[Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select

["Daniel P. Berrange" <berrange@redhat.com>]

From: Paolo Bonzini <pbonzini@redhat.com>

On Win32 we cannot directly poll on socket handles. Instead we
create a Win32 event object and associate the socket handle with
the event. When the event signals readyness we then have to
use select to determine which events are ready. Creating Win32
events is moderately heavyweight, so we don't want todo it
every time we create a GSource, so this associates a single
event with a QIOChannel.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 include/io/channel.h |   3 ++
 io/channel-socket.c  |   9 ++++
 io/channel-watch.c   | 136 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 io/channel.c         |  14 ++++++
 4 files changed, 161 insertions(+), 1 deletion(-)

diff --git a/include/io/channel.h b/include/io/channel.h
index 0a1f1ce..20b973a 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -78,6 +78,9 @@ typedef gboolean (*QIOChannelFunc)(QIOChannel *ioc,
 struct QIOChannel {
     Object parent;
     unsigned int features; /* bitmask of QIOChannelFeatures */
+#ifdef _WIN32
+    HANDLE event; /* For use with GSource on Win23 */
+#endif
 };
 
 /**
diff --git a/io/channel-socket.c b/io/channel-socket.c
index 6f7f594..ff49853 100644
--- a/io/channel-socket.c
+++ b/io/channel-socket.c
@@ -55,6 +55,10 @@ qio_channel_socket_new(void)
     ioc = QIO_CHANNEL(sioc);
     ioc->features |= (1 << QIO_CHANNEL_FEATURE_SHUTDOWN);
 
+#ifdef WIN32
+    ioc->event = CreateEvent(NULL, FALSE, FALSE, NULL);
+#endif
+
     trace_qio_channel_socket_new(sioc);
 
     return sioc;
@@ -341,6 +345,11 @@ qio_channel_socket_accept(QIOChannelSocket *ioc,
     cioc->remoteAddrLen = sizeof(ioc->remoteAddr);
     cioc->localAddrLen = sizeof(ioc->localAddr);
 
+#ifdef WIN32
+    ((QIOChannel *)cioc)->event = CreateEvent(NULL, FALSE, FALSE, NULL);
+#endif
+
+
  retry:
     trace_qio_channel_socket_accept(ioc);
     cioc->fd = accept(ioc->fd, (struct sockaddr *)&cioc->remoteAddr,
diff --git a/io/channel-watch.c b/io/channel-watch.c
index dfac8f8..c5ee69f 100644
--- a/io/channel-watch.c
+++ b/io/channel-watch.c
@@ -30,6 +30,20 @@ struct QIOChannelFDSource {
 };
 
 
+#ifdef CONFIG_WIN32
+typedef struct QIOChannelSocketSource QIOChannelSocketSource;
+struct QIOChannelSocketSource {
+    GSource parent;
+    GPollFD fd;
+    QIOChannel *ioc;
+    SOCKET socket;
+    int revents;
+    GIOCondition condition;
+};
+
+#endif
+
+
 typedef struct QIOChannelFDPairSource QIOChannelFDPairSource;
 struct QIOChannelFDPairSource {
     GSource parent;
@@ -82,6 +96,104 @@ qio_channel_fd_source_finalize(GSource *source)
 }
 
