Class Buffer

      object --+        
               |        
debug.debugmixin --+    
                   |    
      BufferVFSMixin --+
                       |
                      Buffer

Abstraction around a file-like object obtained from a url.

Each buffer instance corresponds a unique url, handles the interaction between the file-like object that is used to read the data and the STCInterface that is used to hold the representation in memory.

The STCInterface provides the low-level access to the file, and there is a one-to-one mapping from a buffer to an STCInterface instance.