proof_of_work.go

package main

import (
	"bytes"
	"crypto/sha256"
	"fmt"
	"math/big"
)

type ProofOfWork struct {
	block  *Block
	target *big.Int
}

func NewProofOfWork(b *Block) *ProofOfWork {
	target := big.NewInt(1)
	target.Lsh(target, uint(256-targetBits))

	pow := ProofOfWork{
		block:  b,
		target: target,
	}

	return &pow
}

func (pow *ProofOfWork) prepareData(nonce int) []byte {
	data := bytes.Join(
		[][]byte{
			pow.block.PrevBlockHash,
			pow.block.Data,
			intToHex(int64(targetBits)),
			intToHex(int64(nonce)),
		},
		[]byte{},
	)

	return data
}

func (pow *ProofOfWork) Run() (int, []byte) {
	var hashInt big.Int
	var hash [32]byte
	nonce := 0

	fmt.Printf("Mining the block containing %s\n", pow.block.Data)
	for nonce < maxNonce {
		data := pow.prepareData(nonce)
		hash = sha256.Sum256(data)

		fmt.Printf("\r%x", hash)

		hashInt.SetBytes(hash[:])

		if hashInt.Cmp(pow.target) == -1 {
			break
		}

		nonce++
	}

	fmt.Print("\n\n")

	return nonce, hash[:]

}

func (pow *ProofOfWork) Validate() bool {
	var hashInt big.Int

	data := pow.prepareData(pow.block.Nonce)
	hash := sha256.Sum256(data)
	hashInt.SetBytes(hash[:])

	return hashInt.Cmp(pow.target) == -1
}