« back to all changes in this revision
Viewing changes to urlgrabber/byterange.py
- browse files at revision 45
- compare with another revision
- download diff
- download tarball
- view history from revision 45
- Committer: Martin Pool
- Date: 2005-03-14 07:07:24 UTC
- Revision ID: mbp@sourcefrog.net-20050314070724-ba6c85db7d96c508
- add setup.py and install instructions
- rename main script to just bzr
- rename main script to just bzr
- files added:
- doc/roadmap.txt
- files removed:
- .rsyncexclude
- elementtree
- urlgrabber
- files modified:
- .bzrignore
added
removed
urlgrabber/byterange.py
1
# This library is free software; you can redistribute it and/or
2
# modify it under the terms of the GNU Lesser General Public
3
# License as published by the Free Software Foundation; either
4
# version 2.1 of the License, or (at your option) any later version.
5
#
6
# This library is distributed in the hope that it will be useful,
7
# but WITHOUT ANY WARRANTY; without even the implied warranty of
8
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
9
# Lesser General Public License for more details.
10
#
11
# You should have received a copy of the GNU Lesser General Public
12
# License along with this library; if not, write to the
13
# Free Software Foundation, Inc.,
14
# 59 Temple Place, Suite 330,
15
# Boston, MA 02111-1307 USA
16
17
# This file is part of urlgrabber, a high-level cross-protocol url-grabber
18
# Copyright 2002-2004 Michael D. Stenner, Ryan Tomayko
19
20
# $Id: byterange.py,v 1.9 2005/02/14 21:55:07 mstenner Exp $
21
22
import os
23
import stat
24
import urllib
25
import urllib2
26
import rfc822
27
28
try:
29
from cStringIO import StringIO
30
except ImportError, msg:
31
from StringIO import StringIO
32
33
class RangeError(IOError):
34
"""Error raised when an unsatisfiable range is requested."""
35
pass
36
37
class HTTPRangeHandler(urllib2.BaseHandler):
38
"""Handler that enables HTTP Range headers.
39
40
This was extremely simple. The Range header is a HTTP feature to
41
begin with so all this class does is tell urllib2 that the
42
"206 Partial Content" reponse from the HTTP server is what we
43
expected.
44
45
Example:
46
import urllib2
47
import byterange
48
49
range_handler = range.HTTPRangeHandler()
50
opener = urllib2.build_opener(range_handler)
51
52
# install it
53
urllib2.install_opener(opener)
54
55
# create Request and set Range header
56
req = urllib2.Request('http://www.python.org/')
57
req.header['Range'] = 'bytes=30-50'
58
f = urllib2.urlopen(req)
59
"""
60
61
def http_error_206(self, req, fp, code, msg, hdrs):
62
# 206 Partial Content Response
63
r = urllib.addinfourl(fp, hdrs, req.get_full_url())
64
r.code = code
65
r.msg = msg
66
return r
67
68
def http_error_416(self, req, fp, code, msg, hdrs):
69
# HTTP's Range Not Satisfiable error
70
raise RangeError('Requested Range Not Satisfiable')
71
72
class RangeableFileObject:
73
"""File object wrapper to enable raw range handling.
74
This was implemented primarilary for handling range
75
specifications for file:// urls. This object effectively makes
76
a file object look like it consists only of a range of bytes in
77
the stream.
78
79
Examples:
80
# expose 10 bytes, starting at byte position 20, from
81
# /etc/aliases.
82
>>> fo = RangeableFileObject(file('/etc/passwd', 'r'), (20,30))
83
# seek seeks within the range (to position 23 in this case)
84
>>> fo.seek(3)
85
# tell tells where your at _within the range_ (position 3 in
86
# this case)
87
>>> fo.tell()
88
# read EOFs if an attempt is made to read past the last
89
# byte in the range. the following will return only 7 bytes.
90
>>> fo.read(30)
91
"""
92
93
def __init__(self, fo, rangetup):
94
"""Create a RangeableFileObject.
95
fo -- a file like object. only the read() method need be
96
supported but supporting an optimized seek() is
97
preferable.
98
rangetup -- a (firstbyte,lastbyte) tuple specifying the range
99
to work over.
100
The file object provided is assumed to be at byte offset 0.
