|
|
// ref_sharing.rs
|
|
|
//
|
|
|
// Copyright 2019 Raphaël Gomès <rgomes@octobus.net>
|
|
|
//
|
|
|
// Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
|
// of this software and associated documentation files (the "Software"), to
|
|
|
// deal in the Software without restriction, including without limitation the
|
|
|
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
|
|
|
// sell copies of the Software, and to permit persons to whom the Software is
|
|
|
// furnished to do so, subject to the following conditions:
|
|
|
//
|
|
|
// The above copyright notice and this permission notice shall be included in
|
|
|
// all copies or substantial portions of the Software.
|
|
|
//
|
|
|
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
|
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
|
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
|
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
|
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
|
|
|
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
|
|
|
// IN THE SOFTWARE.
|
|
|
|
|
|
//! Macros for use in the `hg-cpython` bridge library.
|
|
|
|
|
|
use crate::exceptions::AlreadyBorrowed;
|
|
|
use cpython::{PyClone, PyObject, PyResult, Python};
|
|
|
use std::cell::{Cell, Ref, RefCell, RefMut};
|
|
|
|
|
|
/// Manages the shared state between Python and Rust
|
|
|
#[derive(Debug, Default)]
|
|
|
struct PySharedState {
|
|
|
leak_count: Cell<usize>,
|
|
|
mutably_borrowed: Cell<bool>,
|
|
|
}
|
|
|
|
|
|
// &PySharedState can be Send because any access to inner cells is
|
|
|
// synchronized by the GIL.
|
|
|
unsafe impl Sync for PySharedState {}
|
|
|
|
|
|
impl PySharedState {
|
|
|
fn borrow_mut<'a, T>(
|
|
|
&'a self,
|
|
|
py: Python<'a>,
|
|
|
pyrefmut: RefMut<'a, T>,
|
|
|
) -> PyResult<PyRefMut<'a, T>> {
|
|
|
if self.mutably_borrowed.get() {
|
|
|
return Err(AlreadyBorrowed::new(
|
|
|
py,
|
|
|
"Cannot borrow mutably while there exists another \
|
|
|
mutable reference in a Python object",
|
|
|
));
|
|
|
}
|
|
|
match self.leak_count.get() {
|
|
|
0 => {
|
|
|
self.mutably_borrowed.replace(true);
|
|
|
Ok(PyRefMut::new(py, pyrefmut, self))
|
|
|
}
|
|
|
// TODO
|
|
|
// For now, this works differently than Python references
|
|
|
// in the case of iterators.
|
|
|
// Python does not complain when the data an iterator
|
|
|
// points to is modified if the iterator is never used
|
|
|
// afterwards.
|
|
|
// Here, we are stricter than this by refusing to give a
|
|
|
// mutable reference if it is already borrowed.
|
|
|
// While the additional safety might be argued for, it
|
|
|
// breaks valid programming patterns in Python and we need
|
|
|
// to fix this issue down the line.
|
|
|
_ => Err(AlreadyBorrowed::new(
|
|
|
py,
|
|
|
"Cannot borrow mutably while there are \
|
|
|
immutable references in Python objects",
|
|
|
)),
|
|
|
}
|
|
|
}
|
|
|
|
|
|
/// Return a reference to the wrapped data and its state with an
|
|
|
/// artificial static lifetime.
|
|
|
/// We need to be protected by the GIL for thread-safety.
|
|
|
///
|
|
|
/// # Safety
|
|
|
///
|
|
|
/// This is highly unsafe since the lifetime of the given data can be
|
|
|
/// extended. Do not call this function directly.
