Exemplo n.º 1
0
// limitNumOrphans limits the number of orphan transactions by evicting a random
// orphan if adding a new one would cause it to overflow the max allowed.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *TxPool) limitNumOrphans() error {
	if len(mp.orphans)+1 > mp.cfg.Policy.MaxOrphanTxs &&
		mp.cfg.Policy.MaxOrphanTxs > 0 {

		// Generate a cryptographically random hash.
		randHashBytes := make([]byte, chainhash.HashSize)
		_, err := rand.Read(randHashBytes)
		if err != nil {
			return err
		}
		randHashNum := new(big.Int).SetBytes(randHashBytes)

		// Try to find the first entry that is greater than the random
		// hash.  Use the first entry (which is already pseudorandom due
		// to Go's range statement over maps) as a fallback if none of
		// the hashes in the orphan pool are larger than the random
		// hash.
		var foundHash *chainhash.Hash
		for txHash := range mp.orphans {
			if foundHash == nil {
				foundHash = &txHash
			}
			txHashNum := blockchain.HashToBig(&txHash)
			if txHashNum.Cmp(randHashNum) > 0 {
				foundHash = &txHash
				break
			}
		}

		mp.removeOrphan(foundHash)
	}

	return nil
}
Exemplo n.º 2
0
// solveBlock attempts to find a nonce which makes the passed block header hash
// to a value less than the target difficulty. When a successful solution is
// found true is returned and the nonce field of the passed header is updated
// with the solution. False is returned if no solution exists.
func solveBlock(header *wire.BlockHeader, targetDifficulty *big.Int) bool {
	// sbResult is used by the solver goroutines to send results.
	type sbResult struct {
		found bool
		nonce uint32
	}

	// solver accepts a block header and a nonce range to test. It is
	// intended to be run as a goroutine.
	quit := make(chan bool)
	results := make(chan sbResult)
	solver := func(hdr wire.BlockHeader, startNonce, stopNonce uint32) {
		// We need to modify the nonce field of the header, so make sure
		// we work with a copy of the original header.
		for i := startNonce; i >= startNonce && i <= stopNonce; i++ {
			select {
			case <-quit:
				return
			default:
				hdr.Nonce = i
				hash := hdr.BlockHash()
				if blockchain.HashToBig(&hash).Cmp(targetDifficulty) <= 0 {
					results <- sbResult{true, i}
					return
				}
			}
		}
		results <- sbResult{false, 0}
	}

	startNonce := uint32(0)
	stopNonce := uint32(math.MaxUint32)
	numCores := uint32(runtime.NumCPU())
	noncesPerCore := (stopNonce - startNonce) / numCores
	for i := uint32(0); i < numCores; i++ {
		rangeStart := startNonce + (noncesPerCore * i)
		rangeStop := startNonce + (noncesPerCore * (i + 1)) - 1
		if i == numCores-1 {
			rangeStop = stopNonce
		}
		go solver(*header, rangeStart, rangeStop)
	}
	for i := uint32(0); i < numCores; i++ {
		result := <-results
		if result.found {
			close(quit)
			header.Nonce = result.nonce
			return true
		}
	}

	return false
}
Exemplo n.º 3
0
// solveBlock attempts to find some combination of a nonce, extra nonce, and
// current timestamp which makes the passed block hash to a value less than the
// target difficulty.  The timestamp is updated periodically and the passed
// block is modified with all tweaks during this process.  This means that
// when the function returns true, the block is ready for submission.
//
// This function will return early with false when conditions that trigger a
// stale block such as a new block showing up or periodically when there are
// new transactions and enough time has elapsed without finding a solution.
func (m *CPUMiner) solveBlock(msgBlock *wire.MsgBlock, blockHeight int32,
	ticker *time.Ticker, quit chan struct{}) bool {

	// Choose a random extra nonce offset for this block template and
	// worker.
	enOffset, err := wire.RandomUint64()
	if err != nil {
		log.Errorf("Unexpected error while generating random "+
			"extra nonce offset: %v", err)
		enOffset = 0
	}

	// Create some convenience variables.
	header := &msgBlock.Header
	targetDifficulty := blockchain.CompactToBig(header.Bits)

	// Initial state.
	lastGenerated := time.Now()
	lastTxUpdate := m.g.TxSource().LastUpdated()
	hashesCompleted := uint64(0)

	// Note that the entire extra nonce range is iterated and the offset is
	// added relying on the fact that overflow will wrap around 0 as
	// provided by the Go spec.
	for extraNonce := uint64(0); extraNonce < maxExtraNonce; extraNonce++ {
		// Update the extra nonce in the block template with the
		// new value by regenerating the coinbase script and
		// setting the merkle root to the new value.
		m.g.UpdateExtraNonce(msgBlock, blockHeight, extraNonce+enOffset)

		// Search through the entire nonce range for a solution while
		// periodically checking for early quit and stale block
		// conditions along with updates to the speed monitor.
		for i := uint32(0); i <= maxNonce; i++ {
			select {
			case <-quit:
				return false

			case <-ticker.C:
				m.updateHashes <- hashesCompleted
				hashesCompleted = 0

				// The current block is stale if the best block
				// has changed.
				best := m.g.BestSnapshot()
				if !header.PrevBlock.IsEqual(best.Hash) {
					return false
				}

				// The current block is stale if the memory pool
				// has been updated since the block template was
				// generated and it has been at least one
				// minute.
				if lastTxUpdate != m.g.TxSource().LastUpdated() &&
					time.Now().After(lastGenerated.Add(time.Minute)) {

					return false
				}

				m.g.UpdateBlockTime(msgBlock)

			default:
				// Non-blocking select to fall through
			}

			// Update the nonce and hash the block header.  Each
			// hash is actually a double sha256 (two hashes), so
			// increment the number of hashes completed for each
			// attempt accordingly.
			header.Nonce = i
			hash := header.BlockHash()
			hashesCompleted += 2

			// The block is solved when the new block hash is less
			// than the target difficulty.  Yay!
			if blockchain.HashToBig(&hash).Cmp(targetDifficulty) <= 0 {
				m.updateHashes <- hashesCompleted
				return true
			}
		}
	}

	return false
}