101
"""
102
self.fo = fo
103
(self.firstbyte, self.lastbyte) = range_tuple_normalize(rangetup)
104
self.realpos = 0
105
self._do_seek(self.firstbyte)
106
107
def __getattr__(self, name):
108
"""This effectively allows us to wrap at the instance level.
109
Any attribute not found in _this_ object will be searched for
110
in self.fo. This includes methods."""
111
if hasattr(self.fo, name):
112
return getattr(self.fo, name)
113
raise AttributeError, name
114
115
def tell(self):
116
"""Return the position within the range.
117
This is different from fo.seek in that position 0 is the
118
first byte position of the range tuple. For example, if
119
this object was created with a range tuple of (500,899),
120
tell() will return 0 when at byte position 500 of the file.
121
"""
122
return (self.realpos - self.firstbyte)
123
124
def seek(self,offset,whence=0):
125
"""Seek within the byte range.
126
Positioning is identical to that described under tell().
127
"""
128
assert whence in (0, 1, 2)
129
if whence == 0: # absolute seek
130
realoffset = self.firstbyte + offset
131
elif whence == 1: # relative seek
132
realoffset = self.realpos + offset
133
elif whence == 2: # absolute from end of file
134
# XXX: are we raising the right Error here?
135
raise IOError('seek from end of file not supported.')
136
137
# do not allow seek past lastbyte in range
138
if self.lastbyte and (realoffset >= self.lastbyte):
139
realoffset = self.lastbyte
140
141
self._do_seek(realoffset - self.realpos)
142
143
def read(self, size=-1):
144
"""Read within the range.
145
This method will limit the size read based on the range.
146
"""
147
size = self._calc_read_size(size)
148
rslt = self.fo.read(size)
149
self.realpos += len(rslt)
150
return rslt
151
152
def readline(self, size=-1):
153
"""Read lines within the range.
154
This method will limit the size read based on the range.
155
"""
156
size = self._calc_read_size(size)
157
rslt = self.fo.readline(size)
158
self.realpos += len(rslt)
159
return rslt
160
161
def _calc_read_size(self, size):
162
"""Handles calculating the amount of data to read based on
163
the range.
164
"""
165
if self.lastbyte:
166
if size > -1:
167
if ((self.realpos + size) >= self.lastbyte):
168
size = (self.lastbyte - self.realpos)
169
else:
170
size = (self.lastbyte - self.realpos)
171
return size
172
173
def _do_seek(self,offset):
174
"""Seek based on whether wrapped object supports seek().
175
offset is relative to the current position (self.realpos).
176
"""
177
assert offset >= 0
178
if not hasattr(self.fo, 'seek'):
179
self._poor_mans_seek(offset)
180
else:
181
self.fo.seek(self.realpos + offset)
182
self.realpos+= offset
183
184
def _poor_mans_seek(self,offset):
185
"""Seek by calling the wrapped file objects read() method.
186
This is used for file like objects that do not have native
187
seek support. The wrapped objects read() method is called
188
to manually seek to the desired position.
189
offset -- read this number of bytes from the wrapped
190
file object.
191
raise RangeError if we encounter EOF before reaching the
192
specified offset.
193
"""
194
pos = 0
195
bufsize = 1024
196
while pos < offset:
197
if (pos + bufsize) > offset:
198
bufsize = offset - pos
199
buf = self.fo.read(bufsize)
200
if len(buf) != bufsize:
201
raise RangeError('Requested Range Not Satisfiable')
202
pos+= bufsize
203
204
class FileRangeHandler(urllib2.FileHandler):
205
"""FileHandler subclass that adds Range support.
206
This class handles Range headers exactly like an HTTP
207
server would.
