RustPython/crates/stdlib/src/_queue.rs at main · RustPython/RustPython · GitHub

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pub(crate) use _queue::module_def;

#[pymodule]

mod _queue {

use alloc::collections::VecDeque;

use core::time::Duration;

use std::time::Instant;

use crate::vm::{

AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,

builtins::{PyBaseExceptionRef, PyException, PyGenericAlias, PyStr, PyType, PyTypeRef},

function::{PyComparisonValue, TimeoutSeconds},

protocol::PyNumberMethods,

types::{AsNumber, Comparable, Constructor, PyComparisonOp, Representable},

};

type BufInner = VecDeque<PyObjectRef>;

cfg_select! {

feature = "threading" => {

use parking_lot::{Condvar, Mutex, MutexGuard};

type Buf = Mutex<BufInner>;

_ => {

use crate::common::lock::PyMutex;

type Buf = PyMutex<BufInner>;

}

const INITIAL_RING_BUF_CAPACITY: usize = 8;

/// `parking_lot`'s `Condvar` doesn't expose a mid-wait signal to us (unlike

/// CPython's raw `sem_timedwait`, which reports `EINTR`), so we poll instead.

// FIXME: interim stopgap. The signal already interrupts the wait with EINTR

// (SA_RESTART cleared via `siginterrupt`), but `parking_lot::Condvar` swallows

// it and re-parks, forcing this poll. Replace with a shared interruptible

// timed-wait that surfaces EINTR (`poll`/wakeup-fd, portable incl. macOS; or

// `sem_timedwait` where available) -- `_thread` lock and `Thread.join` share

// this defect. Then this constant and the chunking loop go away.

#[cfg(feature = "threading")]

const SIGNAL_CHECK_INTERVAL: Duration = Duration::from_millis(50);

#[pyattr]

#[pyclass(module = "_queue", name = "Empty", base = PyException)]

#[repr(transparent)]

pub(crate) struct PyEmptyError(PyException);

#[pyclass(flags(HAS_WEAKREF))]

impl PyEmptyError {}

/// ## See Also

///

/// [`empty_error`](https://github.com/python/cpython/blob/v3.14.5/Modules/_queuemodule.c#L347-L355).

fn empty_error(vm: &VirtualMachine) -> PyBaseExceptionRef {

vm.new_exception_empty(PyEmptyError::class(&vm.ctx).to_owned())

}

#[cfg(feature = "threading")]

#[derive(Debug)]

struct Semaphore {

mutex: Mutex<usize>,

cond: Condvar,

}

#[cfg(feature = "threading")]

impl Semaphore {

#[must_use]

fn new() -> Self {

Self {

mutex: Mutex::new(0),

cond: Condvar::new(),

}

/// Take `mutex`, detaching first so that blocking on it cannot stall a

/// stop-the-world request.

///

/// A waiter holds this mutex across its `allow_threads` wait, so it can

/// still hold it when it is stopped. An attached thread blocking on it

/// would then never reach a safepoint, the stop would never complete,

/// and the holder would never be resumed to release it.

fn lock_count(&self, vm: &VirtualMachine) -> parking_lot::MutexGuard<'_, usize> {

vm.allow_threads(|| self.mutex.lock())

}

fn release(&self, vm: &VirtualMachine) {

{

let mut count = self.lock_count(vm);

*count += 1;

} // lock dropped. now we can notify a waiting thread

self.cond.notify_one();

}

/// `Ok(true)` if acquired, `Ok(false)` on timeout, `Err` if a signal

/// handler raised (e.g. `KeyboardInterrupt`) while we were waiting.

fn acquire(

&self,

block: bool,

deadline: Option<Instant>,

vm: &VirtualMachine,

) -> PyResult<bool> {

loop {

// Guard must be dropped before check_signals() below, since a

// signal handler may call back into this same queue.

{

let mut count = self.lock_count(vm);

if *count > 0 {

*count -= 1;

return Ok(true);

}

if !block {

return Ok(false);

}

let now = Instant::now();

let chunk_deadline = deadline.map_or_else(

|| now + SIGNAL_CHECK_INTERVAL,

|dl| dl.min(now + SIGNAL_CHECK_INTERVAL),

);

vm.allow_threads(|| self.cond.wait_until(&mut count, chunk_deadline));

if *count > 0 {

*count -= 1;

return Ok(true);

}

if let Some(dl) = deadline

&& Instant::now() >= dl

{

return Ok(false);

}

vm.check_signals()?;

}

#[pyattr]

#[pyclass(module = "_queue", name = "SimpleQueue", unhashable = true)]

#[derive(Debug, PyPayload)]

struct PySimpleQueue {

buf: Buf,

#[cfg(feature = "threading")]

sem: Semaphore,

}

impl Default for PySimpleQueue {

fn default() -> Self {

Self {

buf: Buf::new(VecDeque::with_capacity(INITIAL_RING_BUF_CAPACITY)),

#[cfg(feature = "threading")]

sem: Semaphore::new(),

}

impl PySimpleQueue {

#[cfg_attr(

not(feature = "threading"),

expect(unused_variables, reason = "only the semaphore needs the vm")

)]

fn push(&self, item: PyObjectRef, vm: &VirtualMachine) {

self.buf.lock().push_back(item);

#[cfg(feature = "threading")]

self.sem.release(vm);

}

/// Returns a strong reference from the head of the buffer.

