qga: add windows implementation for guest-get-time

Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

1 files changed, 25 insertions, 2 deletions

diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index b19be9db48..d98e3eeff0 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -22,6 +22,12 @@
 #define SHTDN_REASON_FLAG_PLANNED 0x80000000
 #endif
 
+/* multiple of 100 nanoseconds elapsed between windows baseline
+ *    (1/1/1601) and Unix Epoch (1/1/1970), accounting for leap years */
+#define W32_FT_OFFSET (10000000ULL * 60 * 60 * 24 * \
+                       (365 * (1970 - 1601) +       \
+                        (1970 - 1601) / 4 - 3))
+
 static void acquire_privilege(const char *name, Error **err)
 {
     HANDLE token;
@@ -280,8 +286,25 @@ GuestNetworkInterfaceList *qmp_guest_network_get_interfaces(Error **err)
 
 int64_t qmp_guest_get_time(Error **errp)
 {
-    error_set(errp, QERR_UNSUPPORTED);
-    return -1;
+    SYSTEMTIME ts = {0};
+    int64_t time_ns;
+    FILETIME tf;
+
+    GetSystemTime(&ts);
+    if (ts.wYear < 1601 || ts.wYear > 30827) {
+        error_setg(errp, "Failed to get time");
+        return -1;
+    }
+
+    if (!SystemTimeToFileTime(&ts, &tf)) {
+        error_setg(errp, "Failed to convert system time: %d", (int)GetLastError());
+        return -1;
+    }
+
+    time_ns = ((((int64_t)tf.dwHighDateTime << 32) | tf.dwLowDateTime)
+                - W32_FT_OFFSET) * 100;
+
+    return time_ns;
 }
 
 void qmp_guest_set_time(int64_t time_ns, Error **errp)