1// Copyright 2018 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	"runtime"
21
22	"github.com/ethereum/go-ethereum/core/types"
23)
24
25// senderCacher is a concurrent transaction sender recoverer and cacher.
26var senderCacher = newTxSenderCacher(runtime.NumCPU())
27
28// txSenderCacherRequest is a request for recovering transaction senders with a
29// specific signature scheme and caching it into the transactions themselves.
30//
31// The inc field defines the number of transactions to skip after each recovery,
32// which is used to feed the same underlying input array to different threads but
33// ensure they process the early transactions fast.
34type txSenderCacherRequest struct {
35	signer types.Signer
36	txs    []*types.Transaction
37	inc    int
38}
39
40// txSenderCacher is a helper structure to concurrently ecrecover transaction
41// senders from digital signatures on background threads.
42type txSenderCacher struct {
43	threads int
44	tasks   chan *txSenderCacherRequest
45}
46
47// newTxSenderCacher creates a new transaction sender background cacher and starts
48// as many processing goroutines as allowed by the GOMAXPROCS on construction.
49func newTxSenderCacher(threads int) *txSenderCacher {
50	cacher := &txSenderCacher{
51		tasks:   make(chan *txSenderCacherRequest, threads),
52		threads: threads,
53	}
54	for i := 0; i < threads; i++ {
55		go cacher.cache()
56	}
57	return cacher
58}
59
60// cache is an infinite loop, caching transaction senders from various forms of
61// data structures.
62func (cacher *txSenderCacher) cache() {
63	for task := range cacher.tasks {
64		for i := 0; i < len(task.txs); i += task.inc {
65			types.Sender(task.signer, task.txs[i])
66		}
67	}
68}
69
70// recover recovers the senders from a batch of transactions and caches them
71// back into the same data structures. There is no validation being done, nor
72// any reaction to invalid signatures. That is up to calling code later.
73func (cacher *txSenderCacher) recover(signer types.Signer, txs []*types.Transaction) {
74	// If there's nothing to recover, abort
75	if len(txs) == 0 {
76		return
77	}
78	// Ensure we have meaningful task sizes and schedule the recoveries
79	tasks := cacher.threads
80	if len(txs) < tasks*4 {
81		tasks = (len(txs) + 3) / 4
82	}
83	for i := 0; i < tasks; i++ {
84		cacher.tasks <- &txSenderCacherRequest{
85			signer: signer,
86			txs:    txs[i:],
87			inc:    tasks,
88		}
89	}
90}
91
92// recoverFromBlocks recovers the senders from a batch of blocks and caches them
93// back into the same data structures. There is no validation being done, nor
94// any reaction to invalid signatures. That is up to calling code later.
95func (cacher *txSenderCacher) recoverFromBlocks(signer types.Signer, blocks []*types.Block) {
96	count := 0
97	for _, block := range blocks {
98		count += len(block.Transactions())
99	}
100	txs := make([]*types.Transaction, 0, count)
101	for _, block := range blocks {
102		txs = append(txs, block.Transactions()...)
103	}
104	cacher.recover(signer, txs)
105}
106