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October 27, 2013 04:06
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Javaデザパタ本 マルチスレッド編 section6 「read-write lockパターン」
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// read-write lockパターン | |
// 読む処理同士が衝突しないことを利用してパフォーマンスをあげる | |
// コンテキスト | |
// - 読む処理が重く、ひとつのReaderがリソースを占有するとパフォーマンスが落ちる状況 | |
// - 読む頻度が書く頻度よりも高い状況 | |
package main | |
import "fmt" | |
import "sync" | |
import "time" | |
import "math/rand" | |
// shared resource役 | |
type Data struct { | |
Size int | |
Buffer []string | |
sync.RWMutex // readwrite lock役 | |
} | |
func (self *Data) Init(size int) { | |
self.Size = size | |
for i := 0; i < self.Size; i++ { | |
self.Buffer = append(self.Buffer, "*") | |
} | |
} | |
func (self *Data) Read() []string { | |
defer self.RUnlock() | |
// 読み込みのためのロック。アンロックされるまで書き込めない | |
self.RLock() | |
return self.doRead() | |
} | |
func (self *Data) Write(s string) { | |
defer self.Unlock() | |
// 読み込み・書き込みのロック。アンロックされるまで読み込めない、書き込めない | |
self.Lock() | |
self.doWrite(s) | |
} | |
func (self *Data) doRead() []string { | |
newbuf := make([]string, 10) | |
copy(newbuf, self.Buffer) | |
self.slowly() | |
return newbuf | |
} | |
func (self *Data) doWrite(s string) { | |
for i := 0; i < len(self.Buffer); i++ { | |
self.Buffer[i] = s | |
} | |
self.slowly() | |
} | |
func (self *Data) slowly() { | |
time.Sleep(time.Millisecond*50) | |
} | |
// writer 役 | |
type Writer struct { | |
data *Data | |
filler string | |
index int | |
} | |
func (self *Writer) Start() { | |
for { | |
s := self.nextStr() | |
self.data.Write(s) | |
time.Sleep(time.Millisecond*time.Duration(rand.Intn(3000))) | |
} | |
} | |
func (self *Writer) nextStr() string { | |
s := string(self.filler[self.index]) | |
self.index += 1 | |
if self.index >= len(self.filler) { | |
self.index = 0 | |
} | |
return s | |
} | |
// reader 役 | |
type Reader struct { | |
data *Data | |
} | |
func (self *Reader) Start() { | |
for { | |
readbuf := self.data.Read() | |
fmt.Println("reads ", readbuf) | |
} | |
} | |
func main() { | |
data := &Data{} | |
data.Init(10) | |
reader1 := &Reader{data} | |
reader2 := &Reader{data} | |
reader3 := &Reader{data} | |
reader4 := &Reader{data} | |
reader5 := &Reader{data} | |
reader6 := &Reader{data} | |
writer1 := &Writer{data, "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 0} | |
writer2 := &Writer{data, "abcdefghijklmnopqrstuvwxyz", 0} | |
go reader1.Start() | |
go reader2.Start() | |
go reader3.Start() | |
go reader4.Start() | |
go reader5.Start() | |
go reader6.Start() | |
go writer1.Start() | |
go writer2.Start() | |
for { | |
time.Sleep(100) | |
} | |
} |
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