58 lines
1.9 KiB
Python
58 lines
1.9 KiB
Python
#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# 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, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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'''
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Utilities for creating short ID strings based on a random UUID. The IDs
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each comprise 12 (lower-case) alphanumeric characters.
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'''
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import base64
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import uuid
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def _to_byte_string(value, num_bits):
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'''
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Convert an integer to a big-endian string of bytes, with any padding
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required added at the end (i.e. after the least-significant bit).
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'''
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shifts = xrange(num_bits - 8, -8, -8)
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byte_at = lambda off: (value >> off if off >= 0 else value << -off) & 0xff
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return ''.join(chr(byte_at(offset)) for offset in shifts)
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def get_id(source_uuid):
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'''
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Derive a short (12 character) id from a random UUID.
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The supplied UUID must be a version 4 UUID object.
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'''
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if isinstance(source_uuid, basestring):
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source_uuid = uuid.UUID(source_uuid)
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if source_uuid.version != 4:
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raise ValueError(_('Invalid UUID version (%d)') % source_uuid.version)
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# The "time" field of a v4 UUID contains 60 random bits
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# (see RFC4122, Section 4.4)
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random_bytes = _to_byte_string(source_uuid.time, 60)
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# The first 12 bytes (= 60 bits) of base32-encoded output is our data
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encoded = base64.b32encode(random_bytes)[:12]
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return encoded.lower()
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def generate_id():
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'''
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Generate a short (12 character), random id.
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'''
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return get_id(uuid.uuid4())
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