Changeset 38686 in vbox for trunk/src/VBox/Runtime/common/misc

Timestamp:

Sep 8, 2011 9:30:17 AM (13 years ago)

Author:

vboxsync

Message:

Runtime/Sg: Leave early if there is no memory left in the S/G buffer

File:

• trunk/src/VBox/Runtime/common/misc/sg.cpp (modified) (3 diffs)

trunk/src/VBox/Runtime/common/misc/sg.cpp

@@ -36 +36 @@
 static void *sgBufGet(PRTSGBUF pSgBuf, size_t *pcbData)
 {
-    size_t cbData = RT_MIN(*pcbData, pSgBuf->cbSegLeft);
-    void *pvBuf = pSgBuf->pvSegCur;
+    size_t cbData;
+    void *pvBuf;
+
+    /* Check that the S/G buffer has memory left. */
+    if (RT_UNLIKELY(   pSgBuf->idxSeg == pSgBuf->cSegs
+                    && !pSgBuf->cbSegLeft))
+    {
+        *pcbData = 0;
+        return NULL;
+    }
 
     AssertReleaseMsg(      pSgBuf->cbSegLeft <= 5 * _1M
@@ -46 +54 @@
                       pSgBuf->idxSeg, pSgBuf->paSegs[pSgBuf->idxSeg].pvSeg, pSgBuf->idxSeg, pSgBuf->paSegs[pSgBuf->idxSeg].cbSeg));
 
+    cbData = RT_MIN(*pcbData, pSgBuf->cbSegLeft);
+    pvBuf  = pSgBuf->pvSegCur;
     pSgBuf->cbSegLeft -= cbData;
 
@@ -53 +63 @@
         pSgBuf->idxSeg++;
 
-        if (RT_UNLIKELY(pSgBuf->idxSeg == pSgBuf->cSegs))
-        {
-            pSgBuf->cbSegLeft = 0;
-            pSgBuf->pvSegCur  = NULL;
-        }
-        else
+        if (pSgBuf->idxSeg < pSgBuf->cSegs)
         {
             pSgBuf->pvSegCur  = pSgBuf->paSegs[pSgBuf->idxSeg].pvSeg;