This file is indexed.

/usr/lib/python3/dist-packages/flask/helpers.py is in python3-flask 0.10.1-2build1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
# -*- coding: utf-8 -*-
"""
    flask.helpers
    ~~~~~~~~~~~~~

    Implements various helpers.

    :copyright: (c) 2011 by Armin Ronacher.
    :license: BSD, see LICENSE for more details.
"""

import os
import sys
import pkgutil
import posixpath
import mimetypes
from time import time
from zlib import adler32
from threading import RLock
from werkzeug.routing import BuildError
from functools import update_wrapper

try:
    from werkzeug.urls import url_quote
except ImportError:
    from urlparse import quote as url_quote

from werkzeug.datastructures import Headers
from werkzeug.exceptions import NotFound

# this was moved in 0.7
try:
    from werkzeug.wsgi import wrap_file
except ImportError:
    from werkzeug.utils import wrap_file

from jinja2 import FileSystemLoader

from .signals import message_flashed
from .globals import session, _request_ctx_stack, _app_ctx_stack, \
     current_app, request
from ._compat import string_types, text_type


# sentinel
_missing = object()


# what separators does this operating system provide that are not a slash?
# this is used by the send_from_directory function to ensure that nobody is
# able to access files from outside the filesystem.
_os_alt_seps = list(sep for sep in [os.path.sep, os.path.altsep]
                    if sep not in (None, '/'))


def _endpoint_from_view_func(view_func):
    """Internal helper that returns the default endpoint for a given
    function.  This always is the function name.
    """
    assert view_func is not None, 'expected view func if endpoint ' \
                                  'is not provided.'
    return view_func.__name__


def stream_with_context(generator_or_function):
    """Request contexts disappear when the response is started on the server.
    This is done for efficiency reasons and to make it less likely to encounter
    memory leaks with badly written WSGI middlewares.  The downside is that if
    you are using streamed responses, the generator cannot access request bound
    information any more.

    This function however can help you keep the context around for longer::

        from flask import stream_with_context, request, Response

        @app.route('/stream')
        def streamed_response():
            @stream_with_context
            def generate():
                yield 'Hello '
                yield request.args['name']
                yield '!'
            return Response(generate())

    Alternatively it can also be used around a specific generator::

        from flask import stream_with_context, request, Response

        @app.route('/stream')
        def streamed_response():
            def generate():
                yield 'Hello '
                yield request.args['name']
                yield '!'
            return Response(stream_with_context(generate()))

    .. versionadded:: 0.9
    """
    try:
        gen = iter(generator_or_function)
    except TypeError:
        def decorator(*args, **kwargs):
            gen = generator_or_function()
            return stream_with_context(gen)
        return update_wrapper(decorator, generator_or_function)

    def generator():
        ctx = _request_ctx_stack.top
        if ctx is None:
            raise RuntimeError('Attempted to stream with context but '
                'there was no context in the first place to keep around.')
        with ctx:
            # Dummy sentinel.  Has to be inside the context block or we're
            # not actually keeping the context around.
            yield None

            # The try/finally is here so that if someone passes a WSGI level
            # iterator in we're still running the cleanup logic.  Generators
            # don't need that because they are closed on their destruction
            # automatically.
            try:
                for item in gen:
                    yield item
            finally:
                if hasattr(gen, 'close'):
                    gen.close()

    # The trick is to start the generator.  Then the code execution runs until
    # the first dummy None is yielded at which point the context was already
    # pushed.  This item is discarded.  Then when the iteration continues the
    # real generator is executed.
    wrapped_g = generator()
    next(wrapped_g)
    return wrapped_g


def make_response(*args):
    """Sometimes it is necessary to set additional headers in a view.  Because
    views do not have to return response objects but can return a value that
    is converted into a response object by Flask itself, it becomes tricky to
    add headers to it.  This function can be called instead of using a return
    and you will get a response object which you can use to attach headers.

