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import struct

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import base64

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import shelve

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import os.path

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from log import index

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def int2key (id) :

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    """

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        Turn an integer into a short-as-possible url-safe string

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    """

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    for type in ('B', 'H', 'I') :

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        try :

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            return base64.b64encode(struct.pack(type, id), '-_').rstrip('=')

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        except struct.error :

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            continue

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    raise Exception("ID overflow: %s" % id)

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def updateDB (root) :

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    """

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        DeGAL <= 0.2 used a simple key => path mapping, but now we use

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        something more structured, key => (type, dirpath, fname), where

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        type    - one of 'img', 'dir'

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        dirpath - the path to the directory, e.g. '.', './foobar', './foobar/quux'

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        fname   - the filename, one of '', 'DSC9839.JPG', 'this.png', etc.

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    """

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    db = shelve.open('shorturls2', 'c', writeback=True)

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    id = db.get('_id', 1)

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    dirqueue = [root]

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    # dict of path -> obj

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    paths = {}

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    index.info("Processing ShortURLs...")

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    while dirqueue :

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        dir = dirqueue.pop(0)

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        dirqueue.extend(dir.subdirs.itervalues())

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        if dir.alive :

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            paths[dir.path] = dir

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        for img in dir.images.itervalues() :

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            paths[img.path] = img

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    for key in db.keys() :

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        if key.startswith('_') :

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            continue

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        type, dirpath, fname = db[key]

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        path = os.path.join(dirpath, fname).rstrip(os.sep)

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        try :

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            paths.pop(path).shorturl_code = key

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            index.debug("Code for `%s' is %s", path, key)

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        except KeyError :

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            index.debug("Path `%s' in DB does not exist?", path)

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    for obj in paths.itervalues() :

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        key = int2key(id)

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        id += 1

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        index.info("Alloc code `%s' for `%s'", key, obj.html_path)

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        obj.shorturl_code = key

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        db[key] = obj.getObjInfo()

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    db['_id'] = id

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    db.close()