apple_cf/

dispatch_queue.rs

//! Dispatch Queue wrapper for custom queue management
//!
//! This module provides a safe Rust wrapper around GCD (Grand Central Dispatch) queues
//! that can be used with `ScreenCaptureKit` streams.
//!
//! ## When to Use Custom Queues
//!
//! By default, stream output handlers are called on a system-managed queue. Use a custom
//! queue when you need:
//!
//! - **Priority control** - Use `UserInteractive` `QoS` for low-latency UI updates
//! - **Thread isolation** - Ensure handlers run on a specific queue
//! - **Performance tuning** - Adjust queue priority based on your app's needs
//!
//! ## Example
//!
#![allow(clippy::missing_panics_doc)]

//! ```rust,no_run
//! use apple_cf::dispatch_queue::{dispatch_async_and_wait, DispatchQueue, DispatchQoS};
//!
//! // Create a high-priority queue for frame processing
//! let queue = DispatchQueue::new("com.myapp.capture", DispatchQoS::UserInteractive);
//! dispatch_async_and_wait(&queue, || {
//!     // do queue-bound work here
//! });
//! ```

use crate::utils::panic_safe;
use std::ffi::{c_void, CString};
use std::fmt;
use std::time::Duration;

/// Quality of Service levels for dispatch queues
///
/// These `QoS` levels help the system prioritize work appropriately.
///
/// # Examples
///
/// ```
/// use apple_cf::dispatch_queue::{DispatchQueue, DispatchQoS};
///
/// // High priority for UI-affecting work
/// let queue = DispatchQueue::new("com.myapp.ui", DispatchQoS::UserInteractive);
///
/// // Lower priority for background tasks
/// let bg_queue = DispatchQueue::new("com.myapp.background", DispatchQoS::Background);
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
pub enum DispatchQoS {
    /// Background `QoS` - for maintenance or cleanup tasks
    Background = 0,
    /// Utility `QoS` - for tasks that may take some time
    Utility = 1,
    /// Default `QoS` - standard priority
    #[default]
    Default = 2,
    /// User Initiated `QoS` - for tasks initiated by the user
    UserInitiated = 3,
    /// User Interactive `QoS` - for tasks that affect the UI
    UserInteractive = 4,
}

/// A wrapper around GCD `DispatchQueue`
///
/// This allows you to provide a custom dispatch queue for stream output handling
/// instead of using the default queue.
///
/// # Example
///
/// ```no_run
/// use apple_cf::dispatch_queue::{DispatchQueue, DispatchQoS};
///
/// let queue = DispatchQueue::new("com.myapp.capture", DispatchQoS::UserInteractive);
/// ```
pub struct DispatchQueue {
    ptr: *const c_void,
}

// SAFETY: `dispatch_queue_t` is documented by Apple as safe to use from any
// thread.  The Rust wrapper only holds an opaque pointer and never performs
// interior mutation on it outside of the underlying GCD primitives, which are
// themselves thread-safe.
unsafe impl Send for DispatchQueue {}
unsafe impl Sync for DispatchQueue {}

impl DispatchQueue {
    /// Creates a new dispatch queue with the specified label and `QoS`
    ///
    /// # Arguments
    ///
    /// * `label` - A string label for the queue (e.g., "com.myapp.capture")
    /// * `qos` - The quality of service level for the queue
    ///
    /// # Examples
    ///
    /// ```
    /// use apple_cf::dispatch_queue::{DispatchQueue, DispatchQoS};
    ///
    /// let queue = DispatchQueue::new("com.myapp.capture", DispatchQoS::UserInteractive);
    /// // Use the queue with SCStream's add_output_handler_with_queue
    /// ```
    ///
    /// # Panics
    ///
    /// Panics if the label contains null bytes or if queue creation fails
    #[must_use]
    pub fn new(label: &str, qos: DispatchQoS) -> Self {
        let c_label = CString::new(label).expect("Label contains null byte");
        let ptr = unsafe { crate::ffi::acf_dispatch_queue_create(c_label.as_ptr(), qos as i32) };
        assert!(!ptr.is_null(), "Failed to create dispatch queue");
        Self { ptr }
    }

    /// Returns the raw pointer to the dispatch queue
    ///
    /// This is used internally for FFI calls (and for testing)
    #[must_use]
    pub const fn as_ptr(&self) -> *const c_void {
        self.ptr
    }

