Implementing HTTP 206 Partial Content support for web.py

partial_web.py

###https://code.google.com/p/rctk/source/browse/core/trunk/rctk/webpy.py?r=447#57      
      
        ## experimental partial content support
        ## perhaps this shouldn't be enabled by default
        range = web.ctx.env.get('HTTP_RANGE')
        if range is None:
            return result

        total = len(result)
        _, r = range.split("=")
        partial_start, partial_end = r.split("-")

        start = int(partial_start)

        if not partial_end:
            end = total-1
        else:
            end = int(partial_end)

        chunksize = (end-start)+1

        web.ctx.status = "206 Partial Content"
        web.header("Content-Range", "bytes %d-%d/%d" % (start, end, total))
        web.header("Accept-Ranges", "bytes")
        web.header("Content-Length", chunksize)
        return result[start:end+1]