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# Copyright (C) 2009 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
"""Python implementation of _search_key functions, etc."""
import zlib
import struct
_LeafNode = None
_InternalNode = None
_unknown = None
def _crc32(bit):
# Depending on python version and platform, zlib.crc32 will return either a
# signed (<= 2.5 >= 3.0) or an unsigned (2.5, 2.6).
# http://docs.python.org/library/zlib.html recommends using a mask to force
# an unsigned value to ensure the same numeric value (unsigned) is obtained
# across all python versions and platforms.
# Note: However, on 32-bit platforms this causes an upcast to PyLong, which
# are generally slower than PyInts. However, if performance becomes
# critical, we should probably write the whole thing as an extension
# anyway.
# Though we really don't need that 32nd bit of accuracy. (even 2**24
# is probably enough node fan out for realistic trees.)
return zlib.crc32(bit)&0xFFFFFFFF
def _search_key_16(key):
"""Map the key tuple into a search key string which has 16-way fan out."""
return '\x00'.join(['%08X' % _crc32(bit) for bit in key])
def _search_key_255(key):
"""Map the key tuple into a search key string which has 255-way fan out.
We use 255-way because '\n' is used as a delimiter, and causes problems
while parsing.
"""
bytes = '\x00'.join([struct.pack('>L', _crc32(bit)) for bit in key])
return bytes.replace('\n', '_')
def _deserialise_leaf_node(bytes, key, search_key_func=None):
"""Deserialise bytes, with key key, into a LeafNode.
:param bytes: The bytes of the node.
:param key: The key that the serialised node has.
"""
global _unknown, _LeafNode, _InternalNode
if _LeafNode is None:
from bzrlib import chk_map
_unknown = chk_map._unknown
_LeafNode = chk_map.LeafNode
_InternalNode = chk_map.InternalNode
result = _LeafNode(search_key_func=search_key_func)
# Splitlines can split on '\r' so don't use it, split('\n') adds an
# extra '' if the bytes ends in a final newline.
lines = bytes.split('\n')
trailing = lines.pop()
if trailing != '':
raise AssertionError('We did not have a final newline for %s'
% (key,))
items = {}
if lines[0] != 'chkleaf:':
raise ValueError("not a serialised leaf node: %r" % bytes)
maximum_size = int(lines[1])
width = int(lines[2])
length = int(lines[3])
prefix = lines[4]
pos = 5
while pos < len(lines):
line = prefix + lines[pos]
elements = line.split('\x00')
pos += 1
if len(elements) != width + 1:
raise AssertionError(
'Incorrect number of elements (%d vs %d) for: %r'
% (len(elements), width + 1, line))
num_value_lines = int(elements[-1])
value_lines = lines[pos:pos+num_value_lines]
pos += num_value_lines
value = '\n'.join(value_lines)
items[tuple(elements[:-1])] = value
if len(items) != length:
raise AssertionError("item count (%d) mismatch for key %s,"
" bytes %r" % (length, key, bytes))
result._items = items
result._len = length
result._maximum_size = maximum_size
result._key = key
result._key_width = width
result._raw_size = (sum(map(len, lines[5:])) # the length of the suffix
+ (length)*(len(prefix))
+ (len(lines)-5))
if not items:
result._search_prefix = None
result._common_serialised_prefix = None
else:
result._search_prefix = _unknown
result._common_serialised_prefix = prefix
if len(bytes) != result._current_size():
raise AssertionError('_current_size computed incorrectly')
return result
def _deserialise_internal_node(bytes, key, search_key_func=None):
global _unknown, _LeafNode, _InternalNode
if _InternalNode is None:
from bzrlib import chk_map
_unknown = chk_map._unknown
_LeafNode = chk_map.LeafNode
_InternalNode = chk_map.InternalNode
result = _InternalNode(search_key_func=search_key_func)
# Splitlines can split on '\r' so don't use it, remove the extra ''
# from the result of split('\n') because we should have a trailing
# newline
lines = bytes.split('\n')
if lines[-1] != '':
raise ValueError("last line must be ''")
lines.pop(-1)
items = {}
if lines[0] != 'chknode:':
raise ValueError("not a serialised internal node: %r" % bytes)
maximum_size = int(lines[1])
width = int(lines[2])
length = int(lines[3])
common_prefix = lines[4]
for line in lines[5:]:
line = common_prefix + line
prefix, flat_key = line.rsplit('\x00', 1)
items[prefix] = (flat_key,)
if len(items) == 0:
raise AssertionError("We didn't find any item for %s" % key)
result._items = items
result._len = length
result._maximum_size = maximum_size
result._key = key
result._key_width = width
# XXX: InternalNodes don't really care about their size, and this will
# change if we add prefix compression
result._raw_size = None # len(bytes)
result._node_width = len(prefix)
result._search_prefix = common_prefix
return result
_key_type = tuple
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