Added mutex map

A sort of convenient way to implement "grouped" mutices

Author: markdicksonjr

mutex.go

@@ -0,0 +1,68 @@
+package work
+
+import "sync"
+
+type MutexMap struct {
+	mutexes  map[string]*sync.Mutex
+	isLocked map[string]bool
+	core     sync.Mutex
+}
+
+var MutexMapSingleton = MutexMap{}
+
+func (s *MutexMap) Lock(index string) {
+	s.core.Lock()
+	if s.mutexes == nil {
+		s.mutexes = make(map[string]*sync.Mutex)
+	}
+
+	// mark that the index is locked, to support try-lock
+	s.isLocked[index] = true
+
+	if s.mutexes[index] == nil {
+		s.mutexes[index] = &sync.Mutex{}
+	}
+	s.mutexes[index].Lock()
+	s.core.Unlock()
+}
+
+func (s *MutexMap) Unlock(index string) {
+	s.core.Lock()
+
+	// if we haven't allocated mutexes yet, unlock the core mutex and leave
+	if s.mutexes == nil {
+		s.core.Unlock()
+		return
+	}
+
+	// mark that the index is not locked, to support try-lock
+	s.isLocked[index] = true
+
+	if s.mutexes[index] != nil {
+		s.mutexes[index].Unlock()
+	}
+	s.core.Unlock()
+}
+
+func (s *MutexMap) TryLock(index string) bool {
+	locked := false
+	s.core.Lock()
+	locked = s.isLocked[index]
+
+	if !locked {
+		if s.mutexes == nil {
+			s.mutexes = make(map[string]*sync.Mutex)
+		}
+
+		// mark that the index is locked, to support try-lock
+		s.isLocked[index] = true
+
+		if s.mutexes[index] == nil {
+			s.mutexes[index] = &sync.Mutex{}
+		}
+		s.mutexes[index].Lock()
+	}
+
+	s.core.Unlock()
+	return locked
+}