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
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
|
#!/usr/bin/env python
# -*- mode: python -*-
# -*- coding: utf-8 -*-
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements. See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you 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
#
# https://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.
import hashlib
from io import StringIO
from avro.schema import ARRAY, ENUM, ERROR, FIXED, MAP, RECORD, UNION
def ToParsingCanonicalForm(schema):
"""Returns the "Parsing Canonical Form" of a schema.
The Parsing Canonical Form is defined by the Avro specification.
Args:
schema: The Schema to be normalized.
Returns:
A string containing the canonical JSON schema.
"""
env = {}
with StringIO() as output:
return _BuildCanonicalForm(env, schema, output).getvalue()
def _BuildCanonicalForm(env, s, o):
first_time = True
st = s.type
# The Java Avro implementation represents error records as records with
# a separate error flag. For canonicalization to be consistent across
# implementations we must normalize errors to have record type here.
if st == ERROR:
st = RECORD
if st == UNION:
o.write('[')
for b in s.schemas:
if not first_time:
o.write(',')
else:
first_time = False
_BuildCanonicalForm(env, b, o)
o.write(']')
return o
elif st in {ARRAY, MAP}:
o.write('{"type":"')
o.write(st)
o.write('"')
if st == ARRAY:
o.write(',"items":')
_BuildCanonicalForm(env, s.items, o)
else:
o.write(',"values":')
_BuildCanonicalForm(env, s.values, o)
o.write('}')
return o
elif st in {ENUM, FIXED, RECORD}:
name = s.fullname
if name in env:
o.write(env[name])
return o
qname = '"%s"' % name
env[name] = qname
o.write('{"name":')
o.write(qname)
o.write(',"type":"')
o.write(st)
o.write('"')
if st == ENUM:
o.write(',"symbols":[')
for enum_symbol in s.symbols:
if not first_time:
o.write(',')
else:
first_time = False
o.write('"')
o.write(enum_symbol)
o.write('"')
o.write("]")
elif st == FIXED:
o.write(',"size":')
o.write(str(s.size))
else: # st == RECORD or st == ERROR
o.write(',"fields":[')
for f in s.fields:
if not first_time:
o.write(',')
else:
first_time = False
o.write('{"name":"')
o.write(f.name)
o.write('"')
o.write(',"type":')
_BuildCanonicalForm(env, f.type, o)
o.write('}')
o.write(']')
o.write('}')
return o
else:
# boolean, bytes, double, float, int, long, null, string
o.write('"')
o.write(st)
o.write('"')
return o
def Fingerprint(parsing_normal_form_schema, fingerprint_algorithm_name):
"""Returns a fingerprint of a string of bytes.
Args:
parsing_normal_form_schema: A string containing an Avro
schema in parsing normal form, such as one obtained
by passing a schema object to ToParsingCanonicalForm()
fingerprint_algorithm_name: One of the algorithm names
returned by FingerprintAlgorithmNames(), typically
'CRC-64-AVRO', 'md5' or 'sha256'. See the Avro
specification for guidance on selecting a
fingerprinting algorithm.
Returns:
A bytes object containing the schema fingerprint.
"""
if fingerprint_algorithm_name not in FingerprintAlgorithmNames():
raise ValueError("Unknown schema fingerprint algorithm {!r}"
.format(fingerprint_algorithm_name))
fingerprint_algorithm = _FINGERPRINT_ALIASES_TO_NAMES[fingerprint_algorithm_name]
data = parsing_normal_form_schema.encode('utf-8')
if fingerprint_algorithm in _CRC_64_AVRO:
return _Crc64AvroFingerprint(data)
h = hashlib.new(fingerprint_algorithm, data)
return h.digest()
_CRC_64_AVRO = frozenset({'CRC-64-AVRO'})
_PYTHON_DIGEST_NAMES = frozenset(hashlib.algorithms_guaranteed | _CRC_64_AVRO)
# These are the only three algorithms which Java implementations are
# *required* to support. We provide aliases for them here when the
# Python implementation also supports them, so that key fingerprint
# algorithm names can interoperate between Java and Python.
_JAVA_TO_PYTHON_DIGEST_NAMES = {
'MD5': 'md5',
'SHA-1': 'sha1',
'SHA-256': 'sha256'}
_AVAILABLE_JAVA_TO_PYTHON_DIGEST_NAMES = {
j: p for j, p in _JAVA_TO_PYTHON_DIGEST_NAMES.items()
if p in hashlib.algorithms_guaranteed}
_FINGERPRINT_ALIASES_TO_NAMES = {name: name for name in _PYTHON_DIGEST_NAMES}
_FINGERPRINT_ALIASES_TO_NAMES.update(_AVAILABLE_JAVA_TO_PYTHON_DIGEST_NAMES)
def FingerprintAlgorithmNames():
"""A collection of fingerprint algorithm names.
The same algorithm may be associated with more than one entry
in this collection. For example, 'SHA-1' and 'sha1' might both
be present in the result, in order to facilitate the interoperability
of algorithm names between Python and, say, Java Avro
implementations.
Returns:
A set of strings containing algorithm names, any
one of which can be used as the fingerprint_algorithm
argument of Fingerprint()
"""
return _FINGERPRINT_ALIASES_TO_NAMES.keys()
_EMPTY64 = 0xc15d213aa4d7a795
def _Crc64AvroFingerprint(data):
"""The 64-bit Rabin Fingerprint.
As described in the Avro specification.
Args:
data: A bytes object containing the UTF-8 encoded parsing canonical
form of an Avro schema.
Returns:
A bytes object with a length of eight.
"""
if _FP_TABLE is None:
_PopulateFpTable()
result = _EMPTY64
for b in data:
result = (result >> 8) ^ _FP_TABLE[(result ^ b) & 0xff]
# Although not mentioned in the Avro specification, the Java
# implementation gives fingerprint bytes in little-endian order
return result.to_bytes(length=8, byteorder='little', signed=False)
_FP_TABLE = None
def _PopulateFpTable():
global _FP_TABLE
_FP_TABLE = []
for i in range(256):
fp = i
for j in range(8):
mask = -(fp & 1)
fp = (fp >> 1) ^ (_EMPTY64 & mask)
_FP_TABLE.append(fp)
|
