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# Copyright (C) 2006, 2007 Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
"""Handlers for HTTP Responses.
The purpose of these classes is to provide a uniform interface for clients
to standard HTTP responses, single range responses and multipart range
responses.
"""
import httplib
from cStringIO import StringIO
import rfc822
from bzrlib import (
errors,
trace,
osutils,
)
# A RangeFile expects the following grammar (simplified to outline the
# assumptions we rely upon).
# file: whole_file
# | single_range
# | multiple_range
# whole_file: [content_length_header] data
# single_range: content_range_header data
# multiple_range: boundary_header boundary (content_range_header data boundary)+
class RangeFile(object):
"""File-like object that allow access to partial available data.
All accesses should happen sequentially since the acquisition occurs during
an http response reception (as sockets can't be seeked, we simulate the
seek by just reading and discarding the data).
The access pattern is defined by a set of ranges discovered as reading
progress. Only one range is available at a given time, so all accesses
should happen with monotonically increasing offsets.
"""
# in _checked_read() below, we may have to discard several MB in the worst
# case. To avoid buffering that much, we read and discard by chunks
# instead. The underlying file is either a socket or a StringIO, so reading
# 8k chunks should be fine.
_discarded_buf_size = 8192
# maximum size of read requests -- used to avoid MemoryError issues in recv
_max_read_size = 512 * 1024
def __init__(self, path, infile):
"""Constructor.
:param path: File url, for error reports.
:param infile: File-like socket set at body start.
"""
self._path = path
self._file = infile
self._boundary = None
# When using multi parts response, this will be set with the headers
# associated with the range currently read.
self._headers = None
# Default to the whole file of unspecified size
self.set_range(0, -1)
def set_range(self, start, size):
"""Change the range mapping"""
self._start = start
self._size = size
# Set the new _pos since that's what we want to expose
self._pos = self._start
def set_boundary(self, boundary):
"""Define the boundary used in a multi parts message.
The file should be at the beginning of the body, the first range
definition is read and taken into account.
"""
self._boundary = boundary
# Decode the headers and setup the first range
self.read_boundary()
self.read_range_definition()
def read_boundary(self):
"""Read the boundary headers defining a new range"""
boundary_line = '\r\n'
while boundary_line == '\r\n':
# RFC2616 19.2 Additional CRLFs may precede the first boundary
# string entity.
# To be on the safe side we allow it before any boundary line
boundary_line = self._file.readline()
if boundary_line != '--' + self._boundary + '\r\n':
# rfc822.unquote() incorrectly unquotes strings enclosed in <>
# IIS 6 and 7 incorrectly wrap boundary strings in <>
# together they make a beautiful bug, which we will be gracious
# about here
if (self._unquote_boundary(boundary_line) !=
'--' + self._boundary + '\r\n'):
raise errors.InvalidHttpResponse(
self._path,
"Expected a boundary (%s) line, got '%s'"
% (self._boundary, boundary_line))
def _unquote_boundary(self, b):
return b[:2] + rfc822.unquote(b[2:-2]) + b[-2:]
def read_range_definition(self):
"""Read a new range definition in a multi parts message.
Parse the headers including the empty line following them so that we
are ready to read the data itself.
"""
self._headers = httplib.HTTPMessage(self._file, seekable=0)
# Extract the range definition
content_range = self._headers.getheader('content-range', None)
if content_range is None:
raise errors.InvalidHttpResponse(
self._path,
'Content-Range header missing in a multi-part response')
self.set_range_from_header(content_range)
def set_range_from_header(self, content_range):
"""Helper to set the new range from its description in the headers"""
try:
rtype, values = content_range.split()
except ValueError:
raise errors.InvalidHttpRange(self._path, content_range,
'Malformed header')
if rtype != 'bytes':
raise errors.InvalidHttpRange(self._path, content_range,
"Unsupported range type '%s'" % rtype)
try:
# We don't need total, but note that it may be either the file size
# or '*' if the server can't or doesn't want to return the file
# size.
start_end, total = values.split('/')
start, end = start_end.split('-')
start = int(start)
end = int(end)
except ValueError:
raise errors.InvalidHttpRange(self._path, content_range,
'Invalid range values')
size = end - start + 1
if size <= 0:
raise errors.InvalidHttpRange(self._path, content_range,
'Invalid range, size <= 0')
self.set_range(start, size)
def _checked_read(self, size):
"""Read the file checking for short reads.
The data read is discarded along the way.
