Buffer class changes/bugfix for log roller and fido export

mdl/m_fileio.pas

@@ -63,6 +63,7 @@ Type
   TFileBufferOpenType = (
     fmOpen,
     fmOpenCreate,
+    fmOpenAppend,
     fmCreate
   );
 
@@ -596,7 +597,8 @@ Begin
 
   Case OpenType of
     fmOpen       : If Not ioReset (InFile, 1, OpenMode) Then Exit;
-    fmOpenCreate : If Not ioReset (InFile, 1, OpenMode) Then
+    fmOpenCreate,
+    fmOpenAppend : If Not ioReset (InFile, 1, OpenMode) Then
                      If Not FileExist(FN) Then Begin
                        If Not ioReWrite (InFile, 1, OpenMode) Then Exit;
                      End Else
@@ -604,6 +606,9 @@ Begin
     fmCreate     : If Not ioReWrite (InFile, 1, OpenMode) Then Exit;
   End;
 
+  If OpenType = fmOpenAppend Then
+    ioSeek (InFile, System.FileSize(InFile));
+
   GetMem (Buffer, BufSize);
 
   FillBuffer;
@@ -708,12 +713,26 @@ Begin
     If Offset > 0 Then
       Move (Buf, Buffer^[BufPos], Offset);
 
+    BufRead := BufSize;
+
     FlushBuffer;
+
+    // -----
+    Move (TFileBufferRec(Buf)[Offset], Buffer^[0], Size - Offset);
+
+    BufStart := System.FilePos(InFile);
+    BufEnd   := BufStart + Size - Offset;
+    BufPos   := Size - Offset;
+    BufEOF   := System.EOF(InFile);
+    BufRead  := BufPos;
+
+(*  the above replaces the 3 lines below... but is it reliable?
     FillBuffer;
 
     Move (TFileBufferRec(Buf)[Offset], Buffer^[BufPos], Size - Offset);
 
     BufPos := BufPos + Size - Offset;
+*)
   End Else Begin
     Move (Buf, Buffer^[BufPos], Size);
     Inc  (BufPos, Size);
@@ -778,12 +797,14 @@ End;
 Function TFileBuffer.FileSizeRaw : LongInt;
 Begin
   If BufDirty Then FlushBuffer;
+
   Result := System.FileSize(InFile);
 End;
 
 Function TFileBuffer.FileSizeRecord : LongInt;
 Begin
   If BufDirty Then FlushBuffer;
+
   Result := System.FileSize(InFile) DIV RecSize;
 End;