glib/gpoll.h

   1 /* gpoll.h - poll(2) support
   2  * Copyright (C) 2008 Red Hat, Inc.
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Library General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Library General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Library General Public
  15  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #ifndef __G_POLL_H__
  19 #define __G_POLL_H__
  20
  21 #if !defined (__GLIB_H_INSIDE__) && !defined (__G_MAIN_H__) && !defined (GLIB_COMPILATION)
  22 #error "Only <glib.h> can be included directly."
  23 #endif
  24
  25 #include <glib/gtypes.h>
  26
  27 G_BEGIN_DECLS
  28
  29 /* Any definitions using GPollFD or GPollFunc are primarily
  30  * for Unix and not guaranteed to be the compatible on all
  31  * operating systems on which GLib runs. Right now, the
  32  * GLib does use these functions on Win32 as well, but interprets
  33  * them in a fairly different way than on Unix. If you use
  34  * these definitions, you are should be prepared to recode
  35  * for different operating systems.
  36  *
  37  * Note that on systems with a working poll(2), that function is used
  38  * in place of g_poll(). Thus g_poll() must have the same signature as
  39  * poll(), meaning GPollFD must have the same layout as struct pollfd.
  40  *
  41  *
  42  * On Win32, the fd in a GPollFD should be Win32 HANDLE (*not* a file
  43  * descriptor as provided by the C runtime) that can be used by
  44  * MsgWaitForMultipleObjects. This does *not* include file handles
  45  * from CreateFile, SOCKETs, nor pipe handles. (But you can use
  46  * WSAEventSelect to signal events when a SOCKET is readable).
  47  *
  48  * On Win32, fd can also be the special value G_WIN32_MSG_HANDLE to
  49  * indicate polling for messages.
  50  *
  51  * But note that G_WIN32_MSG_HANDLE GPollFDs should not be used by GDK
  52  * (GTK) programs, as GDK itself wants to read messages and convert them
  53  * to GDK events.
  54  *
  55  * So, unless you really know what you are doing, it's best not to try
  56  * to use the main loop polling stuff for your own needs on
  57  * Windows.
  58  */
  59 typedef struct _GPollFD GPollFD;
  60
  61 /**
  62  * GPollFunc:
  63  * @ufds: an array of #GPollFD elements
  64  * @nfsd: the number of elements in @ufds
  65  * @timeout_: the maximum time to wait for an event of the file descriptors.
  66  *     A negative value indicates an infinite timeout.
  67  *
  68  * Specifies the type of function passed to g_main_context_set_poll_func().
  69  * The semantics of the function should match those of the poll() system call.
  70  *
  71  * Returns: the number of #GPollFD elements which have events or errors
  72  *     reported, or -1 if an error occurred.
  73  */
  74 typedef gint    (*GPollFunc)    (GPollFD *ufds,
  75                                  guint    nfsd,
  76                                  gint     timeout_);
  77
  78 /**
  79  * GPollFD:
  80  * @fd: the file descriptor to poll (or a <type>HANDLE</type> on Win32)
  81  * @events: a bitwise combination from #GIOCondition, specifying which
  82  *     events should be polled for. Typically for reading from a file
  83  *     descriptor you would use %G_IO_IN | %G_IO_HUP | %G_IO_ERR, and
  84  *     for writing you would use %G_IO_OUT | %G_IO_ERR.
  85  * @revents: a bitwise combination of flags from #GIOCondition, returned
  86  *     from the poll() function to indicate which events occurred.
  87  *
  88  * Represents a file descriptor, which events to poll for, and which events
  89  * occurred.
  90  */
  91 struct _GPollFD
  92 {
  93 #if defined (G_OS_WIN32) && GLIB_SIZEOF_VOID_P == 8
  94   gint64        fd;
  95 #else
  96   gint          fd;
  97 #endif
  98   gushort       events;
  99   gushort       revents;
 100 };
 101
 102 #ifdef G_OS_WIN32
 103 #if GLIB_SIZEOF_VOID_P == 8
 104 #define G_POLLFD_FORMAT "%#I64x"
 105 #else
 106 #define G_POLLFD_FORMAT "%#x"
 107 #endif
 108 #else
 109 #define G_POLLFD_FORMAT "%d"
 110 #endif
 111
 112 GLIB_AVAILABLE_IN_ALL
 113 gint g_poll (GPollFD *fds,
 114              guint    nfds,
 115              gint     timeout);
 116
 117 G_END_DECLS
 118
 119 #endif /* __G_POLL_H__ */