gistfile1.py

def wrapper(*args, **kwds):
    # size limited caching that tracks accesses by recency
    key = make_key(args, kwds, typed) if kwds or typed else args
    with lock:
        cache_result = cache_get(key, (None, None))
        last_modified, link = cache_result
        if link is not None and cache_is_valid(last_modified, ttl):
            # record recent use of the key by moving it to the front of the list
            root, = nonlocal_root
            link_prev, link_next, key, result = link
            link_prev[NEXT] = link_next
            link_next[PREV] = link_prev
            last = root[PREV]
            last[NEXT] = root[PREV] = link
            link[PREV] = last
            link[NEXT] = root
            stats[HITS] += 1
            return result
    result = user_function(*args, **kwds)
    with lock:
        root, = nonlocal_root
        if key in cache:
            # getting here means that this same key was added to the
            # cache while the lock was released.  since the link
            # update is already done, we need only return the
            # computed result and update the count of misses.
            pass
        elif _len(cache) >= maxsize:
            # use the old root to store the new key and result
            oldroot = root
            oldroot[KEY] = key
            oldroot[RESULT] = result
            # empty the oldest link and make it the new root
            root = nonlocal_root[0] = oldroot[NEXT]
            oldkey = root[KEY]
            oldvalue = root[RESULT]
            root[KEY] = root[RESULT] = None
            # now update the cache dictionary for the new links
            del cache[oldkey]
            cache[key] = (datetime.now(), oldroot)
        else:
            # put result in a new link at the front of the list
            last = root[PREV]
            link = [last, root, key, result]
            cache[key] = (datetime.now(), link)
            last[NEXT] = root[PREV] = link
        stats[MISSES] += 1
    return result