    If view looked like this and you want to add a new header::

        def index():
            return render_template('index.html', foo=42)

    You can now do something like this::

        def index():
            response = make_response(render_template('index.html', foo=42))
            response.headers['X-Parachutes'] = 'parachutes are cool'
            return response

    This function accepts the very same arguments you can return from a
    view function.  This for example creates a response with a 404 error
    code::

        response = make_response(render_template('not_found.html'), 404)

    The other use case of this function is to force the return value of a
    view function into a response which is helpful with view
    decorators::

        response = make_response(view_function())
        response.headers['X-Parachutes'] = 'parachutes are cool'

    Internally this function does the following things:

    -   if no arguments are passed, it creates a new response argument
    -   if one argument is passed, :meth:`flask.Flask.make_response`
        is invoked with it.
    -   if more than one argument is passed, the arguments are passed
        to the :meth:`flask.Flask.make_response` function as tuple.

    .. versionadded:: 0.6
    """
    if not args:
        return current_app.response_class()
    if len(args) == 1:
        args = args[0]
    return current_app.make_response(args)


def url_for(endpoint, **values):
    """Generates a URL to the given endpoint with the method provided.

    Variable arguments that are unknown to the target endpoint are appended
    to the generated URL as query arguments.  If the value of a query argument
    is `None`, the whole pair is skipped.  In case blueprints are active
    you can shortcut references to the same blueprint by prefixing the
    local endpoint with a dot (``.``).

    This will reference the index function local to the current blueprint::

        url_for('.index')

    For more information, head over to the :ref:`Quickstart <url-building>`.

    To integrate applications, :class:`Flask` has a hook to intercept URL build
    errors through :attr:`Flask.build_error_handler`.  The `url_for` function
    results in a :exc:`~werkzeug.routing.BuildError` when the current app does
    not have a URL for the given endpoint and values.  When it does, the
    :data:`~flask.current_app` calls its :attr:`~Flask.build_error_handler` if
    it is not `None`, which can return a string to use as the result of
    `url_for` (instead of `url_for`'s default to raise the
    :exc:`~werkzeug.routing.BuildError` exception) or re-raise the exception.
    An example::

        def external_url_handler(error, endpoint, **values):
            "Looks up an external URL when `url_for` cannot build a URL."
            # This is an example of hooking the build_error_handler.
            # Here, lookup_url is some utility function you've built
            # which looks up the endpoint in some external URL registry.
            url = lookup_url(endpoint, **values)
            if url is None:
                # External lookup did not have a URL.
                # Re-raise the BuildError, in context of original traceback.
                exc_type, exc_value, tb = sys.exc_info()
                if exc_value is error:
                    raise exc_type, exc_value, tb
                else:
                    raise error
            # url_for will use this result, instead of raising BuildError.
            return url

        app.build_error_handler = external_url_handler

    Here, `error` is the instance of :exc:`~werkzeug.routing.BuildError`, and
    `endpoint` and `**values` are the arguments passed into `url_for`.  Note
    that this is for building URLs outside the current application, and not for
    handling 404 NotFound errors.

    .. versionadded:: 0.10
       The `_scheme` parameter was added.

    .. versionadded:: 0.9
       The `_anchor` and `_method` parameters were added.

    .. versionadded:: 0.9
       Calls :meth:`Flask.handle_build_error` on
       :exc:`~werkzeug.routing.BuildError`.

    :param endpoint: the endpoint of the URL (name of the function)
    :param values: the variable arguments of the URL rule
    :param _external: if set to `True`, an absolute URL is generated. Server
      address can be changed via `SERVER_NAME` configuration variable which
      defaults to `localhost`.
    :param _scheme: a string specifying the desired URL scheme. The `_external`
      parameter must be set to `True` or a `ValueError` is raised.
    :param _anchor: if provided this is added as anchor to the URL.
    :param _method: if provided this explicitly specifies an HTTP method.
    """
    appctx = _app_ctx_stack.top
    reqctx = _request_ctx_stack.top
    if appctx is None:
        raise RuntimeError('Attempted to generate a URL without the '
                           'application context being pushed. This has to be '
                           'executed when application context is available.')

