samp_sdk/omp/

timers.rs

//! Bindings for the Open Multiplayer `ITimersComponent` interface.
//!
//! Open Multiplayer has no native `ProcessTick`-equivalent callback for
//! components. To deliver the SDK's unified [`SampPlugin::on_tick`] on this
//! server, the `samp` crate installs a repeating timer through this
//! interface in `on_ready` and routes its timeout into the plugin.
//!
//! The interval is whatever the plugin requested via
//! `samp::plugin::enable_tick_with(TickConfig::new().omp_interval(...))`,
//! or 5 ms by default (from `enable_tick()`).
//!
//! [`SampPlugin::on_tick`]: ../../../samp/plugin/trait.SampPlugin.html#method.on_tick
//!
//! ## Primary `ITimersComponent` vtable
//!
//! The slot numbering differs per ABI, because Itanium emits two destructor
//! slots (D1 + D0) where MSVC emits a single scalar deleting one, and because
//! Itanium places the `getUID()` override (from `PROVIDE_UID`) in the primary
//! vtable while MSVC keeps it in the secondary `IUIDProvider` vtable.
//!
//! **Itanium ABI** — confirmed by `nm`/vtable dump of the official `Timers.so`:
//! `[0..3]` `IExtensible`, `[4..5]` destructors, `[6..16]` `IComponent`,
//! **[17]** `getUID()`, **[18]** `create(handler, interval, repeating)`,
//! `[19]` `create(handler, initial, interval, count)`, `[20]` `count()`.
//!
//! **MSVC ABI** — confirmed by RTTI + vtable dump of the official `Timers.dll`:
//! `[0..3]` `IExtensible`, `[4]` destructor, `[5..15]` `IComponent`,
//! `[16]` `create(handler, initial, interval, count)`,
//! **[17]** `create(handler, interval, repeating)`, `[18]` `count()`.
//!
//! Note the reversal: MSVC emits an overload set in **reverse declaration
//! order**, so the two `create` overloads swap places against Itanium. Verified
//! by disassembly — slot [16] ends in `ret 0x18` (24 bytes of arguments, the
//! four-argument overload) and slot [17] in `ret 0x10` (16 bytes, the one the
//! SDK calls).
//!
//! ## `ITimer` vtable (slots starting from `IExtensible`)
//!
//! `ITimer` declares no destructor of its own, but inherits the virtual
//! `~IExtensible()`, so the same D1/D0 shift applies.
//!
//! | Method                 | Itanium | MSVC |
//! |------------------------|---------|------|
//! | `IExtensible` (4)      | [0..3]  | [0..3] |
//! | destructor             | [4..5]  | [4]  |
//! | `running() const`      | [6]     | [5]  |
//! | `remaining() const`    | [7]     | [6]  |
//! | `calls() const`        | [8]     | [7]  |
//! | `interval() const`     | [9]     | [8]  |
//! | `trigger()`            | [10]    | [9]  |
//! | `kill()`               | [11]    | [10] |
//! | `handler() const`      | [12]    | [11] |
//!
//! ## `TimerTimeOutHandler` vtable (interface provided by the plugin)
//!
//! No virtual destructor in the header -> 2 slots only:
//! - **[0]** `timeout(ITimer&)`
//! - **[1]** `free(ITimer&)`

use super::component_api::OmpComponentHandle;
use super::server::{ServerComponent, query_component};
use super::types::UID;
use std::ptr::NonNull;

/// UID of the Open Multiplayer `Timers` component.
pub const TIMERS_COMPONENT_UID: UID = 0x2ad8_124c_5ea2_57a3;

/// Slot of `create(handler, interval, repeating)` in the `ITimersComponent` vtable.
///
/// Itanium carries two destructor slots plus `getUID()` in the primary vtable;
/// MSVC has one destructor and keeps `getUID()` in a secondary vtable.
#[cfg(not(target_env = "msvc"))]
const SLOT_CREATE_INTERVAL: usize = 18;

#[cfg(target_env = "msvc")]
const SLOT_CREATE_INTERVAL: usize = 17;

/// Slot of `kill()` in the `ITimer` vtable (shifted by the extra Itanium
/// destructor slot inherited from `IExtensible`).
#[cfg(not(target_env = "msvc"))]
const SLOT_TIMER_KILL: usize = 11;

#[cfg(target_env = "msvc")]
const SLOT_TIMER_KILL: usize = 10;

/// Opaque pointer to the server's `ITimersComponent`.
#[repr(C)]
pub struct ITimersComponent {
    _opaque: [u8; 0],
}

/// Opaque pointer to the server's `ITimer` — returned by `create_timer`.
#[repr(C)]
pub struct ITimer {
    _opaque: [u8; 0],
}

/// `TimerTimeOutHandler` vtable — Itanium ABI.
#[cfg(not(target_env = "msvc"))]
#[repr(C)]
pub struct TimerHandlerVTable {
    pub timeout: unsafe extern "C" fn(*mut TimerTimeOutHandler, *mut ITimer),
    pub free: unsafe extern "C" fn(*mut TimerTimeOutHandler, *mut ITimer),
}

