gdbsupport/event-pipe.cc

   1 /* Event pipe for GDB, the GNU debugger.
   2
   3    Copyright (C) 2021-2023 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/common-defs.h"
  21 #include "gdbsupport/event-pipe.h"
  22 #include "gdbsupport/filestuff.h"
  23
  24 #include <errno.h>
  25 #include <fcntl.h>
  26 #include <unistd.h>
  27
  28 event_pipe::~event_pipe ()
  29 {
  30   if (is_open ())
  31     close_pipe ();
  32 }
  33
  34 /* See event-pipe.h.  */
  35
  36 bool
  37 event_pipe::open_pipe ()
  38 {
  39   if (is_open ())
  40     return false;
  41
  42   if (gdb_pipe_cloexec (m_fds) == -1)
  43     return false;
  44
  45   if (fcntl (m_fds[0], F_SETFL, O_NONBLOCK) == -1
  46       || fcntl (m_fds[1], F_SETFL, O_NONBLOCK) == -1)
  47     {
  48       close_pipe ();
  49       return false;
  50     }
  51
  52   return true;
  53 }
  54
  55 /* See event-pipe.h.  */
  56
  57 void
  58 event_pipe::close_pipe ()
  59 {
  60   ::close (m_fds[0]);
  61   ::close (m_fds[1]);
  62   m_fds[0] = -1;
  63   m_fds[1] = -1;
  64 }
  65
  66 /* See event-pipe.h.  */
  67
  68 void
  69 event_pipe::flush ()
  70 {
  71   int ret;
  72   char buf;
  73
  74   do
  75     {
  76       ret = read (m_fds[0], &buf, 1);
  77     }
  78   while (ret >= 0 || (ret == -1 && errno == EINTR));
  79 }
  80
  81 /* See event-pipe.h.  */
  82
  83 void
  84 event_pipe::mark ()
  85 {
  86   int ret;
  87
  88   /* It doesn't really matter what the pipe contains, as long we end
  89      up with something in it.  Might as well flush the previous
  90      left-overs.  */
  91   flush ();
  92
  93   do
  94     {
  95       ret = write (m_fds[1], "+", 1);
  96     }
  97   while (ret == -1 && errno == EINTR);
  98
  99   /* Ignore EAGAIN.  If the pipe is full, the event loop will already
 100      be awakened anyway.  */
 101 }