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author | Colin Cross <ccross@android.com> | 2018-11-04 17:38:11 -0800 |
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committer | android-build-merger <android-build-merger@google.com> | 2018-11-04 17:38:11 -0800 |
commit | de855a84c0fc34ea72db8c2c8e714059981c19e8 (patch) | |
tree | 172e736d6c7428f6afd8f706fb3eae2e8ac786b3 /src/google/protobuf/stubs/once.h | |
parent | 6e463f53f1f82dfe0a74e25ae729601a9678730c (diff) | |
parent | f4fe6ab6726e235448020c5fd203e4fc1dad728e (diff) | |
download | protobuf-javalite-de855a84c0fc34ea72db8c2c8e714059981c19e8.tar.gz |
Merge tag 'v3.0.1-javalite'
am: f4fe6ab672
Change-Id: Ia6204209550ecc61ae07e90d854bc07ba6ee2b0c
Diffstat (limited to 'src/google/protobuf/stubs/once.h')
-rw-r--r-- | src/google/protobuf/stubs/once.h | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/src/google/protobuf/stubs/once.h b/src/google/protobuf/stubs/once.h new file mode 100644 index 00000000..1f082c37 --- /dev/null +++ b/src/google/protobuf/stubs/once.h @@ -0,0 +1,167 @@ +// 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 <google/protobuf/stubs/atomicops.h> +#include <google/protobuf/stubs/callback.h> +#include <google/protobuf/stubs/common.h> + +namespace google { +namespace protobuf { + +#ifdef GOOGLE_PROTOBUF_NO_THREAD_SAFETY + +typedef bool ProtobufOnceType; + +#define GOOGLE_PROTOBUF_ONCE_INIT false + +inline void GoogleOnceInit(ProtobufOnceType* once, void (*init_func)()) { + if (!*once) { + *once = true; + init_func(); + } +} + +template <typename Arg> +inline void GoogleOnceInit(ProtobufOnceType* once, void (*init_func)(Arg), + Arg arg) { + if (!*once) { + *once = true; + init_func(arg); + } +} + +#else + +enum { + ONCE_STATE_UNINITIALIZED = 0, + ONCE_STATE_EXECUTING_CLOSURE = 1, + ONCE_STATE_DONE = 2 +}; + +typedef internal::AtomicWord ProtobufOnceType; + +#define GOOGLE_PROTOBUF_ONCE_INIT ::google::protobuf::ONCE_STATE_UNINITIALIZED + +LIBPROTOBUF_EXPORT +void GoogleOnceInitImpl(ProtobufOnceType* once, Closure* closure); + +inline void GoogleOnceInit(ProtobufOnceType* once, void (*init_func)()) { + if (internal::Acquire_Load(once) != ONCE_STATE_DONE) { + internal::FunctionClosure0 func(init_func, false); + GoogleOnceInitImpl(once, &func); + } +} + +template <typename Arg> +inline void GoogleOnceInit(ProtobufOnceType* once, void (*init_func)(Arg*), + Arg* arg) { + if (internal::Acquire_Load(once) != ONCE_STATE_DONE) { + internal::FunctionClosure1<Arg*> func(init_func, false, arg); + GoogleOnceInitImpl(once, &func); + } +} + +#endif // GOOGLE_PROTOBUF_NO_THREAD_SAFETY + +class GoogleOnceDynamic { + public: + GoogleOnceDynamic() : state_(GOOGLE_PROTOBUF_ONCE_INIT) { } + + // 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) { + GoogleOnceInit<T>(&this->state_, + func_with_arg, + arg); + } + private: + ProtobufOnceType state_; +}; + +#define GOOGLE_PROTOBUF_DECLARE_ONCE(NAME) \ + ::google::protobuf::ProtobufOnceType NAME = GOOGLE_PROTOBUF_ONCE_INIT + +} // namespace protobuf +} // namespace google + +#endif // GOOGLE_PROTOBUF_STUBS_ONCE_H__ |