[tkreuzer] 58081: [WIN32K] Exchange fields individually in PDEVOBJ_vSwitchPdev() instead of duplicating a full PDEV structure on the stack. This saves a lot of stack space.

Author: tkreuzer
Date: Tue Jan  1 11:57:58 2013
New Revision: 58081

URL: http://svn.reactos.org/svn/reactos?rev=58081&view=rev
Log:
[WIN32K]
Exchange fields individually in PDEVOBJ_vSwitchPdev() instead of duplicating a full PDEV structure on the stack. This saves a lot of stack space.

Modified:
    trunk/reactos/win32ss/gdi/eng/pdevobj.c

Modified: trunk/reactos/win32ss/gdi/eng/pdevobj.c
URL: http://svn.reactos.org/svn/reactos/trunk/reactos/win32ss/gdi/eng/pdevobj.c?r...
==============================================================================
--- trunk/reactos/win32ss/gdi/eng/pdevobj.c [iso-8859-1] (original)
+++ trunk/reactos/win32ss/gdi/eng/pdevobj.c [iso-8859-1] Tue Jan  1 11:57:58 2013
@@ -342,51 +342,67 @@
 }

VOID
+FORCEINLINE
+SwitchPointer(
+    _Inout_ PVOID pvPointer1,
+    _Inout_ PVOID pvPointer2)
+{
+    PVOID *ppvPointer1 = pvPointer1;
+    PVOID *ppvPointer2 = pvPointer2;
+    PVOID pvTemp;
+
+    pvTemp = *ppvPointer1;
+    *ppvPointer1 = *ppvPointer2;
+    *ppvPointer2 = pvTemp;
+}
+
+VOID
 NTAPI
 PDEVOBJ_vSwitchPdev(
     PPDEVOBJ ppdev,
     PPDEVOBJ ppdev2)
 {
-    PDEVOBJ pdevTmp;
-    DWORD tmpStateFlags;
-
-    /* Exchange data */
-    pdevTmp = *ppdev;
+    union
+    {
+        DRIVER_FUNCTIONS pfn;
+        GDIINFO gdiinfo;
+        DEVINFO devinfo;
+        DWORD StateFlags;
+    } temp;

/* Exchange driver functions */
+    temp.pfn = ppdev->pfn;
     ppdev->pfn = ppdev2->pfn;
-    ppdev2->pfn = pdevTmp.pfn;
+    ppdev2->pfn = temp.pfn;

/* Exchange LDEVs */
-    ppdev->pldev = ppdev2->pldev;
-    ppdev2->pldev = pdevTmp.pldev;
+    SwitchPointer(&ppdev->pldev, &ppdev2->pldev);

/* Exchange DHPDEV */
-    ppdev->dhpdev = ppdev2->dhpdev;
-    ppdev2->dhpdev = pdevTmp.dhpdev;
+    SwitchPointer(&ppdev->dhpdev, &ppdev2->dhpdev);

/* Exchange surfaces and associate them with their new PDEV */
-    ppdev->pSurface = ppdev2->pSurface;
-    ppdev2->pSurface = pdevTmp.pSurface;
+    SwitchPointer(&ppdev->pSurface, &ppdev2->pSurface);
     ppdev->pSurface->SurfObj.hdev = (HDEV)ppdev;
     ppdev2->pSurface->SurfObj.hdev = (HDEV)ppdev2;

/* Exchange devinfo */
+    temp.devinfo = ppdev->devinfo;
     ppdev->devinfo = ppdev2->devinfo;
-    ppdev2->devinfo = pdevTmp.devinfo;
+    ppdev2->devinfo = temp.devinfo;

/* Exchange gdiinfo */
+    temp.gdiinfo = ppdev->gdiinfo;
     ppdev->gdiinfo = ppdev2->gdiinfo;
-    ppdev2->gdiinfo = pdevTmp.gdiinfo;
+    ppdev2->gdiinfo = temp.gdiinfo;

/* Exchange DEVMODE */
-    ppdev->pdmwDev = ppdev2->pdmwDev;
-    ppdev2->pdmwDev = pdevTmp.pdmwDev;
+    SwitchPointer(&ppdev->pdmwDev, &ppdev2->pdmwDev);

/* Exchange state flags */
-    tmpStateFlags = ppdev->pGraphicsDevice->StateFlags;
+    temp.StateFlags = ppdev->pGraphicsDevice->StateFlags;
     ppdev->pGraphicsDevice->StateFlags = ppdev2->pGraphicsDevice->StateFlags;
-    ppdev2->pGraphicsDevice->StateFlags = tmpStateFlags;
+    ppdev2->pGraphicsDevice->StateFlags = temp.StateFlags;

/* Notify each driver instance of its new HDEV association */
     ppdev->pfn.CompletePDEV(ppdev->dhpdev, (HDEV)ppdev);
@@ -407,6 +423,7 @@

/* Lock the PDEV */
     EngAcquireSemaphore(ppdev->hsemDevLock);
+
     /* And everything else */
     EngAcquireSemaphore(ghsemPDEV);

@@ -613,9 +630,10 @@

/** Exported functions ********************************************************/

+_Must_inspect_result_ _Ret_z_
 LPWSTR
 APIENTRY
-EngGetDriverName(IN HDEV hdev)
+EngGetDriverName(_In_ HDEV hdev)
 {
     PPDEVOBJ ppdev = (PPDEVOBJ)hdev;