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/state_prefetcher.go | 85 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 core/state_prefetcher.go

(limited to 'core/state_prefetcher.go')

diff --git a/core/state_prefetcher.go b/core/state_prefetcher.go
new file mode 100644
index 0000000..f408098
--- /dev/null
+++ b/core/state_prefetcher.go
@@ -0,0 +1,85 @@
+// 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/atomic"
+
+	"github.com/ava-labs/go-ethereum/common"
+	"github.com/ava-labs/go-ethereum/consensus"
+	"github.com/ava-labs/go-ethereum/core/state"
+	"github.com/ava-labs/go-ethereum/core/types"
+	"github.com/ava-labs/go-ethereum/core/vm"
+	"github.com/ava-labs/go-ethereum/params"
+)
+
+// statePrefetcher is a basic Prefetcher, which blindly executes a block on top
+// of an arbitrary state with the goal of prefetching potentially useful state
+// data from disk before the main block processor start executing.
+type statePrefetcher struct {
+	config *params.ChainConfig // Chain configuration options
+	bc     *BlockChain         // Canonical block chain
+	engine consensus.Engine    // Consensus engine used for block rewards
+}
+
+// newStatePrefetcher initialises a new statePrefetcher.
+func newStatePrefetcher(config *params.ChainConfig, bc *BlockChain, engine consensus.Engine) *statePrefetcher {
+	return &statePrefetcher{
+		config: config,
+		bc:     bc,
+		engine: engine,
+	}
+}
+
+// Prefetch processes the state changes according to the Ethereum rules by running
+// the transaction messages using the statedb, but any changes are discarded. The
+// only goal is to pre-cache transaction signatures and state trie nodes.
+func (p *statePrefetcher) Prefetch(block *types.Block, statedb *state.StateDB, cfg vm.Config, interrupt *uint32) {
+	var (
+		header  = block.Header()
+		gaspool = new(GasPool).AddGas(block.GasLimit())
+	)
+	// Iterate over and process the individual transactions
+	for i, tx := range block.Transactions() {
+		// If block precaching was interrupted, abort
+		if interrupt != nil && atomic.LoadUint32(interrupt) == 1 {
+			return
+		}
+		// Block precaching permitted to continue, execute the transaction
+		statedb.Prepare(tx.Hash(), block.Hash(), i)
+		if err := precacheTransaction(p.config, p.bc, nil, gaspool, statedb, header, tx, cfg); err != nil {
+			return // Ugh, something went horribly wrong, bail out
+		}
+	}
+}
+
+// precacheTransaction attempts to apply a transaction to the given state database
+// and uses the input parameters for its environment. The goal is not to execute
+// the transaction successfully, rather to warm up touched data slots.
+func precacheTransaction(config *params.ChainConfig, bc ChainContext, author *common.Address, gaspool *GasPool, statedb *state.StateDB, header *types.Header, tx *types.Transaction, cfg vm.Config) error {
+	// Convert the transaction into an executable message and pre-cache its sender
+	msg, err := tx.AsMessage(types.MakeSigner(config, header.Number))
+	if err != nil {
+		return err
+	}
+	// Create the EVM and execute the transaction
+	context := NewEVMContext(msg, header, bc, author)
+	vm := vm.NewEVM(context, statedb, config, cfg)
+
+	_, _, _, err = ApplyMessage(vm, msg, gaspool)
+	return err
+}
-- 
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