|
|
|
unsafe fn leak_immutable<T>(
|
|
|
&self,
|
|
|
py: Python,
|
|
|
data: &PySharedRefCell<T>,
|
|
|
) -> PyResult<(&'static T, &'static PySharedState)> {
|
|
|
if self.mutably_borrowed.get() {
|
|
|
return Err(AlreadyBorrowed::new(
|
|
|
py,
|
|
|
"Cannot borrow immutably while there is a \
|
|
|
mutable reference in Python objects",
|
|
|
));
|
|
|
}
|
|
|
// TODO: it's weird that self is data.py_shared_state. Maybe we
|
|
|
// can move stuff to PySharedRefCell?
|
|
|
let ptr = data.as_ptr();
|
|
|
let state_ptr: *const PySharedState = &data.py_shared_state;
|
|
|
self.leak_count.replace(self.leak_count.get() + 1);
|
|
|
Ok((&*ptr, &*state_ptr))
|
|
|
}
|
|
|
|
|
|
/// # Safety
|
|
|
///
|
|
|
/// It's up to you to make sure the reference is about to be deleted
|
|
|
/// when updating the leak count.
|
|
|
fn decrease_leak_count(&self, _py: Python, mutable: bool) {
|
|
|
if mutable {
|
|
|
assert_eq!(self.leak_count.get(), 0);
|
|
|
assert!(self.mutably_borrowed.get());
|
|
|
self.mutably_borrowed.replace(false);
|
|
|
} else {
|
|
|
let count = self.leak_count.get();
|
|
|
assert!(count > 0);
|
|
|
self.leak_count.replace(count - 1);
|
|
|
}
|
|
|
}
|
|
|
}
|
|
|
|
|
|
/// `RefCell` wrapper to be safely used in conjunction with `PySharedState`.
|
|
|
///
|
|
|
/// This object can be stored in a `py_class!` object as a data field. Any
|
|
|
/// operation is allowed through the `PySharedRef` interface.
|
|
|
#[derive(Debug)]
|
|
|
pub struct PySharedRefCell<T> {
|
|
|
inner: RefCell<T>,
|
|
|
py_shared_state: PySharedState,
|
|
|
}
|
|
|
|
|
|
impl<T> PySharedRefCell<T> {
|
|
|
pub fn new(value: T) -> PySharedRefCell<T> {
|
|
|
Self {
|
|
|
inner: RefCell::new(value),
|
|
|
py_shared_state: PySharedState::default(),
|
|
|
}
|
|
|
}
|
|
|
|
|
|
fn borrow<'a>(&'a self, _py: Python<'a>) -> Ref<'a, T> {
|
|
|
// py_shared_state isn't involved since
|
|
|
// - inner.borrow() would fail if self is mutably borrowed,
|
|
|
// - and inner.borrow_mut() would fail while self is borrowed.
|
|
|
self.inner.borrow()
|
|
|
}
|
|
|
|
|
|
fn as_ptr(&self) -> *mut T {
|
|
|
self.inner.as_ptr()
|
|
|
}
|
|
|
|
|
|
// TODO: maybe this should be named as try_borrow_mut(), and use
|
|
|
// inner.try_borrow_mut(). The current implementation panics if
|
|
|
// self.inner has been borrowed, but returns error if py_shared_state
|
|
|
// refuses to borrow.
|
|
|
fn borrow_mut<'a>(&'a self, py: Python<'a>) -> PyResult<PyRefMut<'a, T>> {
|
|
|
self.py_shared_state.borrow_mut(py, self.inner.borrow_mut())
|
|
|
}
|
|
|
}
|
|
|
|
|
|
/// Sharable data member of type `T` borrowed from the `PyObject`.
|
|
|
pub struct PySharedRef<'a, T> {
|
|
|
py: Python<'a>,
|
|
|
owner: &'a PyObject,
|
|
|
data: &'a PySharedRefCell<T>,
|
|
|
}
|
|
|
|
|
|
impl<'a, T> PySharedRef<'a, T> {
|
|
|
/// # Safety
|
|
|
///
|
|
|
/// The `data` must be owned by the `owner`. Otherwise, the leak count
|
|
|
/// would get wrong.
