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TMessagesProj/jni/voip/webrtc/base/threading/platform_thread.h

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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// WARNING: You should *NOT* be using this class directly.  PlatformThread is
+// the low-level platform-specific abstraction to the OS's threading interface.
+// You should instead be using a message-loop driven Thread, see thread.h.
+
+#ifndef BASE_THREADING_PLATFORM_THREAD_H_
+#define BASE_THREADING_PLATFORM_THREAD_H_
+
+#include <stddef.h>
+
+#include "base/base_export.h"
+#include "base/macros.h"
+#include "base/time/time.h"
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include "base/win/windows_types.h"
+#elif defined(OS_FUCHSIA)
+#include <zircon/types.h>
+#elif defined(OS_MACOSX)
+#include <mach/mach_types.h>
+#elif defined(OS_POSIX)
+#include <pthread.h>
+#include <unistd.h>
+#endif
+
+namespace base {
+
+// Used for logging. Always an integer value.
+#if defined(OS_WIN)
+typedef DWORD PlatformThreadId;
+#elif defined(OS_FUCHSIA)
+typedef zx_handle_t PlatformThreadId;
+#elif defined(OS_MACOSX)
+typedef mach_port_t PlatformThreadId;
+#elif defined(OS_POSIX)
+typedef pid_t PlatformThreadId;
+#endif
+
+// Used for thread checking and debugging.
+// Meant to be as fast as possible.
+// These are produced by PlatformThread::CurrentRef(), and used to later
+// check if we are on the same thread or not by using ==. These are safe
+// to copy between threads, but can't be copied to another process as they
+// have no meaning there. Also, the internal identifier can be re-used
+// after a thread dies, so a PlatformThreadRef cannot be reliably used
+// to distinguish a new thread from an old, dead thread.
+class PlatformThreadRef {
+ public:
+#if defined(OS_WIN)
+  typedef DWORD RefType;
+#else  //  OS_POSIX
+  typedef pthread_t RefType;
+#endif
+  constexpr PlatformThreadRef() : id_(0) {}
+
+  explicit constexpr PlatformThreadRef(RefType id) : id_(id) {}
+
+  bool operator==(PlatformThreadRef other) const {
+    return id_ == other.id_;
+  }
+
+  bool operator!=(PlatformThreadRef other) const { return id_ != other.id_; }
+
+  bool is_null() const {
+    return id_ == 0;
+  }
+ private:
+  RefType id_;
+};
+
+// Used to operate on threads.
+class PlatformThreadHandle {
+ public:
+#if defined(OS_WIN)
+  typedef void* Handle;
+#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
+  typedef pthread_t Handle;
+#endif
+
+  constexpr PlatformThreadHandle() : handle_(0) {}
+
+  explicit constexpr PlatformThreadHandle(Handle handle) : handle_(handle) {}
+
+  bool is_equal(const PlatformThreadHandle& other) const {
+    return handle_ == other.handle_;
+  }
+
+  bool is_null() const {
+    return !handle_;
+  }
+
+  Handle platform_handle() const {
+    return handle_;
+  }
+
+ private:
+  Handle handle_;
+};
+
+const PlatformThreadId kInvalidThreadId(0);
+
+// Valid values for priority of Thread::Options and SimpleThread::Options, and
+// SetCurrentThreadPriority(), listed in increasing order of importance.
+enum class ThreadPriority : int {
+  // Suitable for threads that shouldn't disrupt high priority work.
+  BACKGROUND,
+  // Default priority level.
+  NORMAL,
+  // Suitable for threads which generate data for the display (at ~60Hz).
+  DISPLAY,
+  // Suitable for low-latency, glitch-resistant audio.
+  REALTIME_AUDIO,
+};
+
+// A namespace for low-level thread functions.
+class BASE_EXPORT PlatformThread {
+ public:
+  // Implement this interface to run code on a background thread.  Your
+  // ThreadMain method will be called on the newly created thread.
+  class BASE_EXPORT Delegate {
+   public:
+    virtual void ThreadMain() = 0;
+
+   protected:
+    virtual ~Delegate() = default;
+  };
+
+  // Gets the current thread id, which may be useful for logging purposes.
+  static PlatformThreadId CurrentId();
+
+  // Gets the current thread reference, which can be used to check if
+  // we're on the right thread quickly.
+  static PlatformThreadRef CurrentRef();
+
+  // Get the handle representing the current thread. On Windows, this is a
+  // pseudo handle constant which will always represent the thread using it and
+  // hence should not be shared with other threads nor be used to differentiate
+  // the current thread from another.
+  static PlatformThreadHandle CurrentHandle();
+
+  // Yield the current thread so another thread can be scheduled.
+  static void YieldCurrentThread();
+
+  // Sleeps for the specified duration (real-time; ignores time overrides).
