feat: support for snapshot cheatcodes #427
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karmacoma-eth
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Dec 11, 2024
daejunpark
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src/halmos/cheatcodes.py
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| """ | ||
| Generates a snapshot ID by hashing the current state (code, storage, and balance). | ||
| """ | ||
| m = hashlib.sha3_256() |
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since we don't need the hash to be cryptographically secure for this, we'd be better off using a high quality regular hash function like xxh3_64 from https://pypi.org/project/xxhash/, about 10x faster:
# built-in sha3_256, not keccak
$ python -m timeit --setup="from hashlib import sha3_256" "sha3_256(b'').digest()"
500000 loops, best of 5: 892 nsec per loop
# xxh64, requires `pip install xxhash`
$ python -m timeit --setup="from xxhash import xxh64_digest" "xxh64_digest(b'')"
2000000 loops, best of 5: 101 nsec per loop
# xxh3_64, requires `pip install xxhash`
$ python -m timeit --setup="from xxhash import xxh3_64_digest" "xxh3_64_digest(b'')"
5000000 loops, best of 5: 98.3 nsec per loop
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thanks for suggestion!
| addr = addr if isinstance(addr, int) else addr.as_long() | ||
| m.update(int.to_bytes(addr, length=32)) | ||
| # simply the object address is used, as code remains unchanged after deployment | ||
| m.update(int.to_bytes(id(code), length=32)) |
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spidey sense: I would normally avoid using the value of id in computations, since it changes from run to run
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agree, but it's acceptable in this case. actually, i'm not sure if z3.get_id() would be guaranteed to be deterministic. we also use uuid() for unique variable naming, so they would change from run to run anyway.
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support for state and storage snapshots:
note: two structurally identical symbolic storages/states are given the same snapshot id, but those that are semantically equivalent may not be assigned the same snapshot id. (see SnapshotTest for examples.)