http.py 文件源码

def modified(date=None, etag=None):
    n = web.ctx.env.get('HTTP_IF_NONE_MATCH')
    m = net.parsehttpdate(web.ctx.env.get('HTTP_IF_MODIFIED_SINCE', '').split(';')[0])
    validate = False
    if etag:
        raise NotImplementedError, "no etag support yet"
        # should really be a warning
    if date and m:
        # we subtract a second because 
        # HTTP dates don't have sub-second precision
        if date-datetime.timedelta(seconds=1) <= m:
            validate = True

    if validate: web.ctx.status = '304 Not Modified'
    return not validate