use std::{any::TypeId, marker::PhantomData, ptr::addr_of};
use tracing::{Dispatch, Id, Subscriber};
use tracing_subscriber::{layer::Context, registry::LookupSpan, Layer};
use crate::token::UnsafeAllocationGroupToken;
pub(crate) struct WithAllocationGroup {
with_allocation_group: fn(&Dispatch, &Id, UnsafeAllocationGroupToken),
}
impl WithAllocationGroup {
pub fn with_allocation_group(
&self,
dispatch: &Dispatch,
id: &Id,
unsafe_token: UnsafeAllocationGroupToken,
) {
(self.with_allocation_group)(dispatch, id, unsafe_token);
}
}
#[cfg_attr(docsrs, doc(cfg(feature = "tracing-compat")))]
pub struct AllocationLayer<S> {
ctx: WithAllocationGroup,
_subscriber: PhantomData<fn(S)>,
}
impl<S> AllocationLayer<S>
where
S: Subscriber + for<'span> LookupSpan<'span>,
{
#[must_use]
pub fn new() -> Self {
let ctx = WithAllocationGroup {
with_allocation_group: Self::with_allocation_group,
};
Self {
ctx,
_subscriber: PhantomData,
}
}
fn with_allocation_group(
dispatch: &Dispatch,
id: &Id,
unsafe_token: UnsafeAllocationGroupToken,
) {
let subscriber = dispatch
.downcast_ref::<S>()
.expect("subscriber should downcast to expected type; this is a bug!");
let span = subscriber
.span(id)
.expect("registry should have a span for the current ID");
span.extensions_mut().insert(unsafe_token);
}
}
impl<S> Layer<S> for AllocationLayer<S>
where
S: Subscriber + for<'a> LookupSpan<'a>,
{
fn on_enter(&self, id: &Id, ctx: Context<'_, S>) {
if let Some(span_ref) = ctx.span(id) {
if let Some(token) = span_ref
.extensions_mut()
.get_mut::<UnsafeAllocationGroupToken>()
{
token.enter();
}
}
}
fn on_exit(&self, id: &Id, ctx: Context<'_, S>) {
if let Some(span_ref) = ctx.span(id) {
if let Some(token) = span_ref
.extensions_mut()
.get_mut::<UnsafeAllocationGroupToken>()
{
token.exit();
}
}
}
unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()> {
match id {
id if id == TypeId::of::<Self>() => Some(addr_of!(self).cast::<()>()),
id if id == TypeId::of::<WithAllocationGroup>() => {
Some(addr_of!(self.ctx).cast::<()>())
}
_ => None,
}
}
}
impl<S> Default for AllocationLayer<S>
where
S: Subscriber + for<'span> LookupSpan<'span>,
{
fn default() -> Self {
AllocationLayer::new()
}
}