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Copy pathiter.rs
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302 lines (273 loc) · 8.7 KB
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use crate::{
AsObject, PyObject, PyObjectRef, PyPayload, PyResult, TryFromObject, VirtualMachine,
builtins::iter::PySequenceIterator,
convert::{ToPyObject, ToPyResult},
object::{Traverse, TraverseFn},
};
use core::borrow::Borrow;
use core::ops::Deref;
/// [Iterator Protocol](https://docs.python.org/3/c-api/iter.html).
#[derive(Debug, Clone)]
#[repr(transparent)]
pub struct PyIter<O = PyObjectRef>(O)
where
O: Borrow<PyObject>;
unsafe impl<O: Borrow<PyObject>> Traverse for PyIter<O> {
fn traverse(&self, tracer_fn: &mut TraverseFn<'_>) {
// Report the iterator itself, not its referents: an owner holding a
// `PyIter` owns the iterator object, and reporting what the iterator
// points at instead leaves the iterator's own reference unaccounted
// for, so a cycle running through it is never collected.
tracer_fn(self.0.borrow());
}
}
impl PyIter<PyObjectRef> {
pub fn check(obj: &PyObject) -> bool {
obj.class().slots.iternext.load().is_some()
}
}
impl<O> PyIter<O>
where
O: Borrow<PyObject>,
{
#[must_use]
pub const fn new(obj: O) -> Self {
Self(obj)
}
pub fn next(&self, vm: &VirtualMachine) -> PyResult<PyIterReturn> {
let iternext = self
.0
.borrow()
.class()
.slots
.iternext
.load()
.ok_or_else(|| {
vm.new_type_error(format!(
"'{}' object is not an iterator",
self.0.borrow().class().slot_name()
))
})?;
iternext(self.0.borrow(), vm)
}
/// Walks the iterator without asking it how long it is. Almost nothing
/// asks: a loop over an iterator takes no room up front, so what the
/// object would have answered -- slowly, or by raising -- never runs.
pub fn iter<'a, 'b, U>(
&'b self,
vm: &'a VirtualMachine,
) -> PyResult<PyIterIter<'a, U, &'b PyObject>> {
Ok(PyIterIter::new(vm, self.0.borrow(), None))
}
}
impl PyIter<PyObjectRef> {
/// Returns an iterator over this sequence of objects. See [`Self::iter`]
/// for why it does not ask how long the iterator is.
pub fn into_iter<U>(self, vm: &VirtualMachine) -> PyIterIter<'_, U, PyObjectRef> {
PyIterIter::new(vm, self.0, None)
}
/// [`Self::into_iter`] for a caller that fills a sized container from the
/// iterator, the way `PySequence_Fast()` does. It asks how much room that
/// takes and answers with whatever asking raised.
pub fn into_iter_sized<U>(
self,
vm: &VirtualMachine,
) -> PyResult<PyIterIter<'_, U, PyObjectRef>> {
let length_hint = vm.length_hint_opt(self.as_object().to_owned())?;
Ok(PyIterIter::new(vm, self.0, length_hint))
}
}
impl From<PyIter<Self>> for PyObjectRef {
fn from(value: PyIter<Self>) -> Self {
value.0
}
}
impl<O> Borrow<PyObject> for PyIter<O>
where
O: Borrow<PyObject>,
{
#[inline(always)]
fn borrow(&self) -> &PyObject {
self.0.borrow()
}
}
impl<O> AsRef<PyObject> for PyIter<O>
where
O: Borrow<PyObject>,
{
#[inline(always)]
fn as_ref(&self) -> &PyObject {
self.0.borrow()
}
}
impl<O> Deref for PyIter<O>
where
O: Borrow<PyObject>,
{
type Target = PyObject;
#[inline(always)]
fn deref(&self) -> &Self::Target {
self.0.borrow()
}
}
impl ToPyObject for PyIter<PyObjectRef> {
#[inline(always)]
fn to_pyobject(self, _vm: &VirtualMachine) -> PyObjectRef {
self.into()
}
}
impl TryFromObject for PyIter<PyObjectRef> {
// This helper function is called at multiple places. First, it is called
// in the vm when a for loop is entered. Next, it is used when the builtin
// function 'iter' is called.
