golang thread safe map implementation

The secure map found on the net is achieved with a mutex or read-write lock, here with a single coroutine to achieve, that is, all the add, delete, check and change operations are integrated into 1 goroutine, this will certainly not appear multithreaded concurrent access to the problem.

The basic idea is to start a long-running goroutine in the background and accept the request of req in its own channel blocking. req is divided into different requests, such as reading key, writing key, etc., and then carry out various operations in this goroutine.

Example: the Get method sends a request to readSig (channel). The request is a pointer to readReq. When the run method receives the signal, it reads the underlying map and writes the value to value of readReq (value is channel). The Get method blocks the received value and returns value when received.

ps: It took me more than two hours to write it. I just did a simple test without in-depth test. In addition, The performance was not tested.

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  For the time being synchronous and asynchronous may have usage issues. 
}
 
//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 address: https: / / github com/hackssssss/safemap