"""
pos = self._pos
remaining = size
while remaining > 0:
data = self._file.read(min(remaining, self._discarded_buf_size))
remaining -= len(data)
if not data:
raise errors.ShortReadvError(self._path, pos, size,
size - remaining)
self._pos += size
def _seek_to_next_range(self):
# We will cross range boundaries
if self._boundary is None:
# If we don't have a boundary, we can't find another range
raise errors.InvalidRange(self._path, self._pos,
"Range (%s, %s) exhausted"
% (self._start, self._size))
self.read_boundary()
self.read_range_definition()
def read(self, size=-1):
"""Read size bytes from the current position in the file.
Reading across ranges is not supported. We rely on the underlying http
client to clean the socket if we leave bytes unread. This may occur for
the final boundary line of a multipart response or for any range
request not entirely consumed by the client (due to offset coalescing)
:param size: The number of bytes to read. Leave unspecified or pass
-1 to read to EOF.
"""
if (self._size > 0
and self._pos == self._start + self._size):
if size == 0:
return ''
else:
self._seek_to_next_range()
elif self._pos < self._start:
raise errors.InvalidRange(
self._path, self._pos,
"Can't read %s bytes before range (%s, %s)"
% (size, self._start, self._size))
if self._size > 0:
if size > 0 and self._pos + size > self._start + self._size:
raise errors.InvalidRange(
self._path, self._pos,
"Can't read %s bytes across range (%s, %s)"
% (size, self._start, self._size))
# read data from file
buffer = StringIO()
limited = size
if self._size > 0:
# Don't read past the range definition
limited = self._start + self._size - self._pos
if size >= 0:
limited = min(limited, size)
osutils.pumpfile(self._file, buffer, limited, self._max_read_size)
data = buffer.getvalue()
# Update _pos respecting the data effectively read
self._pos += len(data)
return data
def seek(self, offset, whence=0):
start_pos = self._pos
if whence == 0:
final_pos = offset
elif whence == 1:
final_pos = start_pos + offset
elif whence == 2:
if self._size > 0:
final_pos = self._start + self._size + offset # offset < 0
else:
raise errors.InvalidRange(
self._path, self._pos,
"RangeFile: can't seek from end while size is unknown")
else:
raise ValueError("Invalid value %s for whence." % whence)
if final_pos < self._pos:
# Can't seek backwards
raise errors.InvalidRange(
self._path, self._pos,
'RangeFile: trying to seek backwards to %s' % final_pos)
if self._size > 0:
cur_limit = self._start + self._size
while final_pos > cur_limit:
# We will cross range boundaries
remain = cur_limit - self._pos
if remain > 0:
# Finish reading the current range
self._checked_read(remain)
self._seek_to_next_range()
cur_limit = self._start + self._size
size = final_pos - self._pos
if size > 0: # size can be < 0 if we crossed a range boundary
# We don't need the data, just read it and throw it away
self._checked_read(size)
def tell(self):
return self._pos
def handle_response(url, code, msg, data):
"""Interpret the code & headers and wrap the provided data in a RangeFile.
This is a factory method which returns an appropriate RangeFile based on
the code & headers it's given.
:param url: The url being processed. Mostly for error reporting
:param code: The integer HTTP response code
:param msg: An HTTPMessage containing the headers for the response
:param data: A file-like object that can be read() to get the
requested data
:return: A file-like object that can seek()+read() the
ranges indicated by the headers.
"""
rfile = RangeFile(url, data)
if code == 200:
# A whole file
size = msg.getheader('content-length', None)
if size is None:
size = -1
else:
size = int(size)
rfile.set_range(0, size)
elif code == 206:
content_type = msg.getheader('content-type', None)
if content_type is None:
# When there is no content-type header we treat the response as
# being of type 'application/octet-stream' as per RFC2616 section
# 7.2.1.
# Therefore it is obviously not multipart
content_type = 'application/octet-stream'
is_multipart = False
else:
is_multipart = (msg.getmaintype() == 'multipart'
and msg.getsubtype() == 'byteranges')
if is_multipart:
# Full fledged multipart response
rfile.set_boundary(msg.getparam('boundary'))
else:
# A response to a range request, but not multipart
content_range = msg.getheader('content-range', None)
if content_range is None:
raise errors.InvalidHttpResponse(url,
'Missing the Content-Range header in a 206 range response')
rfile.set_range_from_header(content_range)
else:
raise errors.InvalidHttpResponse(url,
'Unknown response code %s' % code)
return rfile
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