(submit/cleanup-vidmode-dispatch) Xext: vidmode: untwist ProcVidModeGetAllModeLines() and use stack buffer

The ProcVidModeGetAllModeLines() is a bit complicated, because reply structs
differ depending the active protocol version. In order to make it easier to
understand and allow further simplification of the request/reply marshalling
(see ticket #1701), splitting the two protocol versions into separate functions.

Also collecting the whole payload in a stack buffer (size is already known
anyways), in order to save arbirary number of individual WriteToClient() calls,
but send out the whole reply in one pass, which in turn allows further
simplifications in the sending path.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

Xext/vidmode.c

@@ -310,6 +310,72 @@ ProcVidModeGetModeLine(ClientPtr client)
     return Success;
 }
 
+static char *fillModeInfoV1(ClientPtr client, char *buf, int dotClock, DisplayModePtr mode)
+{
+    xXF86OldVidModeModeInfo info = {
+        .dotclock = dotClock,
+        .hdisplay = VidModeGetModeValue(mode, VIDMODE_H_DISPLAY),
+        .hsyncstart = VidModeGetModeValue(mode, VIDMODE_H_SYNCSTART),
+        .hsyncend = VidModeGetModeValue(mode, VIDMODE_H_SYNCEND),
+        .htotal = VidModeGetModeValue(mode, VIDMODE_H_TOTAL),
+        .vdisplay = VidModeGetModeValue(mode, VIDMODE_V_DISPLAY),
+        .vsyncstart = VidModeGetModeValue(mode, VIDMODE_V_SYNCSTART),
+        .vsyncend = VidModeGetModeValue(mode, VIDMODE_V_SYNCEND),
+        .vtotal = VidModeGetModeValue(mode, VIDMODE_V_TOTAL),
+        .flags = VidModeGetModeValue(mode, VIDMODE_FLAGS),
+    };
+
+    if (client->swapped) {
+        swapl(&info.dotclock);
+        swaps(&info.hdisplay);
+        swaps(&info.hsyncstart);
+        swaps(&info.hsyncend);
+        swaps(&info.htotal);
+        swaps(&info.vdisplay);
+        swaps(&info.vsyncstart);
+        swaps(&info.vsyncend);
+        swaps(&info.vtotal);
+        swapl(&info.flags);
+    }
+
+    memcpy(buf, &info, sizeof(info));
+    return buf + sizeof(info);
+}
+
+static char *fillModeInfoV2(ClientPtr client, char *buf, int dotClock, DisplayModePtr mode)
+{
+    xXF86VidModeModeInfo info = {
+        .dotclock = dotClock,
+        .hdisplay = VidModeGetModeValue(mode, VIDMODE_H_DISPLAY),
+        .hsyncstart = VidModeGetModeValue(mode, VIDMODE_H_SYNCSTART),
+        .hsyncend = VidModeGetModeValue(mode, VIDMODE_H_SYNCEND),
+        .htotal = VidModeGetModeValue(mode, VIDMODE_H_TOTAL),
+        .hskew = VidModeGetModeValue(mode, VIDMODE_H_SKEW),
+        .vdisplay = VidModeGetModeValue(mode, VIDMODE_V_DISPLAY),
+        .vsyncstart = VidModeGetModeValue(mode, VIDMODE_V_SYNCSTART),
+        .vsyncend = VidModeGetModeValue(mode, VIDMODE_V_SYNCEND),
+        .vtotal = VidModeGetModeValue(mode, VIDMODE_V_TOTAL),
+        .flags = VidModeGetModeValue(mode, VIDMODE_FLAGS),
+    };
+
+    if (client->swapped) {
+        swapl(&info.dotclock);
+        swaps(&info.hdisplay);
+        swaps(&info.hsyncstart);
+        swaps(&info.hsyncend);
+        swaps(&info.htotal);
+        swapl(&info.hskew);
+        swaps(&info.vdisplay);
+        swaps(&info.vsyncstart);
+        swaps(&info.vsyncend);
+        swaps(&info.vtotal);
+        swapl(&info.flags);
+    }
+
+    memcpy(buf, &info, sizeof(info));
+    return buf + sizeof(info);
+}
+
 static int
 ProcVidModeGetAllModeLines(ClientPtr client)
 {
@@ -357,57 +423,16 @@ ProcVidModeGetAllModeLines(ClientPtr client)
     }
     WriteToClient(client, sizeof(xXF86VidModeGetAllModeLinesReply), &rep);
 
-    do {
+    char payload[payload_len];
-        xXF86VidModeModeInfo mdinf = {
+    char *walk = payload;
-            .dotclock = dotClock,
-            .hdisplay = VidModeGetModeValue(mode, VIDMODE_H_DISPLAY),
-            .hsyncstart = VidModeGetModeValue(mode, VIDMODE_H_SYNCSTART),
-            .hsyncend = VidModeGetModeValue(mode, VIDMODE_H_SYNCEND),
-            .htotal = VidModeGetModeValue(mode, VIDMODE_H_TOTAL),
-            .hskew = VidModeGetModeValue(mode, VIDMODE_H_SKEW),
-            .vdisplay = VidModeGetModeValue(mode, VIDMODE_V_DISPLAY),
-            .vsyncstart = VidModeGetModeValue(mode, VIDMODE_V_SYNCSTART),
-            .vsyncend = VidModeGetModeValue(mode, VIDMODE_V_SYNCEND),
-            .vtotal = VidModeGetModeValue(mode, VIDMODE_V_TOTAL),
-            .flags = VidModeGetModeValue(mode, VIDMODE_FLAGS),
-            .privsize = 0
-        };
-        if (client->swapped) {
-            swapl(&mdinf.dotclock);
-            swaps(&mdinf.hdisplay);
-            swaps(&mdinf.hsyncstart);
-            swaps(&mdinf.hsyncend);
-            swaps(&mdinf.htotal);
-            swapl(&mdinf.hskew);
-            swaps(&mdinf.vdisplay);
-            swaps(&mdinf.vsyncstart);
-            swaps(&mdinf.vsyncend);
-            swaps(&mdinf.vtotal);
-            swapl(&mdinf.flags);
-            swapl(&mdinf.privsize);
-        }
-        if (ver < 2) {
-            xXF86OldVidModeModeInfo oldmdinf = {
-                .dotclock = mdinf.dotclock,
-                .hdisplay = mdinf.hdisplay,
-                .hsyncstart = mdinf.hsyncstart,
-                .hsyncend = mdinf.hsyncend,
-                .htotal = mdinf.htotal,
-                .vdisplay = mdinf.vdisplay,
-                .vsyncstart = mdinf.vsyncstart,
-                .vsyncend = mdinf.vsyncend,
-                .vtotal = mdinf.vtotal,
-                .flags = mdinf.flags,
-                .privsize = mdinf.privsize
-            };
-            WriteToClient(client, sizeof(xXF86OldVidModeModeInfo), &oldmdinf);
-        }
-        else {
-            WriteToClient(client, sizeof(xXF86VidModeModeInfo), &mdinf);
-        }
 
+    do {
+        walk = (ver < 2) ? fillModeInfoV1(client, walk, dotClock, mode)
+                         : fillModeInfoV2(client, walk, dotClock, mode);
     } while (pVidMode->GetNextModeline(pScreen, &mode, &dotClock));
 
+    WriteToClient(client, sizeof(payload), payload);
+
     return Success;
 }