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use std::convert::TryInto;
use std::ffi::c_void;
use std::time::Duration;
use crate::raw;
use crate::raw::RedisModuleTimerID;
use crate::{Context, ValkeyError};
// We use `repr(C)` since we access the underlying data field directly.
// The order matters: the data field must come first.
#[repr(C)]
struct CallbackData<F: FnOnce(&Context, T), T> {
data: T,
callback: F,
}
impl Context {
/// Wrapper for `RedisModule_CreateTimer`.
///
/// This function takes ownership of the provided data, and transfers it to Redis.
/// The callback will get the original data back in a type safe manner.
/// When the callback is done, the data will be dropped.
pub fn create_timer<F, T: 'static>(
&self,
period: Duration,
callback: F,
data: T,
) -> RedisModuleTimerID
where
F: FnOnce(&Self, T),
{
let cb_data = CallbackData { data, callback };
// Store the user-provided data on the heap before passing ownership of it to Redis,
// so that it will outlive the current scope.
let data = Box::from(cb_data);
// Take ownership of the data inside the box and obtain a raw pointer to pass to Redis.
let data = Box::into_raw(data);
unsafe {
raw::RedisModule_CreateTimer.unwrap()(
self.ctx,
period
.as_millis()
.try_into()
.expect("Value must fit in 64 bits"),
Some(raw_callback::<F, T>),
data.cast::<c_void>(),
)
}
}
/// Wrapper for `RedisModule_StopTimer`.
///
/// The caller is responsible for specifying the correct type for the returned data.
/// This function has no way to know what the original type of the data was, so the
/// same data type that was used for `create_timer` needs to be passed here to ensure
/// their types are identical.
pub fn stop_timer<T>(&self, timer_id: RedisModuleTimerID) -> Result<T, ValkeyError> {
let mut data: *mut c_void = std::ptr::null_mut();
let status: raw::Status =
unsafe { raw::RedisModule_StopTimer.unwrap()(self.ctx, timer_id, &mut data) }.into();
if status != raw::Status::Ok {
return Err(ValkeyError::Str(
"RedisModule_StopTimer failed, timer may not exist",
));
}
let data: T = take_data(data);
Ok(data)
}
/// Wrapper for `RedisModule_GetTimerInfo`.
///
/// The caller is responsible for specifying the correct type for the returned data.
/// This function has no way to know what the original type of the data was, so the
/// same data type that was used for `create_timer` needs to be passed here to ensure
/// their types are identical.
pub fn get_timer_info<T>(
&self,
timer_id: RedisModuleTimerID,
) -> Result<(Duration, &T), ValkeyError> {
let mut remaining: u64 = 0;
let mut data: *mut c_void = std::ptr::null_mut();
let status: raw::Status = unsafe {
raw::RedisModule_GetTimerInfo.unwrap()(self.ctx, timer_id, &mut remaining, &mut data)
}
.into();
if status != raw::Status::Ok {
return Err(ValkeyError::Str(
"RedisModule_GetTimerInfo failed, timer may not exist",
));
}
// Cast the *mut c_void supplied by the Valkey API to a raw pointer of our custom type.
let data = data.cast::<T>();
// Dereference the raw pointer (we know this is safe, since Valkey should return our
// original pointer which we know to be good) and turn it into a safe reference
let data = unsafe { &*data };
Ok((Duration::from_millis(remaining), data))
}
}
fn take_data<T>(data: *mut c_void) -> T {
// Cast the *mut c_void supplied by the Valkey API to a raw pointer of our custom type.
let data = data.cast::<T>();
// Take back ownership of the original boxed data, so we can unbox it safely.
// If we don't do this, the data's memory will be leaked.
let data = unsafe { Box::from_raw(data) };
*data
}
extern "C" fn raw_callback<F, T>(ctx: *mut raw::RedisModuleCtx, data: *mut c_void)
where
F: FnOnce(&Context, T),
{
let ctx = &Context::new(ctx);
if data.is_null() {
ctx.log_debug("[callback] Data is null; this should not happen!");
return;
}
let cb_data: CallbackData<F, T> = take_data(data);
(cb_data.callback)(ctx, cb_data.data);
}