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//! Typed loader events for [`Load::on`](crate::Load::on).
//!
//! Events from the server are raised on its game thread: keep handlers short,
//! and leave slow work to a thread of the mod's own. On a client they come
//! from the built-in server while it hosts a game, solo play included; each
//! hosted game starts with [`WorldLoaded`] and ends with [`ShutdownStarted`], so
//! state of one game is reset there.
//!
//! Each event is named for what happened, a subject and a verb in the past
//! tense, and its [`Event`] constant is the same name in capitals:
//! [`PlayerJoined`] is [`Event::PLAYER_JOINED`].
use core::ffi::c_void;
use crate::abi::{
BuildingData, ChunkData, Event, KnowledgeData, PlayerData, PlayerDeathData, QuestData, TickData,
};
mod sealed {
pub trait Sealed {}
}
/// An event with its data type; implemented by the types in this module only.
///
/// # Examples
///
/// ```
/// use enshwick::abi::Event;
/// use enshwick::events::{Kind, PlayerJoined};
///
/// assert!(PlayerJoined::EVENT == Event::PLAYER_JOINED);
/// ```
pub trait Kind: sealed::Sealed + 'static {
/// The raw event.
const EVENT: Event;
/// What a handler gets: an ABI struct, or `()` for events without data.
type Data: Copy + 'static;
/// The event's data from the raw pointer the loader passes; `None` when
/// it is missing.
///
/// # Safety
///
/// - `raw` is null or the pointer the loader passed with [`Kind::EVENT`]:
/// a [`Kind::Data`] the loader wrote, readable for the size its header
/// states; no alignment is needed.
/// - No other thread writes that struct during the call.
unsafe fn data(raw: *const c_void) -> Option<Self::Data>;
}
macro_rules! without_data {
($($(#[$doc:meta])* $name:ident = $event:ident;)*) => {$(
$(#[$doc])*
///
/// # Examples
///
/// See [`Load::on`](crate::Load::on).
#[derive(Debug, Clone, Copy)]
pub struct $name;
impl sealed::Sealed for $name {}
impl Kind for $name {
const EVENT: Event = Event::$event;
type Data = ();
unsafe fn data(_raw: *const c_void) -> Option<()> {
Some(())
}
}
)*};
}
macro_rules! with_data {
($($(#[$doc:meta])* $name:ident = $event:ident: $data:ty, $born:expr;)*) => {$(
$(#[$doc])*
///
/// # Examples
///
/// See [`Load::on`](crate::Load::on).
#[derive(Debug, Clone, Copy)]
pub struct $name;
impl sealed::Sealed for $name {}
impl Kind for $name {
const EVENT: Event = Event::$event;
type Data = $data;
unsafe fn data(raw: *const c_void) -> Option<$data> {
// SAFETY: the caller guarantees `raw` is null or this event's
// data, readable for the size its header states with no
// concurrent writer, which is the contract of `read_headed`.
unsafe { crate::abi::read_headed(raw.cast::<$data>(), $born) }
}
}
)*};
}
without_data! {
/// [`Event::SETTINGS_CHANGED`], on no fixed thread;
/// [`Load::on_config_change`](crate::Load::on_config_change) re-reads the
/// settings for you.
SettingsChanged = SETTINGS_CHANGED;
/// [`Event::LOADER_SETTINGS_CHANGED`].
LoaderSettingsChanged = LOADER_SETTINGS_CHANGED;
/// [`Event::WORLD_LOADED`].
WorldLoaded = WORLD_LOADED;
/// [`Event::WORLD_SAVED`].
WorldSaved = WORLD_SAVED;
/// [`Event::SHUTDOWN_STARTED`].
ShutdownStarted = SHUTDOWN_STARTED;
/// [`Event::JOIN_REFUSED`]; [`crate::mods::join_missing`] lists the mods.
JoinRefused = JOIN_REFUSED;
/// [`Event::ALTARS_CHANGED`]; [`crate::altars::Altars::list`] lists them.
AltarsChanged = ALTARS_CHANGED;
/// [`Event::DAY_STARTED`]; [`crate::daytime::Clock::now`] reads the clock.
DayStarted = DAY_STARTED;
/// [`Event::NIGHT_STARTED`].
NightStarted = NIGHT_STARTED;
/// [`Event::SETTINGS_REPLACED`]; [`Load::on_config_change`](crate::Load::on_config_change)
/// re-reads the settings for you, the ones that wait for a start too.
