upload_monkey_patch.rb

# If you've ever worked with file uploads in Rails, you've probably realized that Rails
# handles uploads with a filesize under 10K differently than files over 10K. 
# I prefer things to be as similar as possible so I wrote this quick monkey patch.
# Drop it in your config/initializers directory and you're off to the races.
#
# You should also check out Paperclip, acts_as_attachment, file_column, etc. because
# they take care of all this business for you.



# Monkey patch so we don't ever have to deal with small file uploads being represented as 
# UploadedStringIO objects.
# Only UploadedTempfile's from here on out, baby!

module ActionController
  
  class AbstractRequest

    class << self
      
      UPLOADED_STRING_IO_MAX_SIZE = -1      # never user UploadedStringIO, only UploadedTempfile
      #UPLOADED_STRING_IO_MAX_SIZE = 10240  # the previous value
      
      def read_multipart(body, boundary, content_length, env)
        params = Hash.new([])
        boundary = "--" + boundary
        quoted_boundary = Regexp.quote(boundary)
        buf = ""
        bufsize = 10 * 1024
        boundary_end=""

        # start multipart/form-data
        body.binmode if defined? body.binmode
        boundary_size = boundary.size + EOL.size
        content_length -= boundary_size
        status = body.read(boundary_size)
        if nil == status
          raise EOFError, "no content body"
        elsif boundary + EOL != status
          raise EOFError, "bad content body"
        end

        loop do
          head = nil
          content =
            if UPLOADED_STRING_IO_MAX_SIZE < content_length
              UploadedTempfile.new("CGI")
            else
              UploadedStringIO.new
            end
          content.binmode if defined? content.binmode

          until head and /#{quoted_boundary}(?:#{EOL}|--)/n.match(buf)

            if (not head) and /#{EOL}#{EOL}/n.match(buf)
              buf = buf.sub(/\A((?:.|\n)*?#{EOL})#{EOL}/n) do
                head = $1.dup
                ""
              end
              next
            end

            if head and ( (EOL + boundary + EOL).size < buf.size )
              content.print buf[0 ... (buf.size - (EOL + boundary + EOL).size)]
              buf[0 ... (buf.size - (EOL + boundary + EOL).size)] = ""
            end

            c = if bufsize < content_length
                  body.read(bufsize)
                else
                  body.read(content_length)
                end
            if c.nil? || c.empty?
              raise EOFError, "bad content body"
            end
            buf.concat(c)
            content_length -= c.size
          end

          buf = buf.sub(/\A((?:.|\n)*?)(?:[\r\n]{1,2})?#{quoted_boundary}([\r\n]{1,2}|--)/n) do
            content.print $1
            if "--" == $2
              content_length = -1
            end
           boundary_end = $2.dup
            ""
          end

          content.rewind

          head =~ /Content-Disposition:.* filename=(?:"((?:\\.|[^\"])*)"|([^;]*))/ni
          if filename = $1 || $2
            if /Mac/ni.match(env['HTTP_USER_AGENT']) and
                /Mozilla/ni.match(env['HTTP_USER_AGENT']) and
                (not /MSIE/ni.match(env['HTTP_USER_AGENT']))
              filename = CGI.unescape(filename)
            end
            content.original_path = filename.dup
          end

          head =~ /Content-Type: ([^\r]*)/ni
          content.content_type = $1.dup if $1

          head =~ /Content-Disposition:.* name="?([^\";]*)"?/ni
          name = $1.dup if $1

          if params.has_key?(name)
            params[name].push(content)
          else
            params[name] = [content]
          end
          break if buf.size == 0
          break if content_length == -1
        end
        raise EOFError, "bad boundary end of body part" unless boundary_end=~/--/

  begin
          body.rewind if body.respond_to?(:rewind)
  rescue Errno::ESPIPE
          # Handles exceptions raised by input streams that cannot be rewound
          # such as when using plain CGI under Apache
  end

        params
      end
    end


  end # end AbstractRequest
end # end ActionController