--- /dev/null
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.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 sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+use ptr;
+use mem;
+use cell::Cell;
+use num::NonZeroUsize;
+use self::sync_bitset::*;
+
+#[cfg(target_pointer_width="64")]
+const USIZE_BITS: usize = 64;
+const TLS_KEYS: usize = 128; // Same as POSIX minimum
+const TLS_KEYS_BITSET_SIZE: usize = (TLS_KEYS + (USIZE_BITS - 1)) / USIZE_BITS;
+
+static TLS_KEY_IN_USE: SyncBitset = SYNC_BITSET_INIT;
+macro_rules! dup {
+ ((* $($exp:tt)*) $($val:tt)*) => (dup!( ($($exp)*) $($val)* $($val)* ));
+ (() $($val:tt)*) => ([$($val),*])
+}
+static TLS_DESTRUCTOR: [AtomicUsize; TLS_KEYS] = dup!((* * * * * * *) ATOMIC_USIZE_INIT);
+
+extern "C" {
+ fn get_tls_ptr() -> *const u8;
+ fn set_tls_ptr(tls: *const u8);
+}
+
+#[derive(Copy, Clone)]
+#[repr(C)]
+pub struct Key(NonZeroUsize);
+
+impl Key {
+ fn to_index(self) -> usize {
+ self.0.get() - 1
+ }
+
+ fn from_index(index: usize) -> Self {
+ Key(NonZeroUsize::new(index + 1).unwrap())
+ }
+
+ pub fn as_usize(self) -> usize {
+ self.0.get()
+ }
+
+ pub fn from_usize(index: usize) -> Self {
+ Key(NonZeroUsize::new(index).unwrap())
+ }
+}
+
+#[repr(C)]
+pub struct Tls {
+ data: [Cell<*mut u8>; TLS_KEYS]
+}
+
+pub struct ActiveTls<'a> {
+ tls: &'a Tls
+}
+
+impl<'a> Drop for ActiveTls<'a> {
+ fn drop(&mut self) {
+ let value_with_destructor = |key: usize| {
+ let ptr = TLS_DESTRUCTOR[key].load(Ordering::Relaxed);
+ unsafe { mem::transmute::<_,Option<unsafe extern fn(*mut u8)>>(ptr) }
+ .map(|dtor| (&self.tls.data[key], dtor))
+ };
+
+ let mut any_non_null_dtor = true;
+ while any_non_null_dtor {
+ any_non_null_dtor = false;
+ for (value, dtor) in TLS_KEY_IN_USE.iter().filter_map(&value_with_destructor) {
+ let value = value.replace(ptr::null_mut());
+ if value != ptr::null_mut() {
+ any_non_null_dtor = true;
+ unsafe { dtor(value) }
+ }
+ }
+ }
+ }
+}
+
+impl Tls {
+ pub fn new() -> Tls {
+ Tls { data: dup!((* * * * * * *) (Cell::new(ptr::null_mut()))) }
+ }
+
+ pub unsafe fn activate(&self) -> ActiveTls {
+ set_tls_ptr(self as *const Tls as _);
+ ActiveTls { tls: self }
+ }
+
+ #[allow(unused)]
+ pub unsafe fn activate_persistent(self: Box<Self>) {
+ set_tls_ptr((&*self) as *const Tls as _);
+ mem::forget(self);
+ }
+
+ unsafe fn current<'a>() -> &'a Tls {
+ &*(get_tls_ptr() as *const Tls)
+ }
+
+ pub fn create(dtor: Option<unsafe extern fn(*mut u8)>) -> Key {
+ let index = TLS_KEY_IN_USE.set().expect("TLS limit exceeded");
+ TLS_DESTRUCTOR[index].store(dtor.map_or(0, |f| f as usize), Ordering::Relaxed);
+ Key::from_index(index)
+ }
+
+ pub fn set(key: Key, value: *mut u8) {
+ let index = key.to_index();
+ assert!(TLS_KEY_IN_USE.get(index));
+ unsafe { Self::current() }.data[index].set(value);
+ }
+
+ pub fn get(key: Key) -> *mut u8 {
+ let index = key.to_index();
+ assert!(TLS_KEY_IN_USE.get(index));
+ unsafe { Self::current() }.data[index].get()
+ }
+
+ pub fn destroy(key: Key) {
+ TLS_KEY_IN_USE.clear(key.to_index());
+ }
+}
+
+mod sync_bitset {
+ use sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+ use iter::{Enumerate, Peekable};
+ use slice::Iter;
+ use super::{TLS_KEYS_BITSET_SIZE, USIZE_BITS};
+
+ /// A bitset that can be used synchronously.
