1 files changed, 113 insertions, 0 deletions
diff --git a/vendor/git.iim.gay/grufwub/go-mutexes/map.go b/vendor/git.iim.gay/grufwub/go-mutexes/map.go
new file mode 100644
index 000000000..1e5b2781a
--- /dev/null
+++ b/vendor/git.iim.gay/grufwub/go-mutexes/map.go
@@ -0,0 +1,113 @@
+package mutexes
+
+import (
+	"sync"
+)
+
+// MutexMap is a structure that allows having a map of self-evicting mutexes
+// by key. You do not need to worry about managing the contents of the map,
+// only requesting RLock/Lock for keys, and ensuring to call the returned
+// unlock functions.
+type MutexMap interface {
+	// Lock acquires a mutex lock for supplied key, returning an Unlock function
+	Lock(key string) (unlock func())
+
+	// RLock acquires a mutex read lock for supplied key, returning an RUnlock function
+	RLock(key string) (runlock func())
+}
+
+type mutexMap struct {
+	// NOTE:
+	// Individual keyed mutexes should ONLY ever
+	// be locked within the protection of the outer
+	// mapMu lock. If you lock these outside the
+	// protection of this, there is a chance for
+	// deadlocks
+
+	mus   map[string]RWMutex
+	mapMu sync.Mutex
+	pool  sync.Pool
+}
+
+// NewMap returns a new MutexMap instance based on supplied
+// RWMutex allocator function, nil implies use default
+func NewMap(newFn func() RWMutex) MutexMap {
+	if newFn == nil {
+		newFn = NewRW
+	}
+	return &mutexMap{
+		mus:   make(map[string]RWMutex),
+		mapMu: sync.Mutex{},
+		pool: sync.Pool{
+			New: func() interface{} {
+				return newFn()
+			},
+		},
+	}
+}
+
+func (mm *mutexMap) evict(key string, mu RWMutex) {
+	// Acquire map lock
+	mm.mapMu.Lock()
+
+	// Toggle mutex lock to
+	// ensure it is unused
+	unlock := mu.Lock()
+	unlock()
+
+	// Delete mutex key
+	delete(mm.mus, key)
+	mm.mapMu.Unlock()
+
+	// Release to pool
+	mm.pool.Put(mu)
+}
+
+// GetRLock acquires a mutex read lock for supplied key, returning an RUnlock function
+func (mm *mutexMap) RLock(key string) func() {
+	return mm.getLock(key, func(mu RWMutex) func() {
+		return mu.RLock()
+	})
+}
+
+// GetLock acquires a mutex lock for supplied key, returning an Unlock function
+func (mm *mutexMap) Lock(key string) func() {
+	return mm.getLock(key, func(mu RWMutex) func() {
+		return mu.Lock()
+	})
+}
+
+func (mm *mutexMap) getLock(key string, doLock func(RWMutex) func()) func() {
+	// Get map lock
+	mm.mapMu.Lock()
+
+	// Look for mutex
+	mu, ok := mm.mus[key]
+	if ok {
+		// Lock and return
+		// its unlocker func
+		unlock := doLock(mu)
+		mm.mapMu.Unlock()
+		return unlock
+	}
+
+	// Note: even though the mutex data structure is
+	// small, benchmarking does actually show that pooled
+	// alloc of mutexes here is faster
+
+	// Acquire mu + add
+	mu = mm.pool.Get().(RWMutex)
+	mm.mus[key] = mu
+
+	// Lock mutex + unlock map
+	unlockFn := doLock(mu)
+	mm.mapMu.Unlock()
+
+	return func() {
+		// Unlock mutex
+		unlockFn()
+
+		// Release function
+		go mm.evict(key, mu)
+	}
+}