github.com/linapex/ethereum-dpos-chinese@v0.0.0-20190316121959-b78b3a4a1ece/accounts/keystore/account_cache.go

//<developer>
//    <name>linapex 曹一峰</name>
//    <email>linapex@163.com</email>
//    <wx>superexc</wx>
//    <qqgroup>128148617</qqgroup>
//    <url>https://jsq.ink</url>
//    <role>pku engineer</role>
//    <date>2019-03-16 12:09:26</date>
//</624342584738713600>


package keystore

import (
	"bufio"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"time"

	mapset "github.com/deckarep/golang-set"
	"github.com/ethereum/go-ethereum/accounts"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/log"
)

//缓存重新加载之间的最短时间间隔。此限制适用于平台
//不支持更改通知。如果keystore目录没有
//尽管存在，代码最多也会尝试创建一个观察程序。
const minReloadInterval = 2 * time.Second

type accountsByURL []accounts.Account

func (s accountsByURL) Len() int           { return len(s) }
func (s accountsByURL) Less(i, j int) bool { return s[i].URL.Cmp(s[j].URL) < 0 }
func (s accountsByURL) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }

//尝试解锁时返回ambiguousaddrror
//存在多个文件的地址。
type AmbiguousAddrError struct {
	Addr    common.Address
	Matches []accounts.Account
}

func (err *AmbiguousAddrError) Error() string {
	files := ""
	for i, a := range err.Matches {
		files += a.URL.Path
		if i < len(err.Matches)-1 {
			files += ", "
		}
	}
	return fmt.Sprintf("multiple keys match address (%s)", files)
}

//accountcache是密钥库中所有帐户的实时索引。
type accountCache struct {
	keydir   string
	watcher  *watcher
	mu       sync.Mutex
	all      accountsByURL
	byAddr   map[common.Address][]accounts.Account
	throttle *time.Timer
	notify   chan struct{}
	fileC    fileCache
}

func newAccountCache(keydir string) (*accountCache, chan struct{}) {
	ac := &accountCache{
		keydir: keydir,
		byAddr: make(map[common.Address][]accounts.Account),
		notify: make(chan struct{}, 1),
		fileC:  fileCache{all: mapset.NewThreadUnsafeSet()},
	}
	ac.watcher = newWatcher(ac)
	return ac, ac.notify
}

func (ac *accountCache) accounts() []accounts.Account {
	ac.maybeReload()
	ac.mu.Lock()
	defer ac.mu.Unlock()
	cpy := make([]accounts.Account, len(ac.all))
	copy(cpy, ac.all)
	return cpy
}

func (ac *accountCache) hasAddress(addr common.Address) bool {
	ac.maybeReload()
	ac.mu.Lock()
	defer ac.mu.Unlock()
	return len(ac.byAddr[addr]) > 0
}

func (ac *accountCache) add(newAccount accounts.Account) {
	ac.mu.Lock()
	defer ac.mu.Unlock()

	i := sort.Search(len(ac.all), func(i int) bool { return ac.all[i].URL.Cmp(newAccount.URL) >= 0 })
	if i < len(ac.all) && ac.all[i] == newAccount {
		return
	}
//NewAccount不在缓存中。
	ac.all = append(ac.all, accounts.Account{})
	copy(ac.all[i+1:], ac.all[i:])
	ac.all[i] = newAccount
	ac.byAddr[newAccount.Address] = append(ac.byAddr[newAccount.Address], newAccount)
}

//注意：删除的文件必须是唯一的（即必须同时设置文件和地址）。
func (ac *accountCache) delete(removed accounts.Account) {
	ac.mu.Lock()
	defer ac.mu.Unlock()

	ac.all = removeAccount(ac.all, removed)
	if ba := removeAccount(ac.byAddr[removed.Address], removed); len(ba) == 0 {
		delete(ac.byAddr, removed.Address)
	} else {
		ac.byAddr[removed.Address] = ba
	}
}

//DeleteByFile删除由给定路径引用的帐户。
func (ac *accountCache) deleteByFile(path string) {
	ac.mu.Lock()
	defer ac.mu.Unlock()
	i := sort.Search(len(ac.all), func(i int) bool { return ac.all[i].URL.Path >= path })

	if i < len(ac.all) && ac.all[i].URL.Path == path {
		removed := ac.all[i]
		ac.all = append(ac.all[:i], ac.all[i+1:]...)
		if ba := removeAccount(ac.byAddr[removed.Address], removed); len(ba) == 0 {
			delete(ac.byAddr, removed.Address)
		} else {
			ac.byAddr[removed.Address] = ba
		}
	}
}

func removeAccount(slice []accounts.Account, elem accounts.Account) []accounts.Account {
	for i := range slice {
		if slice[i] == elem {
			return append(slice[:i], slice[i+1:]...)
		}
	}
	return slice
}