    #[must_use]
    const fn as_mut_ptr(&self) -> *mut c_void {
        self.ptr.cast_mut()
    }
}

crate::utils::retained::cf_retained!(
    DispatchQueue,
    field = ptr,
    retain = crate::ffi::dispatch_queue_retain,
    release = crate::ffi::dispatch_queue_release,
    drop = unchecked,
);

impl fmt::Debug for DispatchQueue {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("DispatchQueue")
            .field("ptr", &self.ptr)
            .finish()
    }
}

impl fmt::Display for DispatchQueue {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "DispatchQueue")
    }
}

fn timeout_ms(timeout: Option<Duration>) -> i64 {
    timeout.map_or(-1, |duration| {
        i64::try_from(duration.as_millis()).unwrap_or(i64::MAX)
    })
}

struct DispatchOnceTask {
    site: &'static str,
    work: Option<Box<dyn FnOnce() + Send + 'static>>,
}

struct DispatchApplyTask {
    work: Box<dyn Fn(usize) + Send + Sync + 'static>,
}

extern "C" fn dispatch_once_trampoline(context: *mut c_void) {
    if context.is_null() {
        return;
    }
    let mut task = unsafe { Box::from_raw(context.cast::<DispatchOnceTask>()) };
    if let Some(work) = task.work.take() {
        panic_safe::catch_user_panic(task.site, work);
    }
}

extern "C" fn dispatch_apply_trampoline(iteration: usize, context: *mut c_void) {
    if context.is_null() {
        return;
    }
    let task = unsafe { &*context.cast::<DispatchApplyTask>() };
    panic_safe::catch_user_panic("dispatch_apply", || (task.work)(iteration));
}

/// Submit `work` to `queue` and return immediately.
pub fn dispatch_async<F>(queue: &DispatchQueue, work: F)
where
    F: FnOnce() + Send + 'static,
{
    let task = Box::new(DispatchOnceTask {
        site: "dispatch_async",
        work: Some(Box::new(work)),
    });
    unsafe {
        crate::ffi::acf_dispatch_async_f(
            queue.as_mut_ptr(),
            Box::into_raw(task).cast(),
            dispatch_once_trampoline,
        );
    }
}

/// Submit `work` to `queue` and wait until it finishes.
pub fn dispatch_async_and_wait<F>(queue: &DispatchQueue, work: F)
where
    F: FnOnce() + Send + 'static,
{
    let task = Box::new(DispatchOnceTask {
        site: "dispatch_async_and_wait",
        work: Some(Box::new(work)),
    });
    unsafe {
        crate::ffi::acf_dispatch_async_and_wait_f(
            queue.as_mut_ptr(),
            Box::into_raw(task).cast(),
            dispatch_once_trampoline,
        );
    }
}

/// Run `work` for every `iteration` on `queue`, waiting for all iterations to finish.
pub fn dispatch_apply<F>(iterations: usize, queue: &DispatchQueue, work: F)
where
    F: Fn(usize) + Send + Sync + 'static,
{
    if iterations == 0 {
        return;
    }
    let task = Box::new(DispatchApplyTask {
        work: Box::new(work),
    });
    let raw = Box::into_raw(task);
    unsafe {
        crate::ffi::acf_dispatch_apply_f(
            iterations,
            queue.as_mut_ptr(),
            raw.cast(),
            dispatch_apply_trampoline,
        );
        drop(Box::from_raw(raw));
    }
}

/// Wrapper around `DispatchGroup`.
#[derive(PartialEq, Eq, Hash)]
pub struct DispatchGroup {
    ptr: *mut c_void,
}

// SAFETY: `dispatch_group_t` is a thread-safe GCD primitive; it is safe to
// share across threads and to send between threads.
unsafe impl Send for DispatchGroup {}
unsafe impl Sync for DispatchGroup {}

impl DispatchGroup {
    /// Create a new empty group.
    #[must_use]
    pub fn new() -> Self {
        let ptr = unsafe { crate::ffi::acf_dispatch_group_create() };
        assert!(!ptr.is_null(), "failed to create DispatchGroup");
        Self { ptr }
    }

    /// Enter the group.
    pub fn enter(&self) {
        unsafe { crate::ffi::acf_dispatch_group_enter(self.ptr) };
    }

    /// Leave the group.
    pub fn leave(&self) {
        unsafe { crate::ffi::acf_dispatch_group_leave(self.ptr) };
    }