|
|
|
pub unsafe fn new(
|
|
|
py: Python<'a>,
|
|
|
owner: &'a PyObject,
|
|
|
data: &'a PySharedRefCell<T>,
|
|
|
) -> Self {
|
|
|
Self { py, owner, data }
|
|
|
}
|
|
|
|
|
|
pub fn borrow(&self) -> Ref<'a, T> {
|
|
|
self.data.borrow(self.py)
|
|
|
}
|
|
|
|
|
|
pub fn borrow_mut(&self) -> PyResult<PyRefMut<'a, T>> {
|
|
|
self.data.borrow_mut(self.py)
|
|
|
}
|
|
|
|
|
|
/// Returns a leaked reference.
|
|
|
pub fn leak_immutable(&self) -> PyResult<PyLeakedRef<&'static T>> {
|
|
|
let state = &self.data.py_shared_state;
|
|
|
unsafe {
|
|
|
let (static_ref, static_state_ref) =
|
|
|
state.leak_immutable(self.py, self.data)?;
|
|
|
Ok(PyLeakedRef::new(
|
|
|
self.py,
|
|
|
self.owner,
|
|
|
static_ref,
|
|
|
static_state_ref,
|
|
|
))
|
|
|
}
|
|
|
}
|
|
|
}
|
|
|
|
|
|
/// Holds a mutable reference to data shared between Python and Rust.
|
|
|
pub struct PyRefMut<'a, T> {
|
|
|
py: Python<'a>,
|
|
|
inner: RefMut<'a, T>,
|
|
|
py_shared_state: &'a PySharedState,
|
|
|
}
|
|
|
|
|
|
impl<'a, T> PyRefMut<'a, T> {
|
|
|
// Must be constructed by PySharedState after checking its leak_count.
|
|
|
// Otherwise, drop() would incorrectly update the state.
|
|
|
fn new(
|
|
|
py: Python<'a>,
|
|
|
inner: RefMut<'a, T>,
|
|
|
py_shared_state: &'a PySharedState,
|
|
|
) -> Self {
|
|
|
Self {
|
|
|
py,
|
|
|
inner,
|
|
|
py_shared_state,
|
|
|
}
|
|
|
}
|
|
|
}
|
|
|
|
|
|
impl<'a, T> std::ops::Deref for PyRefMut<'a, T> {
|
|
|
type Target = RefMut<'a, T>;
|
|
|
|
|
|
fn deref(&self) -> &Self::Target {
|
|
|
&self.inner
|
|
|
}
|
|
|
}
|
|
|
impl<'a, T> std::ops::DerefMut for PyRefMut<'a, T> {
|
|
|
fn deref_mut(&mut self) -> &mut Self::Target {
|
|
|
&mut self.inner
|
|
|
}
|
|
|
}
|
|
|
|
|
|
impl<'a, T> Drop for PyRefMut<'a, T> {
|
|
|
fn drop(&mut self) {
|
|
|
self.py_shared_state.decrease_leak_count(self.py, true);
|
|
|
}
|
|
|
}
|
|
|
|
|
|
/// Allows a `py_class!` generated struct to share references to one of its
|
|
|
/// data members with Python.
|
|
|
///
|
|
|
/// # Warning
|
|
|
///
|
|
|
/// TODO allow Python container types: for now, integration with the garbage
|
|
|
/// collector does not extend to Rust structs holding references to Python
|
|
|
/// objects. Should the need surface, `__traverse__` and `__clear__` will
|
|
|
/// need to be written as per the `rust-cpython` docs on GC integration.
|
|
|
///
|
|
|
/// # Parameters
|
|
|
///
|
|
|
/// * `$name` is the same identifier used in for `py_class!` macro call.
|
|
|
/// * `$inner_struct` is the identifier of the underlying Rust struct
|
|
|
/// * `$data_member` is the identifier of the data member of `$inner_struct`
|
|
|
/// that will be shared.
