# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, see
# <http://www.gnu.org/licenses/>.
# This file is part of urlgrabber, a high-level cross-protocol url-grabber
# Copyright 2002-2004 Michael D. Stenner, Ryan Tomayko
# $Id: byterange.py,v 1.9 2005/02/14 21:55:07 mstenner Exp $
import os
import stat
import urllib
import urllib2
import email.Utils
class RangeError(IOError):
"""Error raised when an unsatisfiable range is requested."""
pass
class HTTPRangeHandler(urllib2.BaseHandler):
"""Handler that enables HTTP Range headers.
This was extremely simple. The Range header is a HTTP feature to
begin with so all this class does is tell urllib2 that the
"206 Partial Content" response from the HTTP server is what we
expected.
Example:
import urllib2
import byterange
range_handler = range.HTTPRangeHandler()
opener = urllib2.build_opener(range_handler)
# install it
urllib2.install_opener(opener)
# create Request and set Range header
req = urllib2.Request('http://www.python.org/')
req.header['Range'] = 'bytes=30-50'
f = urllib2.urlopen(req)
"""
def http_error_206(self, req, fp, code, msg, hdrs):
# 206 Partial Content Response
r = urllib.addinfourl(fp, hdrs, req.get_full_url())
r.code = code
r.msg = msg
return r
def http_error_416(self, req, fp, code, msg, hdrs):
# HTTP's Range Not Satisfiable error
raise RangeError('Requested Range Not Satisfiable')
class RangeableFileObject(object):
"""File object wrapper to enable raw range handling.
This was implemented primarily for handling range
specifications for file:// urls. This object effectively makes
a file object look like it consists only of a range of bytes in
the stream.
Examples:
# expose 10 bytes, starting at byte position 20, from
# /etc/aliases.
>>> fo = RangeableFileObject(file('/etc/passwd', 'r'), (20,30))
# seek seeks within the range (to position 23 in this case)
>>> fo.seek(3)
# tell tells where your at _within the range_ (position 3 in
# this case)
>>> fo.tell()
# read EOFs if an attempt is made to read past the last
# byte in the range. the following will return only 7 bytes.
>>> fo.read(30)
"""
def __init__(self, fo, rangetup):
"""Create a RangeableFileObject.
fo -- a file like object. only the read() method need be
supported but supporting an optimized seek() is
preferable.
rangetup -- a (firstbyte,lastbyte) tuple specifying the range
to work over.
The file object provided is assumed to be at byte offset 0.
"""
self.fo = fo
(self.firstbyte, self.lastbyte) = range_tuple_normalize(rangetup)
self.realpos = 0
self._do_seek(self.firstbyte)
def __getattr__(self, name):
"""This effectively allows us to wrap at the instance level.
Any attribute not found in _this_ object will be searched for
in self.fo. This includes methods."""
return getattr(self.fo, name)
def tell(self):
"""Return the position within the range.
This is different from fo.seek in that position 0 is the
first byte position of the range tuple. For example, if
this object was created with a range tuple of (500,899),
tell() will return 0 when at byte position 500 of the file.
"""
return (self.realpos - self.firstbyte)
def seek(self, offset, whence=0):
"""Seek within the byte range.
Positioning is identical to that described under tell().
"""
assert whence in (0, 1, 2)
if whence == 0: # absolute seek
realoffset = self.firstbyte + offset
elif whence == 1: # relative seek
realoffset = self.realpos + offset
elif whence == 2: # absolute from end of file
# XXX: are we raising the right Error here?
raise IOError('seek from end of file not supported.')
# do not allow seek past lastbyte in range
if self.lastbyte and (realoffset >= self.lastbyte):
realoffset = self.lastbyte
self._do_seek(realoffset - self.realpos)
def read(self, size=-1):
"""Read within the range.
This method will limit the size read based on the range.
"""
size = self._calc_read_size(size)
rslt = self.fo.read(size)
self.realpos += len(rslt)
return rslt
def readline(self, size=-1):
"""Read lines within the range.
This method will limit the size read based on the range.
"""
size = self._calc_read_size(size)
rslt = self.fo.readline(size)
self.realpos += len(rslt)
return rslt
def _calc_read_size(self, size):
"""Handles calculating the amount of data to read based on
the range.
"""
if self.lastbyte:
if size > -1:
if ((self.realpos + size) >= self.lastbyte):
size = (self.lastbyte - self.realpos)
else:
size = (self.lastbyte - self.realpos)
return size
def _do_seek(self, offset):
"""Seek based on whether wrapped object supports seek().
offset is relative to the current position (self.realpos).
