTXOs, out)
}
}
}
return nil
})
return UTXOs, err
}
// Update updates the UTXO set with transactions from the Block
// The Block is considered to be the tip of a blockchain
func (u UTXOSet) Update(block *Block) error {
db := u.Blockchain.DB
err := db.Update(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(utxoBucket))
for _, tx := range block.Transactions {
if tx.IsCoinbase() == false {
for _, vin := range tx.Vin {
updatedOuts := TXOutputs{}
outsBytes := b.Get(vin.Txid)
outs := DeserializeOutputs(outsBytes)
for outIdx, out := range outs.Outputs {
if outIdx != vin.Vout {
updatedOuts.Outputs = append(updatedOuts.Outputs, out)
}
}
if len(updatedOuts.Outputs) == 0 {
err := b.Delete(vin.Txid)
if err != nil {
return err
}
} else {
err := b.Put(vin.Txid, updatedOuts.Serialize())
if err != nil {
return err
}
}
}
}
newOutputs := TXOutputs{}
for _, out := range tx.Vout {
newOutputs.Outputs = append(newOutputs.Outputs, out)
}
err := b.Put(tx.ID, newOutputs.Serialize())
if err != nil {
return err
}
}
return nil
})
return err
}
// CountTransactions returns the number of transactions in the UTXO set
func (u UTXOSet) CountTransactions() (int, error) {
db := u.Blockchain.DB
counter := 0
err := db.View(func(tx *bolt.Tx) error {
b := tx.Bucket([]byte(utxoBucket))
c := b.Cursor()
for k, _ := c.First(); k != nil; k, _ = c.Next() {
counter++
}
return nil
})
return counter, err
}