Enhanced RDF::Reader to automatically rewind the input stream once al…

…l input has been consumed.

This helps make RDF::Reader more compatible with RDF::Enumerable, allowing subsequent operations on readers to work much as if readers were file-backed repositories.

However, since not all input streams are rewindable, this is currently defined as optional behavior; RDF.rb 0.3.0-compatible reader implementations SHOULD implement automatic rewinding where possible, but are not required to.

lib/rdf/reader.rb

@@ -252,6 +252,7 @@ def each_statement(&block)
         begin
           loop { block.call(read_statement) }
         rescue EOFError => e
+          rewind rescue nil
         end
       end
       enum_for(:each_statement)
@@ -285,6 +286,7 @@ def each_triple(&block)
         begin
           loop { block.call(*read_triple) }
         rescue EOFError => e
+          rewind rescue nil
         end
       end
       enum_for(:each_triple)