網(wǎng)上找的協(xié)程安全的map都是用互斥鎖或者讀寫鎖實(shí)現(xiàn)的，這里用單個(gè)協(xié)程來實(shí)現(xiàn)下，即所有的增刪查改操作都集成到一個(gè)goroutine中，這樣肯定不會(huì)出現(xiàn)多線程并發(fā)訪問的問題。
基本思路是后臺(tái)啟動(dòng)一個(gè)長(zhǎng)期運(yùn)行的goroutine，阻塞的接受自己channel中的請(qǐng)求req，req分為不同的請(qǐng)求，比如讀key，寫key等，然后在這個(gè)goroutine中進(jìn)行各種操作。
例： Get方法向readSig（channel）中發(fā)送一條請(qǐng)求。請(qǐng)求是readReq的指針，當(dāng)run方法接收到信號(hào)時(shí)，讀取底層map，將值寫入readReq的value中（value是個(gè)channel），Get方法阻塞的接收value，接收到就返回value。
ps：花了兩個(gè)多小時(shí)寫完，只是簡(jiǎn)單的做了測(cè)試，沒有深入測(cè)試，另外性能也沒有測(cè)過，以后有空會(huì)深入測(cè)試一下正確性以及相比加鎖的寫法其性能如何。
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 暫時(shí)先是同步的，異步的可能存在使用方面的問題。
}
//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
}