/// `TimerTimeOutHandler` vtable — MSVC ABI (`this` in ECX).
#[cfg(target_env = "msvc")]
#[repr(C)]
pub struct TimerHandlerVTable {
    pub timeout: unsafe extern "thiscall" fn(*mut TimerTimeOutHandler, *mut ITimer),
    pub free: unsafe extern "thiscall" fn(*mut TimerTimeOutHandler, *mut ITimer),
}

/// Object the server will invoke on each timer timeout.
///
/// `#[repr(C)]` layout: vtable pointer at offset 0 + the handler's own data.
/// The server treats it as an opaque `TimerTimeOutHandler*` and only interacts
/// via the vtable.
#[repr(C)]
pub struct TimerTimeOutHandler {
    pub vtable: *const TimerHandlerVTable,
}

unsafe impl Send for TimerTimeOutHandler {}
unsafe impl Sync for TimerTimeOutHandler {}

/// Signature of `ITimersComponent::create(handler, interval, repeating)`.
///
/// `Milliseconds` is `std::chrono::milliseconds` in C++, a wrapper over `int64_t`.
/// At the ABI it is passed as 8 bytes on the stack (or hidden in registers,
/// depending on the compiler).
#[cfg(not(target_env = "msvc"))]
type CreateFn = unsafe extern "C" fn(
    this: *mut ITimersComponent,
    handler: *mut TimerTimeOutHandler,
    interval_ms: i64,
    repeating: bool,
) -> *mut ITimer;

#[cfg(target_env = "msvc")]
type CreateFn = unsafe extern "thiscall" fn(
    this: *mut ITimersComponent,
    handler: *mut TimerTimeOutHandler,
    interval_ms: i64,
    repeating: bool,
) -> *mut ITimer;

#[cfg(not(target_env = "msvc"))]
type KillFn = unsafe extern "C" fn(this: *mut ITimer);

#[cfg(target_env = "msvc")]
type KillFn = unsafe extern "thiscall" fn(this: *mut ITimer);

/// Queries `ITimersComponent` in the server's component list.
///
/// # Safety
/// `core` must point to a valid `ICore`. Internally uses `query_component`,
/// which casts the `ServerComponent` from the list — follows its contract.
pub unsafe fn query_timers_component(
    components: *mut super::server::ServerComponentList,
) -> *mut ITimersComponent {
    if components.is_null() {
        return std::ptr::null_mut();
    }
    let raw = unsafe { query_component(components, TIMERS_COMPONENT_UID) };
    raw.cast::<ITimersComponent>()
}

/// Creates a repeating timer on the Open Multiplayer server.
///
/// Returns the server's `ITimer*` (non-owning — the server owns it). Use
/// [`kill_timer`] at shutdown to stop it and free the server's resources.
///
/// # Safety
/// - `timers` must be a valid `ITimersComponent` pointer (from `query_timers_component`)
/// - `handler` must remain alive while the timer is active (allocate on the heap via `Box::into_raw`)
pub unsafe fn create_repeating_timer(
    timers: *mut ITimersComponent,
    handler: *mut TimerTimeOutHandler,
    interval_ms: i64,
) -> *mut ITimer {
    if handler.is_null() {
        return std::ptr::null_mut();
    }
    let Some((_, slot)) = (unsafe {
        super::vtable::secondary_call_target_ptr(timers.cast::<u8>(), 0, SLOT_CREATE_INTERVAL)
    }) else {
        return std::ptr::null_mut();
    };
    let create: CreateFn = unsafe { std::mem::transmute(slot) };
    unsafe { create(timers, handler, interval_ms, true) }
}

// ---------------------------------------------------------------------------
// TimersComponent — high-level typed wrapper
// ---------------------------------------------------------------------------

/// Typed wrapper for the Open Multiplayer server's `ITimersComponent`.
///
/// Obtained via `samp::plugin::omp_query::<TimersComponent>()`. Exposes
/// `create_repeating` for timer creation and the generic `IComponent` methods
/// (`name`, `version`).
#[derive(Debug, Clone, Copy)]
pub struct TimersComponent {
    ptr: NonNull<ServerComponent>,
}

impl OmpComponentHandle for TimersComponent {
    const UID: UID = TIMERS_COMPONENT_UID;

    unsafe fn from_raw(ptr: NonNull<ServerComponent>) -> Self {
        Self { ptr }
    }

    fn as_raw(&self) -> NonNull<ServerComponent> {
        self.ptr
    }
}

impl TimersComponent {
    /// Returns the component name.
    #[must_use]
    pub fn name(&self) -> Option<String> {
        super::component_api::component_name(self)
    }

    /// Returns the component version.
    #[must_use]
    pub fn version(&self) -> Option<super::types::SemanticVersion> {
        super::component_api::component_version(self)
    }

