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-rw-r--r--pow/ethash_algo_go1.8.go57
1 files changed, 57 insertions, 0 deletions
diff --git a/pow/ethash_algo_go1.8.go b/pow/ethash_algo_go1.8.go
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+// 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 pow
+
+import "math/big"
+
+// cacheSize calculates and returns the size of the ethash verification cache that
+// belongs to a certain block number. The cache size grows linearly, however, we
+// always take the highest prime below the linearly growing threshold in order to
+// reduce the risk of accidental regularities leading to cyclic behavior.
+func cacheSize(block uint64) uint64 {
+ // If we have a pre-generated value, use that
+ epoch := int(block / epochLength)
+ if epoch < len(cacheSizes) {
+ return cacheSizes[epoch]
+ }
+ // No known cache size, calculate manually (sanity branch only)
+ size := uint64(cacheInitBytes + cacheGrowthBytes*uint64(epoch) - hashBytes)
+ for !new(big.Int).SetUint64(size / hashBytes).ProbablyPrime(1) { // Always accurate for n < 2^64
+ size -= 2 * hashBytes
+ }
+ return size
+}
+
+// datasetSize calculates and returns the size of the ethash mining dataset that
+// belongs to a certain block number. The dataset size grows linearly, however, we
+// always take the highest prime below the linearly growing threshold in order to
+// reduce the risk of accidental regularities leading to cyclic behavior.
+func datasetSize(block uint64) uint64 {
+ // If we have a pre-generated value, use that
+ epoch := int(block / epochLength)
+ if epoch < len(datasetSizes) {
+ return datasetSizes[epoch]
+ }
+ // No known dataset size, calculate manually (sanity branch only)
+ size := uint64(datasetInitBytes + datasetGrowthBytes*uint64(epoch) - mixBytes)
+ for !new(big.Int).SetUint64(size / mixBytes).ProbablyPrime(1) { // Always accurate for n < 2^64
+ size -= 2 * mixBytes
+ }
+ return size
+}