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81 lines
2.5 KiB
Python
81 lines
2.5 KiB
Python
import secrets
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import time
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class Snowflake:
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"""
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Snowflake ID generator and parser.
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"""
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# Epoch is 2022/1/1 at midnight, as these are used for _created_ times in our
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# own database, not original publish times (which would need an earlier one)
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EPOCH = 1641020400
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TYPE_POST = 0b000
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TYPE_POST_INTERACTION = 0b001
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TYPE_IDENTITY = 0b010
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TYPE_REPORT = 0b011
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TYPE_FOLLOW = 0b100
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@classmethod
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def generate(cls, type_id: int) -> int:
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"""
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Generates a snowflake-style ID for the given "type". They are designed
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to fit inside 63 bits (a signed bigint)
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ID layout is:
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* 41 bits of millisecond-level timestamp (enough for EPOCH + 69 years)
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* 19 bits of random data (1% chance of clash at 10000 per millisecond)
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* 3 bits of type information
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We use random data rather than a sequence ID to try and avoid pushing
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this job onto the DB - we may do that in future. If a clash does
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occur, the insert will fail and Stator will retry the work for anything
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that's coming in remotely, leaving us to just handle that scenario for
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our own posts, likes, etc.
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"""
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# Get the current time in milliseconds
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now: int = int((time.time() - cls.EPOCH) * 1000)
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# Generate random data
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rand_seq: int = secrets.randbits(19)
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# Compose them together
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return (now << 22) | (rand_seq << 3) | type_id
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@classmethod
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def get_type(cls, snowflake: int) -> int:
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"""
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Returns the type of a given snowflake ID
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"""
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if snowflake < (1 << 22):
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raise ValueError("Not a valid Snowflake ID")
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return snowflake & 0b111
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@classmethod
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def get_time(cls, snowflake: int) -> float:
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"""
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Returns the generation time (in UNIX timestamp seconds) of the ID
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"""
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if snowflake < (1 << 22):
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raise ValueError("Not a valid Snowflake ID")
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return ((snowflake >> 22) / 1000) + cls.EPOCH
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# Handy pre-baked methods for django model defaults
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@classmethod
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def generate_post(cls) -> int:
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return cls.generate(cls.TYPE_POST)
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@classmethod
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def generate_post_interaction(cls) -> int:
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return cls.generate(cls.TYPE_POST_INTERACTION)
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@classmethod
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def generate_identity(cls) -> int:
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return cls.generate(cls.TYPE_IDENTITY)
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@classmethod
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def generate_report(cls) -> int:
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return cls.generate(cls.TYPE_REPORT)
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@classmethod
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def generate_follow(cls) -> int:
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return cls.generate(cls.TYPE_FOLLOW)
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