From dec87937ca8e3f1c2c6b7ad1bd191bf11560b61c Mon Sep 17 00:00:00 2001
From: Daniel Barney <daniel@pagodabox.com>
Date: Wed, 7 Oct 2015 11:36:38 -0600
Subject: [PATCH] changed how the mutexes were handled, aka fixed some possible
 deadlocks

---
 scribble.go | 47 +++++++++++++++--------------------------------
 1 file changed, 15 insertions(+), 32 deletions(-)

diff --git a/scribble.go b/scribble.go
index e22fa7c..50f8583 100644
--- a/scribble.go
+++ b/scribble.go
@@ -99,6 +99,7 @@ func (d *Driver) write(trans Transaction) error {
 
 	mutex := d.getOrCreateMutex(trans.Collection)
 	mutex.Lock()
+	defer mutex.Unlock()
 
 	//
 	dir := d.dir + "/" + trans.Collection
@@ -123,11 +124,7 @@ func (d *Driver) write(trans Transaction) error {
 	}
 
 	// move final file into place
-	err = os.Rename(tmpPath, finalPath)
-
-	mutex.Unlock()
-
-	return err
+	return os.Rename(tmpPath, finalPath)
 }
 
 // read does the opposite operation as write. Reading a record from the database
@@ -144,11 +141,7 @@ func (d *Driver) read(trans Transaction) error {
 	}
 
 	// unmarshal data into the transaction.Container
-	if err := json.Unmarshal(b, trans.Container); err != nil {
-		return err
-	}
-
-	return nil
+	return json.Unmarshal(b, trans.Container)
 }
 
 // readAll does the same operation as read, reading all the records in the specified
@@ -180,11 +173,7 @@ func (d *Driver) readAll(trans Transaction) error {
 	}
 
 	// unmarhsal the read files as a comma delimeted byte array
-	if err := json.Unmarshal([]byte("["+strings.Join(f, ",")+"]"), trans.Container); err != nil {
-		return err
-	}
-
-	return nil
+	return json.Unmarshal([]byte("["+strings.Join(f, ",")+"]"), trans.Container)
 }
 
 // delete locks that database and then proceeds to remove the record (specified by
@@ -193,18 +182,12 @@ func (d *Driver) delete(trans Transaction) error {
 
 	mutex := d.getOrCreateMutex(trans.Collection)
 	mutex.Lock()
+	defer mutex.Unlock()
 
 	dir := d.dir + "/" + trans.Collection
 
 	// remove record from database
-	err := os.Remove(dir + "/" + trans.ResourceID)
-	if err != nil {
-		return err
-	}
-
-	mutex.Unlock()
-
-	return nil
+	return os.Remove(dir + "/" + trans.ResourceID)
 }
 
 // helpers
@@ -217,8 +200,8 @@ func (d *Driver) getOrCreateMutex(collection string) sync.Mutex {
 
 	// if the mutex doesn't exist make it
 	if !ok {
-		d.mutexes[collection] = sync.Mutex{}
-		return d.mutexes[collection]
+		c = sync.Mutex{}
+		d.mutexes[collection] = c
 	}
 
 	return c
@@ -226,17 +209,17 @@ func (d *Driver) getOrCreateMutex(collection string) sync.Mutex {
 
 // mkDir is a simple wrapper that attempts to make a directory at a specified
 // location
-func mkDir(d string) error {
+func mkDir(d string) (err error) {
 
 	//
 	dir, _ := os.Stat(d)
 
-	if dir == nil {
-		err := os.MkdirAll(d, 0755)
-		if err != nil {
-			return err
-		}
+	switch {
+	case dir == nil:
+		err = os.MkdirAll(d, 0755)
+	case !dir.IsDir():
+		err = os.ErrInvalid
 	}
 
-	return nil
+	return
 }