From 79b1169a9ff0b54ddf3b520a70a79c78ba5c988d Mon Sep 17 00:00:00 2001
From: Determinant <ted.sybil@gmail.com>
Date: Mon, 21 Oct 2019 14:47:51 -0400
Subject: customize Blockchain code

---
 core/tx_noncer.go | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 core/tx_noncer.go

(limited to 'core/tx_noncer.go')

diff --git a/core/tx_noncer.go b/core/tx_noncer.go
new file mode 100644
index 0000000..d52e267
--- /dev/null
+++ b/core/tx_noncer.go
@@ -0,0 +1,79 @@
+// Copyright 2019 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 (
+	"sync"
+
+	"github.com/ava-labs/go-ethereum/common"
+	"github.com/ava-labs/go-ethereum/core/state"
+)
+
+// txNoncer is a tiny virtual state database to manage the executable nonces of
+// accounts in the pool, falling back to reading from a real state database if
+// an account is unknown.
+type txNoncer struct {
+	fallback *state.StateDB
+	nonces   map[common.Address]uint64
+	lock     sync.Mutex
+}
+
+// newTxNoncer creates a new virtual state database to track the pool nonces.
+func newTxNoncer(statedb *state.StateDB) *txNoncer {
+	return &txNoncer{
+		fallback: statedb.Copy(),
+		nonces:   make(map[common.Address]uint64),
+	}
+}
+
+// get returns the current nonce of an account, falling back to a real state
+// database if the account is unknown.
+func (txn *txNoncer) get(addr common.Address) uint64 {
+	// We use mutex for get operation is the underlying
+	// state will mutate db even for read access.
+	txn.lock.Lock()
+	defer txn.lock.Unlock()
+
+	if _, ok := txn.nonces[addr]; !ok {
+		txn.nonces[addr] = txn.fallback.GetNonce(addr)
+	}
+	return txn.nonces[addr]
+}
+
+// set inserts a new virtual nonce into the virtual state database to be returned
+// whenever the pool requests it instead of reaching into the real state database.
+func (txn *txNoncer) set(addr common.Address, nonce uint64) {
+	txn.lock.Lock()
+	defer txn.lock.Unlock()
+
+	txn.nonces[addr] = nonce
+}
+
+// setIfLower updates a new virtual nonce into the virtual state database if the
+// the new one is lower.
+func (txn *txNoncer) setIfLower(addr common.Address, nonce uint64) {
+	txn.lock.Lock()
+	defer txn.lock.Unlock()
+
+	if _, ok := txn.nonces[addr]; !ok {
+		txn.nonces[addr] = txn.fallback.GetNonce(addr)
+	}
+	if txn.nonces[addr] <= nonce {
+		return
+	}
+	txn.nonces[addr] = nonce
+}
-- 
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