|
|
|
/// * `$shared_accessor` is the function name to be generated, which allows
|
|
|
/// safe access to the data member.
|
|
|
///
|
|
|
/// # Safety
|
|
|
///
|
|
|
/// `$data_member` must persist while the `$name` object is alive. In other
|
|
|
/// words, it must be an accessor to a data field of the Python object.
|
|
|
///
|
|
|
/// # Example
|
|
|
///
|
|
|
/// ```
|
|
|
/// struct MyStruct {
|
|
|
/// inner: Vec<u32>;
|
|
|
/// }
|
|
|
///
|
|
|
/// py_class!(pub class MyType |py| {
|
|
|
/// data inner: PySharedRefCell<MyStruct>;
|
|
|
/// });
|
|
|
///
|
|
|
/// py_shared_ref!(MyType, MyStruct, inner, inner_shared);
|
|
|
/// ```
|
|
|
macro_rules! py_shared_ref {
|
|
|
(
|
|
|
$name: ident,
|
|
|
$inner_struct: ident,
|
|
|
$data_member: ident,
|
|
|
$shared_accessor: ident
|
|
|
) => {
|
|
|
impl $name {
|
|
|
/// Returns a safe reference to the shared `$data_member`.
|
|
|
///
|
|
|
/// This function guarantees that `PySharedRef` is created with
|
|
|
/// the valid `self` and `self.$data_member(py)` pair.
|
|
|
fn $shared_accessor<'a>(
|
|
|
&'a self,
|
|
|
py: Python<'a>,
|
|
|
) -> $crate::ref_sharing::PySharedRef<'a, $inner_struct> {
|
|
|
use cpython::PythonObject;
|
|
|
use $crate::ref_sharing::PySharedRef;
|
|
|
let owner = self.as_object();
|
|
|
let data = self.$data_member(py);
|
|
|
unsafe { PySharedRef::new(py, owner, data) }
|
|
|
}
|
|
|
}
|
|
|
};
|
|
|
}
|
|
|
|
|
|
/// Manage immutable references to `PyObject` leaked into Python iterators.
|
|
|
pub struct PyLeakedRef<T> {
|
|
|
inner: PyObject,
|
|
|
data: Option<T>,
|
|
|
py_shared_state: &'static PySharedState,
|
|
|
}
|
|
|
|
|
|
// DO NOT implement Deref for PyLeakedRef<T>! Dereferencing PyLeakedRef
|
|
|
// without taking Python GIL wouldn't be safe.
|
|
|
|
|
|
impl<T> PyLeakedRef<T> {
|
|
|
/// # Safety
|
|
|
///
|
|
|
/// The `py_shared_state` must be owned by the `inner` Python object.
|
|
|
fn new(
|
|
|
py: Python,
|
|
|
inner: &PyObject,
|
|
|
data: T,
|
|
|
py_shared_state: &'static PySharedState,
|
|
|
) -> Self {
|
|
|
Self {
|
|
|
inner: inner.clone_ref(py),
|
|
|
data: Some(data),
|
|
|
py_shared_state,
|
|
|
}
|
|
|
}
|
|
|
|
|
|
/// Returns an immutable reference to the inner value.
|
|
|
pub fn get_ref<'a>(&'a self, _py: Python<'a>) -> &'a T {
|
|
|
self.data.as_ref().unwrap()
|
|
|
}
|
|
|
|
|
|
/// Returns a mutable reference to the inner value.
|
|
|
///
|
|
|
/// Typically `T` is an iterator. If `T` is an immutable reference,
|
|
|
/// `get_mut()` is useless since the inner value can't be mutated.
|
|
|
pub fn get_mut<'a>(&'a mut self, _py: Python<'a>) -> &'a mut T {
|
|
|
self.data.as_mut().unwrap()
|
|
|
}
|
|
|
|
|
|
/// Converts the inner value by the given function.
