golang线程安全的map实现

网上找的协程安全的map都是用互斥锁或者读写锁实现的，这里用单个协程来实现下，即所有的增删查改操作都集成到一个goroutine中，这样肯定不会出现多线程并发访问的问题。

基本思路是后台启动一个长期运行的goroutine，阻塞的接受自己channel中的请求req，req分为不同的请求，比如读key，写key等，然后在这个goroutine中进行各种操作。

例： Get方法向readSig（channel）中发送一条请求。请求是readReq的指针，当run方法接收到信号时，读取底层map，将值写入readReq的value中（value是个channel），Get方法阻塞的接收value，接收到就返回value。

ps：花了两个多小时写完，只是简单的做了测试，没有深入测试，另外性能也没有测过，以后有空会深入测试一下正确性以及相比加锁的写法其性能如何。

package util

type smap struct {
 m      map[interface{}]interface{}
 readSig   chan *readReq
 writeSig   chan *writeReq
 lenSig    chan *lenReq
 terminateSig chan bool
 delSig    chan *delReq
 scanSig   chan *scanReq
}

type readReq struct {
 key  interface{}
 value interface{}
 ok  chan bool
}

type writeReq struct {
 key  interface{}
 value interface{}
 ok  chan bool
}

type lenReq struct {
 len chan int
}

type delReq struct {
 key interface{}
 ok chan bool
}

type scanReq struct {
 do     func(interface{}, interface{})
 doWithBreak func(interface{}, interface{}) bool
 brea    int
 done    chan bool
}
// NewSmap returns an instance of the pointer of safemap
func NewSmap() *smap {
 var mp smap
 mp.m = make(map[interface{}]interface{})
 mp.readSig = make(chan *readReq)
 mp.writeSig = make(chan *writeReq)
 mp.lenSig = make(chan *lenReq)
 mp.delSig = make(chan *delReq)
 mp.scanSig = make(chan *scanReq)
 go mp.run()
 return &mp
}

//background function to operate map in one goroutine
//this can ensure that the map is Concurrent security.
func (s *smap) run() {
 for {
 select {
 case read := <-s.readSig:
  if value, ok := s.m[read.key]; ok {
  read.value = value
  read.ok <- true
  } else {
  read.ok <- false
  }
 case write := <-s.writeSig:
  s.m[write.key] = write.value
  write.ok <- true
 case l := <-s.lenSig:
  l.len <- len(s.m)
 case sc := <-s.scanSig:
  if sc.brea == 0 {
  for k, v := range s.m {
   sc.do(k, v)
  }
  } else {
  for k, v := range s.m {
   ret := sc.doWithBreak(k, v)
   if ret {
   break
   }
  }
  }
  sc.done <- true
 case d := <-s.delSig:
  delete(s.m, d.key)
  d.ok <- true
 case <-s.terminateSig:
  return
 }
 }
}

//Get returns the value of key which provided.
//if the key not found in map, ok will be false.
func (s *smap) Get(key interface{}) (interface{}, bool) {
 req := &readReq{
 key: key,
 ok: make(chan bool),
 }
 s.readSig <- req
 ok := <-req.ok
 return req.value, ok
}

//Set set the key and value to map
//ok returns true indicates that key and value is successfully added to map
func (s *smap) Set(key interface{}, value interface{}) bool {
 req := &writeReq{
 key:  key,
 value: value,
 ok:  make(chan bool),
 }
 s.writeSig <- req
 return <-req.ok //TODO 暂时先是同步的，异步的可能存在使用方面的问题。
}

//Clear clears all the key and value in map.
func (s *smap) Clear() {
 s.m = make(map[interface{}]interface{})
}

//Size returns the size of map.
func (s *smap) Size() int {
 req := &lenReq{
 len: make(chan int),
 }
 s.lenSig <- req
 return <-req.len
}

//terminate s.Run function. this function is usually called for debug.
//after this do NOT use smap again, because it can make your program block.
func (s *smap) TerminateBackGoroutine() {
 s.terminateSig <- true
}

//Del delete the key in map
func (s *smap) Del(key interface{}) bool {
 req := &delReq{
 key: key,
 ok: make(chan bool),
 }
 s.delSig <- req
 return <-req.ok
}

//scan the map. do is a function which operate all of the key and value in map
func (s *smap) EachItem(do func(interface{}, interface{})) {
 req := &scanReq{
 do:  do,
 brea: 0,
 done: make(chan bool),
 }
 s.scanSig <- req
 <-req.done
}

//scan the map util function 'do' returns true. do is a function which operate all of the key and value in map
func (s *smap) EachItemBreak(do func(interface{}, interface{}) bool, condition bool) {
 req := &scanReq{
 doWithBreak: do,
 brea:    1,
 done:    make(chan bool),
 }
 s.scanSig <- req
 <-req.done
}

//Exists checks whether the key which provided is exists in map
func (s *smap) Exists(key interface{}) bool {
 if _,found := s.Get(key); found {
 return true
 }
 return false
}

github地址：https://github.com/hackssssss/safemap

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