    /// Wait for the group to finish.
    #[must_use]
    pub fn wait(&self, timeout: Option<Duration>) -> bool {
        unsafe { crate::ffi::acf_dispatch_group_wait(self.ptr, timeout_ms(timeout)) }
    }
}

impl Default for DispatchGroup {
    fn default() -> Self {
        Self::new()
    }
}

crate::utils::retained::cf_retained!(
    DispatchGroup,
    field = ptr,
    retain = crate::ffi::acf_object_retain,
    release = crate::ffi::acf_object_release,
    drop = unchecked,
);

impl fmt::Debug for DispatchGroup {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("DispatchGroup")
            .field("ptr", &self.ptr)
            .finish()
    }
}

/// Wrapper around `DispatchSemaphore`.
#[derive(PartialEq, Eq, Hash)]
pub struct DispatchSemaphore {
    ptr: *mut c_void,
}

// SAFETY: `dispatch_semaphore_t` is a thread-safe GCD primitive designed
// explicitly for cross-thread signalling.
unsafe impl Send for DispatchSemaphore {}
unsafe impl Sync for DispatchSemaphore {}

impl DispatchSemaphore {
    /// Create a semaphore with an initial signal count.
    #[must_use]
    pub fn new(value: i64) -> Self {
        let ptr = unsafe { crate::ffi::acf_dispatch_semaphore_create(value) };
        assert!(!ptr.is_null(), "failed to create DispatchSemaphore");
        Self { ptr }
    }

    /// Signal the semaphore.
    #[must_use]
    pub fn signal(&self) -> i64 {
        unsafe { crate::ffi::acf_dispatch_semaphore_signal(self.ptr) }
    }

    /// Wait for the semaphore.
    #[must_use]
    pub fn wait(&self, timeout: Option<Duration>) -> bool {
        unsafe { crate::ffi::acf_dispatch_semaphore_wait(self.ptr, timeout_ms(timeout)) }
    }
}

crate::utils::retained::cf_retained!(
    DispatchSemaphore,
    field = ptr,
    retain = crate::ffi::acf_object_retain,
    release = crate::ffi::acf_object_release,
    drop = unchecked,
);

impl fmt::Debug for DispatchSemaphore {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("DispatchSemaphore")
            .field("ptr", &self.ptr)
            .finish()
    }
}

/// Minimal timer-backed `DispatchSource` wrapper.
#[derive(PartialEq, Eq, Hash)]
pub struct DispatchSource {
    ptr: *mut c_void,
}

// SAFETY: `dispatch_source_t` is a thread-safe GCD primitive, and the bridge
// holder synchronizes its activation, cancellation, and fire-count state.
unsafe impl Send for DispatchSource {}
unsafe impl Sync for DispatchSource {}

impl DispatchSource {
    /// Create a repeating timer source.
    #[must_use]
    pub fn timer(interval: Duration, leeway: Duration) -> Self {
        let interval_ms = u64::try_from(interval.as_millis()).unwrap_or(u64::MAX);
        let leeway_ms = u64::try_from(leeway.as_millis()).unwrap_or(u64::MAX);
        let ptr = unsafe { crate::ffi::acf_dispatch_source_timer_create(interval_ms, leeway_ms) };
        assert!(!ptr.is_null(), "failed to create DispatchSource timer");
        Self { ptr }
    }

    /// Activate the timer source after creation.
    ///
    /// Repeated or concurrent calls are idempotent.
    pub fn resume(&self) {
        unsafe { crate::ffi::acf_dispatch_source_timer_resume(self.ptr) };
    }

    /// Cancel the source.
    ///
    /// Repeated or concurrent calls are idempotent. Activating after
    /// cancellation is a no-op.
    pub fn cancel(&self) {
        unsafe { crate::ffi::acf_dispatch_source_timer_cancel(self.ptr) };
    }

    /// Number of timer firings observed by the bridge.
    #[must_use]
    pub fn fire_count(&self) -> u64 {
        unsafe { crate::ffi::acf_dispatch_source_timer_fire_count(self.ptr) }
    }
}

crate::utils::retained::cf_retained!(
    DispatchSource,
    field = ptr,
    retain = crate::ffi::acf_object_retain,
    release = crate::ffi::acf_object_release,
    drop = unchecked,
);

impl fmt::Debug for DispatchSource {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("DispatchSource")
            .field("ptr", &self.ptr)
            .field("fire_count", &self.fire_count())
            .finish()
    }
}