drop in replacement for mongoengine's GridFSStorage

mongo_storage.py

# refs: http://stackoverflow.com/questions/5041996/django-with-pluggable-mongodb-storage-troubles
from django.conf import settings
from django.core.files.storage import Storage
from gridfs import GridFS
from pymongo import Connection
import urlparse


class GridFSStorage(Storage):
    def __init__(self, host=None, port=None, db_name=None, base_url=None):
        for s in ('host', 'port', 'db_name'):
            name = 'GRIDFS_' + s.upper()
            if hasattr(settings, name):
                setattr(self, s, getattr(settings, name))
        for s, v in zip(('host', 'port', 'db_name'), (host, port, db_name)):
            if v:
                setattr(self, s, v)
        self.db = Connection(host=self.host, port=self.port)[self.db_name]
        self.fs = GridFS(self.db)
        self.base_url = base_url or settings.GRIDFS_BASE_URL

    def _save(self, name, content):
        self.fs.put(content, filename=name)
        return name

    def _open(self, name, *args, **kwars):
        return self.fs.get_last_version(filename=name)

    def delete(self, name):
        oid = self.fs.get_last_version(filename=name)._id
        self.fs.delete(oid)

    def exists(self, name):
        return self.fs.exists({'filename': name})

    def size(self, name):
        return self.fs.get_last_version(filename=name).length

    def url(self, name):
        if self.base_url is None:
            raise ValueError("This file is not accessible via a URL.")
        return urlparse.urljoin(self.base_url, name).replace('\\', '/')