a tool to pull the binaries out of a fat json tiddlers collection

extractbin.py

# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import base64
import json
import os
import sys


def process(filename):
    """Read a fat JSON tiddlers collection and dump out any images.

    The output file is named $bag.name-${tiddler.title}.${type}.
    """
    with open(filename) as data:
        try:
            tiddlers = json.loads(data.read())
        except ValueError as exc:
            # If the file doesn't contain json this can happen. That
            # can happen if there was a timeout from the server.
            sys.stderr.write('unable to process %s: %s\n' % (filename, exc))
            return
        for tiddler in tiddlers:
            if tiddler['type'] and tiddler['type'].startswith('image/'):
                ext = tiddler['type'].split('/')[1]
                text_data = tiddler['text']
                bag = tiddler['bag']
                title = tiddler['title']
                binary_data = base64.b64decode(text_data)
                output_filename = 'binaries/%s-%s.%s' % (bag, title, ext)
                with open(output_filename, 'wb') as output:
                    output.write(binary_data)
                    print('...wrote %s' % output_filename)


if __name__ == '__main__':
    if not os.path.isdir('binaries'):
        os.mkdir('binaries')
    filenames = sys.argv[1:]
    if not filenames:
        sys.stderr.write(
            'provide a list of filenames (or shell glob "*.json") as args\n')
        sys.exit(1)
    for filename in filenames:
        print(filename)
        process(filename)