~bzr-pqm/bzr/bzr.dev

# Copyright (C) 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

"""Container format for Bazaar data.

"Containers" and "records" are described in doc/developers/container-format.txt.

"""

from cStringIO import StringIO

import re

from bzrlib import errors

FORMAT_ONE = "Bazaar pack format 1 (introduced in 0.18)"

_whitespace_re = re.compile('[\t\n\x0b\x0c\r ]')

def _check_name(name):

    """Do some basic checking of 'name'.

    At the moment, this just checks that there are no whitespace characters in a

    name.

    :raises InvalidRecordError: if name is not valid.

    :seealso: _check_name_encoding

    """

    if _whitespace_re.search(name) is not None:

        raise errors.InvalidRecordError("%r is not a valid name." % (name,))

def _check_name_encoding(name):

    """Check that 'name' is valid UTF-8.

    This is separate from _check_name because UTF-8 decoding is relatively

    expensive, and we usually want to avoid it.

    :raises InvalidRecordError: if name is not valid UTF-8.

    """

    try:

        name.decode('utf-8')

    except UnicodeDecodeError, e:

        raise errors.InvalidRecordError(str(e))

class ContainerWriter(object):

    """A class for writing containers.

    :attribute records_written: The number of user records added to the

        container. This does not count the prelude or suffix of the container

        introduced by the begin() and end() methods.

    """

    def __init__(self, write_func):

        """Constructor.

        :param write_func: a callable that will be called when this

            ContainerWriter needs to write some bytes.

        """

        self._write_func = write_func

        self.current_offset = 0

        self.records_written = 0

    def begin(self):

        """Begin writing a container."""

        self.write_func(FORMAT_ONE + "\n")

    def write_func(self, bytes):

        self._write_func(bytes)

        self.current_offset += len(bytes)

    def end(self):

        """Finish writing a container."""

        self.write_func("E")

    def add_bytes_record(self, bytes, names):

        """Add a Bytes record with the given names.

        :param bytes: The bytes to insert.

        :param names: The names to give the inserted bytes. Each name is

            a tuple of bytestrings. The bytestrings may not contain

            whitespace.

        :return: An offset, length tuple. The offset is the offset

            of the record within the container, and the length is the

            length of data that will need to be read to reconstitute the

            record. These offset and length can only be used with the pack

            interface - they might be offset by headers or other such details

            and thus are only suitable for use by a ContainerReader.

        """

        current_offset = self.current_offset

        # Kind marker

        byte_sections = ["B"]

        # Length

        byte_sections.append(str(len(bytes)) + "\n")

        # Names

        for name_tuple in names:

            # Make sure we're writing valid names.  Note that we will leave a

            # half-written record if a name is bad!

            for name in name_tuple:

                _check_name(name)

            byte_sections.append('\x00'.join(name_tuple) + "\n")

        # End of headers

        byte_sections.append("\n")

        # Finally, the contents.

        byte_sections.append(bytes)

        # XXX: This causes a memory copy of bytes in size, but is usually

        # faster than two write calls (12 vs 13 seconds to output a gig of

        # 1k records.) - results may differ on significantly larger records

        # like .iso's but as they should be rare in any case and thus not

        # likely to be the common case. The biggest issue is causing extreme

        # memory pressure in that case. One possibly improvement here is to

        # check the size of the content before deciding to join here vs call

        # write twice.

        self.write_func(''.join(byte_sections))

        self.records_written += 1

        # return a memo of where we wrote data to allow random access.

        return current_offset, self.current_offset - current_offset

class ReadVFile(object):

    """Adapt a readv result iterator to a file like protocol."""

    def __init__(self, readv_result):

        self.readv_result = readv_result

        # the most recent readv result block

        self._string = None

    def _next(self):

        if (self._string is None or

            self._string.tell() == self._string_length):

            length, data = self.readv_result.next()

            self._string_length = len(data)

            self._string = StringIO(data)

    def read(self, length):

        self._next()

        result = self._string.read(length)

        if len(result) < length:

            raise errors.BzrError('request for too much data from a readv hunk.')

        return result

    def readline(self):

        """Note that readline will not cross readv segments."""

        self._next()

        result = self._string.readline()

        if self._string.tell() == self._string_length and result[-1] != '\n':

            raise errors.BzrError('short readline in the readvfile hunk.')

        return result

def make_readv_reader(transport, filename, requested_records):

    """Create a ContainerReader that will read selected records only.

    :param transport: The transport the pack file is located on.

    :param filename: The filename of the pack file.

    :param requested_records: The record offset, length tuples as returned

        by add_bytes_record for the desired records.

    """

    readv_blocks = [(0, len(FORMAT_ONE)+1)]

    readv_blocks.extend(requested_records)

    result = ContainerReader(ReadVFile(

        transport.readv(filename, readv_blocks)))

    return result

class BaseReader(object):

    def __init__(self, source_file):

        """Constructor.

