16 /// Thread ID manager which allocates thread IDs. It attempts to aggressively
17 /// reuse thread IDs where possible to avoid cases where a ThreadLocal grows
38                 .expect("Ran out of thread IDs");  in alloc()
49 /// Data which is unique to the current thread while it is running.
50 /// A thread ID may be reused after a thread exits.
52 pub(crate) struct Thread {  struct
53     /// The thread ID obtained from the thread ID manager.
55     /// The bucket this thread's local storage will be in.
57     /// The size of the bucket this thread's local storage will be in.
59     /// The index into the bucket this thread's local storage is in.
62 impl Thread {  argument
63     fn new(id: usize) -> Thread {  in new()  argument
68         Thread {  in new()
79         // This is split into 2 thread-local variables so that we can check whether the
80         // thread is initialized without having to register a thread-local destructor.
84         static mut THREAD: Option<Thread> = None;  constant
87         // Guard to ensure the thread ID is released on thread exit.
89             // We keep a copy of the thread ID in the ThreadGuard: we can't
90             // reliably access THREAD in our Drop impl due to the unpredictable
97                 // Release the thread ID. Any further accesses to the thread ID
101                     THREAD = None;
107         /// Returns a thread ID for the current thread, allocating one if needed.
109         pub(crate) fn get() -> Thread {
110             if let Some(thread) = unsafe { THREAD } {
111                 thread
117         /// Out-of-line slow path for allocating a thread ID.
119          fn get_slow() -> Thread {
120             let new = Thread::new(THREAD_ID_MANAGER.lock().unwrap().alloc());
122                 THREAD = Some(new);
128         // This is split into 2 thread-local variables so that we can check whether the
129         // thread is initialized without having to register a thread-local destructor.
132         thread_local! { static THREAD: Cell<Option<Thread>> = const { Cell::new(None) }; }
135         // Guard to ensure the thread ID is released on thread exit.
137             // We keep a copy of the thread ID in the ThreadGuard: we can't
138             // reliably access THREAD in our Drop impl due to the unpredictable
145                 // Release the thread ID. Any further accesses to the thread ID
148                 let _ = THREAD.try_with(|thread| thread.set(None));
153         /// Returns a thread ID for the current thread, allocating one if needed.
155         pub(crate) fn get() -> Thread {
156             THREAD.with(|thread| {
157                 if let Some(thread) = thread.get() {
158                     thread
160                     get_slow(thread)
165         /// Out-of-line slow path for allocating a thread ID.
167         fn get_slow(thread: &Cell<Option<Thread>>) -> Thread {
168             let new = Thread::new(THREAD_ID_MANAGER.lock().unwrap().alloc());
169             thread.set(Some(new));
178     let thread = Thread::new(0);  in test_thread()  localVariable
179     assert_eq!(thread.id, 0);  in test_thread()
180     assert_eq!(thread.bucket, 0);  in test_thread()
181     assert_eq!(thread.bucket_size, 1);  in test_thread()
182     assert_eq!(thread.index, 0);  in test_thread()
184     let thread = Thread::new(1);  in test_thread()  localVariable
185     assert_eq!(thread.id, 1);  in test_thread()
186     assert_eq!(thread.bucket, 1);  in test_thread()
187     assert_eq!(thread.bucket_size, 1);  in test_thread()
188     assert_eq!(thread.index, 0);  in test_thread()
190     let thread = Thread::new(2);  in test_thread()  localVariable
191     assert_eq!(thread.id, 2);  in test_thread()
192     assert_eq!(thread.bucket, 2);  in test_thread()
193     assert_eq!(thread.bucket_size, 2);  in test_thread()
194     assert_eq!(thread.index, 0);  in test_thread()
196     let thread = Thread::new(3);  in test_thread()  localVariable
197     assert_eq!(thread.id, 3);  in test_thread()
198     assert_eq!(thread.bucket, 2);  in test_thread()
199     assert_eq!(thread.bucket_size, 2);  in test_thread()
200     assert_eq!(thread.index, 1);  in test_thread()
202     let thread = Thread::new(19);  in test_thread()  localVariable
203     assert_eq!(thread.id, 19);  in test_thread()
204     assert_eq!(thread.bucket, 5);  in test_thread()
205     assert_eq!(thread.bucket_size, 16);  in test_thread()
206     assert_eq!(thread.index, 3);  in test_thread()