Squashed 'third_party/protobuf/' content from commit e35e248
Change-Id: I6cbe123d09fe50fdcad0e51466665daeee7433c7
git-subtree-dir: third_party/protobuf
git-subtree-split: e35e24800fb8d694bdeea5fd63dc7d1b14d68723
diff --git a/src/google/protobuf/stubs/once.cc b/src/google/protobuf/stubs/once.cc
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+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc. All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: kenton@google.com (Kenton Varda)
+//
+// emulates google3/base/once.h
+//
+// This header is intended to be included only by internal .cc files and
+// generated .pb.cc files. Users should not use this directly.
+
+#include <google/protobuf/stubs/once.h>
+
+#ifndef GOOGLE_PROTOBUF_NO_THREAD_SAFETY
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <sched.h>
+#endif
+
+#include <google/protobuf/stubs/atomicops.h>
+
+namespace google {
+namespace protobuf {
+
+namespace {
+
+void SchedYield() {
+#ifdef _WIN32
+ Sleep(0);
+#else // POSIX
+ sched_yield();
+#endif
+}
+
+} // namespace
+
+void GoogleOnceInitImpl(ProtobufOnceType* once, Closure* closure) {
+ internal::AtomicWord state = internal::Acquire_Load(once);
+ // Fast path. The provided closure was already executed.
+ if (state == ONCE_STATE_DONE) {
+ return;
+ }
+ // The closure execution did not complete yet. The once object can be in one
+ // of the two following states:
+ // - UNINITIALIZED: We are the first thread calling this function.
+ // - EXECUTING_CLOSURE: Another thread is already executing the closure.
+ //
+ // First, try to change the state from UNINITIALIZED to EXECUTING_CLOSURE
+ // atomically.
+ state = internal::Acquire_CompareAndSwap(
+ once, ONCE_STATE_UNINITIALIZED, ONCE_STATE_EXECUTING_CLOSURE);
+ if (state == ONCE_STATE_UNINITIALIZED) {
+ // We are the first thread to call this function, so we have to call the
+ // closure.
+ closure->Run();
+ internal::Release_Store(once, ONCE_STATE_DONE);
+ } else {
+ // Another thread has already started executing the closure. We need to
+ // wait until it completes the initialization.
+ while (state == ONCE_STATE_EXECUTING_CLOSURE) {
+ // Note that futex() could be used here on Linux as an improvement.
+ SchedYield();
+ state = internal::Acquire_Load(once);
+ }
+ }
+}
+
+} // namespace protobuf
+} // namespace google
+
+#endif // GOOGLE_PROTOBUF_NO_THREAD_SAFETY