opening an empty file should raise a MalformedPDFError

* add an integration spec to prove it
* closes #69

lib/pdf/reader/buffer.rb

@@ -115,6 +115,9 @@ def token
     # return the byte offset where the first XRef table in th source can be found.
     #
     def find_first_xref_offset
+      if @io.size == 0
+        raise MalformedPDFError, "PDF file is empty"
+      end
       @io.seek(-1024, IO::SEEK_END) rescue @io.seek(0)
       data = @io.read(1024)
 

lib/pdf/reader/object_hash.rb

@@ -41,8 +41,8 @@ class ObjectHash
     #
     def initialize(input, opts = {})
       @io          = extract_io_from(input)
-      @pdf_version = read_version
       @xref        = PDF::Reader::XRef.new(@io)
+      @pdf_version = read_version
       @trailer     = @xref.trailer
       @cache       = opts[:cache] || PDF::Reader::ObjectCache.new
       @sec_handler = build_security_handler(opts)

lib/pdf/reader/xref.rb

@@ -237,6 +237,8 @@ def calc_junk_offset(io)
       end
       io.rewind
       offset < 50 ? offset : nil
+    rescue EOFError
+      return nil
     end
   end
   ################################################################################

spec/integration_spec.rb

@@ -134,6 +134,12 @@
     }.should raise_error(PDF::Reader::MalformedPDFError)
   end
 
+  it "should raise an exception if the file is empty" do
+    lambda {
+      PDF::Reader.new(StringIO.new(""))
+    }.should raise_error(PDF::Reader::MalformedPDFError)
+  end
+
   it "should correctly process a PDF that uses an ASCII85Decode filter" do
     filename = pdf_spec_file("ascii85_filter")