    # If request specific information is available we have some extra
    # features that support "relative" urls.
    if reqctx is not None:
        url_adapter = reqctx.url_adapter
        blueprint_name = request.blueprint
        if not reqctx.request._is_old_module:
            if endpoint[:1] == '.':
                if blueprint_name is not None:
                    endpoint = blueprint_name + endpoint
                else:
                    endpoint = endpoint[1:]
        else:
            # TODO: get rid of this deprecated functionality in 1.0
            if '.' not in endpoint:
                if blueprint_name is not None:
                    endpoint = blueprint_name + '.' + endpoint
            elif endpoint.startswith('.'):
                endpoint = endpoint[1:]
        external = values.pop('_external', False)

    # Otherwise go with the url adapter from the appctx and make
    # the urls external by default.
    else:
        url_adapter = appctx.url_adapter
        if url_adapter is None:
            raise RuntimeError('Application was not able to create a URL '
                               'adapter for request independent URL generation. '
                               'You might be able to fix this by setting '
                               'the SERVER_NAME config variable.')
        external = values.pop('_external', True)

    anchor = values.pop('_anchor', None)
    method = values.pop('_method', None)
    scheme = values.pop('_scheme', None)
    appctx.app.inject_url_defaults(endpoint, values)

    if scheme is not None:
        if not external:
            raise ValueError('When specifying _scheme, _external must be True')
        url_adapter.url_scheme = scheme

    try:
        rv = url_adapter.build(endpoint, values, method=method,
                               force_external=external)
    except BuildError as error:
        # We need to inject the values again so that the app callback can
        # deal with that sort of stuff.
        values['_external'] = external
        values['_anchor'] = anchor
        values['_method'] = method
        return appctx.app.handle_url_build_error(error, endpoint, values)

    if anchor is not None:
        rv += '#' + url_quote(anchor)
    return rv


def get_template_attribute(template_name, attribute):
    """Loads a macro (or variable) a template exports.  This can be used to
    invoke a macro from within Python code.  If you for example have a
    template named `_cider.html` with the following contents:

    .. sourcecode:: html+jinja

       {% macro hello(name) %}Hello {{ name }}!{% endmacro %}

    You can access this from Python code like this::

        hello = get_template_attribute('_cider.html', 'hello')
        return hello('World')

    .. versionadded:: 0.2

    :param template_name: the name of the template
    :param attribute: the name of the variable of macro to access
    """
    return getattr(current_app.jinja_env.get_template(template_name).module,
                   attribute)


def flash(message, category='message'):
    """Flashes a message to the next request.  In order to remove the
    flashed message from the session and to display it to the user,
    the template has to call :func:`get_flashed_messages`.

    .. versionchanged:: 0.3
       `category` parameter added.

    :param message: the message to be flashed.
    :param category: the category for the message.  The following values
                     are recommended: ``'message'`` for any kind of message,
                     ``'error'`` for errors, ``'info'`` for information
                     messages and ``'warning'`` for warnings.  However any
                     kind of string can be used as category.
    """
    # Original implementation:
    #
    #     session.setdefault('_flashes', []).append((category, message))
    #
    # This assumed that changes made to mutable structures in the session are
    # are always in sync with the sess on object, which is not true for session
    # implementations that use external storage for keeping their keys/values.
    flashes = session.get('_flashes', [])
    flashes.append((category, message))
    session['_flashes'] = flashes
    message_flashed.send(current_app._get_current_object(),
                         message=message, category=category)


def get_flashed_messages(with_categories=False, category_filter=[]):
    """Pulls all flashed messages from the session and returns them.
    Further calls in the same request to the function will return
    the same messages.  By default just the messages are returned,
    but when `with_categories` is set to `True`, the return value will
    be a list of tuples in the form ``(category, message)`` instead.

