man/sd_event_get_fd.3

   1 '\" t
   2 .TH "SD_EVENT_GET_FD" "3" "" "systemd 219" "sd_event_get_fd"
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   7 .\" http://bugs.debian.org/507673
   8 .\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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  20 .\" * MAIN CONTENT STARTS HERE *
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  22 .SH "NAME"
  23 sd_event_get_fd \- Obtain a file descriptor to poll for event loop events
  24 .SH "SYNOPSIS"
  25 .sp
  26 .ft B
  27 .nf
  28 #include <systemd/sd\-bus\&.h>
  29 .fi
  30 .ft
  31 .HP \w'int\ sd_event_get_fd('u
  32 .BI "int sd_event_get_fd(sd_bus\ *" "event" ");"
  33 .SH "DESCRIPTION"
  34 .PP
  35 \fBsd_event_get_fd()\fR
  36 returns the file descriptor that the event loop object returned by the
  37 \fBsd_event_new\fR(3)
  38 function uses to wait for events\&. This file descriptor can be polled for events\&. This makes it possible to embed the
  39 \fBsd-event\fR(3)
  40 event loop inside of another event loop\&.
  41 .SH "RETURN VALUE"
  42 .PP
  43 On success,
  44 \fBsd_event_get_fd()\fR
  45 returns a non\-negative integer\&. On failure, it returns a negative errno\-style error code\&.
  46 .SH "ERRORS"
  47 .PP
  48 Returned errors may indicate the following problems:
  49 .PP
  50 \fB\-EINVAL\fR
  51 .RS 4
  52 \fIevent\fR
  53 is not a valid pointer to an
  54 sd_event
  55 structure\&.
  56 .RE
  57 .PP
  58 \fB\-ECHILD\fR
  59 .RS 4
  60 The event loop has been created in a different process\&.
  61 .RE
  62 .SH "EXAMPLES"
  63 .PP
  64 \fBExample\ \&1.\ \&Integration in glib event loop\fR
  65 .sp
  66 .if n \{\
  67 .RS 4
  68 .\}
  69 .nf
  70 /***
  71   Copyright 2014 Tom Gundersen
  72
  73   Permission is hereby granted, free of charge, to any person
  74   obtaining a copy of this software and associated documentation files
  75   (the "Software"), to deal in the Software without restriction,
  76   including without limitation the rights to use, copy, modify, merge,
  77   publish, distribute, sublicense, and/or sell copies of the Software,
  78   and to permit persons to whom the Software is furnished to do so,
  79   subject to the following conditions:
  80
  81   The above copyright notice and this permission notice shall be
  82   included in all copies or substantial portions of the Software\&.
  83
  84   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  85   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  86   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  87   NONINFRINGEMENT\&. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  88   BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  89   ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  90   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  91   SOFTWARE\&.
  92 ***/
  93
  94 #include <stdlib\&.h>
  95
  96 typedef struct SDEventSource {
  97         GSource source;
  98         GPollFD pollfd;
  99         sd_event *event;
 100 } SDEventSource;
 101
 102 static gboolean event_prepare(GSource *source, gint *timeout_) {
 103         return sd_event_prepare(((SDEventSource *)source)\->event) > 0;
 104 }
 105
 106 static gboolean event_check(GSource *source) {
 107         return sd_event_wait(((SDEventSource *)source)\->event, 0) > 0;
 108 }
 109
 110 static gboolean event_dispatch(GSource *source, GSourceFunc callback, gpointer user_data) {
 111         return sd_event_dispatch(((SDEventSource *)source)\->event) > 0;
 112 }
 113
 114 static void event_finalize(GSource *source) {
 115         sd_event_unref(((SDEventSource *)source)\->event);
 116 }
 117
 118 static GSourceFuncs event_funcs = {
 119         \&.prepare = event_prepare,
 120         \&.check = event_check,
 121         \&.dispatch = event_dispatch,
 122         \&.finalize = event_finalize,
 123 };
 124
 125 GSource *g_sd_event_create_source(sd_event *event) {
 126         SDEventSource *source;
 127
 128         source = (SDEventSource *)g_source_new(&event_funcs, sizeof(SDEventSource));
 129
 130         source\->event = sd_event_ref(event);
 131         source\->pollfd\&.fd = sd_event_get_fd(event);
 132         source\->pollfd\&.events = G_IO_IN | G_IO_HUP | G_IO_ERR;
 133
 134         g_source_add_poll((GSource *)source, &source\->pollfd);
 135
 136         return (GSource *)source;
 137 }
 138 .fi
 139 .if n \{\
 140 .RE
 141 .\}
 142 .SH "NOTES"
 143 .PP
 144 \fBsd_event_get_fd()\fR
 145 is available as a shared library, which can be compiled and linked to with the
 146 \fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
 147 file\&.
 148 .SH "SEE ALSO"
 149 .PP
 150 \fBsd-event\fR(3),
 151 \fBsd_event_new\fR(3),
 152 \fBsd_event_ref\fR(3)