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# -*- coding: utf-8 -*-
#
# File: portato/eix/parser.py
# This file is part of the Portato-Project, a graphical portage-frontend.
#
# Copyright (C) 2006-2009 René 'Necoro' Neumann
# This is free software. You may redistribute copies of it under the terms of
# the GNU General Public License version 2.
# There is NO WARRANTY, to the extent permitted by law.
#
# Written by René 'Necoro' Neumann <necoro@necoro.net>
from __future__ import absolute_import, with_statement
import os
import struct
from .helper import debug
from . import exceptions as ex
def _get_bytes (file, length, expect_list = False):
s = file.read(length)
if len(s) != length:
raise EndOfFileException, file.name
if length == 1 and not expect_list:
return ord(s) # is faster than unpack and we have a scalar
else:
return struct.unpack("%sB" % length, s)
def number (file):
n = _get_bytes(file, 1)
if n < 0xFF:
value = n
else:
count = 0
while (n == 0xFF):
count += 1
n = _get_bytes(file, 1)
if n == 0:
n = 0xFF # 0xFF is encoded as 0xFF 0x00
count -= 1
value = n << (count*8)
if count > 0:
rest = _get_bytes(file, count, expect_list = True)
for i, r in enumerate(rest):
value += r << ((count - i - 1)*8)
return value
def vector (file, get_type, skip = False):
nelems = number(file)
if skip:
for i in range(nelems):
get_type(file, skip = True)
else:
return [get_type(file) for i in range(nelems)]
def string (file, skip = False):
nelems = number(file)
if skip:
file.seek(nelems, os.SEEK_CUR)
else:
s = file.read(nelems)
if len(s) != nelems:
raise EndOfFileException, file.name
return s
def overlay (file, skip = False):
if skip:
string(file, skip = True) # path
string(file, skip = True) # label
else:
return (string(file), string(file))
class LazyElement (object):
def __init__ (self, get_type, file):
self.file = file
self.get_type = get_type
self._value = None
self.pos = file.tell()
get_type(skip=True) # skip it for the moment
@property
def value (self):
if self._value is None:
old_pos = self.file.tell()
self.file.seek(self.pos)
self._value = self.get_type(skip = False)
self.file.seek(old_pos)
return self._value
def __call__ (self):
return self.value
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