208
"""
209
def open_local_file(self, req):
210
import mimetypes
211
import mimetools
212
host = req.get_host()
213
file = req.get_selector()
214
localfile = urllib.url2pathname(file)
215
stats = os.stat(localfile)
216
size = stats[stat.ST_SIZE]
217
modified = rfc822.formatdate(stats[stat.ST_MTIME])
218
mtype = mimetypes.guess_type(file)[0]
219
if host:
220
host, port = urllib.splitport(host)
221
if port or socket.gethostbyname(host) not in self.get_names():
222
raise URLError('file not on local host')
223
fo = open(localfile,'rb')
224
brange = req.headers.get('Range',None)
225
brange = range_header_to_tuple(brange)
226
assert brange != ()
227
if brange:
228
(fb,lb) = brange
229
if lb == '': lb = size
230
if fb < 0 or fb > size or lb > size:
231
raise RangeError('Requested Range Not Satisfiable')
232
size = (lb - fb)
233
fo = RangeableFileObject(fo, (fb,lb))
234
headers = mimetools.Message(StringIO(
235
'Content-Type: %s\nContent-Length: %d\nLast-modified: %s\n' %
236
(mtype or 'text/plain', size, modified)))
237
return urllib.addinfourl(fo, headers, 'file:'+file)
238
239
240
# FTP Range Support
241
# Unfortunately, a large amount of base FTP code had to be copied
242
# from urllib and urllib2 in order to insert the FTP REST command.
243
# Code modifications for range support have been commented as
244
# follows:
245
# -- range support modifications start/end here
246
247
from urllib import splitport, splituser, splitpasswd, splitattr, \
248
unquote, addclosehook, addinfourl
249
import ftplib
250
import socket
251
import sys
252
import ftplib
253
import mimetypes
254
import mimetools
255
256
class FTPRangeHandler(urllib2.FTPHandler):
257
def ftp_open(self, req):
258
host = req.get_host()
259
if not host:
260
raise IOError, ('ftp error', 'no host given')
261
host, port = splitport(host)
262
if port is None:
263
port = ftplib.FTP_PORT
264
265
# username/password handling
266
user, host = splituser(host)
267
if user:
268
user, passwd = splitpasswd(user)
269
else:
270
passwd = None
271
host = unquote(host)
272
user = unquote(user or '')
273
passwd = unquote(passwd or '')
274
275
try:
276
host = socket.gethostbyname(host)
277
except socket.error, msg:
278
raise URLError(msg)
279
path, attrs = splitattr(req.get_selector())
280
dirs = path.split('/')
281
dirs = map(unquote, dirs)
282
dirs, file = dirs[:-1], dirs[-1]
283
if dirs and not dirs[0]:
284
dirs = dirs[1:]
285
try:
286
fw = self.connect_ftp(user, passwd, host, port, dirs)
287
type = file and 'I' or 'D'
288
for attr in attrs:
289
attr, value = splitattr(attr)
290
if attr.lower() == 'type' and \
291
value in ('a', 'A', 'i', 'I', 'd', 'D'):
292
type = value.upper()
293
294
# -- range support modifications start here
295
rest = None
296
range_tup = range_header_to_tuple(req.headers.get('Range',None))
297
assert range_tup != ()
298
if range_tup:
299
(fb,lb) = range_tup
300
if fb > 0: rest = fb
301
# -- range support modifications end here
302
303
fp, retrlen = fw.retrfile(file, type, rest)
304
305
# -- range support modifications start here
306
if range_tup:
307
(fb,lb) = range_tup
308
if lb == '':
309
if retrlen is None or retrlen == 0:
310
raise RangeError('Requested Range Not Satisfiable due to unobtainable file length.')
311
lb = retrlen
312
retrlen = lb - fb
313
if retrlen < 0:
314
# beginning of range is larger than file
315
raise RangeError('Requested Range Not Satisfiable')
316
else:
317
retrlen = lb - fb
318
fp = RangeableFileObject(fp, (0,retrlen))
319
# -- range support modifications end here
320
321
headers = ""
322
mtype = mimetypes.guess_type(req.get_full_url())[0]
323
if mtype:
324
headers += "Content-Type: %s\n" % mtype
325
if retrlen is not None and retrlen >= 0:
326
headers += "Content-Length: %d\n" % retrlen
327
sf = StringIO(headers)
328
headers = mimetools.Message(sf)
329
return addinfourl(fp, headers, req.get_full_url())
330
except ftplib.all_errors, msg:
331
raise IOError, ('ftp error', msg), sys.exc_info()[2]
332
333
def connect_ftp(self, user, passwd, host, port, dirs):
334
fw = ftpwrapper(user, passwd, host, port, dirs)
335
return fw
336
337
class ftpwrapper(urllib.ftpwrapper):
338
# range support note:
339
# this ftpwrapper code is copied directly from
340
# urllib. The only enhancement is to add the rest
341
# argument and pass it on to ftp.ntransfercmd
342
def retrfile(self, file, type, rest=None):
343
self.endtransfer()
344
if type in ('d', 'D'): cmd = 'TYPE A'; isdir = 1
345
else: cmd = 'TYPE ' + type; isdir = 0
346
try:
347
self.ftp.voidcmd(cmd)
348
except ftplib.all_errors:
349
self.init()
350
self.ftp.voidcmd(cmd)
351
conn = None
352
if file and not isdir:
353
# Use nlst to see if the file exists at all
354
try:
355
self.ftp.nlst(file)
356
except ftplib.error_perm, reason:
357
raise IOError, ('ftp error', reason), sys.exc_info()[2]
