Added sanity check in OSDParser.DeserializeLLSDBinary() to check if the stream is seekable

git-svn-id: http://libopenmetaverse.googlecode.com/svn/libopenmetaverse/trunk@2324 52acb1d6-8a22-11de-b505-999d5b087335

OpenMetaverse/StructuredData/BinaryLLSD.cs

@@ -91,11 +91,14 @@ namespace OpenMetaverse.StructuredData
         /// <returns></returns>
         public static OSD DeserializeLLSDBinary(Stream stream)
         {
+            if (!stream.CanSeek)
+                throw new OSDException("Cannot deserialize binary LLSD from unseekable streams");
+
             SkipWhiteSpace(stream);
 
             bool result = FindByteArray(stream, llsdBinaryHead);
             if (!result)
-                throw new OSDException("No binary encoded SD.");
+                throw new OSDException("Failed to decode binary LLSD");
 
             return ParseLLSDBinaryElement(stream);
         }