1 files changed, 127 insertions, 0 deletions
diff --git a/vendor/thread_local/src/thread_id.rs b/vendor/thread_local/src/thread_id.rs
new file mode 100644
index 000000000..6eb0f616f
--- /dev/null
+++ b/vendor/thread_local/src/thread_id.rs
@@ -0,0 +1,127 @@
+// Copyright 2017 Amanieu d'Antras
+//
+// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
+// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
+// http://opensource.org/licenses/MIT>, at your option. This file may not be
+// copied, modified, or distributed except according to those terms.
+
+use crate::POINTER_WIDTH;
+use once_cell::sync::Lazy;
+use std::cmp::Reverse;
+use std::collections::BinaryHeap;
+use std::sync::Mutex;
+use std::usize;
+
+/// Thread ID manager which allocates thread IDs. It attempts to aggressively
+/// reuse thread IDs where possible to avoid cases where a ThreadLocal grows
+/// indefinitely when it is used by many short-lived threads.
+struct ThreadIdManager {
+    free_from: usize,
+    free_list: BinaryHeap<Reverse<usize>>,
+}
+impl ThreadIdManager {
+    fn new() -> ThreadIdManager {
+        ThreadIdManager {
+            free_from: 0,
+            free_list: BinaryHeap::new(),
+        }
+    }
+    fn alloc(&mut self) -> usize {
+        if let Some(id) = self.free_list.pop() {
+            id.0
+        } else {
+            let id = self.free_from;
+            self.free_from = self
+                .free_from
+                .checked_add(1)
+                .expect("Ran out of thread IDs");
+            id
+        }
+    }
+    fn free(&mut self, id: usize) {
+        self.free_list.push(Reverse(id));
+    }
+}
+static THREAD_ID_MANAGER: Lazy<Mutex<ThreadIdManager>> =
+    Lazy::new(|| Mutex::new(ThreadIdManager::new()));
+
+/// Data which is unique to the current thread while it is running.
+/// A thread ID may be reused after a thread exits.
+#[derive(Clone, Copy)]
+pub(crate) struct Thread {
+    /// The thread ID obtained from the thread ID manager.
+    pub(crate) id: usize,
+    /// The bucket this thread's local storage will be in.
+    pub(crate) bucket: usize,
+    /// The size of the bucket this thread's local storage will be in.
+    pub(crate) bucket_size: usize,
+    /// The index into the bucket this thread's local storage is in.
+    pub(crate) index: usize,
+}
+impl Thread {
+    fn new(id: usize) -> Thread {
+        let bucket = usize::from(POINTER_WIDTH) - id.leading_zeros() as usize;
+        let bucket_size = 1 << bucket.saturating_sub(1);
+        let index = if id != 0 { id ^ bucket_size } else { 0 };
+
+        Thread {
+            id,
+            bucket,
+            bucket_size,
+            index,
+        }
+    }
+}
+
+/// Wrapper around `Thread` that allocates and deallocates the ID.
+struct ThreadHolder(Thread);
+impl ThreadHolder {
+    fn new() -> ThreadHolder {
+        ThreadHolder(Thread::new(THREAD_ID_MANAGER.lock().unwrap().alloc()))
+    }
+}
+impl Drop for ThreadHolder {
+    fn drop(&mut self) {
+        THREAD_ID_MANAGER.lock().unwrap().free(self.0.id);
+    }
+}
+
+thread_local!(static THREAD_HOLDER: ThreadHolder = ThreadHolder::new());
+
+/// Get the current thread.
+pub(crate) fn get() -> Thread {
+    THREAD_HOLDER.with(|holder| holder.0)
+}
+
+#[test]
+fn test_thread() {
+    let thread = Thread::new(0);
+    assert_eq!(thread.id, 0);
+    assert_eq!(thread.bucket, 0);
+    assert_eq!(thread.bucket_size, 1);
+    assert_eq!(thread.index, 0);
+
+    let thread = Thread::new(1);
+    assert_eq!(thread.id, 1);
+    assert_eq!(thread.bucket, 1);
+    assert_eq!(thread.bucket_size, 1);
+    assert_eq!(thread.index, 0);
+
+    let thread = Thread::new(2);
+    assert_eq!(thread.id, 2);
+    assert_eq!(thread.bucket, 2);
+    assert_eq!(thread.bucket_size, 2);
+    assert_eq!(thread.index, 0);
+
+    let thread = Thread::new(3);
+    assert_eq!(thread.id, 3);
+    assert_eq!(thread.bucket, 2);
+    assert_eq!(thread.bucket_size, 2);
+    assert_eq!(thread.index, 1);
+
+    let thread = Thread::new(19);
+    assert_eq!(thread.id, 19);
+    assert_eq!(thread.bucket, 5);
+    assert_eq!(thread.bucket_size, 16);
+    assert_eq!(thread.index, 3);
+}