Changeset 40292 in vbox for trunk/src/VBox/Runtime/common/vfs/vfsmemory.cpp

Timestamp:

Feb 29, 2012 11:29:35 AM (13 years ago)

Author:

vboxsync

Message:

RTVfsMemFile bugfix: rtVfsMemFile_Write regression from previous fix.

File:

• trunk/src/VBox/Runtime/common/vfs/vfsmemory.cpp (modified) (12 diffs)

trunk/src/VBox/Runtime/common/vfs/vfsmemory.cpp

@@ -172 +172 @@
     if (!pExtent || pExtent->off < off)
     {
-        pExtent = RTListGetFirst(&pThis->ExtentHead, RTVFSMEMEXTENT, Entry);
+        /* Consider the last entry first (for writes). */
+        pExtent = RTListGetLast(&pThis->ExtentHead, RTVFSMEMEXTENT, Entry);
         if (!pExtent)
         {
@@ -178 +179 @@
             return NULL;
         }
+        if (off - pExtent->off < pExtent->cb)
+        {
+            *pfHit = true;
+            pThis->pCurExt = pExtent;
+            return pExtent;
+        }
+
+        /* Otherwise, start from the head. */
+        pExtent = RTListGetFirst(&pThis->ExtentHead, RTVFSMEMEXTENT, Entry);
     }
 
@@ -188 +198 @@
         {
             *pfHit = false;
-            return pExtent;
+            return pNext;
         }
 
@@ -201 +211 @@
 
 /**
- * Locates the extent covering the specified offset, or then one before it.
+ * Locates the extent covering the specified offset, or the one after it.
  *
  * @returns The closest extent.  NULL if off is 0 and there are no extent
@@ -285 +295 @@
         for (;;)
         {
-            PRTVFSMEMEXTENT pNext;
-            size_t          cbThisRead;
-            Assert(!pExtent || pExtent->off <= offUnsigned);
+            size_t      cbThisRead;
 
             /*
-             * Do we hit an extent covering the the current file surface?
+             * Do we hit an extent covering the current file surface?
              */
             if (fHit)
             {
+                /* Yes, copy the data. */
+                Assert(offUnsigned - pExtent->off < pExtent->cb);
                 size_t const offExtent = (size_t)(offUnsigned - pExtent->off);
                 cbThisRead = pExtent->cb - offExtent;
@@ -307 +317 @@
                 pbDst        += cbThisRead;
 
-                pNext = RTListGetNext(&pThis->ExtentHead, pExtent, RTVFSMEMEXTENT, Entry);
+                /* Advance, looping immediately if not sparse. */
+                PRTVFSMEMEXTENT pNext = RTListGetNext(&pThis->ExtentHead, pExtent, RTVFSMEMEXTENT, Entry);
                 if (   pNext
                     && pNext->off == pExtent->off + pExtent->cb)
@@ -314 +325 @@
                     continue;
                 }
+
+                Assert(!pNext || pNext->off > pExtent->off);
+                pExtent = pNext;
                 fHit = false;
             }
+            else
+                Assert(!pExtent || pExtent->off > offUnsigned);
 
             /*
-             * No extent of this portion (sparse file).
+             * No extent of this portion (sparse file) - Read zeros.
              */
-            else if (pExtent)
-                pNext = RTListGetNext(&pThis->ExtentHead, pExtent, RTVFSMEMEXTENT, Entry);
-            else
-                pNext = NULL;
-            Assert(!pNext || pNext->off > pExtent->off);
-
-            if (   !pNext
-                || offUnsigned + cbLeftToRead <= pNext->off)
+            if (   !pExtent
+                || offUnsigned + cbLeftToRead <= pExtent->off)
                 cbThisRead = cbLeftToRead;
             else
-                cbThisRead = (size_t)(pNext->off - offUnsigned);
+                cbThisRead = (size_t)(pExtent->off - offUnsigned);
 
             RT_BZERO(pbDst, cbThisRead);
@@ -341 +351 @@
 
             /* Go on and read content from the next extent. */
-            fHit     = true;
-            pExtent  = pNext;
+            fHit = true;
         }
     }
@@ -359 +368 @@
  * @param   cbToWrite           The number of bytes we're interested in writing
  *                              starting at @a offUnsigned.
- * @param   pPrev               The extention before @a offUnsigned.  NULL if
- *                              none.
+ * @param   pNext               The extention after @a offUnsigned.  NULL if
+ *                              none, i.e. we're allocating space at the end of
+ *                              the file.
  */
 static PRTVFSMEMEXTENT rtVfsMemFile_AllocExtent(PRTVFSMEMFILE pThis, uint64_t offUnsigned, size_t cbToWrite,
-                                                PRTVFSMEMEXTENT pPrev)
+                                                PRTVFSMEMEXTENT pNext)
 {
     /*
@@ -395 +405 @@
     uint32_t        cbExtent  = pThis->cbExtent;
 
+    PRTVFSMEMEXTENT pPrev     = pNext
+                              ? RTListGetPrev(&pThis->ExtentHead, pNext, RTVFSMEMEXTENT, Entry)
+                              : RTListGetLast(&pThis->ExtentHead, RTVFSMEMEXTENT, Entry);
     uint64_t const  offPrev   = pPrev ? pPrev->off + pPrev->cb : 0;
     if (offExtent < offPrev)
         offExtent = offPrev;
 
-    PRTVFSMEMEXTENT pNext     = pPrev
-                              ? RTListGetNext(&pThis->ExtentHead, pPrev, RTVFSMEMEXTENT, Entry)
-                              : RTListGetFirst(&pThis->ExtentHead, RTVFSMEMEXTENT, Entry);
     if (pNext)
     {
@@ -462 +472 @@
         if (!fHit)
         {
-            Assert(!pExtent || offUnsigned < pExtent->off);
+            Assert(!pExtent || pExtent->off > offUnsigned);
 
             /* Skip leading zeros if there is a whole bunch of them. */
@@ -493 +503 @@
             }
         }
+        Assert(offUnsigned - pExtent->off < pExtent->cb);
 
         /*