text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2020 The Bitcoin Core and Devcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <shutdown.h>
  
  #include <logging.h>
  #include <node/ui_interface.h>
  #include <util/tokenpipe.h>
  #include <warnings.h>
  
  #include <config/devcoin-config.h>
  
  #include <assert.h>
  #include <atomic>
  #ifdef WIN32
  #include <condition_variable>
  #endif
  
  bool AbortNode(const std::string& strMessage, bilingual_str user_message)
  {
      SetMiscWarning(Untranslated(strMessage));
      LogPrintf("*** %s\n", strMessage);
      if (user_message.empty()) {
          user_message = _("A fatal internal error occurred, see debug.log for details");
      }
      AbortError(user_message);
      StartShutdown();
      return false;
  }
  
  static std::atomic<bool> fRequestShutdown(false);
  #ifdef WIN32
  /** On windows it is possible to simply use a condition variable. */
  std::mutex g_shutdown_mutex;
  std::condition_variable g_shutdown_cv;
  #else
  /** On UNIX-like operating systems use the self-pipe trick.
   */
  static TokenPipeEnd g_shutdown_r;
  static TokenPipeEnd g_shutdown_w;
  #endif
  
  bool InitShutdownState()
  {
  #ifndef WIN32
      std::optional<TokenPipe> pipe = TokenPipe::Make();
      if (!pipe) return false;
      g_shutdown_r = pipe->TakeReadEnd();
      g_shutdown_w = pipe->TakeWriteEnd();
  #endif
      return true;
  }
  
  void StartShutdown()
  {
  #ifdef WIN32
      std::unique_lock<std::mutex> lk(g_shutdown_mutex);
      fRequestShutdown = true;
      g_shutdown_cv.notify_one();
  #else
      // This must be reentrant and safe for calling in a signal handler, so using a condition variable is not safe.
      // Make sure that the token is only written once even if multiple threads call this concurrently or in
      // case of a reentrant signal.
      if (!fRequestShutdown.exchange(true)) {
          // Write an arbitrary byte to the write end of the shutdown pipe.
          int res = g_shutdown_w.TokenWrite('x');
          if (res != 0) {
              LogPrintf("Sending shutdown token failed\n");
              assert(0);
          }
      }
  #endif
  }
  
  void AbortShutdown()
  {
      if (fRequestShutdown) {
          // Cancel existing shutdown by waiting for it, this will reset condition flags and remove
          // the shutdown token from the pipe.
          WaitForShutdown();
      }
      fRequestShutdown = false;
  }
  
  bool ShutdownRequested()
  {
      return fRequestShutdown;
  }
  
  void WaitForShutdown()
  {
  #ifdef WIN32
      std::unique_lock<std::mutex> lk(g_shutdown_mutex);
      g_shutdown_cv.wait(lk, [] { return fRequestShutdown.load(); });
  #else
      int res = g_shutdown_r.TokenRead();
      if (res != 'x') {
          LogPrintf("Reading shutdown token failed\n");
          assert(0);
      }
  #endif
  }
  