"""
assert offset >= 0
seek = getattr(self.fo, 'seek', self._poor_mans_seek)
seek(self.realpos + offset)
self.realpos += offset
def _poor_mans_seek(self, offset):
"""Seek by calling the wrapped file objects read() method.
This is used for file like objects that do not have native
seek support. The wrapped objects read() method is called
to manually seek to the desired position.
offset -- read this number of bytes from the wrapped
file object.
raise RangeError if we encounter EOF before reaching the
specified offset.
"""
pos = 0
bufsize = 1024
while pos < offset:
if (pos + bufsize) > offset:
bufsize = offset - pos
buf = self.fo.read(bufsize)
if len(buf) != bufsize:
raise RangeError('Requested Range Not Satisfiable')
pos += bufsize
class FileRangeHandler(urllib2.FileHandler):
"""FileHandler subclass that adds Range support.
This class handles Range headers exactly like an HTTP
server would.
"""
def open_local_file(self, req):
import mimetypes
import email
host = req.get_host()
file = req.get_selector()
localfile = urllib.url2pathname(file)
stats = os.stat(localfile)
size = stats[stat.ST_SIZE]
modified = email.Utils.formatdate(stats[stat.ST_MTIME])
mtype = mimetypes.guess_type(file)[0]
if host:
host, port = urllib.splitport(host)
if port or socket.gethostbyname(host) not in self.get_names():
raise urllib2.URLError('file not on local host')
fo = open(localfile,'rb')
brange = req.headers.get('Range', None)
brange = range_header_to_tuple(brange)
assert brange != ()
if brange:
(fb, lb) = brange
if lb == '':
lb = size
if fb < 0 or fb > size or lb > size:
raise RangeError('Requested Range Not Satisfiable')
size = (lb - fb)
fo = RangeableFileObject(fo, (fb, lb))
headers = email.message_from_string(
'Content-Type: %s\nContent-Length: %d\nLast-Modified: %s\n' %
(mtype or 'text/plain', size, modified))
return urllib.addinfourl(fo, headers, 'file:'+file)
# FTP Range Support
# Unfortunately, a large amount of base FTP code had to be copied
# from urllib and urllib2 in order to insert the FTP REST command.
# Code modifications for range support have been commented as
# follows:
# -- range support modifications start/end here
from urllib import splitport, splituser, splitpasswd, splitattr, \
unquote, addclosehook, addinfourl
import ftplib
import socket
import mimetypes
import email
class FTPRangeHandler(urllib2.FTPHandler):
def ftp_open(self, req):
host = req.get_host()
if not host:
raise IOError('ftp error', 'no host given')
host, port = splitport(host)
if port is None:
port = ftplib.FTP_PORT
else:
port = int(port)
# username/password handling
user, host = splituser(host)
if user:
user, passwd = splitpasswd(user)
else:
passwd = None
host = unquote(host)
user = unquote(user or '')
passwd = unquote(passwd or '')
try:
host = socket.gethostbyname(host)
except socket.error, msg:
raise urllib2.URLError(msg)
path, attrs = splitattr(req.get_selector())
dirs = path.split('/')
dirs = map(unquote, dirs)
dirs, file = dirs[:-1], dirs[-1]
if dirs and not dirs[0]:
dirs = dirs[1:]
try:
fw = self.connect_ftp(user, passwd, host, port, dirs)
type = file and 'I' or 'D'
for attr in attrs:
attr, value = splitattr(attr)
if attr.lower() == 'type' and \
value in ('a', 'A', 'i', 'I', 'd', 'D'):
type = value.upper()
# -- range support modifications start here
rest = None
range_tup = range_header_to_tuple(req.headers.get('Range', None))
assert range_tup != ()
if range_tup:
(fb, lb) = range_tup
if fb > 0:
rest = fb
# -- range support modifications end here
fp, retrlen = fw.retrfile(file, type, rest)
# -- range support modifications start here
if range_tup:
(fb, lb) = range_tup
if lb == '':
if retrlen is None or retrlen == 0:
raise RangeError('Requested Range Not Satisfiable due'
' to unobtainable file length.')