+ pub(super) struct SyncBitset([AtomicUsize; TLS_KEYS_BITSET_SIZE]);
+
+ pub(super) const SYNC_BITSET_INIT: SyncBitset =
+ SyncBitset([ATOMIC_USIZE_INIT, ATOMIC_USIZE_INIT]);
+
+ impl SyncBitset {
+ pub fn get(&self, index: usize) -> bool {
+ let (hi, lo) = Self::split(index);
+ (self.0[hi].load(Ordering::Relaxed) & lo) != 0
+ }
+
+ /// Not atomic.
+ pub fn iter(&self) -> SyncBitsetIter {
+ SyncBitsetIter {
+ iter: self.0.iter().enumerate().peekable(),
+ elem_idx: 0,
+ }
+ }
+
+ pub fn clear(&self, index: usize) {
+ let (hi, lo) = Self::split(index);
+ self.0[hi].fetch_and(!lo, Ordering::Relaxed);
+ }
+
+ /// Set any unset bit. Not atomic. Returns `None` if all bits were
+ /// observed to be set.
+ pub fn set(&self) -> Option<usize> {
+ 'elems: for (idx, elem) in self.0.iter().enumerate() {
+ let mut current = elem.load(Ordering::Relaxed);
+ loop {
+ if 0 == !current {
+ continue 'elems;
+ }
+ let trailing_ones = (!current).trailing_zeros() as usize;
+ match elem.compare_exchange(
+ current,
+ current | (1 << trailing_ones),
+ Ordering::AcqRel,
+ Ordering::Relaxed
+ ) {
+ Ok(_) => return Some(idx * USIZE_BITS + trailing_ones),
+ Err(previous) => current = previous,
+ }
+ }
+ }
+ None
+ }
+
+ fn split(index: usize) -> (usize, usize) {
+ (index / USIZE_BITS, 1 << (index % USIZE_BITS))
+ }
+ }
+
+ pub(super) struct SyncBitsetIter<'a> {
+ iter: Peekable<Enumerate<Iter<'a, AtomicUsize>>>,
+ elem_idx: usize,
+ }
+
+ impl<'a> Iterator for SyncBitsetIter<'a> {
+ type Item = usize;
+
+ fn next(&mut self) -> Option<usize> {
+ self.iter.peek().cloned().and_then(|(idx, elem)| {
+ let elem = elem.load(Ordering::Relaxed);
+ let low_mask = (1 << self.elem_idx) - 1;
+ let next = elem & !low_mask;
+ let next_idx = next.trailing_zeros() as usize;
+ self.elem_idx = next_idx + 1;
+ if self.elem_idx >= 64 {
+ self.elem_idx = 0;
+ self.iter.next();
+ }
+ match next_idx {
+ 64 => self.next(),
+ _ => Some(idx * USIZE_BITS + next_idx),
+ }
+ })
+ }
+ }
+
+ #[cfg(test)]
+ mod tests {
+ use super::*;
+
+ fn test_data(bitset: [usize; 2], bit_indices: &[usize]) {
+ let set = SyncBitset([AtomicUsize::new(bitset[0]), AtomicUsize::new(bitset[1])]);
+ assert_eq!(set.iter().collect::<Vec<_>>(), bit_indices);
+ for &i in bit_indices {
+ assert!(set.get(i));
+ }
+ }
+
+ #[test]
+ fn iter() {
+ test_data([0b0110_1001, 0], &[0, 3, 5, 6]);
+ test_data([0x8000_0000_0000_0000, 0x8000_0000_0000_0001], &[63, 64, 127]);
+ test_data([0, 0], &[]);
+ }
+
+ #[test]
+ fn set_get_clear() {
+ let set = SYNC_BITSET_INIT;
+ let key = set.set().unwrap();
+ assert!(set.get(key));
+ set.clear(key);
+ assert!(!set.get(key));
+ }
+ }
+}
projects / rust.git / commitdiff