core: separate and contain POW verifier, extensive tests

core/chain_pow.go

@@ -0,0 +1,87 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package core
+
+import (
+	"runtime"
+
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/pow"
+)
+
+// nonceCheckResult contains the result of a nonce verification.
+type nonceCheckResult struct {
+	index int  // Index of the item verified from an input array
+	valid bool // Result of the nonce verification
+}
+
+// verifyNoncesFromHeaders starts a concurrent header nonce verification,
+// returning a quit channel to abort the operations and a results channel
+// to retrieve the async verifications.
+func verifyNoncesFromHeaders(checker pow.PoW, headers []*types.Header) (chan<- struct{}, <-chan nonceCheckResult) {
+	items := make([]pow.Block, len(headers))
+	for i, header := range headers {
+		items[i] = types.NewBlockWithHeader(header)
+	}
+	return verifyNonces(checker, items)
+}
+
+// verifyNoncesFromBlocks starts a concurrent block nonce verification,
+// returning a quit channel to abort the operations and a results channel
+// to retrieve the async verifications.
+func verifyNoncesFromBlocks(checker pow.PoW, blocks []*types.Block) (chan<- struct{}, <-chan nonceCheckResult) {
+	items := make([]pow.Block, len(blocks))
+	for i, block := range blocks {
+		items[i] = block
+	}
+	return verifyNonces(checker, items)
+}
+
+// verifyNonces starts a concurrent nonce verification, returning a quit channel
+// to abort the operations and a results channel to retrieve the async checks.
+func verifyNonces(checker pow.PoW, items []pow.Block) (chan<- struct{}, <-chan nonceCheckResult) {
+	// Spawn as many workers as allowed threads
+	workers := runtime.GOMAXPROCS(0)
+	if len(items) < workers {
+		workers = len(items)
+	}
+	// Create a task channel and spawn the verifiers
+	tasks := make(chan int, workers)
+	results := make(chan nonceCheckResult, len(items)) // Buffered to make sure all workers stop
+	for i := 0; i < workers; i++ {
+		go func() {
+			for index := range tasks {
+				results <- nonceCheckResult{index: index, valid: checker.Verify(items[index])}
+			}
+		}()
+	}
+	// Feed item indices to the workers until done or aborted
+	abort := make(chan struct{})
+	go func() {
+		defer close(tasks)
+
+		for i := range items {
+			select {
+			case tasks <- i:
+				continue
+			case <-abort:
+				return
+			}
+		}
+	}()
+	return abort, results
+}