    Filter the flashed messages to one or more categories by providing those
    categories in `category_filter`.  This allows rendering categories in
    separate html blocks.  The `with_categories` and `category_filter`
    arguments are distinct:

    * `with_categories` controls whether categories are returned with message
      text (`True` gives a tuple, where `False` gives just the message text).
    * `category_filter` filters the messages down to only those matching the
      provided categories.

    See :ref:`message-flashing-pattern` for examples.

    .. versionchanged:: 0.3
       `with_categories` parameter added.

    .. versionchanged:: 0.9
        `category_filter` parameter added.

    :param with_categories: set to `True` to also receive categories.
    :param category_filter: whitelist of categories to limit return values
    """
    flashes = _request_ctx_stack.top.flashes
    if flashes is None:
        _request_ctx_stack.top.flashes = flashes = session.pop('_flashes') \
            if '_flashes' in session else []
    if category_filter:
        flashes = list(filter(lambda f: f[0] in category_filter, flashes))
    if not with_categories:
        return [x[1] for x in flashes]
    return flashes


def send_file(filename_or_fp, mimetype=None, as_attachment=False,
              attachment_filename=None, add_etags=True,
              cache_timeout=None, conditional=False):
    """Sends the contents of a file to the client.  This will use the
    most efficient method available and configured.  By default it will
    try to use the WSGI server's file_wrapper support.  Alternatively
    you can set the application's :attr:`~Flask.use_x_sendfile` attribute
    to ``True`` to directly emit an `X-Sendfile` header.  This however
    requires support of the underlying webserver for `X-Sendfile`.

    By default it will try to guess the mimetype for you, but you can
    also explicitly provide one.  For extra security you probably want
    to send certain files as attachment (HTML for instance).  The mimetype
    guessing requires a `filename` or an `attachment_filename` to be
    provided.

    Please never pass filenames to this function from user sources without
    checking them first.  Something like this is usually sufficient to
    avoid security problems::

        if '..' in filename or filename.startswith('/'):
            abort(404)

    .. versionadded:: 0.2

    .. versionadded:: 0.5
       The `add_etags`, `cache_timeout` and `conditional` parameters were
       added.  The default behavior is now to attach etags.

    .. versionchanged:: 0.7
       mimetype guessing and etag support for file objects was
       deprecated because it was unreliable.  Pass a filename if you are
       able to, otherwise attach an etag yourself.  This functionality
       will be removed in Flask 1.0

    .. versionchanged:: 0.9
       cache_timeout pulls its default from application config, when None.

    :param filename_or_fp: the filename of the file to send.  This is
                           relative to the :attr:`~Flask.root_path` if a
                           relative path is specified.
                           Alternatively a file object might be provided
                           in which case `X-Sendfile` might not work and
                           fall back to the traditional method.  Make sure
                           that the file pointer is positioned at the start
                           of data to send before calling :func:`send_file`.
    :param mimetype: the mimetype of the file if provided, otherwise
                     auto detection happens.
    :param as_attachment: set to `True` if you want to send this file with
                          a ``Content-Disposition: attachment`` header.
    :param attachment_filename: the filename for the attachment if it
                                differs from the file's filename.
    :param add_etags: set to `False` to disable attaching of etags.
    :param conditional: set to `True` to enable conditional responses.

    :param cache_timeout: the timeout in seconds for the headers. When `None`
                          (default), this value is set by
                          :meth:`~Flask.get_send_file_max_age` of
                          :data:`~flask.current_app`.
    """
    mtime = None
    if isinstance(filename_or_fp, string_types):
        filename = filename_or_fp
        file = None
    else:
        from warnings import warn
        file = filename_or_fp
        filename = getattr(file, 'name', None)

