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# EFILTER Forensic Query Language
#
# Copyright 2015 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Implements IRepeated for text files and some common formats.
"""
__author__ = "Adam Sindelar <adamsh@google.com>"
import six
import threading
from efilter.protocols import counted
from efilter.protocols import repeated
class LazyLineReader(object):
"""Reads in a line at a time and supports restarting."""
fd = None
_seek_lock = None
def __init__(self, fd):
self.fd = fd
self._seek_lock = threading.Lock()
def __iter__(self):
return self.getvalues()
def __del__(self):
"""Close 'fd' if it hasn't been closed already.
If LazyLineReader was instantiated using EFILTER's stdlib.io functions
then it won't be inside of a with block and we need to close fd when
the repeated is deallocated.
"""
if not self.fd.closed:
self.fd.close()
# IRepeated implementation.
def readline_at_offset(self, offset):
self._seek_lock.acquire()
self.fd.seek(offset)
line = self.fd.readline()
new_offset = self.fd.tell()
self._seek_lock.release()
return line, new_offset
def getvalues(self):
line, offset = self.readline_at_offset(0)
while line:
yield line
line, offset = self.readline_at_offset(offset)
def value_type(self):
return six.string_types[0]
def value_eq(self, other):
if isinstance(other, type(self)):
return self.fd == other.fd
return list(self) == list(other)
def value_apply(self, f):
for value in self:
yield f(value)
# Counted implementation.
def count(self):
c = 0
for _ in self:
c += 1
return c
counted.ICounted.implicit_static(for_type=LazyLineReader)
repeated.IRepeated.implicit_static(LazyLineReader)
if six.PY2:
# Python 3 doesn't have a file class. open() just returns a StringIO
repeated.lines.implement(for_type=file, implementation=LazyLineReader)
if six.PY3:
import io
repeated.lines.implement(for_type=io.IOBase, implementation=LazyLineReader)
repeated.lines.implement(for_type=six.StringIO, implementation=LazyLineReader)
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