|
|
|
///
|
|
|
/// Typically `T` is a static reference to a container, and `U` is an
|
|
|
/// iterator of that container.
|
|
|
///
|
|
|
/// # Safety
|
|
|
///
|
|
|
/// The lifetime of the object passed in to the function `f` is cheated.
|
|
|
/// It's typically a static reference, but is valid only while the
|
|
|
/// corresponding `PyLeakedRef` is alive. Do not copy it out of the
|
|
|
/// function call.
|
|
|
pub unsafe fn map<U>(
|
|
|
mut self,
|
|
|
py: Python,
|
|
|
f: impl FnOnce(T) -> U,
|
|
|
) -> PyLeakedRef<U> {
|
|
|
// f() could make the self.data outlive. That's why map() is unsafe.
|
|
|
// In order to make this function safe, maybe we'll need a way to
|
|
|
// temporarily restrict the lifetime of self.data and translate the
|
|
|
// returned object back to Something<'static>.
|
|
|
let new_data = f(self.data.take().unwrap());
|
|
|
PyLeakedRef {
|
|
|
inner: self.inner.clone_ref(py),
|
|
|
data: Some(new_data),
|
|
|
py_shared_state: self.py_shared_state,
|
|
|
}
|
|
|
}
|
|
|
}
|
|
|
|
|
|
impl<T> Drop for PyLeakedRef<T> {
|
|
|
fn drop(&mut self) {
|
|
|
// py_shared_state should be alive since we do have
|
|
|
// a Python reference to the owner object. Taking GIL makes
|
|
|
// sure that the state is only accessed by this thread.
|
|
|
let gil = Python::acquire_gil();
|
|
|
let py = gil.python();
|
|
|
if self.data.is_none() {
|
|
|
return; // moved to another PyLeakedRef
|
|
|
}
|
|
|
self.py_shared_state.decrease_leak_count(py, false);
|
|
|
}
|
|
|
}
|
|
|
|
|
|
/// Defines a `py_class!` that acts as a Python iterator over a Rust iterator.
|
|
|
///
|
|
|
/// TODO: this is a bit awkward to use, and a better (more complicated)
|
|
|
/// procedural macro would simplify the interface a lot.
|
|
|
///
|
|
|
/// # Parameters
|
|
|
///
|
|
|
/// * `$name` is the identifier to give to the resulting Rust struct.
|
|
|
/// * `$leaked` corresponds to `$leaked` in the matching `py_shared_ref!` call.
|
|
|
/// * `$iterator_type` is the type of the Rust iterator.
|
|
|
/// * `$success_func` is a function for processing the Rust `(key, value)`
|
|
|
/// tuple on iteration success, turning it into something Python understands.
|
|
|
/// * `$success_func` is the return type of `$success_func`
|
|
|
///
|
|
|
/// # Example
|
|
|
///
|
|
|
/// ```
|
|
|
/// struct MyStruct {
|
|
|
/// inner: HashMap<Vec<u8>, Vec<u8>>;
|
|
|
/// }
|
|
|
///
|
|
|
/// py_class!(pub class MyType |py| {
|
|
|
/// data inner: PySharedRefCell<MyStruct>;
|
|
|
///
|
|
|
/// def __iter__(&self) -> PyResult<MyTypeItemsIterator> {
|
|
|
/// let leaked_ref = self.inner_shared(py).leak_immutable()?;
|
|
|
/// MyTypeItemsIterator::from_inner(
|
|
|
/// py,
|
|
|