        # XXX: this behavior is now deprecated because it was unreliable.
        # removed in Flask 1.0
        if not attachment_filename and not mimetype \
           and isinstance(filename, string_types):
            warn(DeprecationWarning('The filename support for file objects '
                'passed to send_file is now deprecated.  Pass an '
                'attach_filename if you want mimetypes to be guessed.'),
                stacklevel=2)
        if add_etags:
            warn(DeprecationWarning('In future flask releases etags will no '
                'longer be generated for file objects passed to the send_file '
                'function because this behavior was unreliable.  Pass '
                'filenames instead if possible, otherwise attach an etag '
                'yourself based on another value'), stacklevel=2)

    if filename is not None:
        if not os.path.isabs(filename):
            filename = os.path.join(current_app.root_path, filename)
    if mimetype is None and (filename or attachment_filename):
        mimetype = mimetypes.guess_type(filename or attachment_filename)[0]
    if mimetype is None:
        mimetype = 'application/octet-stream'

    headers = Headers()
    if as_attachment:
        if attachment_filename is None:
            if filename is None:
                raise TypeError('filename unavailable, required for '
                                'sending as attachment')
            attachment_filename = os.path.basename(filename)
        headers.add('Content-Disposition', 'attachment',
                    filename=attachment_filename)

    if current_app.use_x_sendfile and filename:
        if file is not None:
            file.close()
        headers['X-Sendfile'] = filename
        headers['Content-Length'] = os.path.getsize(filename)
        data = None
    else:
        if file is None:
            file = open(filename, 'rb')
            mtime = os.path.getmtime(filename)
            headers['Content-Length'] = os.path.getsize(filename)
        data = wrap_file(request.environ, file)

    rv = current_app.response_class(data, mimetype=mimetype, headers=headers,
                                    direct_passthrough=True)

    # if we know the file modification date, we can store it as the
    # the time of the last modification.
    if mtime is not None:
        rv.last_modified = int(mtime)

    rv.cache_control.public = True
    if cache_timeout is None:
        cache_timeout = current_app.get_send_file_max_age(filename)
    if cache_timeout is not None:
        rv.cache_control.max_age = cache_timeout
        rv.expires = int(time() + cache_timeout)

    if add_etags and filename is not None:
        rv.set_etag('flask-%s-%s-%s' % (
            os.path.getmtime(filename),
            os.path.getsize(filename),
            adler32(
                filename.encode('utf-8') if isinstance(filename, text_type)
                else filename
            ) & 0xffffffff
        ))
        if conditional:
            rv = rv.make_conditional(request)
            # make sure we don't send x-sendfile for servers that
            # ignore the 304 status code for x-sendfile.
            if rv.status_code == 304:
                rv.headers.pop('x-sendfile', None)
    return rv


def safe_join(directory, filename):
    """Safely join `directory` and `filename`.

    Example usage::

        @app.route('/wiki/<path:filename>')
        def wiki_page(filename):
            filename = safe_join(app.config['WIKI_FOLDER'], filename)
            with open(filename, 'rb') as fd:
                content = fd.read() # Read and process the file content...

    :param directory: the base directory.
    :param filename: the untrusted filename relative to that directory.
    :raises: :class:`~werkzeug.exceptions.NotFound` if the resulting path
             would fall out of `directory`.
    """
    filename = posixpath.normpath(filename)
    for sep in _os_alt_seps:
        if sep in filename:
            raise NotFound()
    if os.path.isabs(filename) or \
       filename == '..' or \
       filename.startswith('../'):
        raise NotFound()
    return os.path.join(directory, filename)


def send_from_directory(directory, filename, **options):
    """Send a file from a given directory with :func:`send_file`.  This
    is a secure way to quickly expose static files from an upload folder
    or something similar.

    Example usage::

        @app.route('/uploads/<path:filename>')
        def download_file(filename):
            return send_from_directory(app.config['UPLOAD_FOLDER'],
                                       filename, as_attachment=True)

    .. admonition:: Sending files and Performance

       It is strongly recommended to activate either `X-Sendfile` support in
       your webserver or (if no authentication happens) to tell the webserver
       to serve files for the given path on its own without calling into the
       web application for improved performance.

    .. versionadded:: 0.5

    :param directory: the directory where all the files are stored.
    :param filename: the filename relative to that directory to
                     download.
    :param options: optional keyword arguments that are directly
                    forwarded to :func:`send_file`.
    """
    filename = safe_join(directory, filename)
    if not os.path.isfile(filename):
        raise NotFound()
    options.setdefault('conditional', True)
    return send_file(filename, **options)


def get_root_path(import_name):
    """Returns the path to a package or cwd if that cannot be found.  This
    returns the path of a package or the folder that contains a module.

    Not to be confused with the package path returned by :func:`find_package`.
    """
    # Module already imported and has a file attribute.  Use that first.
    mod = sys.modules.get(import_name)
    if mod is not None and hasattr(mod, '__file__'):
        return os.path.dirname(os.path.abspath(mod.__file__))

    # Next attempt: check the loader.
    loader = pkgutil.get_loader(import_name)

    # Loader does not exist or we're referring to an unloaded main module
    # or a main module without path (interactive sessions), go with the
    # current working directory.
    if loader is None or import_name == '__main__':
        return os.getcwd()

    # For .egg, zipimporter does not have get_filename until Python 2.7.
    # Some other loaders might exhibit the same behavior.
    if hasattr(loader, 'get_filename'):
        filepath = loader.get_filename(import_name)
    else:
        # Fall back to imports.
        __import__(import_name)
        filepath = sys.modules[import_name].__file__

    # filepath is import_name.py for a module, or __init__.py for a package.
    return os.path.dirname(os.path.abspath(filepath))


def find_package(import_name):
    """Finds a package and returns the prefix (or None if the package is
    not installed) as well as the folder that contains the package or
    module as a tuple.  The package path returned is the module that would
    have to be added to the pythonpath in order to make it possible to
    import the module.  The prefix is the path below which a UNIX like
    folder structure exists (lib, share etc.).
    """
    root_mod_name = import_name.split('.')[0]
    loader = pkgutil.get_loader(root_mod_name)
    if loader is None or import_name == '__main__':
        # import name is not found, or interactive/main module
        package_path = os.getcwd()
    else:
        # For .egg, zipimporter does not have get_filename until Python 2.7.
        if hasattr(loader, 'get_filename'):
            filename = loader.get_filename(root_mod_name)
        elif hasattr(loader, 'archive'):
            # zipimporter's loader.archive points to the .egg or .zip
            # archive filename is dropped in call to dirname below.
            filename = loader.archive
        else:
            # At least one loader is missing both get_filename and archive:
            # Google App Engine's HardenedModulesHook
            #
            # Fall back to imports.
            __import__(import_name)
            filename = sys.modules[import_name].__file__
        package_path = os.path.abspath(os.path.dirname(filename))
        # package_path ends with __init__.py for a package
        if loader.is_package(root_mod_name):
            package_path = os.path.dirname(package_path)

    site_parent, site_folder = os.path.split(package_path)
    py_prefix = os.path.abspath(sys.prefix)
    if package_path.startswith(py_prefix):
        return py_prefix, package_path
    elif site_folder.lower() == 'site-packages':
        parent, folder = os.path.split(site_parent)
        # Windows like installations
        if folder.lower() == 'lib':
            base_dir = parent
        # UNIX like installations
        elif os.path.basename(parent).lower() == 'lib':
            base_dir = os.path.dirname(parent)
        else:
            base_dir = site_parent
        return base_dir, package_path
    return None, package_path


class locked_cached_property(object):
    """A decorator that converts a function into a lazy property.  The
    function wrapped is called the first time to retrieve the result
    and then that calculated result is used the next time you access
    the value.  Works like the one in Werkzeug but has a lock for
    thread safety.
    """

    def __init__(self, func, name=None, doc=None):
        self.__name__ = name or func.__name__
        self.__module__ = func.__module__
        self.__doc__ = doc or func.__doc__
        self.func = func
        self.lock = RLock()

    def __get__(self, obj, type=None):
        if obj is None:
            return self
        with self.lock:
            value = obj.__dict__.get(self.__name__, _missing)
            if value is _missing:
                value = self.func(obj)
                obj.__dict__[self.__name__] = value
            return value


class _PackageBoundObject(object):

    def __init__(self, import_name, template_folder=None):
        #: The name of the package or module.  Do not change this once
        #: it was set by the constructor.
        self.import_name = import_name

        #: location of the templates.  `None` if templates should not be
        #: exposed.
        self.template_folder = template_folder

        #: Where is the app root located?
        self.root_path = get_root_path(self.import_name)

        self._static_folder = None
        self._static_url_path = None

    def _get_static_folder(self):
        if self._static_folder is not None:
            return os.path.join(self.root_path, self._static_folder)
    def _set_static_folder(self, value):
        self._static_folder = value
    static_folder = property(_get_static_folder, _set_static_folder)
    del _get_static_folder, _set_static_folder

    def _get_static_url_path(self):
        if self._static_url_path is None:
            if self.static_folder is None:
                return None
            return '/' + os.path.basename(self.static_folder)
        return self._static_url_path
    def _set_static_url_path(self, value):
        self._static_url_path = value
    static_url_path = property(_get_static_url_path, _set_static_url_path)
    del _get_static_url_path, _set_static_url_path

    @property
    def has_static_folder(self):
        """This is `True` if the package bound object's container has a
        folder named ``'static'``.

        .. versionadded:: 0.5
        """
        return self.static_folder is not None

    @locked_cached_property
    def jinja_loader(self):
        """The Jinja loader for this package bound object.

        .. versionadded:: 0.5
        """
        if self.template_folder is not None:
            return FileSystemLoader(os.path.join(self.root_path,
                                                 self.template_folder))

    def get_send_file_max_age(self, filename):
        """Provides default cache_timeout for the :func:`send_file` functions.

        By default, this function returns ``SEND_FILE_MAX_AGE_DEFAULT`` from
        the configuration of :data:`~flask.current_app`.

        Static file functions such as :func:`send_from_directory` use this
        function, and :func:`send_file` calls this function on
        :data:`~flask.current_app` when the given cache_timeout is `None`. If a
        cache_timeout is given in :func:`send_file`, that timeout is used;
        otherwise, this method is called.

        This allows subclasses to change the behavior when sending files based
        on the filename.  For example, to set the cache timeout for .js files
        to 60 seconds::

            class MyFlask(flask.Flask):
                def get_send_file_max_age(self, name):
                    if name.lower().endswith('.js'):
                        return 60
                    return flask.Flask.get_send_file_max_age(self, name)

        .. versionadded:: 0.9
        """
        return current_app.config['SEND_FILE_MAX_AGE_DEFAULT']

    def send_static_file(self, filename):
        """Function used internally to send static files from the static
        folder to the browser.

        .. versionadded:: 0.5
        """
        if not self.has_static_folder:
            raise RuntimeError('No static folder for this object')
        # Ensure get_send_file_max_age is called in all cases.
        # Here, we ensure get_send_file_max_age is called for Blueprints.
        cache_timeout = self.get_send_file_max_age(filename)
        return send_from_directory(self.static_folder, filename,
                                   cache_timeout=cache_timeout)

    def open_resource(self, resource, mode='rb'):
        """Opens a resource from the application's resource folder.  To see
        how this works, consider the following folder structure::

            /myapplication.py
            /schema.sql
            /static
                /style.css
            /templates
                /layout.html
                /index.html

        If you want to open the `schema.sql` file you would do the
        following::

            with app.open_resource('schema.sql') as f:
                contents = f.read()
                do_something_with(contents)

        :param resource: the name of the resource.  To access resources within
                         subfolders use forward slashes as separator.
        :param mode: resource file opening mode, default is 'rb'.
        """
        if mode not in ('r', 'rb'):
            raise ValueError('Resources can only be opened for reading')
        return open(os.path.join(self.root_path, resource), mode)