core, consensus: pluggable consensus engines (#3817)

This commit adds pluggable consensus engines to go-ethereum. In short, it
introduces a generic consensus interface, and refactors the entire codebase to
use this interface.

consensus/ethash/algorithm_go1.8_test.go

@@ -0,0 +1,46 @@
+// Copyright 2017 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/>.
+
+// +build go1.8
+
+package ethash
+
+import "testing"
+
+// Tests whether the dataset size calculator work correctly by cross checking the
+// hard coded lookup table with the value generated by it.
+func TestSizeCalculations(t *testing.T) {
+	var tests []uint64
+
+	// Verify all the cache sizes from the lookup table
+	defer func(sizes []uint64) { cacheSizes = sizes }(cacheSizes)
+	tests, cacheSizes = cacheSizes, []uint64{}
+
+	for i, test := range tests {
+		if size := cacheSize(uint64(i*epochLength) + 1); size != test {
+			t.Errorf("cache %d: cache size mismatch: have %d, want %d", i, size, test)
+		}
+	}
+	// Verify all the dataset sizes from the lookup table
+	defer func(sizes []uint64) { datasetSizes = sizes }(datasetSizes)
+	tests, datasetSizes = datasetSizes, []uint64{}
+
+	for i, test := range tests {
+		if size := datasetSize(uint64(i*epochLength) + 1); size != test {
+			t.Errorf("dataset %d: dataset size mismatch: have %d, want %d", i, size, test)
+		}
+	}
+}