From 0fd88fbe3fc483c5f7ab3b9e75558b0061402c0e Mon Sep 17 00:00:00 2001
From: Tobias Koppers <tobias.koppers@googlemail.com>
Date: Fri, 25 Nov 2022 12:07:10 +0100
Subject: [PATCH] enable id reusing

---
 Cargo.lock                           |  1 +
 crates/turbo-tasks/Cargo.toml        |  1 +
 crates/turbo-tasks/src/id_factory.rs | 14 ++++++++++----
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 0dd55a7e20452..794dd3d76968d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -6371,6 +6371,7 @@ dependencies = [
  "anyhow",
  "auto-hash-map",
  "bitflags",
+ "concurrent-queue",
  "dashmap",
  "erased-serde",
  "event-listener",
diff --git a/crates/turbo-tasks/Cargo.toml b/crates/turbo-tasks/Cargo.toml
index f50be5505ac92..a4a6c0c9428d9 100644
--- a/crates/turbo-tasks/Cargo.toml
+++ b/crates/turbo-tasks/Cargo.toml
@@ -20,6 +20,7 @@ any_key = "0.1.1"
 anyhow = "1.0.47"
 auto-hash-map = { path = "../auto-hash-map" }
 bitflags = "1.3.2"
+concurrent-queue = "1.2.2"
 dashmap = "5.4.0"
 erased-serde = "0.3.20"
 event-listener = "2.5.3"
diff --git a/crates/turbo-tasks/src/id_factory.rs b/crates/turbo-tasks/src/id_factory.rs
index f269220dbf4f7..5335862466742 100644
--- a/crates/turbo-tasks/src/id_factory.rs
+++ b/crates/turbo-tasks/src/id_factory.rs
@@ -4,10 +4,12 @@ use std::{
     sync::atomic::{AtomicUsize, Ordering},
 };
 
+use concurrent_queue::ConcurrentQueue;
+use once_cell::sync::Lazy;
+
 pub struct IdFactory<T> {
     next_id: AtomicUsize,
-    // TODO
-    // free_ids: AtomicPtr<...>
+    free_ids: Lazy<ConcurrentQueue<T>>,
     phantom_data: PhantomData<T>,
 }
 
@@ -21,18 +23,22 @@ impl<T: From<usize> + Deref<Target = usize>> IdFactory<T> {
     pub const fn new() -> Self {
         Self {
             next_id: AtomicUsize::new(1),
+            free_ids: Lazy::new(|| ConcurrentQueue::unbounded()),
             phantom_data: PhantomData,
         }
     }
 
     pub fn get(&self) -> T {
+        if let Ok(id) = self.free_ids.pop() {
+            return id;
+        }
         self.next_id.fetch_add(1, Ordering::Relaxed).into()
     }
 
     /// # Safety
     ///
     /// It must be ensured that the id is no longer used
-    pub unsafe fn reuse(&self, _id: T) {
-        // TODO
+    pub unsafe fn reuse(&self, id: T) {
+        let _ = self.free_ids.push(id);
     }
 }