[NaCl SDK] Support non blocking TCP/UDP

native_client_sdk/src/libraries/sdk_util/auto_lock.h

Index: native_client_sdk/src/libraries/sdk_util/auto_lock.h
diff --git a/native_client_sdk/src/libraries/sdk_util/auto_lock.h b/native_client_sdk/src/libraries/sdk_util/auto_lock.h
index b969416ad78dee5ddf01f6a3730843cb974d2908..9342a21d624608ac557cdd3e1883f52112288bfb 100644
--- a/native_client_sdk/src/libraries/sdk_util/auto_lock.h
+++ b/native_client_sdk/src/libraries/sdk_util/auto_lock.h
@@ -16,6 +16,8 @@ namespace sdk_util {
 #define AUTO_LOCK(lock)                         \
   ::sdk_util::AutoLock Lock##__LINE__(lock);
 
+class AutoUnlock;
+
 class AutoLock {
  public:
   AutoLock(const SimpleLock& lock) {
@@ -35,9 +37,46 @@ class AutoLock {
  private:
   pthread_mutex_t* lock_;
 
+  friend class AutoUnlock;
   DISALLOW_COPY_AND_ASSIGN(AutoLock);
 };
 
+
+class AutoUnlock {
+ public:
+  AutoUnlock() {
+    simple_lock_ = NULL;
+  }
+
+  ~AutoUnlock() {
+    Unlock();
+  }
+
+  void Unlock() {
+    if (simple_lock_)
+      simple_lock_->Unlock();
+
+    simple_lock_ = NULL;
+  }
+
+  void Take(const SimpleLock& lock) {
+    if (simple_lock_ != &lock)
+      Unlock();
+
+    simple_lock_ = &lock;
+  }
+
+  const SimpleLock* Give() {
+    const SimpleLock* out = simple_lock_;
+    simple_lock_ = NULL;
+    return out;
+  }
+
+ private:
+  const SimpleLock* simple_lock_;
+  DISALLOW_COPY_AND_ASSIGN(AutoUnlock);
+};
+
 }  // namespace sdk_util
 
 #endif  // LIBRARIES_SDK_UTIL_AUTO_LOCK_H_