    /// Creates a repeating timer on the server.
    ///
    /// `handler` must be heap-allocated (e.g. `Box::into_raw`) and must be
    /// dropped inside the `TimerHandlerVTable::free` callback.
    ///
    /// # Safety
    /// `handler` must point to a live [`TimerTimeOutHandler`] while the timer
    /// is active.
    pub unsafe fn create_repeating(
        &self,
        handler: *mut TimerTimeOutHandler,
        interval_ms: i64,
    ) -> *mut ITimer {
        unsafe {
            create_repeating_timer(
                self.ptr.as_ptr().cast::<ITimersComponent>(),
                handler,
                interval_ms,
            )
        }
    }
}

/// Kills an active timer, stopping future fires.
///
/// After `kill`, the server calls `TimerTimeOutHandler::free(timer)` allowing
/// the heap-allocated handler to be released. Without it, the handler leaks.
///
/// # Safety
/// `timer` must be a valid pointer returned by `create_repeating_timer`.
pub unsafe fn kill_timer(timer: *mut ITimer) {
    let Some((_, slot)) = (unsafe {
        super::vtable::secondary_call_target_ptr(timer.cast::<u8>(), 0, SLOT_TIMER_KILL)
    }) else {
        return;
    };
    let kill: KillFn = unsafe { std::mem::transmute(slot) };
    unsafe { kill(timer) };
}

#[cfg(test)]
mod tests {
    //! Tests for the `timers` module.
    //!
    //! Cover: UID constant, `TimerTimeOutHandler` layout, defensive behavior
    //! of `create_repeating_timer` and `kill_timer` against null or invalid
    //! inputs.

    use super::*;

    /// Slots verified against the official binaries shipped with open.mp
    /// 1.5.8.3079: vtable dump of `Timers.so` (Itanium) and of `Timers.dll`
    /// via its RTTI (MSVC). Getting these wrong is silent: the server returns
    /// a non-null pointer from the wrong virtual function and no timer runs.
    #[test]
    fn slots_match_the_official_binaries() {
        #[cfg(not(target_env = "msvc"))]
        {
            assert_eq!(SLOT_CREATE_INTERVAL, 18, "Timers.so vtable [18] = create");
            assert_eq!(SLOT_TIMER_KILL, 11, "Timer vtable [11] = kill");
        }
        #[cfg(target_env = "msvc")]
        {
            assert_eq!(
                SLOT_CREATE_INTERVAL, 17,
                "Timers.dll vtable [17] = create(handler, interval, repeating); \
                 MSVC reverses the overload set, [16] is the four-argument one"
            );
            assert_eq!(SLOT_TIMER_KILL, 10, "Timer vtable [10] = kill");
        }
    }

    #[test]
    fn timers_component_uid_is_known_value() {
        // Value declared in `timers.hpp:44` of the Open Multiplayer SDK.
        assert_eq!(TIMERS_COMPONENT_UID, 0x2ad8_124c_5ea2_57a3);
    }

    #[test]
    fn timers_component_uid_via_trait() {
        assert_eq!(
            <TimersComponent as OmpComponentHandle>::UID,
            TIMERS_COMPONENT_UID
        );
    }

    #[test]
    fn timer_handler_has_vtable_at_offset_zero() {
        // The server reads the vtable at offset 0 of the handler — confirm layout.
        assert_eq!(std::mem::offset_of!(TimerTimeOutHandler, vtable), 0);
    }

    #[test]
    fn timer_handler_size_is_one_pointer() {
        // No own data: only the vtable pointer.
        assert_eq!(
            std::mem::size_of::<TimerTimeOutHandler>(),
            std::mem::size_of::<*const ()>()
        );
    }

    #[test]
    fn timer_handler_vtable_has_two_slots() {
        // IUIDProvider does not declare a destructor -> 2 slots (timeout, free).
        assert_eq!(
            std::mem::size_of::<TimerHandlerVTable>(),
            2 * std::mem::size_of::<*const ()>()
        );
    }

    #[test]
    fn create_repeating_timer_returns_null_when_handler_is_null() {
        let timers = std::ptr::null_mut::<ITimersComponent>();
        let ret = unsafe { create_repeating_timer(timers, std::ptr::null_mut(), 5) };
        assert!(ret.is_null());
    }

    #[test]
    fn create_repeating_timer_returns_null_when_component_is_null() {
        // Dummy handler: since timers is null, it should not even try to deref the handler.
        let fake_handler = std::ptr::dangling_mut::<TimerTimeOutHandler>();
        let ret = unsafe { create_repeating_timer(std::ptr::null_mut(), fake_handler, 5) };
        assert!(ret.is_null());
    }

    #[test]
    fn kill_timer_is_noop_for_null_pointer() {
        // Must not panic or segfault.
        unsafe { kill_timer(std::ptr::null_mut()) };
    }

    #[test]
    fn query_timers_component_returns_null_for_null_list() {
        let ret = unsafe { query_timers_component(std::ptr::null_mut()) };
        assert!(ret.is_null());
    }
}