fn try_from_object(vm: &VirtualMachine, iter_target: PyObjectRef) -> PyResult<Self> {
let get_iter = iter_target.class().slots.iter.load();
if let Some(get_iter) = get_iter {
let iter = get_iter(iter_target, vm)?;
if Self::check(&iter) {
Ok(Self(iter))
} else {
Err(vm.new_type_error(format!(
"iter() returned non-iterator of type '{}'",
iter.class().slot_name()
)))
}
} else if let Ok(seq_iter) = PySequenceIterator::new(iter_target.clone(), vm) {
Ok(Self(seq_iter.into_pyobject(vm)))
} else {
Err(vm.new_type_error(format!(
"'{}' object is not iterable",
iter_target.class().slot_name()
)))
}
}
}
#[derive(result_like::ResultLike)]
pub enum PyIterReturn<T = PyObjectRef> {
Return(T),
StopIteration(Option<PyObjectRef>),
}
unsafe impl<T: Traverse> Traverse for PyIterReturn<T> {
fn traverse(&self, tracer_fn: &mut TraverseFn<'_>) {
match self {
Self::Return(r) => r.traverse(tracer_fn),
Self::StopIteration(Some(obj)) => obj.traverse(tracer_fn),
_ => (),
}
}
}
impl PyIterReturn {
pub fn from_pyresult(result: PyResult, vm: &VirtualMachine) -> PyResult<Self> {
match result {
Ok(obj) => Ok(Self::Return(obj)),
Err(err) if err.fast_isinstance(vm.ctx.exceptions.stop_iteration) => {
let args = err.get_arg(0);
Ok(Self::StopIteration(args))
}
Err(err) => Err(err),
}
}
pub fn from_getitem_result(result: PyResult, vm: &VirtualMachine) -> PyResult<Self> {
match result {
Ok(obj) => Ok(Self::Return(obj)),
Err(err) if err.fast_isinstance(vm.ctx.exceptions.index_error) => {
Ok(Self::StopIteration(None))
}
Err(err) if err.fast_isinstance(vm.ctx.exceptions.stop_iteration) => {
let args = err.get_arg(0);
Ok(Self::StopIteration(args))
}
Err(err) => Err(err),
}
}
pub fn into_async_pyresult(self, vm: &VirtualMachine) -> PyResult {
match self {
Self::Return(obj) => Ok(obj),
Self::StopIteration(v) => Err({
let args = v.map_or_else(Vec::new, |v| vec![v]);
vm.new_exception(vm.ctx.exceptions.stop_async_iteration.to_owned(), args)
}),
}
}
}
impl ToPyResult for PyIterReturn {
fn to_pyresult(self, vm: &VirtualMachine) -> PyResult {
match self {
Self::Return(obj) => Ok(obj),
Self::StopIteration(v) => Err(vm.new_stop_iteration(v)),
}
}
}
impl ToPyResult for PyResult<PyIterReturn> {
fn to_pyresult(self, vm: &VirtualMachine) -> PyResult {
self?.to_pyresult(vm)
}
}
// Typical rust `Iter` object for `PyIter`
pub struct PyIterIter<'a, T, O = PyObjectRef>
where
O: Borrow<PyObject>,
{
vm: &'a VirtualMachine,
obj: O, // creating PyIter<O> is zero-cost
length_hint: Option<usize>,
_phantom: core::marker::PhantomData<T>,
}
unsafe impl<T, O> Traverse for PyIterIter<'_, T, O>
where
O: Traverse + Borrow<PyObject>,
{
fn traverse(&self, tracer_fn: &mut TraverseFn<'_>) {
self.obj.traverse(tracer_fn)
}
}
impl<'a, T, O> PyIterIter<'a, T, O>
where
O: Borrow<PyObject>,
{
pub const fn new(vm: &'a VirtualMachine, obj: O, length_hint: Option<usize>) -> Self {
Self {
vm,
obj,
length_hint,
_phantom: core::marker::PhantomData,
}
}
}
impl<T, O> Iterator for PyIterIter<'_, T, O>
where
T: TryFromObject,
O: Borrow<PyObject>,
{
type Item = PyResult<T>;
fn next(&mut self) -> Option<Self::Item> {
let imp = |next: PyResult<PyIterReturn>| -> PyResult<Option<T>> {
let Some(obj) = next?.into_result().ok() else {
return Ok(None);
};
Ok(Some(T::try_from_object(self.vm, obj)?))
};
let next = PyIter::new(self.obj.borrow()).next(self.vm);
imp(next).transpose()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
(self.length_hint.unwrap_or(0), self.length_hint)
}
}
/// Macro to handle `PyIterReturn` values in iterator implementations.
///
/// Extracts the object from `PyIterReturn::Return(obj)` or performs early return
/// for `PyIterReturn::StopIteration(v)`. This macro should only be used within
/// functions that return `PyResult<PyIterReturn>`.
#[macro_export]
macro_rules! raise_if_stop {
($input:expr) => {
match $input {
$crate::protocol::PyIterReturn::Return(obj) => obj,
$crate::protocol::PyIterReturn::StopIteration(v) => {
return Ok($crate::protocol::PyIterReturn::StopIteration(v))
}
}
};
}
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