//如果存在唯一匹配项，find返回地址的缓存帐户。
//accounts.account的文档解释了精确的匹配规则。
//呼叫者必须持有AC.MU。
func (ac *accountCache) find(a accounts.Account) (accounts.Account, error) {
//如果可能的话，限制搜索以满足候选人的要求。
	matches := ac.all
	if (a.Address != common.Address{}) {
		matches = ac.byAddr[a.Address]
	}
	if a.URL.Path != "" {
//如果只指定了basename，请完成路径。
		if !strings.ContainsRune(a.URL.Path, filepath.Separator) {
			a.URL.Path = filepath.Join(ac.keydir, a.URL.Path)
		}
		for i := range matches {
			if matches[i].URL == a.URL {
				return matches[i], nil
			}
		}
		if (a.Address == common.Address{}) {
			return accounts.Account{}, ErrNoMatch
		}
	}
	switch len(matches) {
	case 1:
		return matches[0], nil
	case 0:
		return accounts.Account{}, ErrNoMatch
	default:
		err := &AmbiguousAddrError{Addr: a.Address, Matches: make([]accounts.Account, len(matches))}
		copy(err.Matches, matches)
		sort.Sort(accountsByURL(err.Matches))
		return accounts.Account{}, err
	}
}

func (ac *accountCache) maybeReload() {
	ac.mu.Lock()

	if ac.watcher.running {
		ac.mu.Unlock()
return //观察程序正在运行并将保持缓存的最新状态。
	}
	if ac.throttle == nil {
		ac.throttle = time.NewTimer(0)
	} else {
		select {
		case <-ac.throttle.C:
		default:
			ac.mu.Unlock()
return //缓存最近被重新加载。
		}
	}
//没有观察者在运行，启动它。
	ac.watcher.start()
	ac.throttle.Reset(minReloadInterval)
	ac.mu.Unlock()
	ac.scanAccounts()
}

func (ac *accountCache) close() {
	ac.mu.Lock()
	ac.watcher.close()
	if ac.throttle != nil {
		ac.throttle.Stop()
	}
	if ac.notify != nil {
		close(ac.notify)
		ac.notify = nil
	}
	ac.mu.Unlock()
}

//scanaccounts检查文件系统是否发生任何更改，以及
//相应地更新帐户缓存
func (ac *accountCache) scanAccounts() error {
//扫描整个文件夹元数据以查找文件更改
	creates, deletes, updates, err := ac.fileC.scan(ac.keydir)
	if err != nil {
		log.Debug("Failed to reload keystore contents", "err", err)
		return err
	}
	if creates.Cardinality() == 0 && deletes.Cardinality() == 0 && updates.Cardinality() == 0 {
		return nil
	}
//创建一个助手方法来扫描密钥文件的内容
	var (
		buf = new(bufio.Reader)
		key struct {
			Address string `json:"address"`
		}
	)
	readAccount := func(path string) *accounts.Account {
		fd, err := os.Open(path)
		if err != nil {
			log.Trace("Failed to open keystore file", "path", path, "err", err)
			return nil
		}
		defer fd.Close()
		buf.Reset(fd)
//分析地址。
		key.Address = ""
		err = json.NewDecoder(buf).Decode(&key)
		addr := common.HexToAddress(key.Address)
		switch {
		case err != nil:
			log.Debug("Failed to decode keystore key", "path", path, "err", err)
		case (addr == common.Address{}):
			log.Debug("Failed to decode keystore key", "path", path, "err", "missing or zero address")
		default:
			return &accounts.Account{Address: addr, URL: accounts.URL{Scheme: KeyStoreScheme, Path: path}}
		}
		return nil
	}
//处理所有文件差异
	start := time.Now()

	for _, p := range creates.ToSlice() {
		if a := readAccount(p.(string)); a != nil {
			ac.add(*a)
		}
	}
	for _, p := range deletes.ToSlice() {
		ac.deleteByFile(p.(string))
	}
	for _, p := range updates.ToSlice() {
		path := p.(string)
		ac.deleteByFile(path)
		if a := readAccount(path); a != nil {
			ac.add(*a)
		}
	}
	end := time.Now()

	select {
	case ac.notify <- struct{}{}:
	default:
	}
	log.Trace("Handled keystore changes", "time", end.Sub(start))
	return nil
}