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81 lines
1.5 KiB
81 lines
1.5 KiB
package pow
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import (
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"bytes"
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"crypto/sha256"
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"encoding/binary"
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"fmt"
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"math"
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"math/big"
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)
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var (
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maxNonce = math.MaxUint32
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)
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const targetBits = 24
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// ProofOfWork represents a proof-of-work
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type ProofOfWork struct {
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Challenge uint32
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target *big.Int
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FinalNonce uint32
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}
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// NewProofOfWork builds and returns a ProofOfWork
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func NewProofOfWork(c uint32) *ProofOfWork {
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target := big.NewInt(1)
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target.Lsh(target, uint(256-targetBits))
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pow := &ProofOfWork{Challenge: c, target: target, FinalNonce: 0}
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return pow
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}
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func (pow *ProofOfWork) prepareData(nonce uint32) []byte {
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challenge := make([]byte, 4)
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binary.LittleEndian.PutUint32(challenge, pow.Challenge)
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nonceB := make([]byte, 4)
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binary.LittleEndian.PutUint32(nonceB, nonce)
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data := bytes.Join(
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[][]byte{
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challenge,
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nonceB,
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},
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[]byte{},
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)
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return data
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}
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// Run performs a proof-of-work
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func (pow *ProofOfWork) Run() int {
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var hashInt big.Int
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var hash [32]byte
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nonce := 0
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for nonce < maxNonce {
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data := pow.prepareData(uint32(nonce))
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hash = sha256.Sum256(data)
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fmt.Printf("\r%x", hash)
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hashInt.SetBytes(hash[:])
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if hashInt.Cmp(pow.target) == -1 {
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pow.FinalNonce = uint32(nonce)
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break
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} else {
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nonce++
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}
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}
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fmt.Print("\n\n")
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return nonce
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}
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// Validate validates block's PoW
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func (pow *ProofOfWork) Validate(nonce uint32) bool {
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var hashInt big.Int
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data := pow.prepareData(nonce)
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hash := sha256.Sum256(data)
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hashInt.SetBytes(hash[:])
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isValid := hashInt.Cmp(pow.target) == -1
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return isValid
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}
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