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Fix compatibility of Tuple's hash function #3460

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Fix compatibility of Tuple's hash function #3460

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2 changes: 0 additions & 2 deletions Lib/test/test_tuple.py
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Original file line number Diff line number Diff line change
Expand Up @@ -77,8 +77,6 @@ def f():
# We expect tuples whose base components have deterministic hashes to
# have deterministic hashes too - and, indeed, the same hashes across
# platforms with hash codes of the same bit width.
# TODO: RUSTPYTHON
@unittest.expectedFailure
def test_hash_exact(self):
def check_one_exact(t, e32, e64):
got = hash(t)
Expand Down
42 changes: 38 additions & 4 deletions vm/src/builtins/tuple.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,8 @@
use super::{PositionIterInternal, PyGenericAlias, PyStrRef, PyType, PyTypeRef};
use crate::common::{hash::PyHash, lock::PyMutex};
use crate::common::{
hash::{PyHash, PyUHash},
lock::PyMutex,
};
use crate::object::{Traverse, TraverseFn};
use crate::{
AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject,
Expand Down Expand Up @@ -589,7 +592,38 @@ impl<T: TransmuteFromObject> ToPyObject for PyTupleTyped<T> {
}

pub(super) fn tuple_hash(elements: &[PyObjectRef], vm: &VirtualMachine) -> PyResult<PyHash> {
// TODO: See #3460 for the correct implementation.
// https://github.com/RustPython/RustPython/pull/3460
crate::utils::hash_iter(elements.iter(), vm)
#[cfg(target_pointer_width = "64")]
const PRIME1: PyUHash = 11400714785074694791;
#[cfg(target_pointer_width = "64")]
const PRIME2: PyUHash = 14029467366897019727;
#[cfg(target_pointer_width = "64")]
const PRIME5: PyUHash = 2870177450012600261;
#[cfg(target_pointer_width = "64")]
const ROTATE: u32 = 31;

#[cfg(target_pointer_width = "32")]
const PRIME1: PyUHash = 2654435761;
#[cfg(target_pointer_width = "32")]
const PRIME2: PyUHash = 2246822519;
#[cfg(target_pointer_width = "32")]
const PRIME5: PyUHash = 374761393;
#[cfg(target_pointer_width = "32")]
const ROTATE: u32 = 13;

let mut acc = PRIME5;
let len = elements.len() as PyUHash;

for val in elements {
let lane = val.hash(vm)? as PyUHash;
acc = acc.wrapping_add(lane.wrapping_mul(PRIME2));
acc = acc.rotate_left(ROTATE);
acc = acc.wrapping_mul(PRIME1);
}

acc = acc.wrapping_add(len ^ (PRIME5 ^ 3527539));

if acc as PyHash == -1 {
return Ok(1546275796);
}
Ok(acc as PyHash)
}
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