lib/care.rb in format_parser-0.1.2 vs lib/care.rb in format_parser-0.1.3

@@ -37,10 +37,14 @@
 
     def close
       clear
       @io.close if @io.respond_to?(:close)
     end
+
+    def size
+      @io.size
+    end
   end
 
   # Stores cached pages of data from the given IO as strings.
   # Pages are sized to be `page_size` or less (for the last page).
   class Cache
@@ -56,12 +60,15 @@
     # If the IO has been exhausted, `nil` will be returned
     # instead. Will use the cached pages where available,
     # or fetch pages where necessary
     def byteslice(io, at, n_bytes)
       if n_bytes < 1
-        raise ArgumentError, "The number of bytes to fetch must be a positive Integer" 
+        raise ArgumentError, "The number of bytes to fetch must be a positive Integer"
       end
+      if at < 0
+        raise ArgumentError, "Negative offsets are not supported (got #{at})"
+      end
 
       first_page = at / @page_size
       last_page = (at + n_bytes) / @page_size
 
       relevant_pages = (first_page..last_page).map{|i| hydrate_page(io, i) }
@@ -122,10 +129,10 @@
       elsif read_result.bytesize < @page_size
         # If we read less than we initially wanted we know there are no pages
         # to read following this one, so we can also optimize
         @lowest_known_empty_page = page_i + 1
       end
-        
+
       read_result
     end
   end
 end