drm_hwcomposer: add AutoLock to automatically handle pthread_mutex_lock

For functions that need to hold locks and also handle errors, using AutoLock
will make them much simpler and less prone to mutex handling errors.

Change-Id: Ida6545850e89186c552e3d58b2973c14852494ad

1 files changed, 42 insertions, 0 deletions

diff --git a/autolock.h b/autolock.h
new file mode 100644
index 0000000..3b824e2
--- /dev/null
+++ b/autolock.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <pthread.h>
+
+namespace android {
+
+class AutoLock {
+ public:
+  AutoLock(pthread_mutex_t *mutex, const char *const name)
+      : mutex_(mutex), name_(name) {
+  }
+  ~AutoLock() {
+    if (locked_)
+      Unlock();
+  }
+
+  AutoLock(const AutoLock &rhs) = delete;
+  AutoLock &operator=(const AutoLock &rhs) = delete;
+
+  int Lock();
+  int Unlock();
+
+ private:
+  pthread_mutex_t *const mutex_;
+  bool locked_ = false;
+  const char *const name_;
+};
+}