/brz/remove-bazaar

# 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  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 bzrlib import (

    errors,

    trace,

    )

# 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

    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':

            raise errors.InvalidHttpResponse(

                self._path,

                "Expected a boundary (%s) line, got '%s'" % (self._boundary,

                                                             boundary_line))

    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)

        """

        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))

        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)

            data = self._file.read(limited)

        else:

            # Size of file unknown, the user may have specified a size or not,

            # we delegate that to the filesocket object (-1 means read until

            # EOF)

            data = self._file.read(size)

        # 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