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WIP: Add dynamic borrow checking for dereferencing NumPy arrays.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,170 @@ | ||
| use std::cell::UnsafeCell; | ||
| use std::collections::hash_map::{Entry, HashMap}; | ||
| use std::ops::{Deref, DerefMut}; | ||
|
|
||
| use ndarray::{ArrayView, ArrayViewMut, Dimension}; | ||
| use pyo3::{FromPyObject, PyAny, PyResult}; | ||
|
|
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| use crate::array::PyArray; | ||
| use crate::dtype::Element; | ||
|
|
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| thread_local! { | ||
| static BORROW_FLAGS: UnsafeCell<HashMap<usize, isize>> = UnsafeCell::new(HashMap::new()); | ||
| } | ||
|
|
||
| pub struct PyArrayRef<'a, T, D> { | ||
| array: &'a PyArray<T, D>, | ||
| view: ArrayView<'a, T, D>, | ||
| } | ||
|
|
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| impl<'a, T, D> Deref for PyArrayRef<'a, T, D> { | ||
| type Target = ArrayView<'a, T, D>; | ||
|
|
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| fn deref(&self) -> &Self::Target { | ||
| &self.view | ||
| } | ||
| } | ||
|
|
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| impl<'py, T: Element, D: Dimension> FromPyObject<'py> for PyArrayRef<'py, T, D> { | ||
| fn extract(obj: &'py PyAny) -> PyResult<Self> { | ||
| let array: &'py PyArray<T, D> = obj.extract()?; | ||
| Ok(array.as_array()) | ||
| } | ||
| } | ||
|
|
||
| impl<'a, T, D> PyArrayRef<'a, T, D> | ||
| where | ||
| T: Element, | ||
| D: Dimension, | ||
| { | ||
| pub(crate) fn try_new(array: &'a PyArray<T, D>) -> Option<Self> { | ||
| let address = array as *const PyArray<T, D> as usize; | ||
|
|
||
| BORROW_FLAGS.with(|borrow_flags| { | ||
| // SAFETY: Called on a thread local variable in a leaf function. | ||
| let borrow_flags = unsafe { &mut *borrow_flags.get() }; | ||
|
|
||
| match borrow_flags.entry(address) { | ||
| Entry::Occupied(entry) => { | ||
| let readers = entry.into_mut(); | ||
|
|
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| let new_readers = readers.wrapping_add(1); | ||
|
|
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| if new_readers <= 0 { | ||
| cold(); | ||
| return None; | ||
| } | ||
|
|
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| *readers = new_readers; | ||
| } | ||
| Entry::Vacant(entry) => { | ||
| entry.insert(1); | ||
| } | ||
| } | ||
|
|
||
| // SAFETY: Thread-local borrow flags ensure aliasing discipline on this thread, | ||
| // and `PyArray` is neither `Send` nor `Sync` | ||
| let view = unsafe { array.as_array_unchecked() }; | ||
|
|
||
| Some(Self { array, view }) | ||
| }) | ||
| } | ||
| } | ||
|
|
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| impl<'a, T, D> Drop for PyArrayRef<'a, T, D> { | ||
| fn drop(&mut self) { | ||
| let address = self.array as *const PyArray<T, D> as usize; | ||
|
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||
| BORROW_FLAGS.with(|borrow_flags| { | ||
| // SAFETY: Called on a thread local variable in a leaf function. | ||
| let borrow_flags = unsafe { &mut *borrow_flags.get() }; | ||
|
|
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| let readers = borrow_flags.get_mut(&address).unwrap(); | ||
|
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| *readers -= 1; | ||
|
|
||
| if *readers == 0 { | ||
| borrow_flags.remove(&address).unwrap(); | ||
| } | ||
| }); | ||
| } | ||
| } | ||
|
|
||
| pub struct PyArrayRefMut<'a, T, D> { | ||
| array: &'a PyArray<T, D>, | ||
| view: ArrayViewMut<'a, T, D>, | ||
| } | ||
|
|
||
| impl<'a, T, D> Deref for PyArrayRefMut<'a, T, D> { | ||
| type Target = ArrayViewMut<'a, T, D>; | ||
|
|
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| fn deref(&self) -> &Self::Target { | ||
| &self.view | ||
| } | ||
| } | ||
|
|
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| impl<'a, T, D> DerefMut for PyArrayRefMut<'a, T, D> { | ||
| fn deref_mut(&mut self) -> &mut Self::Target { | ||
| &mut self.view | ||
| } | ||
| } | ||
|
|
||
| impl<'py, T: Element, D: Dimension> FromPyObject<'py> for PyArrayRefMut<'py, T, D> { | ||
| fn extract(obj: &'py PyAny) -> PyResult<Self> { | ||
| let array: &'py PyArray<T, D> = obj.extract()?; | ||
| Ok(array.as_array_mut()) | ||
| } | ||
| } | ||
|
|
||
| impl<'a, T, D> PyArrayRefMut<'a, T, D> | ||
| where | ||
| T: Element, | ||
| D: Dimension, | ||
| { | ||
| pub(crate) fn try_new(array: &'a PyArray<T, D>) -> Option<Self> { | ||
| let address = array as *const PyArray<T, D> as usize; | ||
|
|
||
| BORROW_FLAGS.with(|borrow_flags| { | ||
| // SAFETY: Called on a thread local variable in a leaf function. | ||
| let borrow_flags = unsafe { &mut *borrow_flags.get() }; | ||
|
|
||
| match borrow_flags.entry(address) { | ||
| Entry::Occupied(entry) => { | ||
| let writers = entry.into_mut(); | ||
|
|
||
| if *writers != 0 { | ||
| cold(); | ||
| return None; | ||
| } | ||
|
|
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| *writers = -1; | ||
| } | ||
| Entry::Vacant(entry) => { | ||
| entry.insert(-1); | ||
| } | ||
| } | ||
|
|
||
| // SAFETY: Thread-local borrow flags ensure aliasing discipline on this thread, | ||
| // and `PyArray` is neither `Send` nor `Sync` | ||
| let view = unsafe { array.as_array_mut_unchecked() }; | ||
|
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| Some(Self { array, view }) | ||
| }) | ||
| } | ||
| } | ||
|
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| impl<'a, T, D> Drop for PyArrayRefMut<'a, T, D> { | ||
| fn drop(&mut self) { | ||
| let address = self.array as *const PyArray<T, D> as usize; | ||
|
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| BORROW_FLAGS.with(|borrow_flags| { | ||
| // SAFETY: Called on a thread local variable in a leaf function. | ||
| let borrow_flags = unsafe { &mut *borrow_flags.get() }; | ||
|
|
||
| borrow_flags.remove(&address).unwrap(); | ||
| }); | ||
| } | ||
| } | ||
| #[cold] | ||
| #[inline(always)] | ||
| fn cold() {} |
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