1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
|
# -*- coding: utf-8 -*-
# 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.
"""(EXPERIMENTAL) EFILTER abstract type system."""
import itertools
from efilter import dispatch
from efilter import protocol
from efilter.protocols import repeated
# Declarations:
# pylint: disable=unused-argument
# Determined as good trade-off between memory usage and speed based on the
# hygdata_v3 benchmark.
DEFAULT_CHUNK_SIZE = 4096
@dispatch.multimethod
def fold(reducer, chunk):
"""Reduce 'chunk' into an intermediate value."""
raise NotImplementedError()
@dispatch.multimethod
def merge(reducer, left, right):
"""Merge two intermediate values (from 'merge' or 'fold').
Returns:
Intermediate value merged from 'left' and 'right'.
"""
raise NotImplementedError()
@dispatch.multimethod
def finalize(reducer, intermediate):
"""Convert the 'intermediate' to the final result of the reducer."""
raise NotImplementedError()
def generate_chunks(data, chunk_size=DEFAULT_CHUNK_SIZE):
"""Yield 'chunk_size' items from 'data' at a time."""
iterator = iter(repeated.getvalues(data))
while True:
chunk = list(itertools.islice(iterator, chunk_size))
if not chunk:
return
yield chunk
def reduce(reducer, data, chunk_size=DEFAULT_CHUNK_SIZE):
"""Repeatedly call fold and merge on data and then finalize.
Arguments:
data: Input for the fold function.
reducer: The IReducer to use.
chunk_size: How many items should be passed to fold at a time?
Returns:
Return value of finalize.
"""
if not chunk_size:
return finalize(reducer, fold(reducer, data))
# Splitting the work up into chunks allows us to, e.g. reduce a large file
# without loading everything into memory, while still being significantly
# faster than repeatedly calling the fold function for every element.
chunks = generate_chunks(data, chunk_size)
intermediate = fold(reducer, next(chunks))
for chunk in chunks:
intermediate = merge(reducer, intermediate, fold(reducer, chunk))
return finalize(reducer, intermediate)
class IReducer(protocol.Protocol):
_required_functions = (fold, finalize, merge)
class Compose(object):
"""Reducer that runs multiple other reducers on the same input."""
reducers = None
def __init__(self, *reducers):
self.reducers = reducers
def fold(self, chunk):
return [fold(r, chunk) for r in self.reducers]
def merge(self, left, right):
result = []
for idx, r in enumerate(self.reducers):
result.append(merge(r, left[idx], right[idx]))
return result
def finalize(self, intermediate):
result = []
for idx, r in enumerate(self.reducers):
result.append(finalize(r, intermediate[idx]))
return result
IReducer.implicit_static(Compose)
class Map(object):
"""Reducer that converts the input before calling the delegate."""
delegate = None
mapper = None
def __init__(self, delegate, mapper):
if not callable(mapper):
raise TypeError("Mapper must be callable.")
self.mapper = mapper
self.delegate = delegate
def fold(self, chunk):
return self.delegate.fold(tuple(self.mapper(chunk)))
def merge(self, left, right):
return self.delegate.merge(left, right)
def finalize(self, intermediate):
return self.delegate.finalize(intermediate)
IReducer.implicit_static(Map)
|
