110 lines
3.4 KiB
C++
110 lines
3.4 KiB
C++
// Copyright (C) 2014 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.
|
|
|
|
#ifndef EMUGL_COMMON_THREAD_STORE_H
|
|
#define EMUGL_COMMON_THREAD_STORE_H
|
|
|
|
#ifdef _WIN32
|
|
# define WIN32_LEAN_AND_MEAN 1
|
|
# include <windows.h>
|
|
#else
|
|
# include <pthread.h>
|
|
#endif
|
|
|
|
namespace emugl {
|
|
|
|
// A class to model storage of thread-specific values, that can be
|
|
// destroyed on thread exit.
|
|
//
|
|
// Note that on Windows, a thread must call OnThreadExit() explicitly
|
|
// here to ensure that the values are probably discarded. This is an
|
|
// unfortunate requirement of the Win32 API, which doesn't support
|
|
// destructors at all.
|
|
//
|
|
// There are various hacks on the web to try to achieve this automatically
|
|
// (e.g. [1]) but they rely on using the Microsoft build tools,
|
|
// which doesn't work for us.
|
|
//
|
|
// Note another important issue with ThreadStore instances: if you create
|
|
// one instance in a shared library, you need to make sure that it is
|
|
// always destroyed before the library is unloaded. Otherwise, future
|
|
// thread exit will likely crash, due to calling a destructor function
|
|
// that is no longer in the process' address space.
|
|
//
|
|
// Finally, destroying an instance does _not_ free the corresponding values,
|
|
// because doing so properly requires coordinating all participating threads,
|
|
// which is impossible to achieve in the most general case. Thus, consider
|
|
// that thread-local values are always leaked on library unload, or on
|
|
// program exit.
|
|
//
|
|
// [1] http://stackoverflow.com/questions/14538159/about-tls-callback-in-windows
|
|
|
|
class ThreadStore {
|
|
public:
|
|
// Type of a function used to destroy a thread-specific value that
|
|
// was previously assigned by calling set().
|
|
typedef void (Destructor)(void* value);
|
|
|
|
// Initialize instance so that is hold keys that must be destroyed
|
|
// on thread exit by calling |destroy|.
|
|
explicit ThreadStore(Destructor* destroy);
|
|
|
|
// NOTE: Destructor don't free the thread-local values, but are required
|
|
// to avoid crashes (see note above).
|
|
~ThreadStore();
|
|
|
|
// Retrieve current thread-specific value from store.
|
|
#ifdef _WIN32
|
|
void* get() const;
|
|
#else
|
|
inline void* get() const {
|
|
return pthread_getspecific(mKey);
|
|
}
|
|
#endif
|
|
|
|
// Set the new thread-specific value.
|
|
#ifdef _WIN32
|
|
void set(void* value);
|
|
#else
|
|
inline void set(void* value) {
|
|
pthread_setspecific(mKey, value);
|
|
}
|
|
#endif
|
|
|
|
#ifdef _WIN32
|
|
// Each thread should call this function on exit to ensure that
|
|
// all corresponding TLS values are properly freed.
|
|
static void OnThreadExit();
|
|
#else
|
|
// Nothing to do on Posix.
|
|
static inline void OnThreadExit() {}
|
|
#endif
|
|
|
|
private:
|
|
// Ensure you can't create an empty ThreadStore instance, or simply
|
|
// copy it in any way.
|
|
ThreadStore();
|
|
ThreadStore(const ThreadStore&);
|
|
ThreadStore& operator=(const ThreadStore&);
|
|
|
|
#ifdef _WIN32
|
|
int mKey;
|
|
#else
|
|
pthread_key_t mKey;
|
|
#endif
|
|
};
|
|
|
|
} // namespace emugl
|
|
|
|
#endif // EMUGL_COMMON_THREAD_STORE_H
|