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// Copyright 2008, Google Inc.
// All rights reserved.
//
// 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.
#ifndef BASE_THREAD_H_
#define BASE_THREAD_H_
#include <string>
#include "base/thread_local_storage.h"
class MessageLoop;
// Types that differ
#if defined(OS_WIN)
#include <wtypes.h>
typedef unsigned int ThreadId;
#elif defined(OS_POSIX)
typedef pthread_t ThreadId;
#endif
// A simple thread abstraction that establishes a MessageLoop on a new thread.
// The consumer uses the MessageLoop of the thread to cause code to execute on
// the thread. When this object is destroyed the thread is terminated. All
// pending tasks queued on the thread's message loop will run to completion
// before the thread is terminated.
//
class Thread {
public:
// Constructor.
// name is a display string to identify the thread.
explicit Thread(const char *name);
// Destroys the thread, stopping it if necessary.
//
virtual ~Thread();
// Starts the thread. Returns true if the thread was successfully started;
// otherwise, returns false. Upon successful return, the message_loop()
// getter will return non-null.
//
// Note: This function can't be called on Windows with the loader lock held;
// i.e. during a DllMain, global object construction or destruction, atexit()
// callback.
bool Start();
// Starts the thread. Behaves exactly like Start in addition to allow to
// override the default process stack size. This is not the initial stack size
// but the maximum stack size that thread is allowed to use.
//
// Note: This function can't be called on Windows with the loader lock held;
// i.e. during a DllMain, global object construction or destruction, atexit()
// callback.
bool StartWithStackSize(size_t stack_size);
// Signals the thread to exit and returns once the thread has exited. After
// this method returns, the Thread object is completely reset and may be used
// as if it were newly constructed (i.e., Start may be called again).
//
// Stop may be called multiple times and is simply ignored if the thread is
// already stopped.
//
// NOTE: This method is optional. It is not strictly necessary to call this
// method as the Thread's destructor will take care of stopping the thread if
// necessary.
//
void Stop();
// Signals the thread to exit in the near future.
//
// WARNING: This function is not meant to be commonly used. Use at your own
// risk. Calling this function will cause message_loop() to become invalid in
// the near future. This function was created to workaround a specific
// deadlock on Windows with printer worker thread. In any other case, Stop()
// should be used.
//
// StopSoon should not be called multiple times as it is risky to do so. It
// could cause a timing issue in message_loop() access. Call Stop() to reset
// the thread object once it is known that the thread has quit.
void StopSoon();
// Returns the message loop for this thread. Use the MessageLoop's
// PostTask methods to execute code on the thread. This only returns
// non-null after a successful call to Start. After Stop has been called,
// this will return NULL.
//
// NOTE: You must not call this MessageLoop's Quit method directly. Use
// the Thread's Stop method instead.
//
MessageLoop* message_loop() const {
if (thread_id_)
return message_loop_;
return NULL;
}
// Set the name of this thread (for display in debugger too).
const std::string &thread_name() { return name_; }
#if defined(OS_WIN)
HANDLE thread_handle() { return thread_; }
#endif
// Sets the thread name if a debugger is currently attached. Has no effect
// otherwise. To set the name of the current thread, pass GetCurrentThreadId()
// as the tid parameter.
static void SetThreadName(const char* name, ThreadId tid);
protected:
// Called just prior to starting the message loop
virtual void Init() { }
// Called just after the message loop ends
virtual void CleanUp() { }
static void SetThreadWasQuitProperly(bool flag);
static bool GetThreadWasQuitProperly();
private:
#if defined(OS_WIN)
static unsigned __stdcall ThreadFunc(void* param);
// The thread's handle. Modified by the root thread.
HANDLE thread_;
#endif
// The thread's id. Modified by the root thread. Set to 0 when the thread is
// not ready to receive messages.
ThreadId thread_id_;
// The thread's message loop. Valid only while the thread is alive. Modified
// by the created thread.
MessageLoop* message_loop_;
const std::string name_;
static TLSSlot tls_index_;
friend class ThreadQuitTask;
DISALLOW_COPY_AND_ASSIGN(Thread);
};
#endif // BASE_THREAD_H_
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