45 lines
1.6 KiB
Python
45 lines
1.6 KiB
Python
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# Copyright (C) 2021 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import base64
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class BytesRule:
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"""A marshal between Python strings and protobuf bytes.
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Note: this conversion is asymmetric because Python does have a bytes type.
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It is sometimes necessary to convert proto bytes fields to strings, e.g. for
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JSON encoding, marshalling a message to a dict. Because bytes fields can
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represent arbitrary data, bytes fields are base64 encoded when they need to
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be represented as strings.
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It is necessary to have the conversion be bidirectional, i.e.
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my_message == MyMessage(MyMessage.to_dict(my_message))
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To accomplish this, we need to intercept assignments from strings and
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base64 decode them back into bytes.
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"""
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def to_python(self, value, *, absent: bool = None):
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return value
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def to_proto(self, value):
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if isinstance(value, str):
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value = value.encode("utf-8")
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value += b"=" * (4 - len(value) % 4) # padding
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value = base64.urlsafe_b64decode(value)
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return value
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