 
+#ifdef CONFIG_WIN32
+static gboolean
+qio_channel_socket_source_prepare(GSource *source G_GNUC_UNUSED,
+                                  gint *timeout)
+{
+    *timeout = -1;
+
+    return FALSE;
+}
+
+
+static gboolean
+qio_channel_socket_source_check(GSource *source)
+{
+    static struct timeval tv0;
+
+    QIOChannelSocketSource *ssource = (QIOChannelSocketSource *)source;
+    WSANETWORKEVENTS ev;
+    fd_set rfds, wfds, xfds;
+
+    if (!ssource->condition) {
+        return 0;
+    }
+
+    WSAEnumNetworkEvents(ssource->socket, ssource->ioc->event, &ev);
+
+    /* WSAEnumNetworkEvents is edge-triggered, so we need a separate
+     * call to select to find which events are actually available.
+     * However, if there were no reported events at the time of the last
+     * call, and no new events since then, we know that the socket is
+     * quiescent.
+     */
+    if (!ssource->revents && !ev.lNetworkEvents) {
+        return 0;
+    }
+
+    FD_ZERO(&rfds);
+    FD_ZERO(&wfds);
+    FD_ZERO(&xfds);
+    if (ssource->condition & G_IO_IN) {
+        FD_SET((SOCKET)ssource->socket, &rfds);
+    }
+    if (ssource->condition & G_IO_OUT) {
+        FD_SET((SOCKET)ssource->socket, &wfds);
+    }
+    if (ssource->condition & G_IO_PRI) {
+        FD_SET((SOCKET)ssource->socket, &xfds);
+    }
+    ssource->revents = 0;
+    if (select(0, &rfds, &wfds, &xfds, &tv0) == 0) {
+        return 0;
+    }
+
+    if (FD_ISSET(ssource->socket, &rfds)) {
+        ssource->revents |= G_IO_IN;
+    }
+    if (FD_ISSET(ssource->socket, &wfds)) {
+        ssource->revents |= G_IO_OUT;
+    }
+    if (FD_ISSET(ssource->socket, &xfds)) {
+        ssource->revents |= G_IO_PRI;
+    }
+
+    return ssource->revents;
+}
+
+
+static gboolean
+qio_channel_socket_source_dispatch(GSource *source,
+                                   GSourceFunc callback,
+                                   gpointer user_data)
+{
+    QIOChannelFunc func = (QIOChannelFunc)callback;
+    QIOChannelSocketSource *ssource = (QIOChannelSocketSource *)source;
+
+    return (*func)(ssource->ioc, ssource->revents, user_data);
+}
+
+
+static void
+qio_channel_socket_source_finalize(GSource *source)
+{
+    QIOChannelSocketSource *ssource = (QIOChannelSocketSource *)source;
+
+    WSAEventSelect(ssource->socket, NULL, 0);
+    object_unref(OBJECT(ssource->ioc));
+}
+
+
+GSourceFuncs qio_channel_socket_source_funcs = {
+    qio_channel_socket_source_prepare,
+    qio_channel_socket_source_check,
+    qio_channel_socket_source_dispatch,
+    qio_channel_socket_source_finalize
+};
+#endif
+
+
 static gboolean
 qio_channel_fd_pair_source_prepare(GSource *source G_GNUC_UNUSED,
                                    gint *timeout)
@@ -177,7 +289,29 @@ GSource *qio_channel_create_socket_watch(QIOChannel *ioc,
                                          int socket,
                                          GIOCondition condition)
 {
-    abort();
+    GSource *source;
+    QIOChannelSocketSource *ssource;
+
+    source = g_source_new(&qio_channel_socket_source_funcs,
+                          sizeof(QIOChannelSocketSource));
+    ssource = (QIOChannelSocketSource *)source;
+
+    ssource->ioc = ioc;
+    object_ref(OBJECT(ioc));
+
+    ssource->condition = condition;
+    ssource->socket = socket;
+    ssource->revents = 0;
+
+    ssource->fd.fd = (gintptr)ioc->event;
+    ssource->fd.events = G_IO_IN;
+
+    g_source_add_poll(source, &ssource->fd);
+    WSAEventSelect(ssource->socket, ioc->event,
+                   FD_READ | FD_ACCEPT | FD_CLOSE |
+                   FD_CONNECT | FD_WRITE | FD_OOB);
+
+    return source;
 }
 #else
 GSource *qio_channel_create_socket_watch(QIOChannel *ioc,
diff --git a/io/channel.c b/io/channel.c
index 3fc09f8..dd6fc0e 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -274,10 +274,24 @@ void qio_channel_wait(QIOChannel *ioc,
 }
 
 
+#ifdef _WIN32
+static void qio_channel_finalize(Object *obj)
+{
+    QIOChannel *ioc = QIO_CHANNEL(obj);
+
+    if (ioc->event) {
+        CloseHandle(ioc->event);
+    }
+}
+#endif
+
 static const TypeInfo qio_channel_info = {
     .parent = TYPE_OBJECT,
     .name = TYPE_QIO_CHANNEL,
     .instance_size = sizeof(QIOChannel),
+#ifdef _WIN32
+    .instance_finalize = qio_channel_finalize,
+#endif
     .abstract = true,
     .class_size = sizeof(QIOChannelClass),
 };
-- 
2.5.0