Changeset 31583 in vbox for trunk/src/VBox/Runtime

Timestamp:

Aug 11, 2010 9:34:40 PM (14 years ago)

Author:

vboxsync

Message:

Runtime/Sg: Extend RTSgBufSegArrayCreate to allow just counting the number of required segments

File:

• trunk/src/VBox/Runtime/common/misc/sg.cpp (modified) (1 diff)

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

@@ -342 +342 @@
 {
     AssertPtrReturn(pSgBuf, 0);
-    AssertPtrReturn(paSeg, 0);
     AssertPtrReturn(pcSeg, 0);
 
+    unsigned cSeg = 0;
     size_t   cb = 0;
-    unsigned cSeg = 0;
-
-    while (   cbData
-           && cSeg < *pcSeg)
-    {
-        size_t  cbThisSeg = cbData;
-        void   *pvSeg     = NULL;
-
-        pvSeg = sgBufGet(pSgBuf, &cbThisSeg);
-
-        if (!cbThisSeg)
-        {
-            Assert(!pvSeg);
-            break;
-        }
-
-        AssertMsg(cbThisSeg <= cbData, ("Impossible!\n"));
-
-        paSeg[cSeg].cbSeg = cbThisSeg;
-        paSeg[cSeg].pvSeg = pvSeg;
-        cSeg++;
-        cbData -= cbThisSeg;
-        cb     += cbThisSeg;
+
+    if (!paSeg)
+    {
+        if (pSgBuf->cbSegLeft > 0)
+        {
+            size_t idx = pSgBuf->idxSeg;
+            cSeg = 1;
+
+            cb     += RT_MIN(pSgBuf->cbSegLeft, cbData);
+            cbData -= RT_MIN(pSgBuf->cbSegLeft, cbData);
+
+            while (   cbData
+                   && idx < pSgBuf->cSegs - 1)
+            {
+                idx++;
+                cSeg++;
+                cb     += RT_MIN(pSgBuf->paSegs[idx].cbSeg, cbData);
+                cbData -= RT_MIN(pSgBuf->paSegs[idx].cbSeg, cbData);
+            }
+        }
+    }
+    else
+    {
+        while (   cbData
+               && cSeg < *pcSeg)
+        {
+            size_t  cbThisSeg = cbData;
+            void   *pvSeg     = NULL;
+
+            pvSeg = sgBufGet(pSgBuf, &cbThisSeg);
+
+            if (!cbThisSeg)
+            {
+                Assert(!pvSeg);
+                break;
+            }
+
+            AssertMsg(cbThisSeg <= cbData, ("Impossible!\n"));
+
+            paSeg[cSeg].cbSeg = cbThisSeg;
+            paSeg[cSeg].pvSeg = pvSeg;
+            cSeg++;
+            cbData -= cbThisSeg;
+            cb     += cbThisSeg;
+        }
     }