"""Read and cache directory listings.

The listdir() routine returns a sorted list of the files in a directory,

using a cache to avoid reading the directory more often than necessary.

The annotate() routine appends slashes to directories."""

import os

__all__ = ["listdir", "opendir", "annotate", "reset"]

cache = {}

def reset():

    """Reset the cache completely."""

    global cache

    cache = {}

def listdir(path):

    """List directory contents, using cache."""

    try:

        cached_mtime, list = cache[path]

        del cache[path]

    except KeyError:

        cached_mtime, list = -1, []

    mtime = os.stat(path).st_mtime

    if mtime != cached_mtime:

        list = os.listdir(path)

        list.sort()

    cache[path] = mtime, list

    return list

opendir = listdir # XXX backward compatibility

def annotate(head, list):

    """Add '/' suffixes to directories."""

    for i in range(len(list)):

        if os.path.isdir(os.path.join(head, list[i])):

            list[i] = list[i] + '/'