gdbsupport/event-pipe.cc

   1 /* Event pipe for GDB, the GNU debugger.
   2
   3    Copyright (C) 2021-2024 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 #include "gdbsupport/event-pipe.h"
  21 #include "gdbsupport/filestuff.h"
  22
  23 #include <errno.h>
  24 #include <fcntl.h>
  25 #include <unistd.h>
  26
  27 event_pipe::~event_pipe ()
  28 {
  29   if (is_open ())
  30     close_pipe ();
  31 }
  32
  33 /* See event-pipe.h.  */
  34
  35 bool
  36 event_pipe::open_pipe ()
  37 {
  38   if (is_open ())
  39     return false;
  40
  41   if (gdb_pipe_cloexec (m_fds) == -1)
  42     return false;
  43
  44   if (fcntl (m_fds[0], F_SETFL, O_NONBLOCK) == -1
  45       || fcntl (m_fds[1], F_SETFL, O_NONBLOCK) == -1)
  46     {
  47       close_pipe ();
  48       return false;
  49     }
  50
  51   return true;
  52 }
  53
  54 /* See event-pipe.h.  */
  55
  56 void
  57 event_pipe::close_pipe ()
  58 {
  59   ::close (m_fds[0]);
  60   ::close (m_fds[1]);
  61   m_fds[0] = -1;
  62   m_fds[1] = -1;
  63 }
  64
  65 /* See event-pipe.h.  */
  66
  67 void
  68 event_pipe::flush ()
  69 {
  70   int ret;
  71   char buf;
  72
  73   do
  74     {
  75       ret = read (m_fds[0], &buf, 1);
  76     }
  77   while (ret >= 0 || (ret == -1 && errno == EINTR));
  78 }
  79
  80 /* See event-pipe.h.  */
  81
  82 void
  83 event_pipe::mark ()
  84 {
  85   int ret;
  86
  87   /* It doesn't really matter what the pipe contains, as long we end
  88      up with something in it.  Might as well flush the previous
  89      left-overs.  */
  90   flush ();
  91
  92   do
  93     {
  94       ret = write (m_fds[1], "+", 1);
  95     }
  96   while (ret == -1 && errno == EINTR);
  97
  98   /* Ignore EAGAIN.  If the pipe is full, the event loop will already
  99      be awakened anyway.  */
 100 }