Add wxLZMAOutputStream for compressing data using LZMA

As liblzma API is similar to zlib API, this class is also close to
wxZlibOutputStream, except that it uses reusable functions instead of
repeating their code.

include/wx/lzmastream.h

@@ -71,6 +71,52 @@ private:
     void Init();
 };
 
+// ----------------------------------------------------------------------------
+// Filter for compressing data using LZMA(2) algorithm
+// ----------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxLZMAOutputStream : public wxFilterOutputStream,
+                                            private wxPrivate::wxLZMAData
+{
+public:
+    explicit wxLZMAOutputStream(wxOutputStream& stream, int level = -1)
+        : wxFilterOutputStream(stream)
+    {
+        Init(level);
+    }
+
+    explicit wxLZMAOutputStream(wxOutputStream* stream, int level = -1)
+        : wxFilterOutputStream(stream)
+    {
+        Init(level);
+    }
+
+    virtual ~wxLZMAOutputStream() { Close(); }
+
+    void Sync() wxOVERRIDE { DoFlush(false); }
+    bool Close() wxOVERRIDE;
+    wxFileOffset GetLength() const wxOVERRIDE { return m_pos; }
+
+protected:
+    size_t OnSysWrite(const void *buffer, size_t size) wxOVERRIDE;
+    wxFileOffset OnSysTell() const wxOVERRIDE { return m_pos; }
+
+private:
+    void Init(int level);
+
+    // Write the contents of the internal buffer to the output stream.
+    bool UpdateOutput();
+
+    // Write out the current buffer if necessary, i.e. if no space remains in
+    // it, and reinitialize m_stream to point to it. Returns false on success
+    // or false on error, in which case m_lasterror is updated.
+    bool UpdateOutputIfNecessary();
+
+    // Run LZMA_FINISH (if argument is true) or LZMA_FULL_FLUSH, return true on
+    // success or false on error.
+    bool DoFlush(bool finish);
+};
+
 WXDLLIMPEXP_BASE wxVersionInfo wxGetLibLZMAVersionInfo();
 
 #endif // wxUSE_LIBLZMA && wxUSE_STREAMS