        :param source_file: a file-like object with `read` and `readline`

            methods.

        """

        self._source = source_file

    def reader_func(self, length=None):

        return self._source.read(length)

    def _read_line(self):

        line = self._source.readline()

        if not line.endswith('\n'):

            raise errors.UnexpectedEndOfContainerError()

        return line.rstrip('\n')

class ContainerReader(BaseReader):

    """A class for reading Bazaar's container format."""

    def iter_records(self):

        """Iterate over the container, yielding each record as it is read.

        Each yielded record will be a 2-tuple of (names, callable), where names

        is a ``list`` and bytes is a function that takes one argument,

        ``max_length``.

        You **must not** call the callable after advancing the interator to the

        next record.  That is, this code is invalid::

            record_iter = container.iter_records()

            names1, callable1 = record_iter.next()

            names2, callable2 = record_iter.next()

            bytes1 = callable1(None)

        As it will give incorrect results and invalidate the state of the

        ContainerReader.

        :raises ContainerError: if any sort of containter corruption is

            detected, e.g. UnknownContainerFormatError is the format of the

            container is unrecognised.

        :seealso: ContainerReader.read

        """

        self._read_format()

        return self._iter_records()

    def iter_record_objects(self):

        """Iterate over the container, yielding each record as it is read.

        Each yielded record will be an object with ``read`` and ``validate``

        methods.  Like with iter_records, it is not safe to use a record object

        after advancing the iterator to yield next record.

        :raises ContainerError: if any sort of containter corruption is

            detected, e.g. UnknownContainerFormatError is the format of the

            container is unrecognised.

        :seealso: iter_records

        """

        self._read_format()

        return self._iter_record_objects()

    def _iter_records(self):

        for record in self._iter_record_objects():

            yield record.read()

    def _iter_record_objects(self):

        while True:

            record_kind = self.reader_func(1)

            if record_kind == 'B':

                # Bytes record.

                reader = BytesRecordReader(self._source)

                yield reader

            elif record_kind == 'E':

                # End marker.  There are no more records.

                return

            elif record_kind == '':

                # End of stream encountered, but no End Marker record seen, so

                # this container is incomplete.

                raise errors.UnexpectedEndOfContainerError()

            else:

                # Unknown record type.

                raise errors.UnknownRecordTypeError(record_kind)

    def _read_format(self):

        format = self._read_line()

        if format != FORMAT_ONE:

            raise errors.UnknownContainerFormatError(format)

    def validate(self):

        """Validate this container and its records.

        Validating consumes the data stream just like iter_records and

        iter_record_objects, so you cannot call it after

        iter_records/iter_record_objects.

        :raises ContainerError: if something is invalid.

        """

        all_names = set()

        for record_names, read_bytes in self.iter_records():

            read_bytes(None)

            for name_tuple in record_names:

                for name in name_tuple:

                    _check_name_encoding(name)

                # Check that the name is unique.  Note that Python will refuse

                # to decode non-shortest forms of UTF-8 encoding, so there is no

                # risk that the same unicode string has been encoded two

                # different ways.

                if name_tuple in all_names:

                    raise errors.DuplicateRecordNameError(name_tuple)

                all_names.add(name_tuple)

        excess_bytes = self.reader_func(1)

        if excess_bytes != '':

            raise errors.ContainerHasExcessDataError(excess_bytes)

class BytesRecordReader(BaseReader):

    def read(self):

        """Read this record.

        You can either validate or read a record, you can't do both.

        :returns: A tuple of (names, callable).  The callable can be called

            repeatedly to obtain the bytes for the record, with a max_length

            argument.  If max_length is None, returns all the bytes.  Because

            records can be arbitrarily large, using None is not recommended

            unless you have reason to believe the content will fit in memory.

        """

        # Read the content length.

        length_line = self._read_line()

        try:

            length = int(length_line)

        except ValueError:

            raise errors.InvalidRecordError(

                "%r is not a valid length." % (length_line,))

        # Read the list of names.

        names = []

        while True:

            name_line = self._read_line()

            if name_line == '':

                break

            name_tuple = tuple(name_line.split('\x00'))

            for name in name_tuple:

                _check_name(name)

            names.append(name_tuple)

        self._remaining_length = length

        return names, self._content_reader

    def _content_reader(self, max_length):

        if max_length is None:

            length_to_read = self._remaining_length

        else:

            length_to_read = min(max_length, self._remaining_length)

        self._remaining_length -= length_to_read

        bytes = self.reader_func(length_to_read)

        if len(bytes) != length_to_read:

            raise errors.UnexpectedEndOfContainerError()

        return bytes

    def validate(self):

        """Validate this record.

        You can either validate or read, you can't do both.

        :raises ContainerError: if this record is invalid.

        """

        names, read_bytes = self.read()

        for name_tuple in names:

            for name in name_tuple:

                _check_name_encoding(name)

        read_bytes(None)