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
|
WebOb File-Serving Example
==========================
This document shows how you can make a static-file-serving application
using WebOb. We'll quickly build this up from minimal functionality
to a high-quality file serving application.
.. note:: Starting from 1.2b4, WebOb ships with a :mod:`webob.static` module
which implements a :class:`webob.static.FileApp` WSGI application similar to the
one described below.
This document stays as a didactic example how to serve files with WebOb, but
you should consider using applications from :mod:`webob.static` in
production.
.. comment:
>>> import webob, os
>>> base_dir = os.path.dirname(os.path.dirname(webob.__file__))
>>> doc_dir = os.path.join(base_dir, 'docs')
>>> from doctest import ELLIPSIS
First we'll setup a really simple shim around our application, which
we can use as we improve our application:
.. code-block:: python
>>> from webob import Request, Response
>>> import os
>>> class FileApp(object):
... def __init__(self, filename):
... self.filename = filename
... def __call__(self, environ, start_response):
... res = make_response(self.filename)
... return res(environ, start_response)
>>> import mimetypes
>>> def get_mimetype(filename):
... type, encoding = mimetypes.guess_type(filename)
... # We'll ignore encoding, even though we shouldn't really
... return type or 'application/octet-stream'
Now we can make different definitions of ``make_response``. The
simplest version:
.. code-block:: python
>>> def make_response(filename):
... res = Response(content_type=get_mimetype(filename))
... res.body = open(filename, 'rb').read()
... return res
We'll test it out with a file ``test-file.txt`` in the WebOb doc directory,
which has the following content:
.. literalinclude:: file-example-code/test-file.txt
:language: text
Let's give it a shot:
.. code-block:: python
>>> fn = os.path.join(doc_dir, 'file-example-code/test-file.txt')
>>> open(fn).read()
'This is a test. Hello test people!'
>>> app = FileApp(fn)
>>> req = Request.blank('/')
>>> print req.get_response(app)
200 OK
Content-Type: text/plain; charset=UTF-8
Content-Length: 35
<BLANKLINE>
This is a test. Hello test people!
Well, that worked. But it's not a very fancy object. First, it reads
everything into memory, and that's bad. We'll create an iterator instead:
.. code-block:: python
>>> class FileIterable(object):
... def __init__(self, filename):
... self.filename = filename
... def __iter__(self):
... return FileIterator(self.filename)
>>> class FileIterator(object):
... chunk_size = 4096
... def __init__(self, filename):
... self.filename = filename
... self.fileobj = open(self.filename, 'rb')
... def __iter__(self):
... return self
... def next(self):
... chunk = self.fileobj.read(self.chunk_size)
... if not chunk:
... raise StopIteration
... return chunk
... __next__ = next # py3 compat
>>> def make_response(filename):
... res = Response(content_type=get_mimetype(filename))
... res.app_iter = FileIterable(filename)
... res.content_length = os.path.getsize(filename)
... return res
And testing:
.. code-block:: python
>>> req = Request.blank('/')
>>> print req.get_response(app)
200 OK
Content-Type: text/plain; charset=UTF-8
Content-Length: 35
<BLANKLINE>
This is a test. Hello test people!
Well, that doesn't *look* different, but lets *imagine* that it's
different because we know we changed some code. Now to add some basic
metadata to the response:
.. code-block:: python
>>> def make_response(filename):
... res = Response(content_type=get_mimetype(filename),
... conditional_response=True)
... res.app_iter = FileIterable(filename)
... res.content_length = os.path.getsize(filename)
... res.last_modified = os.path.getmtime(filename)
... res.etag = '%s-%s-%s' % (os.path.getmtime(filename),
... os.path.getsize(filename), hash(filename))
... return res
Now, with ``conditional_response`` on, and with ``last_modified`` and
``etag`` set, we can do conditional requests:
.. code-block:: python
>>> req = Request.blank('/')
>>> res = req.get_response(app)
>>> print res
200 OK
Content-Type: text/plain; charset=UTF-8
Content-Length: 35
Last-Modified: ... GMT
ETag: ...-...
<BLANKLINE>
This is a test. Hello test people!
>>> req2 = Request.blank('/')
>>> req2.if_none_match = res.etag
>>> req2.get_response(app)
<Response ... 304 Not Modified>
>>> req3 = Request.blank('/')
>>> req3.if_modified_since = res.last_modified
>>> req3.get_response(app)
<Response ... 304 Not Modified>
We can even do Range requests, but it will currently involve iterating
through the file unnecessarily. When there's a range request (and you
set ``conditional_response=True``) the application will satisfy that
request. But with an arbitrary iterator the only way to do that is to
run through the beginning of the iterator until you get to the chunk
that the client asked for. We can do better because we can use
``fileobj.seek(pos)`` to move around the file much more efficiently.
So we'll add an extra method, ``app_iter_range``, that ``Response``
looks for:
.. code-block:: python
>>> class FileIterable(object):
... def __init__(self, filename, start=None, stop=None):
... self.filename = filename
... self.start = start
... self.stop = stop
... def __iter__(self):
... return FileIterator(self.filename, self.start, self.stop)
... def app_iter_range(self, start, stop):
... return self.__class__(self.filename, start, stop)
>>> class FileIterator(object):
... chunk_size = 4096
... def __init__(self, filename, start, stop):
... self.filename = filename
... self.fileobj = open(self.filename, 'rb')
... if start:
... self.fileobj.seek(start)
... if stop is not None:
... self.length = stop - start
... else:
... self.length = None
... def __iter__(self):
... return self
... def next(self):
... if self.length is not None and self.length <= 0:
... raise StopIteration
... chunk = self.fileobj.read(self.chunk_size)
... if not chunk:
... raise StopIteration
... if self.length is not None:
... self.length -= len(chunk)
... if self.length < 0:
... # Chop off the extra:
... chunk = chunk[:self.length]
... return chunk
... __next__ = next # py3 compat
Now we'll test it out:
.. code-block:: python
>>> req = Request.blank('/')
>>> res = req.get_response(app)
>>> req2 = Request.blank('/')
>>> # Re-fetch the first 5 bytes:
>>> req2.range = (0, 5)
>>> res2 = req2.get_response(app)
>>> res2
<Response ... 206 Partial Content>
>>> # Let's check it's our custom class:
>>> res2.app_iter
<FileIterable object at ...>
>>> res2.body
'This '
>>> # Now, conditional range support:
>>> req3 = Request.blank('/')
>>> req3.if_range = res.etag
>>> req3.range = (0, 5)
>>> req3.get_response(app)
<Response ... 206 Partial Content>
>>> req3.if_range = 'invalid-etag'
>>> req3.get_response(app)
<Response ... 200 OK>
|
