2 files changed, 175 insertions, 0 deletions
diff --git a/src/futex/linux.rs b/src/futex/linux.rs
new file mode 100755
index 0000000..80ca5a6
--- /dev/null
+++ b/src/futex/linux.rs
@@ -0,0 +1,61 @@
+use core::ops::Deref;
+use core::sync::atomic::{AtomicU32, Ordering};
+
+use libc::{syscall, SYS_futex};
+
+#[repr(C)]
+pub struct Futex(AtomicU32);
+
+pub type Atomic = AtomicU32;
+pub type Primitive = u32;
+
+pub type SmallFutex = Futex;
+pub type SmallAtomic = Atomic;
+pub type SmallPrimitive = Primitive;
+
+impl Futex {
+	#[inline]
+	pub const fn new(initial_value: u32) -> Self {
+		Self(AtomicU32::new(initial_value))
+	}
+
+	#[inline]
+	pub fn wait(&self, expected_start_value: u32) {
+		unsafe {
+			syscall(
+				SYS_futex,
+				core::ptr::from_ref(&self.0),
+				libc::FUTEX_WAIT_BITSET | libc::FUTEX_PRIVATE_FLAG,
+				expected_start_value,
+				core::ptr::null::<()>(),
+				core::ptr::null::<u32>(), // This argument is unused for FUTEX_WAIT_BITSET.
+				!0u32,                    // A full bitmask, to make it behave like a regular FUTEX_WAIT.
+			);
+		}
+	}
+
+	#[inline]
+	pub fn wake(&self) -> bool {
+		let ptr = &self.0 as *const AtomicU32;
+		const OP: libc::c_int = libc::FUTEX_WAKE | libc::FUTEX_PRIVATE_FLAG;
+		unsafe { libc::syscall(libc::SYS_futex, ptr, OP, 1) > 0 }
+	}
+
+	#[inline]
+	pub fn wake_all(&self) {
+		let ptr = &raw const self.0;
+		let op = libc::FUTEX_WAKE | libc::FUTEX_PRIVATE_FLAG;
+		unsafe {
+			syscall(libc::SYS_futex, ptr, op, i32::MAX);
+		}
+	}
+}
+
+impl Deref for Futex {
+	type Target = Atomic;
+
+	#[inline]
+	fn deref(&self) -> &Self::Target {
+		&self.0
+	}
+}
diff --git a/src/futex/windows.rs b/src/futex/windows.rs
new file mode 100755
index 0000000..153d9ef
--- /dev/null
+++ b/src/futex/windows.rs
@@ -0,0 +1,114 @@
+use core::ffi::c_void;
+
+#[cfg(not(target_vendor = "win7"))]
+// Use raw-dylib to import synchronization functions to workaround issues with the older mingw import library.
+#[cfg_attr(
+	target_arch = "x86",
+	link(
+		name = "api-ms-win-core-synch-l1-2-0",
+		kind = "raw-dylib",
+		import_name_type = "undecorated"
+	)
+)]
+#[cfg_attr(
+	not(target_arch = "x86"),
+	link(name = "api-ms-win-core-synch-l1-2-0", kind = "raw-dylib")
+)]
+extern "system" {
+	type BOOL = i32;
+
+	pub const TRUE: BOOL = 1;
+	pub const INFINITE: u32 = 4294967295;
+
+	pub fn WaitOnAddress(
+		address: *const c_void,
+		compareaddress: *const c_void,
+		addresssize: usize,
+		dwmilliseconds: u32,
+	) -> BOOL;
+	pub fn WakeByAddressSingle(address: *const c_void);
+	pub fn WakeByAddressAll(address: *const c_void);
+}
+
+pub struct Futex(AtomicU32);
+pub type Primitive = u32;
+
+impl Futex {
+	#[inline]
+	pub const fn new(initial_value: Primitive) -> Self {
+		Self(AtomicU32::new(initial_value))
+	}
+
+	#[inline]
+	pub fn wait(&self, expected_start_value: Primitive) {
+		const SIZE: u32 = core::mem::size_of::<Atomic>();
+		let addr = core::ptr::from_ref(&self.0).cast::<c_void>();
+		let compare_addr = ptr::addr_of!(compare).cast::<c_void>();
+		WaitOnAddress(addr, expected_start_value, SIZE, INFINITE);
+	}
+
+	#[inline]
+	pub fn wake(&self) -> bool {
+		WakeByAddressSingle(core::ptr::from_ref(&self.0).cast::<c_void>());
+		false
+	}
+
+	#[inline]
+	pub fn wake_all(&self) {
+		unsafe {
+			let addr = core::ptr::from_ref(address).cast::<c_void>();
+			WakeByAddressAll(addr);
+		}
+	}
+}
+
+impl Deref for Futex {
+	type Target = Atomic;
+
+	#[inline]
+	fn deref(&self) -> &Self::Target {
+		&self.0
+	}
+}
+
+pub struct SmallFutex(AtomicU8);
+pub type SmallAtomic = AtomicU8;
+pub type SmallPrimitive = u8;
+
+impl SmallFutex {
+	#[inline]
+	pub const fn new(initial_value: SmallPrimitive) -> Self {
+		Self(AtomicU32::new(initial_value))
+	}
+
+	#[inline]
+	pub fn wait(&self, expected_start_value: SmallPrimitive) {
+		const SIZE: u32 = core::mem::size_of::<SmallAtomic>();
+		let addr = core::ptr::from_ref(&self.0).cast::<c_void>();
+		let compare_addr = ptr::addr_of!(compare).cast::<c_void>();
+		WaitOnAddress(addr, expected_start_value, SIZE, INFINITE);
+	}
+
+	#[inline]
+	pub fn wake(&self) -> bool {
+		WakeByAddressSingle(core::ptr::from_ref(&self.0).cast::<c_void>());
+		false
+	}
+
+	#[inline]
+	pub fn wake_all(&self) {
+		unsafe {
+			let addr = core::ptr::from_ref(address).cast::<c_void>();
+			WakeByAddressAll(addr);
+		}
+	}
+}
+
+impl Deref for SmallFutex {
+	type Target = SmallAtomic;
+
+	#[inline]
+	fn deref(&self) -> &Self::Target {
+		&self.0
+	}
+}