Changeset 79300 in vbox for trunk/src/VBox/Main

Timestamp:

Jun 24, 2019 10:33:35 AM (6 years ago)

Author:

vboxsync

Message:

Main/GuestFileImpl.cpp: doc updates wrt file offsets. bugref:9320

Location:

trunk/src/VBox/Main

Files:

• idl/VirtualBox.xidl (modified) (1 diff)
• src-client/GuestFileImpl.cpp (modified) (5 diffs)

trunk/src/VBox/Main/idl/VirtualBox.xidl

@@ -14161 +14161 @@
         The <link to="IFile::seek"/> is used to change this attribute without
         transfering any file data like read and write does.
+
+        <note> This will not always be correct with older guest additions
+        (version 5.2.30 and earlier, as well as versions 6.0.0 thru 6.0.8)
+        after a calling <link to="IFile::readAt"/> or <link to="IFile::writeAt"/>,
+        or after calling <link to="IFile::write"/> on a file in append mode.
+        The correct file offset can be obtained using <link to="IFile::seek"/>.</note>
+
       </desc>
     </attribute>

trunk/src/VBox/Main/src-client/GuestFileImpl.cpp

@@ -298 +298 @@
     AutoReadLock alock(this COMMA_LOCKVAL_SRC_POS);
 
-/** @todo r=bird: Why do you have both a offset and a tell() function?
- * After a ReadAt or WriteAt with a non-current offset, the tell() result will
- * differ from this value, because mOffCurrent is only ever incremented with
- * data read or written.  */
+    /* Note! This will not be accurate with older (< 5.2.32, 6.0.0 - 6.0.9)
+             guest additions when using writeAt, readAt or writing to a file
+             opened in append mode. */
     *aOffset = mData.mOffCurrent;
 
@@ -507 +506 @@
                 AutoWriteLock alock(this COMMA_LOCKVAL_SRC_POS);
 
-                mData.mOffCurrent += cbRead;
+                mData.mOffCurrent += cbRead; /* Bogus for readAt, which is why we've got GUEST_FILE_NOTIFYTYPE_READ_OFFSET. */
 
                 alock.release();
@@ -569 +568 @@
                 AutoWriteLock alock(this COMMA_LOCKVAL_SRC_POS);
 
-                mData.mOffCurrent += cbWritten;
+                mData.mOffCurrent += cbWritten; /* Bogus for writeAt and append mode, thus GUEST_FILE_NOTIFYTYPE_WRITE_OFFSET. */
 
                 alock.release();
@@ -626 +625 @@
                 alock.release();
 
-                fireGuestFileOffsetChangedEvent(mEventSource, mSession, this, mData.mOffCurrent, 0 /* Processed */);
+                fireGuestFileOffsetChangedEvent(mEventSource, mSession, this, dataCb.u.seek.uOffActual, 0 /* Processed */);
             }
             break;
@@ -632 +631 @@
 
         case GUEST_FILE_NOTIFYTYPE_TELL:
-        {
-            if (pSvcCbData->mParms == 4)
-            {
-                rc = HGCMSvcGetU64(&pSvcCbData->mpaParms[idx++], &dataCb.u.tell.uOffActual);
-                if (RT_FAILURE(rc))
-                    break;
-
-                Log3ThisFunc(("uOffActual=%RU64\n", dataCb.u.tell.uOffActual));
-
-                AutoWriteLock alock(this COMMA_LOCKVAL_SRC_POS);
-
-                mData.mOffCurrent = dataCb.u.tell.uOffActual;
-
-                alock.release();
-
-                fireGuestFileOffsetChangedEvent(mEventSource, mSession, this, mData.mOffCurrent, 0 /* Processed */);
-            }
+            /* We don't issue any HOST_MSG_FILE_TELL, so we shouldn't get these notifications! */
+            AssertFailed();
             break;
-        }
 
         case GUEST_FILE_NOTIFYTYPE_SET_SIZE: