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# -*- coding: utf-8 -*-
This module implements WSGI related helpers.
:copyright: (c) 2011 by the Werkzeug Team, see AUTHORS for more details.
:license: BSD, see LICENSE for more details.
import os
import urllib
import urlparse
import posixpath
import mimetypes
from zlib import adler32
from time import time, mktime
from datetime import datetime
from werkzeug._internal import _patch_wrapper
from werkzeug.http import is_resource_modified, http_date
def responder(f):
"""Marks a function as responder. Decorate a function with it and it
will automatically call the return value as WSGI application.
def application(environ, start_response):
return Response('Hello World!')
return _patch_wrapper(f, lambda *a: f(*a)(*a[-2:]))
def get_current_url(environ, root_only=False, strip_querystring=False,
"""A handy helper function that recreates the full URL for the current
request or parts of it. Here an example:
>>> from werkzeug.test import create_environ
>>> env = create_environ("/?param=foo", "http://localhost/script")
>>> get_current_url(env)
>>> get_current_url(env, root_only=True)
>>> get_current_url(env, host_only=True)
>>> get_current_url(env, strip_querystring=True)
:param environ: the WSGI environment to get the current URL from.
:param root_only: set `True` if you only want the root URL.
:param strip_querystring: set to `True` if you don't want the querystring.
:param host_only: set to `True` if the host URL should be returned.
tmp = [environ['wsgi.url_scheme'], '://', get_host(environ)]
cat = tmp.append
if host_only:
return ''.join(tmp) + '/'
cat(urllib.quote(environ.get('SCRIPT_NAME', '').rstrip('/')))
if root_only:
cat(urllib.quote('/' + environ.get('PATH_INFO', '').lstrip('/')))
if not strip_querystring:
qs = environ.get('QUERY_STRING')
if qs:
cat('?' + qs)
return ''.join(tmp)
def get_host(environ):
"""Return the real host for the given WSGI environment. This takes care
of the `X-Forwarded-Host` header.
:param environ: the WSGI environment to get the host of.
if 'HTTP_X_FORWARDED_HOST' in environ:
return environ['HTTP_X_FORWARDED_HOST']
elif 'HTTP_HOST' in environ:
return environ['HTTP_HOST']
result = environ['SERVER_NAME']
if (environ['wsgi.url_scheme'], environ['SERVER_PORT']) not \
in (('https', '443'), ('http', '80')):
result += ':' + environ['SERVER_PORT']
return result
def pop_path_info(environ):
"""Removes and returns the next segment of `PATH_INFO`, pushing it onto
`SCRIPT_NAME`. Returns `None` if there is nothing left on `PATH_INFO`.
If there are empty segments (``'/foo//bar``) these are ignored but
properly pushed to the `SCRIPT_NAME`:
>>> env = {'SCRIPT_NAME': '/foo', 'PATH_INFO': '/a/b'}
>>> pop_path_info(env)
>>> env['SCRIPT_NAME']
>>> pop_path_info(env)
>>> env['SCRIPT_NAME']
.. versionadded:: 0.5
:param environ: the WSGI environment that is modified.
path = environ.get('PATH_INFO')
if not path:
return None
script_name = environ.get('SCRIPT_NAME', '')
# shift multiple leading slashes over
old_path = path
path = path.lstrip('/')
if path != old_path:
script_name += '/' * (len(old_path) - len(path))
if '/' not in path:
environ['PATH_INFO'] = ''
environ['SCRIPT_NAME'] = script_name + path
return path
segment, path = path.split('/', 1)
environ['PATH_INFO'] = '/' + path
environ['SCRIPT_NAME'] = script_name + segment
return segment
def peek_path_info(environ):
"""Returns the next segment on the `PATH_INFO` or `None` if there
is none. Works like :func:`pop_path_info` without modifying the
>>> env = {'SCRIPT_NAME': '/foo', 'PATH_INFO': '/a/b'}
>>> peek_path_info(env)
>>> peek_path_info(env)
.. versionadded:: 0.5
:param environ: the WSGI environment that is checked.
segments = environ.get('PATH_INFO', '').lstrip('/').split('/', 1)
if segments:
return segments[0]
def extract_path_info(environ_or_baseurl, path_or_url, charset='utf-8',
errors='replace', collapse_http_schemes=True):
"""Extracts the path info from the given URL (or WSGI environment) and
path. The path info returned is a unicode string, not a bytestring
suitable for a WSGI environment. The URLs might also be IRIs.
If the path info could not be determined, `None` is returned.
Some examples:
>>> extract_path_info('', '/app/hello')
>>> extract_path_info('',
... '')
>>> extract_path_info('',
... '',
... collapse_http_schemes=False) is None
Instead of providing a base URL you can also pass a WSGI environment.
.. versionadded:: 0.6
:param environ_or_baseurl: a WSGI environment dict, a base URL or
base IRI. This is the root of the
:param path_or_url: an absolute path from the server root, a
relative path (in which case it's the path info)
or a full URL. Also accepts IRIs and unicode
:param charset: the charset for byte data in URLs
:param errors: the error handling on decode
:param collapse_http_schemes: if set to `False` the algorithm does
not assume that http and https on the
same server point to the same
from werkzeug.urls import uri_to_iri, url_fix
def _as_iri(obj):
if not isinstance(obj, unicode):
return uri_to_iri(obj, charset, errors)
return obj
def _normalize_netloc(scheme, netloc):
parts = netloc.split(u'@', 1)[-1].split(u':', 1)
if len(parts) == 2:
netloc, port = parts
if (scheme == u'http' and port == u'80') or \
(scheme == u'https' and port == u'443'):
port = None
netloc = parts[0]
port = None
if port is not None:
netloc += u':' + port
return netloc
# make sure whatever we are working on is a IRI and parse it
path = _as_iri(path_or_url)
if isinstance(environ_or_baseurl, dict):
environ_or_baseurl = get_current_url(environ_or_baseurl,
base_iri = _as_iri(environ_or_baseurl)
base_scheme, base_netloc, base_path, = \
cur_scheme, cur_netloc, cur_path, = \
urlparse.urlsplit(urlparse.urljoin(base_iri, path))[:3]
# normalize the network location
base_netloc = _normalize_netloc(base_scheme, base_netloc)
cur_netloc = _normalize_netloc(cur_scheme, cur_netloc)
# is that IRI even on a known HTTP scheme?
if collapse_http_schemes:
for scheme in base_scheme, cur_scheme:
if scheme not in (u'http', u'https'):
return None
if not (base_scheme in (u'http', u'https') and \
base_scheme == cur_scheme):
return None
# are the netlocs compatible?
if base_netloc != cur_netloc:
return None
# are we below the application path?
base_path = base_path.rstrip(u'/')
if not cur_path.startswith(base_path):
return None
return u'/' + cur_path[len(base_path):].lstrip(u'/')
class SharedDataMiddleware(object):
"""A WSGI middleware that provides static content for development
environments or simple server setups. Usage is quite simple::
import os
from werkzeug.wsgi import SharedDataMiddleware
app = SharedDataMiddleware(app, {
'/shared': os.path.join(os.path.dirname(__file__), 'shared')
The contents of the folder ``./shared`` will now be available on
````. This is pretty useful during development
because a standalone media server is not required. One can also mount
files on the root folder and still continue to use the application because
the shared data middleware forwards all unhandled requests to the
application, even if the requests are below one of the shared folders.
If `pkg_resources` is available you can also tell the middleware to serve
files from package data::
app = SharedDataMiddleware(app, {
'/shared': ('myapplication', 'shared_files')
This will then serve the ``shared_files`` folder in the `myapplication`
Python package.
The optional `disallow` parameter can be a list of :func:`~fnmatch.fnmatch`
rules for files that are not accessible from the web. If `cache` is set to
`False` no caching headers are sent.
Currently the middleware does not support non ASCII filenames. If the
encoding on the file system happens to be the encoding of the URI it may
work but this could also be by accident. We strongly suggest using ASCII
only file names for static files.
The middleware will guess the mimetype using the Python `mimetype`
module. If it's unable to figure out the charset it will fall back
to `fallback_mimetype`.
.. versionchanged:: 0.5
The cache timeout is configurable now.
.. versionadded:: 0.6
The `fallback_mimetype` parameter was added.
:param app: the application to wrap. If you don't want to wrap an
application you can pass it :exc:`NotFound`.
:param exports: a dict of exported files and folders.
:param disallow: a list of :func:`~fnmatch.fnmatch` rules.
:param fallback_mimetype: the fallback mimetype for unknown files.
:param cache: enable or disable caching headers.
:Param cache_timeout: the cache timeout in seconds for the headers.
def __init__(self, app, exports, disallow=None, cache=True,
cache_timeout=60 * 60 * 12, fallback_mimetype='text/plain'): = app
self.exports = {}
self.cache = cache
self.cache_timeout = cache_timeout
for key, value in exports.iteritems():
if isinstance(value, tuple):
loader = self.get_package_loader(*value)
elif isinstance(value, basestring):
if os.path.isfile(value):
loader = self.get_file_loader(value)
loader = self.get_directory_loader(value)
raise TypeError('unknown def %r' % value)
self.exports[key] = loader
if disallow is not None:
from fnmatch import fnmatch
self.is_allowed = lambda x: not fnmatch(x, disallow)
self.fallback_mimetype = fallback_mimetype
def is_allowed(self, filename):
"""Subclasses can override this method to disallow the access to
certain files. However by providing `disallow` in the constructor
this method is overwritten.
return True
def _opener(self, filename):
return lambda: (
open(filename, 'rb'),
def get_file_loader(self, filename):
return lambda x: (os.path.basename(filename), self._opener(filename))
def get_package_loader(self, package, package_path):
from pkg_resources import DefaultProvider, ResourceManager, \
loadtime = datetime.utcnow()
provider = get_provider(package)
manager = ResourceManager()
filesystem_bound = isinstance(provider, DefaultProvider)
def loader(path):
if path is None:
return None, None
path = posixpath.join(package_path, path)
if not provider.has_resource(path):
return None, None
basename = posixpath.basename(path)
if filesystem_bound:
return basename, self._opener(
provider.get_resource_filename(manager, path))
return basename, lambda: (
provider.get_resource_stream(manager, path),
return loader
def get_directory_loader(self, directory):
def loader(path):
if path is not None:
path = os.path.join(directory, path)
path = directory
if os.path.isfile(path):
return os.path.basename(path), self._opener(path)
return None, None
return loader
def generate_etag(self, mtime, file_size, real_filename):
return 'wzsdm-%d-%s-%s' % (
adler32(real_filename) & 0xffffffff
def __call__(self, environ, start_response):
# sanitize the path for non unix systems
cleaned_path = environ.get('PATH_INFO', '').strip('/')
for sep in os.sep, os.altsep:
if sep and sep != '/':
cleaned_path = cleaned_path.replace(sep, '/')
path = '/'.join([''] + [x for x in cleaned_path.split('/')
if x and x != '..'])
file_loader = None
for search_path, loader in self.exports.iteritems():
if search_path == path:
real_filename, file_loader = loader(None)
if file_loader is not None:
if not search_path.endswith('/'):
search_path += '/'
if path.startswith(search_path):
real_filename, file_loader = loader(path[len(search_path):])
if file_loader is not None:
if file_loader is None or not self.is_allowed(real_filename):
return, start_response)
guessed_type = mimetypes.guess_type(real_filename)
mime_type = guessed_type[0] or self.fallback_mimetype
f, mtime, file_size = file_loader()
headers = [('Date', http_date())]
if self.cache:
timeout = self.cache_timeout
etag = self.generate_etag(mtime, file_size, real_filename)
headers += [
('Etag', '"%s"' % etag),
('Cache-Control', 'max-age=%d, public' % timeout)
if not is_resource_modified(environ, etag, last_modified=mtime):
start_response('304 Not Modified', headers)
return []
headers.append(('Expires', http_date(time() + timeout)))
headers.append(('Cache-Control', 'public'))
('Content-Type', mime_type),
('Content-Length', str(file_size)),
('Last-Modified', http_date(mtime))
start_response('200 OK', headers)
return wrap_file(environ, f)
class DispatcherMiddleware(object):
"""Allows one to mount middlewares or applications in a WSGI application.
This is useful if you want to combine multiple WSGI applications::
app = DispatcherMiddleware(app, {
'/app2': app2,
'/app3': app3
def __init__(self, app, mounts=None): = app
self.mounts = mounts or {}
def __call__(self, environ, start_response):
script = environ.get('PATH_INFO', '')
path_info = ''
while '/' in script:
if script in self.mounts:
app = self.mounts[script]
items = script.split('/')
script = '/'.join(items[:-1])
path_info = '/%s%s' % (items[-1], path_info)
app = self.mounts.get(script,
original_script_name = environ.get('SCRIPT_NAME', '')
environ['SCRIPT_NAME'] = original_script_name + script
environ['PATH_INFO'] = path_info
return app(environ, start_response)
class ClosingIterator(object):
"""The WSGI specification requires that all middlewares and gateways
respect the `close` callback of an iterator. Because it is useful to add
another close action to a returned iterator and adding a custom iterator
is a boring task this class can be used for that::
return ClosingIterator(app(environ, start_response), [cleanup_session,
If there is just one close function it can be passed instead of the list.
A closing iterator is not needed if the application uses response objects
and finishes the processing if the response is started::
return response(environ, start_response)
def __init__(self, iterable, callbacks=None):
iterator = iter(iterable)
self._next =
if callbacks is None:
callbacks = []
elif callable(callbacks):
callbacks = [callbacks]
callbacks = list(callbacks)
iterable_close = getattr(iterator, 'close', None)
if iterable_close:
callbacks.insert(0, iterable_close)
self._callbacks = callbacks
def __iter__(self):
return self
def next(self):
return self._next()
def close(self):
for callback in self._callbacks:
def wrap_file(environ, file, buffer_size=8192):
"""Wraps a file. This uses the WSGI server's file wrapper if available
or otherwise the generic :class:`FileWrapper`.
.. versionadded:: 0.5
If the file wrapper from the WSGI server is used it's important to not
iterate over it from inside the application but to pass it through
unchanged. If you want to pass out a file wrapper inside a response
object you have to set :attr:`~BaseResponse.direct_passthrough` to `True`.
More information about file wrappers are available in :pep:`333`.
:param file: a :class:`file`-like object with a :meth:`` method.
:param buffer_size: number of bytes for one iteration.
return environ.get('wsgi.file_wrapper', FileWrapper)(file, buffer_size)
class FileWrapper(object):
"""This class can be used to convert a :class:`file`-like object into
an iterable. It yields `buffer_size` blocks until the file is fully
You should not use this class directly but rather use the
:func:`wrap_file` function that uses the WSGI server's file wrapper
support if it's available.
.. versionadded:: 0.5
If you're using this object together with a :class:`BaseResponse` you have
to use the `direct_passthrough` mode.
:param file: a :class:`file`-like object with a :meth:`` method.
:param buffer_size: number of bytes for one iteration.
def __init__(self, file, buffer_size=8192):
self.file = file
self.buffer_size = buffer_size
def close(self):
if hasattr(self.file, 'close'):
def __iter__(self):
return self
def next(self):
data =
if data:
return data
raise StopIteration()
def make_line_iter(stream, limit=None, buffer_size=10 * 1024):
"""Safely iterates line-based over an input stream. If the input stream
is not a :class:`LimitedStream` the `limit` parameter is mandatory.
This uses the stream's :meth:`` method internally as opposite
to the :meth:`~file.readline` method that is unsafe and can only be used
in violation of the WSGI specification. The same problem applies to the
`__iter__` function of the input stream which calls :meth:`~file.readline`
without arguments.
If you need line-by-line processing it's strongly recommended to iterate
over the input stream using this helper function.
:param stream: the stream to iterate over.
:param limit: the limit in bytes for the stream. (Usually
content length. Not necessary if the `stream`
is a :class:`LimitedStream`.
:param buffer_size: The optional buffer size.
if not isinstance(stream, LimitedStream):
if limit is None:
raise TypeError('stream not limited and no limit provided.')
stream = LimitedStream(stream, limit)
_read =
buffer = []
while 1:
if len(buffer) > 1:
yield buffer.pop()
# we reverse the chunks because popping from the last
# position of the list is O(1) and the number of chunks
# read will be quite large for binary files.
chunks = _read(buffer_size).splitlines(True)
first_chunk = buffer and buffer[0] or ''
if chunks:
if first_chunk.endswith('\n') or first_chunk.endswith('\r'):
yield first_chunk
first_chunk = ''
first_chunk += chunks.pop()
if not first_chunk:
buffer = chunks
yield first_chunk
class LimitedStream(object):
"""Wraps a stream so that it doesn't read more than n bytes. If the
stream is exhausted and the caller tries to get more bytes from it
:func:`on_exhausted` is called which by default returns an empty
string. The return value of that function is forwarded
to the reader function. So if it returns an empty string
:meth:`read` will return an empty string as well.
The limit however must never be higher than what the stream can
output. Otherwise :meth:`readlines` will try to read past the
The `silent` parameter has no effect if :meth:`is_exhausted` is
overriden by a subclass.
.. versionchanged:: 0.6
Non-silent usage was deprecated because it causes confusion.
If you want that, override :meth:`is_exhausted` and raise a
:exc:`~exceptions.BadRequest` yourself.
.. admonition:: Note on WSGI compliance
calls to :meth:`readline` and :meth:`readlines` are not
WSGI compliant because it passes a size argument to the
readline methods. Unfortunately the WSGI PEP is not safely
implementable without a size argument to :meth:`readline`
because there is no EOF marker in the stream. As a result
of that the use of :meth:`readline` is discouraged.
For the same reason iterating over the :class:`LimitedStream`
is not portable. It internally calls :meth:`readline`.
We strongly suggest using :meth:`read` only or using the
:func:`make_line_iter` which safely iterates line-based
over a WSGI input stream.
:param stream: the stream to wrap.
:param limit: the limit for the stream, must not be longer than
what the string can provide if the stream does not
end with `EOF` (like `wsgi.input`)
:param silent: If set to `True` the stream will allow reading
past the limit and will return an empty string.
def __init__(self, stream, limit, silent=True):
self._read =
self._readline = stream.readline
self._pos = 0
self.limit = limit
self.silent = silent
if not silent:
from warnings import warn
warn(DeprecationWarning('non-silent usage of the '
'LimitedStream is deprecated. If you want to '
'continue to use the stream in non-silent usage '
'override on_exhausted.'), stacklevel=2)
def __iter__(self):
return self
def is_exhausted(self):
"""If the stream is exhausted this attribute is `True`."""
return self._pos >= self.limit
def on_exhausted(self):
"""This is called when the stream tries to read past the limit.
The return value of this function is returned from the reading
Per default this raises a :exc:`~werkzeug.exceptions.BadRequest`.
if self.silent:
return ''
from werkzeug.exceptions import BadRequest
raise BadRequest('input stream exhausted')
def exhaust(self, chunk_size=1024 * 16):
"""Exhaust the stream. This consumes all the data left until the
limit is reached.
:param chunk_size: the size for a chunk. It will read the chunk
until the stream is exhausted and throw away
the results.
to_read = self.limit - self._pos
chunk = chunk_size
while to_read > 0:
chunk = min(to_read, chunk)
to_read -= chunk
def read(self, size=None):
"""Read `size` bytes or if size is not provided everything is read.
:param size: the number of bytes read.
if self._pos >= self.limit:
return self.on_exhausted()
if size is None:
size = self.limit
read = self._read(min(self.limit - self._pos, size))
self._pos += len(read)
return read
def readline(self, size=None):
"""Reads one line from the stream."""
if self._pos >= self.limit:
return self.on_exhausted()
if size is None:
size = self.limit - self._pos
size = min(size, self.limit - self._pos)
line = self._readline(size)
self._pos += len(line)
return line
def readlines(self, size=None):
"""Reads a file into a list of strings. It calls :meth:`readline`
until the file is read to the end. It does support the optional
`size` argument if the underlaying stream supports it for
last_pos = self._pos
result = []
if size is not None:
end = min(self.limit, last_pos + size)
end = self.limit
while 1:
if size is not None:
size -= last_pos - self._pos
if self._pos >= end:
if size is not None:
last_pos = self._pos
return result
def next(self):
line = self.readline()
if line is None:
raise StopIteration()
return line
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