61 lines
1.9 KiB
Python
61 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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"""Utilities for creating short ID strings based on a random UUID.
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The IDs 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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import six
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from heat.common.i18n import _
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def _to_byte_string(value, num_bits):
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"""Convert an integer to a big-endian string of bytes with padding.
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Padding is added at the end (i.e. after the least-significant bit) if
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required.
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"""
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shifts = six.moves.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(six.unichr(byte_at(offset)) for offset in shifts)
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def get_id(source_uuid):
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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, six.string_types):
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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.encode('latin-1'))[:12]
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return encoded.lower().decode('latin-1')
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def generate_id():
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"""Generate a short (12 character), random id."""
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return get_id(uuid.uuid4())
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