1 files changed, 61 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
+	}
+}