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use crate::sys::thread;
use crate::sync::atomic::{AtomicUsize, Ordering::SeqCst};
const MAX_KEYS: usize = 128;
static NEXT_KEY: AtomicUsize = AtomicUsize::new(0);
struct ThreadControlBlock {
keys: [*mut u8; MAX_KEYS],
}
impl ThreadControlBlock {
fn new() -> ThreadControlBlock {
ThreadControlBlock {
keys: [core::ptr::null_mut(); MAX_KEYS],
}
}
fn get() -> *mut ThreadControlBlock {
let ptr = thread::tcb_get();
if !ptr.is_null() {
return ptr as *mut ThreadControlBlock
}
let tcb = Box::into_raw(Box::new(ThreadControlBlock::new()));
thread::tcb_set(tcb as *mut u8);
tcb
}
}
pub type Key = usize;
pub unsafe fn create(dtor: Option<unsafe extern fn(*mut u8)>) -> Key {
drop(dtor); // FIXME: need to figure out how to hook thread exit to run this
let key = NEXT_KEY.fetch_add(1, SeqCst);
if key >= MAX_KEYS {
NEXT_KEY.store(MAX_KEYS, SeqCst);
panic!("cannot allocate space for more TLS keys");
}
// offset by 1 so we never hand out 0. This is currently required by
// `sys_common/thread_local.rs` where it can't cope with keys of value 0
// because it messes up the atomic management.
return key + 1
}
pub unsafe fn set(key: Key, value: *mut u8) {
(*ThreadControlBlock::get()).keys[key - 1] = value;
}
pub unsafe fn get(key: Key) -> *mut u8 {
(*ThreadControlBlock::get()).keys[key - 1]
}
pub unsafe fn destroy(_key: Key) {
// FIXME: should implement this somehow, this isn't typically called but it
// can be called if two threads race to initialize a TLS slot and one ends
// up not being needed.
}
#[inline]
pub fn requires_synchronized_create() -> bool {
false
}
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