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      1 /* Event pipe for GDB, the GNU debugger.
      2 
      3    Copyright (C) 2021-2025 Free Software Foundation, Inc.
      4 
      5    This file is part of GDB.
      6 
      7    This program is free software; you can redistribute it and/or modify
      8    it under the terms of the GNU General Public License as published by
      9    the Free Software Foundation; either version 3 of the License, or
     10    (at your option) any later version.
     11 
     12    This program is distributed in the hope that it will be useful,
     13    but WITHOUT ANY WARRANTY; without even the implied warranty of
     14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     15    GNU General Public License for more details.
     16 
     17    You should have received a copy of the GNU General Public License
     18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
     19 
     20 #ifndef GDBSUPPORT_EVENT_PIPE_H
     21 #define GDBSUPPORT_EVENT_PIPE_H
     22 
     23 /* An event pipe used as a waitable file in the event loop in place of
     24    some other event associated with a signal.  The handler for the
     25    signal marks the event pipe to force a wakeup in the event loop.
     26    This uses the well-known self-pipe trick.  */
     27 
     28 class event_pipe
     29 {
     30 public:
     31   event_pipe() = default;
     32   ~event_pipe();
     33 
     34   DISABLE_COPY_AND_ASSIGN (event_pipe);
     35 
     36   /* Create a new pipe.  */
     37   bool open_pipe ();
     38 
     39   /* Close the pipe.  */
     40   void close_pipe ();
     41 
     42   /* True if the event pipe has been opened.  */
     43   bool is_open () const
     44   { return m_fds[0] != -1; }
     45 
     46   /* The file descriptor of the waitable file to use in the event
     47      loop.  */
     48   int event_fd () const
     49   { return m_fds[0]; }
     50 
     51   /* Flush the event pipe.  */
     52   void flush ();
     53 
     54   /* Put something in the pipe, so the event loop wakes up.  */
     55   void mark ();
     56 private:
     57   int m_fds[2] = { -1, -1 };
     58 };
     59 
     60 #endif /* GDBSUPPORT_EVENT_PIPE_H */
     61