text: // Copyright 2013 The Flutter Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // A class for checking that the current thread is/isn't the same as an initial
  // thread.
  
  #ifndef FLUTTER_FML_MEMORY_THREAD_CHECKER_H_
  #define FLUTTER_FML_MEMORY_THREAD_CHECKER_H_
  
  #include "flutter/fml/build_config.h"
  
  #if defined(OS_WIN)
  #include <windows.h>
  #else
  #include <pthread.h>
  #endif
  
  #include "flutter/fml/logging.h"
  #include "flutter/fml/macros.h"
  
  namespace fml {
  
  // A simple class that records the identity of the thread that it was created
  // on, and at later points can tell if the current thread is the same as its
  // creation thread. This class is thread-safe.
  //
  // Note: Unlike Chromium's |base::ThreadChecker|, this is *not* Debug-only (so
  // #ifdef it out if you want something Debug-only). (Rationale: Having a
  // |CalledOnValidThread()| that lies in Release builds seems bad. Moreover,
  // there's a small space cost to having even an empty class. )
  class ThreadChecker final {
   public:
  #if defined(OS_WIN)
    ThreadChecker() : self_(GetCurrentThreadId()) {}
    ~ThreadChecker() {}
  
    bool IsCreationThreadCurrent() const { return GetCurrentThreadId() == self_; }
  
   private:
    DWORD self_;
  
  #else
    ThreadChecker() : self_(pthread_self()) {}
    ~ThreadChecker() {}
  
    // Returns true if the current thread is the thread this object was created
    // on and false otherwise.
    bool IsCreationThreadCurrent() const {
      pthread_t current_thread = pthread_self();
      bool is_creation_thread_current = !!pthread_equal(current_thread, self_);
  #ifdef __APPLE__
      // TODO(https://github.com/flutter/flutter/issues/45272): Implement for
      // other platforms.
      if (!is_creation_thread_current) {
        static const int buffer_length = 128;
        char expected_thread[buffer_length];
        char actual_thread[buffer_length];
        if (0 == pthread_getname_np(current_thread, actual_thread,
                                    buffer_length) &&
            0 == pthread_getname_np(self_, actual_thread, buffer_length)) {
          FML_DLOG(ERROR) << "IsCreationThreadCurrent expected thread: '"
                          << expected_thread << "' actual thread:'"
                          << actual_thread << "'";
        }
      }
  #endif  // __APPLE__
      return is_creation_thread_current;
    }
  
   private:
    pthread_t self_;
  #endif
  };
  
  #if !defined(NDEBUG)
  #define FML_DECLARE_THREAD_CHECKER(c) fml::ThreadChecker c
  #define FML_DCHECK_CREATION_THREAD_IS_CURRENT(c) \
    FML_DCHECK((c).IsCreationThreadCurrent())
  #else
  #define FML_DECLARE_THREAD_CHECKER(c)
  #define FML_DCHECK_CREATION_THREAD_IS_CURRENT(c) ((void)0)
  #endif
  
  }  // namespace fml
  
  #endif  // FLUTTER_FML_MEMORY_THREAD_CHECKER_H_
  