lb = retrlen
retrlen = lb - fb
if retrlen < 0:
# beginning of range is larger than file
raise RangeError('Requested Range Not Satisfiable')
else:
retrlen = lb - fb
fp = RangeableFileObject(fp, (0, retrlen))
# -- range support modifications end here
headers = ""
mtype = mimetypes.guess_type(req.get_full_url())[0]
if mtype:
headers += "Content-Type: %s\n" % mtype
if retrlen is not None and retrlen >= 0:
headers += "Content-Length: %d\n" % retrlen
headers = email.message_from_string(headers)
return addinfourl(fp, headers, req.get_full_url())
except ftplib.all_errors, msg:
raise IOError('ftp error', msg)
def connect_ftp(self, user, passwd, host, port, dirs):
fw = ftpwrapper(user, passwd, host, port, dirs)
return fw
class ftpwrapper(urllib.ftpwrapper):
# range support note:
# this ftpwrapper code is copied directly from
# urllib. The only enhancement is to add the rest
# argument and pass it on to ftp.ntransfercmd
def retrfile(self, file, type, rest=None):
self.endtransfer()
if type in ('d', 'D'):
cmd = 'TYPE A'
isdir = 1
else:
cmd = 'TYPE ' + type
isdir = 0
try:
self.ftp.voidcmd(cmd)
except ftplib.all_errors:
self.init()
self.ftp.voidcmd(cmd)
conn = None
if file and not isdir:
# Use nlst to see if the file exists at all
try:
self.ftp.nlst(file)
except ftplib.error_perm, reason:
raise IOError('ftp error', reason)
# Restore the transfer mode!
self.ftp.voidcmd(cmd)
# Try to retrieve as a file
try:
cmd = 'RETR ' + file
conn = self.ftp.ntransfercmd(cmd, rest)
except ftplib.error_perm, reason:
if str(reason).startswith('501'):
# workaround for REST not supported error
fp, retrlen = self.retrfile(file, type)
fp = RangeableFileObject(fp, (rest,''))
return (fp, retrlen)
elif not str(reason).startswith('550'):
raise IOError('ftp error', reason)
if not conn:
# Set transfer mode to ASCII!
self.ftp.voidcmd('TYPE A')
# Try a directory listing
if file:
cmd = 'LIST ' + file
else:
cmd = 'LIST'
conn = self.ftp.ntransfercmd(cmd)
self.busy = 1
# Pass back both a suitably decorated object and a retrieval length
return (addclosehook(conn[0].makefile('rb'),
self.endtransfer), conn[1])
####################################################################
# Range Tuple Functions
# XXX: These range tuple functions might go better in a class.
_rangere = None
def range_header_to_tuple(range_header):
"""Get a (firstbyte,lastbyte) tuple from a Range header value.
Range headers have the form "bytes=<firstbyte>-<lastbyte>". This
function pulls the firstbyte and lastbyte values and returns
a (firstbyte,lastbyte) tuple. If lastbyte is not specified in
the header value, it is returned as an empty string in the
tuple.
Return None if range_header is None
Return () if range_header does not conform to the range spec
pattern.
"""
global _rangere
if range_header is None:
return None
if _rangere is None:
import re
_rangere = re.compile(r'^bytes=(\d{1,})-(\d*)')
match = _rangere.match(range_header)
if match:
tup = range_tuple_normalize(match.group(1, 2))
if tup and tup[1]:
tup = (tup[0], tup[1]+1)
return tup
return ()
def range_tuple_to_header(range_tup):
"""Convert a range tuple to a Range header value.
Return a string of the form "bytes=<firstbyte>-<lastbyte>" or None
if no range is needed.
"""
if range_tup is None:
return None
range_tup = range_tuple_normalize(range_tup)
if range_tup:
if range_tup[1]:
range_tup = (range_tup[0], range_tup[1] - 1)
return 'bytes=%s-%s' % range_tup
def range_tuple_normalize(range_tup):
"""Normalize a (first_byte,last_byte) range tuple.
Return a tuple whose first element is guaranteed to be an int
and whose second element will be '' (meaning: the last byte) or
an int. Finally, return None if the normalized tuple == (0,'')
as that is equivalent to retrieving the entire file.
"""
if range_tup is None:
return None
# handle first byte
fb = range_tup[0]
if fb in (None, ''):
fb = 0
else:
fb = int(fb)
# handle last byte
try:
lb = range_tup[1]
except IndexError:
lb = ''
else:
if lb is None:
lb = ''
elif lb != '':
lb = int(lb)
# check if range is over the entire file
if (fb, lb) == (0, ''):
return None
# check that the range is valid
if lb < fb:
raise RangeError('Invalid byte range: %s-%s' % (fb, lb))
return (fb, lb)
|
