feat(sync): rwmutex with 4 mutex

README.md

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+# Coding lab
+
+> Coding GYM
+
+## 更新记录
+
+2023-09-18
+
+- [ ] Channel 实现读写锁：来自本人参加百度 ACG 面试，彼时对于并发控制的理解颇为纸上谈兵，未能表现实为遗憾。
+  我对用 channel 模拟这个复杂的任务十分有兴趣，因为在这个过程中 channel 将会扮演非常重要的角色（传递信号量），我就是想通过此达到加深理解的作用

go.mod

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+module lab.evlic.cn/go/coding-lab
+
+go 1.21.0
+
+require github.com/smartystreets/goconvey v1.8.1
+
+require (
+	github.com/gopherjs/gopherjs v1.17.2 // indirect
+	github.com/jtolds/gls v4.20.0+incompatible // indirect
+	github.com/smarty/assertions v1.15.0 // indirect
+	lab.evlic.cn/go/pkg v1.0.0 // indirect
+)

go.sum

@@ -0,0 +1,12 @@
+github.com/gopherjs/gopherjs v1.17.2 h1:fQnZVsXk8uxXIStYb0N4bGk7jeyTalG/wsZjQ25dO0g=
+github.com/gopherjs/gopherjs v1.17.2/go.mod h1:pRRIvn/QzFLrKfvEz3qUuEhtE/zLCWfreZ6J5gM2i+k=
+github.com/jtolds/gls v4.20.0+incompatible h1:xdiiI2gbIgH/gLH7ADydsJ1uDOEzR8yvV7C0MuV77Wo=
+github.com/jtolds/gls v4.20.0+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
+github.com/smarty/assertions v1.15.0 h1:cR//PqUBUiQRakZWqBiFFQ9wb8emQGDb0HeGdqGByCY=
+github.com/smarty/assertions v1.15.0/go.mod h1:yABtdzeQs6l1brC900WlRNwj6ZR55d7B+E8C6HtKdec=
+github.com/smartystreets/goconvey v1.8.1 h1:qGjIddxOk4grTu9JPOU31tVfq3cNdBlNa5sSznIX1xY=
+github.com/smartystreets/goconvey v1.8.1/go.mod h1:+/u4qLyY6x1jReYOp7GOM2FSt8aP9CzCZL03bI28W60=
+lab.evlic.cn/go/pkg v0.0.0-20230918075852-9ca9becf0967 h1:Jk4Io04lRwRtTo56GDahstQQksv3ZzglK6QxUarpakY=
+lab.evlic.cn/go/pkg v0.0.0-20230918075852-9ca9becf0967/go.mod h1:hvaZsvZvj+ly1Fz59x/d/HyyTAL33T44yTjQx/T/SZ8=
+lab.evlic.cn/go/pkg v1.0.0 h1:IuuGjOLTEG9wAWsm4jXh2L7SN6vCJahHOUGAjZ18uno=
+lab.evlic.cn/go/pkg v1.0.0/go.mod h1:hvaZsvZvj+ly1Fz59x/d/HyyTAL33T44yTjQx/T/SZ8=

sync/rwmutex.go

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+package sync
+
+import "sync"
+
+type RWLocker interface {
+	sync.Locker
+	RLock()
+	RUnlock()
+}

sync/rwmutex_test.go

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+package sync
+
+import (
+	"sync"
+	"testing"
+	"time"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func newSyncRWMutex() RWLocker {
+	return &sync.RWMutex{}
+}
+
+func TestChannelRWMutex(t *testing.T) {
+	testCase := map[string]func() RWLocker{
+		"go-src":      newSyncRWMutex,
+		"rw-mutex_v1": NewRWMutexV1,
+	}
+	Convey("rw_mutex", t, func() {
+		for key, newRWMutexFunc := range testCase {
+			Convey("rw_mutex_"+key, func() {
+				rwLock := newRWMutexFunc()
+				var wg sync.WaitGroup
+
+				// 读操作示例
+				for i := 0; i < 5; i++ {
+					wg.Add(1)
+					go func(id int) {
+						defer wg.Done()
+						rwLock.RLock()
+						defer rwLock.RUnlock()
+						//fmt.Printf("Reader %d is reading...\n", id)
+						time.Sleep(time.Millisecond * 500)
+					}(i)
+				}
+
+				// 写操作示例
+				for i := 0; i < 2; i++ {
+					wg.Add(1)
+					go func(id int) {
+						defer wg.Done()
+						rwLock.Lock()
+						defer rwLock.Unlock()
+						//fmt.Printf("Writer %d is writing...\n", id)
+						time.Sleep(time.Millisecond * 1000)
+					}(i)
+				}
+
+				// 等待所有协程完成
+				wg.Wait()
+			})
+		}
+
+	})
+}
+
+func BenchmarkChannelRWMutex(b *testing.B) {
+	rwLock := NewRWMutexV1()
+	var wg sync.WaitGroup
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			rwLock.RLock()
+			defer rwLock.RUnlock()
+		}()
+	}
+	wg.Wait()
+}

sync/rwmutex_v1.go

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+package sync
+
+import (
+	"sync"
+)
+
+/*
+ChannelRWMutexV1
+	使用四把锁
+*/
+
+type ChannelRWMutexV1 struct {
+	mu  sync.Mutex // 互斥锁
+	rm  sync.Mutex // 读等待锁
+	wm  sync.Mutex // 写等待锁
+	cmu sync.Mutex // 计数锁
+	rn  int        // 读等待
+	wn  int        // 写等待
+}
+
+func NewRWMutexV1() RWLocker {
+	return &ChannelRWMutexV1{}
+}
+
+func (rw *ChannelRWMutexV1) RLock() {
+	rw.cmu.Lock()
+	if rw.wn > 0 {
+		rw.cmu.Unlock()
+		rw.wm.Lock()
+		rw.wm.Unlock()
+	} else {
+		defer rw.cmu.Unlock()
+	}
+
+	rw.rn++
+	if rw.rn == 1 {
+		rw.wm.Lock()
+	}
+}
+
+func (rw *ChannelRWMutexV1) RUnlock() {
+	rw.cmu.Lock()
+	defer rw.cmu.Unlock()
+	rw.rn--
+
+	if rw.rn == 0 {
+		rw.wm.Unlock()
+	}
+}
+
+func (rw *ChannelRWMutexV1) Lock() {
+	rw.cmu.Lock()
+	if rw.rn > 0 {
+		rw.cmu.Unlock()
+		rw.wm.Lock()
+		rw.wm.Unlock()
+	} else {
+		defer rw.cmu.Unlock()
+	}
+
+	rw.wn++
+
+	if rw.wn == 1 {
+		rw.rm.Lock()
+	}
+	rw.mu.Lock()
+}
+
+func (rw *ChannelRWMutexV1) Unlock() {
+	rw.cmu.Lock()
+	defer rw.cmu.Unlock()
+	rw.wn--
+
+	if rw.wn == 0 {
+		rw.rm.Unlock()
+	}
+	rw.mu.Unlock()
+}