1 files changed, 140 insertions, 0 deletions
diff --git a/library/std/src/sys/thread/windows.rs b/library/std/src/sys/thread/windows.rs
new file mode 100644
index 00000000000..a5640c51c4a
--- /dev/null
+++ b/library/std/src/sys/thread/windows.rs
@@ -0,0 +1,140 @@
+use core::ffi::c_void;
+
+use crate::ffi::CStr;
+use crate::num::NonZero;
+use crate::os::windows::io::{AsRawHandle, HandleOrNull};
+use crate::sys::handle::Handle;
+use crate::sys::pal::time::WaitableTimer;
+use crate::sys::pal::{dur2timeout, to_u16s};
+use crate::sys::{c, stack_overflow};
+use crate::sys_common::FromInner;
+use crate::time::Duration;
+use crate::{io, ptr};
+
+pub const DEFAULT_MIN_STACK_SIZE: usize = 2 * 1024 * 1024;
+
+pub struct Thread {
+    handle: Handle,
+}
+
+impl Thread {
+    // unsafe: see thread::Builder::spawn_unchecked for safety requirements
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    pub unsafe fn new(
+        stack: usize,
+        _name: Option<&str>,
+        p: Box<dyn FnOnce()>,
+    ) -> io::Result<Thread> {
+        let p = Box::into_raw(Box::new(p));
+
+        // CreateThread rounds up values for the stack size to the nearest page size (at least 4kb).
+        // If a value of zero is given then the default stack size is used instead.
+        // SAFETY: `thread_start` has the right ABI for a thread's entry point.
+        // `p` is simply passed through to the new thread without being touched.
+        let ret = unsafe {
+            let ret = c::CreateThread(
+                ptr::null_mut(),
+                stack,
+                Some(thread_start),
+                p as *mut _,
+                c::STACK_SIZE_PARAM_IS_A_RESERVATION,
+                ptr::null_mut(),
+            );
+            HandleOrNull::from_raw_handle(ret)
+        };
+        return if let Ok(handle) = ret.try_into() {
+            Ok(Thread { handle: Handle::from_inner(handle) })
+        } else {
+            // The thread failed to start and as a result p was not consumed. Therefore, it is
+            // safe to reconstruct the box so that it gets deallocated.
+            unsafe { drop(Box::from_raw(p)) };
+            Err(io::Error::last_os_error())
+        };
+
+        unsafe extern "system" fn thread_start(main: *mut c_void) -> u32 {
+            // Next, reserve some stack space for if we otherwise run out of stack.
+            stack_overflow::reserve_stack();
+            // Finally, let's run some code.
+            // SAFETY: We are simply recreating the box that was leaked earlier.
+            // It's the responsibility of the one who call `Thread::new` to ensure this is safe to call here.
+            unsafe { Box::from_raw(main as *mut Box<dyn FnOnce()>)() };
+            0
+        }
+    }
+
+    pub fn join(self) {
+        let rc = unsafe { c::WaitForSingleObject(self.handle.as_raw_handle(), c::INFINITE) };
+        if rc == c::WAIT_FAILED {
+            panic!("failed to join on thread: {}", io::Error::last_os_error());
+        }
+    }
+
+    pub fn handle(&self) -> &Handle {
+        &self.handle
+    }
+
+    pub fn into_handle(self) -> Handle {
+        self.handle
+    }
+}
+
+pub fn available_parallelism() -> io::Result<NonZero<usize>> {
+    let res = unsafe {
+        let mut sysinfo: c::SYSTEM_INFO = crate::mem::zeroed();
+        c::GetSystemInfo(&mut sysinfo);
+        sysinfo.dwNumberOfProcessors as usize
+    };
+    match res {
+        0 => Err(io::Error::UNKNOWN_THREAD_COUNT),
+        cpus => Ok(unsafe { NonZero::new_unchecked(cpus) }),
+    }
+}
+
+pub fn current_os_id() -> Option<u64> {
+    // SAFETY: FFI call with no preconditions.
+    let id: u32 = unsafe { c::GetCurrentThreadId() };
+
+    // A return value of 0 indicates failed lookup.
+    if id == 0 { None } else { Some(id.into()) }
+}
+
+pub fn set_name(name: &CStr) {
+    if let Ok(utf8) = name.to_str() {
+        if let Ok(utf16) = to_u16s(utf8) {
+            unsafe {
+                // SAFETY: the vec returned by `to_u16s` ends with a zero value
+                set_name_wide(&utf16)
+            }
+        };
+    };
+}
+
+/// # Safety
+///
+/// `name` must end with a zero value
+pub unsafe fn set_name_wide(name: &[u16]) {
+    unsafe { c::SetThreadDescription(c::GetCurrentThread(), name.as_ptr()) };
+}
+
+pub fn sleep(dur: Duration) {
+    fn high_precision_sleep(dur: Duration) -> Result<(), ()> {
+        let timer = WaitableTimer::high_resolution()?;
+        timer.set(dur)?;
+        timer.wait()
+    }
+    // Attempt to use high-precision sleep (Windows 10, version 1803+).
+    // On error fallback to the standard `Sleep` function.
+    // Also preserves the zero duration behavior of `Sleep`.
+    if dur.is_zero() || high_precision_sleep(dur).is_err() {
+        unsafe { c::Sleep(dur2timeout(dur)) }
+    }
+}
+
+pub fn yield_now() {
+    // This function will return 0 if there are no other threads to execute,
+    // but this also means that the yield was useless so this isn't really a
+    // case that needs to be worried about.
+    unsafe {
+        c::SwitchToThread();
+    }
+}