358
# Restore the transfer mode!
359
self.ftp.voidcmd(cmd)
360
# Try to retrieve as a file
361
try:
362
cmd = 'RETR ' + file
363
conn = self.ftp.ntransfercmd(cmd, rest)
364
except ftplib.error_perm, reason:
365
if str(reason)[:3] == '501':
366
# workaround for REST not supported error
367
fp, retrlen = self.retrfile(file, type)
368
fp = RangeableFileObject(fp, (rest,''))
369
return (fp, retrlen)
370
elif str(reason)[:3] != '550':
371
raise IOError, ('ftp error', reason), sys.exc_info()[2]
372
if not conn:
373
# Set transfer mode to ASCII!
374
self.ftp.voidcmd('TYPE A')
375
# Try a directory listing
376
if file: cmd = 'LIST ' + file
377
else: cmd = 'LIST'
378
conn = self.ftp.ntransfercmd(cmd)
379
self.busy = 1
380
# Pass back both a suitably decorated object and a retrieval length
381
return (addclosehook(conn[0].makefile('rb'),
382
self.endtransfer), conn[1])
383
384
385
####################################################################
386
# Range Tuple Functions
387
# XXX: These range tuple functions might go better in a class.
388
389
_rangere = None
390
def range_header_to_tuple(range_header):
391
"""Get a (firstbyte,lastbyte) tuple from a Range header value.
392
393
Range headers have the form "bytes=<firstbyte>-<lastbyte>". This
394
function pulls the firstbyte and lastbyte values and returns
395
a (firstbyte,lastbyte) tuple. If lastbyte is not specified in
396
the header value, it is returned as an empty string in the
397
tuple.
398
399
Return None if range_header is None
400
Return () if range_header does not conform to the range spec
401
pattern.
402
403
"""
404
global _rangere
405
if range_header is None: return None
406
if _rangere is None:
407
import re
408
_rangere = re.compile(r'^bytes=(\d{1,})-(\d*)')
409
match = _rangere.match(range_header)
410
if match:
411
tup = range_tuple_normalize(match.group(1,2))
412
if tup and tup[1]:
413
tup = (tup[0],tup[1]+1)
414
return tup
415
return ()
416
417
def range_tuple_to_header(range_tup):
418
"""Convert a range tuple to a Range header value.
419
Return a string of the form "bytes=<firstbyte>-<lastbyte>" or None
420
if no range is needed.
421
"""
422
if range_tup is None: return None
423
range_tup = range_tuple_normalize(range_tup)
424
if range_tup:
425
if range_tup[1]:
426
range_tup = (range_tup[0],range_tup[1] - 1)
427
return 'bytes=%s-%s' % range_tup
428
429
def range_tuple_normalize(range_tup):
430
"""Normalize a (first_byte,last_byte) range tuple.
431
Return a tuple whose first element is guaranteed to be an int
432
and whose second element will be '' (meaning: the last byte) or
433
an int. Finally, return None if the normalized tuple == (0,'')
434
as that is equivelant to retrieving the entire file.
435
"""
436
if range_tup is None: return None
437
# handle first byte
438
fb = range_tup[0]
439
if fb in (None,''): fb = 0
440
else: fb = int(fb)
441
# handle last byte
442
try: lb = range_tup[1]
443
except IndexError: lb = ''
444
else:
445
if lb is None: lb = ''
446
elif lb != '': lb = int(lb)
447
# check if range is over the entire file
448
if (fb,lb) == (0,''): return None
449
# check that the range is valid
450
if lb < fb: raise RangeError('Invalid byte range: %s-%s' % (fb,lb))
451
return (fb,lb)
452
Loggerhead is a web-based interface for Breezy
Version: 2.0.1