byterange: replace uses of hasattr with getattr

mercurial/byterange.py

@@ -1,466 +1,462
 #   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, write to the
 #      Free Software Foundation, Inc.,
 #      59 Temple Place, Suite 330,
 #      Boston, MA  02111-1307  USA
 
 # 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" reponse 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 primarilary 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."""
-        if hasattr(self.fo, name):
             return getattr(self.fo, name)
-        raise AttributeError(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
-        if not hasattr(self.fo, 'seek'):
-            self._poor_mans_seek(offset)
-        else:
-            self.fo.seek(self.realpos + offset)
+        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 sys
 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), sys.exc_info()[2]
 
     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), sys.exc_info()[2]
             # 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), sys.exc_info()[2]
         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 equivelant 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)