SettingsReplaced = SETTINGS_REPLACED;
}
// Each event names its data and the size that data had in the minor that
// added the event, the part every loader that runs the mod writes.
with_data! {
/// [`Event::TICKED`].
Ticked = TICKED: TickData, size_of::<TickData>();
/// [`Event::PLAYER_JOINED`].
PlayerJoined = PLAYER_JOINED: PlayerData, size_of::<PlayerData>();
/// [`Event::PLAYER_LEFT`].
PlayerLeft = PLAYER_LEFT: PlayerData, size_of::<PlayerData>();
/// [`Event::BUILDING_PLACED`].
BuildingPlaced = BUILDING_PLACED: BuildingData, size_of::<BuildingData>();
/// [`Event::KNOWLEDGE_CHANGED`]; [`crate::knowledge::Knowledge`] reads and grants.
KnowledgeChanged = KNOWLEDGE_CHANGED: KnowledgeData, size_of::<KnowledgeData>();
/// [`Event::QUEST_COMPLETED`].
QuestCompleted = QUEST_COMPLETED: QuestData, size_of::<QuestData>();
/// [`Event::CHUNK_LOADED`].
ChunkLoaded = CHUNK_LOADED: ChunkData, size_of::<ChunkData>();
/// [`Event::CHUNK_UNLOADED`].
ChunkUnloaded = CHUNK_UNLOADED: ChunkData, size_of::<ChunkData>();
/// [`Event::BUILDING_REMOVED`].
BuildingRemoved = BUILDING_REMOVED: BuildingData, size_of::<BuildingData>();
/// [`Event::PLAYER_DIED`].
PlayerDied = PLAYER_DIED: PlayerDeathData, core::mem::offset_of!(PlayerDeathData, killer_entity);
}
#[cfg(test)]
mod tests {
use super::*;
use crate::abi::Header;
#[test]
fn data_is_read_only_when_it_has_every_field_of_its_minor() {
let player = PlayerData {
header: Header::of::<PlayerData>(),
slot: 2,
entity: 9,
key: 1,
};
let raw = (&raw const player).cast::<c_void>();
// SAFETY: `player` is a whole `PlayerData` on this stack frame,
// readable for the size its header states.
let joined = unsafe { PlayerJoined::data(raw) };
assert_eq!(joined.map(|p| p.entity), Some(9));
// SAFETY: `data` accepts a null pointer and reads nothing.
assert!(unsafe { PlayerLeft::data(core::ptr::null()) }.is_none());
let mut short = player;
short.header.size = 8;
// SAFETY: `short` is a whole `PlayerData` on this stack frame, its
// header stating fewer bytes than it holds.
assert!(unsafe { PlayerJoined::data((&raw const short).cast()) }.is_none());
// SAFETY: `data` of an event without data reads nothing.
assert!(unsafe { WorldSaved::data(core::ptr::null()) }.is_some());
}
#[test]
fn a_death_from_minor_60_reads_without_its_killer_entity() {
let mut death = PlayerDeathData {
header: Header::of::<PlayerDeathData>(),
entity: 3,
cause: PlayerDeathData::HIT,
key: 7,
position: [0.0; 3],
killer: [1; 16],
deadly_shroud: 0,
drowned: 0,
reserved: 0,
killer_entity: 9,
reserved_tail: 0,
};
death.header.size = 56;
// SAFETY: `death` is a whole `PlayerDeathData` on this stack frame,
// its header stating fewer bytes than it holds.
let read = unsafe { PlayerDied::data((&raw const death).cast()) }.unwrap();
assert_eq!((read.entity, read.killer_entity), (3, 0));
}
#[test]
fn data_from_a_newer_loader_is_read() {
#[repr(C)]
struct Newer {
player: PlayerData,
appended: u64,
}
let mut newer = Newer {
player: PlayerData {
header: Header::of::<PlayerData>(),
slot: 2,
entity: 9,
key: 1,
},
appended: 5,
};
newer.player.header.size = u32::try_from(size_of::<Newer>()).unwrap();
// SAFETY: `newer` is on this stack frame and starts with a whole
// `PlayerData` whose header states the size of `Newer`, all of it
// readable.
let joined = unsafe { PlayerJoined::data((&raw const newer).cast()) }.unwrap();
assert_eq!((joined.entity, joined.key), (9, 1));
assert_eq!(newer.appended, 5);
}
}