add comments to NRWMutex

ocis-pkg/sync/mutex.go

@@ -4,6 +4,8 @@ import (
 	"sync"
 )
 
+// NRWMutex works the same as RWMutex, the only difference is that it stores mutexes in a map and reuses them.
+// It's handy if you want to write-lock, write-unlock, read-lock and read-unlock for specific names only.
 type NRWMutex struct {
 	m  sync.Mutex
 	mm map[string]*nrw
@@ -14,10 +16,12 @@ type nrw struct {
 	c int
 }
 
+// NewNRWMutex returns a new instance of NRWMutex.
 func NewNRWMutex() NRWMutex {
 	return NRWMutex{mm: make(map[string]*nrw)}
 }
 
+// Lock locks rw for writing.
 func (c *NRWMutex) Lock(k string) {
 	c.m.Lock()
 	m := c.get(k)
@@ -26,6 +30,7 @@ func (c *NRWMutex) Lock(k string) {
 	m.m.Lock()
 }
 
+// Unlock unlocks rw for writing.
 func (c *NRWMutex) Unlock(k string) {
 	c.m.Lock()
 	defer c.m.Unlock()
@@ -37,6 +42,7 @@ func (c *NRWMutex) Unlock(k string) {
 	}
 }
 
+// RLock locks rw for reading.
 func (c *NRWMutex) RLock(k string) {
 	c.m.Lock()
 	m := c.get(k)
@@ -45,6 +51,7 @@ func (c *NRWMutex) RLock(k string) {
 	m.m.RLock()
 }
 
+// RUnlock undoes a single RLock call.
 func (c *NRWMutex) RUnlock(k string) {
 	c.m.Lock()
 	defer c.m.Unlock()