Split decoders into a read and decode step

We need to split these steps up in preparation for multi-core
support. Reading needs to be done in a serial manner, whilst
decoding can be done in parallel.

This also involved a rather large cleanup of the Tight decoder.
diff --git a/common/rfb/RREDecoder.cxx b/common/rfb/RREDecoder.cxx
index b802644..2dd47cc 100644
--- a/common/rfb/RREDecoder.cxx
+++ b/common/rfb/RREDecoder.cxx
@@ -15,7 +15,11 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
  * USA.
  */
+
 #include <rdr/InStream.h>
+#include <rdr/MemInStream.h>
+#include <rdr/OutStream.h>
+
 #include <rfb/ConnParams.h>
 #include <rfb/PixelBuffer.h>
 #include <rfb/RREDecoder.h>
@@ -41,12 +45,25 @@
 }
 
 void RREDecoder::readRect(const Rect& r, rdr::InStream* is,
-                          const ConnParams& cp, ModifiablePixelBuffer* pb)
+                          const ConnParams& cp, rdr::OutStream* os)
 {
+  rdr::U32 numRects;
+
+  numRects = is->readU32();
+  os->writeU32(numRects);
+
+  os->copyBytes(is, cp.pf().bpp/8 + numRects * (cp.pf().bpp/8 + 8));
+}
+
+void RREDecoder::decodeRect(const Rect& r, const void* buffer,
+                            size_t buflen, const ConnParams& cp,
+                            ModifiablePixelBuffer* pb)
+{
+  rdr::MemInStream is(buffer, buflen);
   const PixelFormat& pf = cp.pf();
   switch (pf.bpp) {
-  case 8:  rreDecode8 (r, is, pf, pb); break;
-  case 16: rreDecode16(r, is, pf, pb); break;
-  case 32: rreDecode32(r, is, pf, pb); break;
+  case 8:  rreDecode8 (r, &is, pf, pb); break;
+  case 16: rreDecode16(r, &is, pf, pb); break;
+  case 32: rreDecode32(r, &is, pf, pb); break;
   }
 }