+  // Note: The sleep duration may be in base::Time or base::TimeTicks, depending
+  // on platform. If you're looking to use this in unit tests testing delayed
+  // tasks, this will be unreliable - instead, use
+  // base::test::TaskEnvironment with MOCK_TIME mode.
+  static void Sleep(base::TimeDelta duration);
+
+  // Sets the thread name visible to debuggers/tools. This will try to
+  // initialize the context for current thread unless it's a WorkerThread.
+  static void SetName(const std::string& name);
+
+  // Gets the thread name, if previously set by SetName.
+  static const char* GetName();
+
+  // Creates a new thread.  The |stack_size| parameter can be 0 to indicate
+  // that the default stack size should be used.  Upon success,
+  // |*thread_handle| will be assigned a handle to the newly created thread,
+  // and |delegate|'s ThreadMain method will be executed on the newly created
+  // thread.
+  // NOTE: When you are done with the thread handle, you must call Join to
+  // release system resources associated with the thread.  You must ensure that
+  // the Delegate object outlives the thread.
+  static bool Create(size_t stack_size,
+                     Delegate* delegate,
+                     PlatformThreadHandle* thread_handle) {
+    return CreateWithPriority(stack_size, delegate, thread_handle,
+                              ThreadPriority::NORMAL);
+  }
+
+  // CreateWithPriority() does the same thing as Create() except the priority of
+  // the thread is set based on |priority|.
+  static bool CreateWithPriority(size_t stack_size, Delegate* delegate,
+                                 PlatformThreadHandle* thread_handle,
+                                 ThreadPriority priority);
+
+  // CreateNonJoinable() does the same thing as Create() except the thread
+  // cannot be Join()'d.  Therefore, it also does not output a
+  // PlatformThreadHandle.
+  static bool CreateNonJoinable(size_t stack_size, Delegate* delegate);
+
+  // CreateNonJoinableWithPriority() does the same thing as CreateNonJoinable()
+  // except the priority of the thread is set based on |priority|.
+  static bool CreateNonJoinableWithPriority(size_t stack_size,
+                                            Delegate* delegate,
+                                            ThreadPriority priority);
+
+  // Joins with a thread created via the Create function.  This function blocks
+  // the caller until the designated thread exits.  This will invalidate
+  // |thread_handle|.
+  static void Join(PlatformThreadHandle thread_handle);
+
+  // Detaches and releases the thread handle. The thread is no longer joinable
+  // and |thread_handle| is invalidated after this call.
+  static void Detach(PlatformThreadHandle thread_handle);
+
+  // Returns true if SetCurrentThreadPriority() should be able to increase the
+  // priority of a thread to |priority|.
+  static bool CanIncreaseThreadPriority(ThreadPriority priority);
+
+  // Toggles the current thread's priority at runtime.
+  //
+  // A thread may not be able to raise its priority back up after lowering it if
+  // the process does not have a proper permission, e.g. CAP_SYS_NICE on Linux.
+  // A thread may not be able to lower its priority back down after raising it
+  // to REALTIME_AUDIO.
+  //
+  // This function must not be called from the main thread on Mac. This is to
+  // avoid performance regressions (https://crbug.com/601270).
+  //
+  // Since changing other threads' priority is not permitted in favor of
+  // security, this interface is restricted to change only the current thread
+  // priority (https://crbug.com/399473).
+  static void SetCurrentThreadPriority(ThreadPriority priority);
+
+  static ThreadPriority GetCurrentThreadPriority();
+
+#if defined(OS_LINUX)
+  // Toggles a specific thread's priority at runtime. This can be used to
+  // change the priority of a thread in a different process and will fail
+  // if the calling process does not have proper permissions. The
+  // SetCurrentThreadPriority() function above is preferred in favor of
+  // security but on platforms where sandboxed processes are not allowed to
+  // change priority this function exists to allow a non-sandboxed process
+  // to change the priority of sandboxed threads for improved performance.
+  // Warning: Don't use this for a main thread because that will change the
+  // whole thread group's (i.e. process) priority.
+  static void SetThreadPriority(PlatformThreadId thread_id,
+                                ThreadPriority priority);
+#endif
+
+  // Returns the default thread stack size set by chrome. If we do not
+  // explicitly set default size then returns 0.
+  static size_t GetDefaultThreadStackSize();
+
+ private:
+  static void SetCurrentThreadPriorityImpl(ThreadPriority priority);
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
+};
+
+namespace internal {
+
+// Initializes the "ThreadPriorities" feature. The feature state is only taken
+// into account after this initialization. This initialization must be
+// synchronized with calls to PlatformThread::SetCurrentThreadPriority().
+void InitializeThreadPrioritiesFeature();
+
+}  // namespace internal
+
+}  // namespace base
+
+#endif  // BASE_THREADING_PLATFORM_THREAD_H_