[libvirt] [PATCH] outline of writing vbox driver

[Taowei]

Define the vboxUniformedAPI struct to handle version conflicts.
The vboxInitialize is rewrited with the new mechanism. Other
functions would be rewriting in the same way.

Here, I still use template to generate functions in vboxUniformedAPI.
Though, these functions may change between different versions, but 
not for every version. Using template could decrease the duplicated code.

For every new feature added by vbox, a flag would indicate whether this
feature is supported in current version. Calling for an unsupported 
feature would lead to a VIR_WARN.

---
 src/vbox/vbox_tmpl.c |   84 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 61 insertions(+), 23 deletions(-)

diff --git a/src/vbox/vbox_tmpl.c b/src/vbox/vbox_tmpl.c
index 1ed2729..4625805 100644
--- a/src/vbox/vbox_tmpl.c
+++ b/src/vbox/vbox_tmpl.c
@@ -826,6 +826,65 @@ static PRUnichar *PRUnicharFromInt(int n) {
 
 #endif /* !(VBOX_API_VERSION == 2002000) */
 
+/* Begin of vboxUniformedAPI */
+
+#define UNUSED(expr) do { (void)(expr); } while (0)
+
+static void _pfnComInitialize(vboxGlobalData *data)
+{
+#if VBOX_XPCOMC_VERSION == 0x00010000U
+    data->pFuncs->pfnComInitialize(&data->vboxObj, &data->vboxSession);
+#else  /* !(VBOX_XPCOMC_VERSION == 0x00010000U) */
+    data->pFuncs->pfnComInitialize(IVIRTUALBOX_IID_STR, &data->vboxObj, ISESSION_IID_STR, &data->vboxSession);
+#endif /* !(VBOX_XPCOMC_VERSION == 0x00010000U) */
+}
+
+#if (VBOX_XPCOMC_VERSION == 0x00010000U) || (VBOX_API_VERSION == 2002000)
+    #define FWATCH_NEED_INITICAL 0
+#else /* (VBOX_XPCOMC_VERSION != 0x00010000U && VBOX_API_VERSION != 2002000) */
+    #define FWATCH_NEED_INITICAL 1
+#endif /* (VBOX_XPCOMC_VERSION != 0x00010000U && VBOX_API_VERSION != 2002000) */
+
+static int _initicalFWatch(vboxGlobalData *data)
+{
+#if FWATCH_NEED_INITICAL == 0
+    /* No event queue functionality in 2.2.* as of now */
+    UNUSED(data);
+    VIR_WARN("There is no fWatch initical in current version");
+#else /* FWATCH_NEED_INITICAL != 0 */
+    /* Initial the fWatch needed for Event Callbacks */
+    data->fdWatch = -1;
+    data->pFuncs->pfnGetEventQueue(&data->vboxQueue);
+    if (data->vboxQueue == NULL) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("nsIEventQueue object is null"));
+        return -1;
+    }
+#endif /* FWATCH_NEED_INITICAL != 0 */
+    return 0;
+}
+
+typedef struct {
+    /* vbox API version */
+    uint32_t uVersion;
+    /* vbox APIs */
+    void  (*pfnComInitialize)(vboxGlobalData *data);
+    int (*initicalFWatch)(vboxGlobalData *data);
+    /* vbox API features */
+    unsigned fWatchNeedInitical : 1;
+} vboxUniformedAPI;
+
+static vboxUniformedAPI vboxAPI = {
+    .uVersion = VBOX_API_VERSION,
+    .pfnComInitialize = _pfnComInitialize,
+    .initicalFWatch = _initicalFWatch,
+    .fWatchNeedInitical = FWATCH_NEED_INITICAL,
+};
+
+static vboxUniformedAPI *pVboxAPI = &vboxAPI;
+
+/* End of vboxUniformedAPI and Begin of common codes */
+
 static PRUnichar *
 vboxSocketFormatAddrUtf16(vboxGlobalData *data, virSocketAddrPtr addr)
 {
@@ -923,31 +982,10 @@ vboxInitialize(vboxGlobalData *data)
     if (data->pFuncs == NULL)
         goto cleanup;
 
-#if VBOX_XPCOMC_VERSION == 0x00010000U
-    data->pFuncs->pfnComInitialize(&data->vboxObj, &data->vboxSession);
-#else  /* !(VBOX_XPCOMC_VERSION == 0x00010000U) */
-    data->pFuncs->pfnComInitialize(IVIRTUALBOX_IID_STR, &data->vboxObj,
-                               ISESSION_IID_STR, &data->vboxSession);
-
-# if VBOX_API_VERSION == 2002000
-
-    /* No event queue functionality in 2.2.* as of now */
-
-# else  /* !(VBOX_API_VERSION == 2002000) */
+    pVboxAPI->pfnComInitialize(data);
 
-    /* Initial the fWatch needed for Event Callbacks */
-    data->fdWatch = -1;
-
-    data->pFuncs->pfnGetEventQueue(&data->vboxQueue);
-
-    if (data->vboxQueue == NULL) {
-        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-                       _("nsIEventQueue object is null"));
+    if (pVboxAPI->fWatchNeedInitical && pVboxAPI->initicalFWatch(data) != 0)
         goto cleanup;
-    }
-
-# endif /* !(VBOX_API_VERSION == 2002000) */
-#endif /* !(VBOX_XPCOMC_VERSION == 0x00010000U) */
 
     if (data->vboxObj == NULL) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-- 
1.7.9.5