/// unsafe { leaked_ref.map(py, |o| o.iter()) },
|
|
|
/// )
|
|
|
/// }
|
|
|
/// });
|
|
|
///
|
|
|
/// impl MyType {
|
|
|
/// fn translate_key_value(
|
|
|
/// py: Python,
|
|
|
/// res: (&Vec<u8>, &Vec<u8>),
|
|
|
/// ) -> PyResult<Option<(PyBytes, PyBytes)>> {
|
|
|
/// let (f, entry) = res;
|
|
|
/// Ok(Some((
|
|
|
/// PyBytes::new(py, f),
|
|
|
/// PyBytes::new(py, entry),
|
|
|
/// )))
|
|
|
/// }
|
|
|
/// }
|
|
|
///
|
|
|
/// py_shared_ref!(MyType, MyStruct, inner, MyTypeLeakedRef);
|
|
|
///
|
|
|
/// py_shared_iterator!(
|
|
|
/// MyTypeItemsIterator,
|
|
|
/// PyLeakedRef<HashMap<'static, Vec<u8>, Vec<u8>>>,
|
|
|
/// MyType::translate_key_value,
|
|
|
/// Option<(PyBytes, PyBytes)>
|
|
|
/// );
|
|
|
/// ```
|
|
|
macro_rules! py_shared_iterator {
|
|
|
(
|
|
|
$name: ident,
|
|
|
$leaked: ty,
|
|
|
$success_func: expr,
|
|
|
$success_type: ty
|
|
|
) => {
|
|
|
py_class!(pub class $name |py| {
|
|
|
data inner: RefCell<Option<$leaked>>;
|
|
|
|
|
|
def __next__(&self) -> PyResult<$success_type> {
|
|
|
let mut inner_opt = self.inner(py).borrow_mut();
|
|
|
if let Some(leaked) = inner_opt.as_mut() {
|
|
|
match leaked.get_mut(py).next() {
|
|
|
None => {
|
|
|
// replace Some(inner) by None, drop $leaked
|
|
|
inner_opt.take();
|
|
|
Ok(None)
|
|
|
}
|
|
|
Some(res) => {
|
|
|
$success_func(py, res)
|
|
|
}
|
|
|
}
|
|
|
} else {
|
|
|
Ok(None)
|
|
|
}
|
|
|
}
|
|
|
|
|
|
def __iter__(&self) -> PyResult<Self> {
|
|
|
Ok(self.clone_ref(py))
|
|
|
}
|
|
|
});
|
|
|
|
|
|
impl $name {
|
|
|
pub fn from_inner(
|
|
|
py: Python,
|
|
|
leaked: $leaked,
|
|
|
) -> PyResult<Self> {
|
|
|
Self::create_instance(
|
|
|
py,
|
|
|
RefCell::new(Some(leaked)),
|
|
|
)
|
|
|
}
|
|
|
}
|
|
|
};
|
|
|
}
|
|
|
|
|
|
#[cfg(test)]
|
|
|
#[cfg(any(feature = "python27-bin", feature = "python3-bin"))]
|
|
|
mod test {
|
|
|
use super::*;
|
|
|
use cpython::{GILGuard, Python};
|
|
|
|
|
|
py_class!(class Owner |py| {
|
|
|
data string: PySharedRefCell<String>;
|
|
|
});
|
|
|
py_shared_ref!(Owner, String, string, string_shared);
|
|
|
|
|
|
fn prepare_env() -> (GILGuard, Owner) {
|
|
|
let gil = Python::acquire_gil();
|
|
|
let py = gil.python();
|
|
|
let owner =
|
|
|
Owner::create_instance(py, PySharedRefCell::new("new".to_owned()))
|
|
|
.unwrap();
|
|
|
(gil, owner)
|
|
|
}
|
|
|
|
|
|
#[test]
|
|
|
fn test_borrow_mut_while_leaked() {
|
|
|
let (gil, owner) = prepare_env();
|
|
|
let py = gil.python();
|
|
|
assert!(owner.string_shared(py).borrow_mut().is_ok());
|
|
|
let _leaked = owner.string_shared(py).leak_immutable().unwrap();
|
|
|
// TODO: will be allowed
|
|
|
assert!(owner.string_shared(py).borrow_mut().is_err());
|
|
|
}
|
|
|
}
|
|
|
|
