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Diffstat (limited to 'third_party/protobuf/3.6.0/src/google/protobuf/stubs/once.h')
-rw-r--r-- | third_party/protobuf/3.6.0/src/google/protobuf/stubs/once.h | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/third_party/protobuf/3.6.0/src/google/protobuf/stubs/once.h b/third_party/protobuf/3.6.0/src/google/protobuf/stubs/once.h new file mode 100644 index 0000000000..f3835ccd04 --- /dev/null +++ b/third_party/protobuf/3.6.0/src/google/protobuf/stubs/once.h @@ -0,0 +1,130 @@ +// 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. +// +// This is basically a portable version of pthread_once(). +// +// This header declares: +// * A type called ProtobufOnceType. +// * A macro GOOGLE_PROTOBUF_DECLARE_ONCE() which declares a variable of type +// ProtobufOnceType. This is the only legal way to declare such a variable. +// The macro may only be used at the global scope (you cannot create local or +// class member variables of this type). +// * A function GoogleOnceInit(ProtobufOnceType* once, void (*init_func)()). +// This function, when invoked multiple times given the same ProtobufOnceType +// object, will invoke init_func on the first call only, and will make sure +// none of the calls return before that first call to init_func has finished. +// * The user can provide a parameter which GoogleOnceInit() forwards to the +// user-provided function when it is called. Usage example: +// int a = 10; +// GoogleOnceInit(&my_once, &MyFunctionExpectingIntArgument, &a); +// * This implementation guarantees that ProtobufOnceType is a POD (i.e. no +// static initializer generated). +// +// This implements a way to perform lazy initialization. It's more efficient +// than using mutexes as no lock is needed if initialization has already +// happened. +// +// Example usage: +// void Init(); +// GOOGLE_PROTOBUF_DECLARE_ONCE(once_init); +// +// // Calls Init() exactly once. +// void InitOnce() { +// GoogleOnceInit(&once_init, &Init); +// } +// +// Note that if GoogleOnceInit() is called before main() has begun, it must +// only be called by the thread that will eventually call main() -- that is, +// the thread that performs dynamic initialization. In general this is a safe +// assumption since people don't usually construct threads before main() starts, +// but it is technically not guaranteed. Unfortunately, Win32 provides no way +// whatsoever to statically-initialize its synchronization primitives, so our +// only choice is to assume that dynamic initialization is single-threaded. + +#ifndef GOOGLE_PROTOBUF_STUBS_ONCE_H__ +#define GOOGLE_PROTOBUF_STUBS_ONCE_H__ + +#include <mutex> +#include <utility> + +namespace google { +namespace protobuf { +namespace internal { + +using once_flag = std::once_flag; +template <typename... Args> +void call_once(Args&&... args ) { + std::call_once(std::forward<Args>(args)...); +} + +} // namespace internal + +// TODO(gerbens) remove this once third_party is fully extracted +using ProtobufOnceType = internal::once_flag; + +inline void GoogleOnceInit(ProtobufOnceType* once, void (*init_func)()) { + std::call_once(*once, init_func); +} + +template <typename Arg> +inline void GoogleOnceInitArg(ProtobufOnceType* once, void (*init_func)(Arg*), + Arg* arg) { + std::call_once(*once, init_func, arg); +} + +class GoogleOnceDynamic { + public: + // If this->Init() has not been called before by any thread, + // execute (*func_with_arg)(arg) then return. + // Otherwise, wait until that prior invocation has finished + // executing its function, then return. + template<typename T> + void Init(void (*func_with_arg)(T*), T* arg) { + GoogleOnceInitArg<T>(&this->state_, func_with_arg, arg); + } + private: + ProtobufOnceType state_; +}; + +#define GOOGLE_PROTOBUF_ONCE_TYPE ::google::protobuf::ProtobufOnceType +#define GOOGLE_PROTOBUF_DECLARE_ONCE(NAME) \ + ::google::protobuf::ProtobufOnceType NAME + +} // namespace protobuf +} // namespace google + +#endif // GOOGLE_PROTOBUF_STUBS_ONCE_H__ |