///

/// ## See Also

///

/// [`RingBuf_Get`](https://github.com/python/cpython/blob/v3.14.5/Modules/_queuemodule.c#L133-L154).

fn get_inner(

#[cfg(feature = "threading")] buf: &mut MutexGuard<'_, BufInner>,

#[cfg(not(feature = "threading"))] buf: &mut BufInner,

) -> Option<PyObjectRef> {

let cap = buf.capacity();

if buf.len() < (cap / 4) {

// Items is less than 25% occupied, shrink it by 50%. This allows for

// growth without immediately needing to resize the underlying items array

buf.shrink_to(cap / 2)

}

buf.pop_front()

}

#[derive(FromArgs)]

struct PutArgs {

#[pyarg(positional)]

item: PyObjectRef,

#[expect(

dead_code,

reason = "Intentional. Provide compatibility with the Queue class"

)]

#[pyarg(any, optional, default = true)]

block: bool,

#[expect(

dead_code,

reason = "Intentional. Provide compatibility with the Queue class"

)]

#[pyarg(any, optional)]

timeout: Option<PyObjectRef>,

}

#[derive(FromArgs)]

struct GetArgs {

#[pyarg(any, optional, default = true)]

block: bool,

#[pyarg(any, optional)]

timeout: Option<TimeoutSeconds>,

}

#[pyclass(

with(Constructor, Comparable, Representable),

flags(BASETYPE, HAS_WEAKREF, IMMUTABLETYPE)

)]

impl PySimpleQueue {

#[pymethod]

fn empty(&self) -> bool {

self.buf.lock().is_empty()

}

#[pymethod]

fn qsize(&self) -> usize {

self.buf.lock().len()

}

#[pymethod]

fn put(&self, args: PutArgs, vm: &VirtualMachine) {

let PutArgs { item, .. } = args;

self.push(item, vm);

}

#[pymethod]

fn put_nowait(&self, item: PyObjectRef, vm: &VirtualMachine) {

self.push(item, vm);

}

#[pymethod]

fn get(&self, args: GetArgs, vm: &VirtualMachine) -> PyResult<PyObjectRef> {

let GetArgs { block, timeout } = args;

// Non-blocking: just try once

if !block {

return Self::get_inner(&mut self.buf.lock()).ok_or_else(|| empty_error(vm));

}

#[cfg_attr(

not(feature = "threading"),

expect(

unused_variables,

reason = "We are still validating the 'timeout' arg even if we don't have threading"

)

)]

let deadline = match timeout.map(|v| v.to_secs_f64()) {

Some(v) if v < 0.0 => {

return Err(vm.new_value_error("'timeout' must be a non-negative number"));

}

Some(v) => Some(Instant::now() + Duration::from_secs_f64(v)),

None => None,

};

#[cfg(feature = "threading")]

{

if !self.sem.acquire(block, deadline, vm)? {

return Err(empty_error(vm));

}

Self::get_inner(&mut self.buf.lock()).ok_or_else(|| empty_error(vm))

}

#[pymethod]

fn get_nowait(&self, vm: &VirtualMachine) -> PyResult<PyObjectRef> {

#[cfg(feature = "threading")]

{

if !self.sem.acquire(false, None, vm)? {

return Err(empty_error(vm));

}

Self::get_inner(&mut self.buf.lock()).ok_or_else(|| empty_error(vm))

}

#[pyclassmethod]

fn __class_getitem__(

cls: PyTypeRef,

args: PyObjectRef,

vm: &VirtualMachine,

) -> PyResult<PyGenericAlias> {

PyGenericAlias::from_args(cls, args, vm)

}

impl Constructor for PySimpleQueue {

type Args = ();

fn py_new(_cls: &Py<PyType>, _args: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {

Ok(Self::default())

}

impl AsNumber for PySimpleQueue {

fn as_number() -> &'static PyNumberMethods {

static AS_NUMBER: PyNumberMethods = PyNumberMethods {

boolean: Some(|number, _vm| {

let zelf = number.obj.downcast_ref::<PySimpleQueue>().unwrap();

Ok(!zelf.buf.lock().is_empty())

}),

..PyNumberMethods::NOT_IMPLEMENTED

};

&AS_NUMBER

}

impl Comparable for PySimpleQueue {

fn cmp(

zelf: &Py<Self>,

other: &PyObject,

op: PyComparisonOp,

_vm: &VirtualMachine,

) -> PyResult<PyComparisonValue> {

Ok(if let Some(res) = op.identical_optimization(zelf, other) {

res.into()

} else {

PyComparisonValue::NotImplemented

})

}

impl Representable for PySimpleQueue {

fn repr(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyRef<PyStr>> {

Ok(vm.ctx.new_str(format!(

"<{} at {:#x}>",

Self::class(&vm.ctx).slot_name(),

zelf.get_id()

)))

}

fn repr_str(_zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<String> {

unreachable!("repr() is overridden directly")

}

RustPython/crates/stdlib/src/_queue.rs at main · RustPython/RustPython · GitHub

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