1// Copyright 2019 The go-ethereum Authors
2// This file is part of the go-ethereum library.
3//
4// The go-ethereum library is free software: you can redistribute it and/or modify
5// it under the terms of the GNU Lesser General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8//
9// The go-ethereum library is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12// GNU Lesser General Public License for more details.
13//
14// You should have received a copy of the GNU Lesser General Public License
15// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
16
17package core
18
19import (
20	"sync/atomic"
21
22	"github.com/ethereum/go-ethereum/consensus"
23	"github.com/ethereum/go-ethereum/core/state"
24	"github.com/ethereum/go-ethereum/core/types"
25	"github.com/ethereum/go-ethereum/core/vm"
26	"github.com/ethereum/go-ethereum/params"
27)
28
29// statePrefetcher is a basic Prefetcher, which blindly executes a block on top
30// of an arbitrary state with the goal of prefetching potentially useful state
31// data from disk before the main block processor start executing.
32type statePrefetcher struct {
33	config *params.ChainConfig // Chain configuration options
34	bc     *BlockChain         // Canonical block chain
35	engine consensus.Engine    // Consensus engine used for block rewards
36}
37
38// newStatePrefetcher initialises a new statePrefetcher.
39func newStatePrefetcher(config *params.ChainConfig, bc *BlockChain, engine consensus.Engine) *statePrefetcher {
40	return &statePrefetcher{
41		config: config,
42		bc:     bc,
43		engine: engine,
44	}
45}
46
47// Prefetch processes the state changes according to the Ethereum rules by running
48// the transaction messages using the statedb, but any changes are discarded. The
49// only goal is to pre-cache transaction signatures and state trie nodes.
50func (p *statePrefetcher) Prefetch(block *types.Block, statedb *state.StateDB, cfg vm.Config, interrupt *uint32) {
51	var (
52		header       = block.Header()
53		gaspool      = new(GasPool).AddGas(block.GasLimit())
54		blockContext = NewEVMBlockContext(header, p.bc, nil)
55		evm          = vm.NewEVM(blockContext, vm.TxContext{}, statedb, p.config, cfg)
56		signer       = types.MakeSigner(p.config, header.Number)
57	)
58	// Iterate over and process the individual transactions
59	byzantium := p.config.IsByzantium(block.Number())
60	for i, tx := range block.Transactions() {
61		// If block precaching was interrupted, abort
62		if interrupt != nil && atomic.LoadUint32(interrupt) == 1 {
63			return
64		}
65		// Convert the transaction into an executable message and pre-cache its sender
66		msg, err := tx.AsMessage(signer, header.BaseFee)
67		if err != nil {
68			return // Also invalid block, bail out
69		}
70		statedb.Prepare(tx.Hash(), i)
71		if err := precacheTransaction(msg, p.config, gaspool, statedb, header, evm); err != nil {
72			return // Ugh, something went horribly wrong, bail out
73		}
74		// If we're pre-byzantium, pre-load trie nodes for the intermediate root
75		if !byzantium {
76			statedb.IntermediateRoot(true)
77		}
78	}
79	// If were post-byzantium, pre-load trie nodes for the final root hash
80	if byzantium {
81		statedb.IntermediateRoot(true)
82	}
83}
84
85// precacheTransaction attempts to apply a transaction to the given state database
86// and uses the input parameters for its environment. The goal is not to execute
87// the transaction successfully, rather to warm up touched data slots.
88func precacheTransaction(msg types.Message, config *params.ChainConfig, gaspool *GasPool, statedb *state.StateDB, header *types.Header, evm *vm.EVM) error {
89	// Update the evm with the new transaction context.
90	evm.Reset(NewEVMTxContext(msg), statedb)
91	// Add addresses to access list if applicable
92	_, err := ApplyMessage(evm, msg, gaspool)
93	return err
94}
95