std: begin moving platform support modules into `pal`

1 files changed, 55 insertions, 0 deletions

diff --git a/library/std/src/sys/pal/wasm/atomics/thread.rs b/library/std/src/sys/pal/wasm/atomics/thread.rs
new file mode 100644
index 00000000000..714b7049227
--- /dev/null
+++ b/library/std/src/sys/pal/wasm/atomics/thread.rs
@@ -0,0 +1,55 @@
+use crate::ffi::CStr;
+use crate::io;
+use crate::num::NonZeroUsize;
+use crate::sys::unsupported;
+use crate::time::Duration;
+
+pub struct Thread(!);
+
+pub const DEFAULT_MIN_STACK_SIZE: usize = 4096;
+
+impl Thread {
+    // unsafe: see thread::Builder::spawn_unchecked for safety requirements
+    pub unsafe fn new(_stack: usize, _p: Box<dyn FnOnce()>) -> io::Result<Thread> {
+        unsupported()
+    }
+
+    pub fn yield_now() {}
+
+    pub fn set_name(_name: &CStr) {}
+
+    pub fn sleep(dur: Duration) {
+        use crate::arch::wasm32;
+        use crate::cmp;
+
+        // Use an atomic wait to block the current thread artificially with a
+        // timeout listed. Note that we should never be notified (return value
+        // of 0) or our comparison should never fail (return value of 1) so we
+        // should always only resume execution through a timeout (return value
+        // 2).
+        let mut nanos = dur.as_nanos();
+        while nanos > 0 {
+            let amt = cmp::min(i64::MAX as u128, nanos);
+            let mut x = 0;
+            let val = unsafe { wasm32::memory_atomic_wait32(&mut x, 0, amt as i64) };
+            debug_assert_eq!(val, 2);
+            nanos -= amt;
+        }
+    }
+
+    pub fn join(self) {}
+}
+
+pub fn available_parallelism() -> io::Result<NonZeroUsize> {
+    unsupported()
+}
+
+pub mod guard {
+    pub type Guard = !;
+    pub unsafe fn current() -> Option<Guard> {
+        None
+    }
+    pub unsafe fn init() -> Option<Guard> {
+        None
+    }
+}