1 files changed, 62 insertions, 0 deletions
diff --git a/third_party/rust/redox_syscall/src/daemon.rs b/third_party/rust/redox_syscall/src/daemon.rs
new file mode 100644
index 0000000000..6433bcd7d2
--- /dev/null
+++ b/third_party/rust/redox_syscall/src/daemon.rs
@@ -0,0 +1,62 @@
+use core::convert::Infallible;
+
+use super::{
+    clone,
+    CloneFlags,
+    close,
+    EIO,
+    Error,
+    exit,
+    pipe2,
+    read,
+    Result,
+    write,
+};
+
+#[must_use = "Daemon::ready must be called"]
+pub struct Daemon {
+    write_pipe: usize,
+}
+
+impl Daemon {
+    pub fn new<F: FnOnce(Daemon) -> Infallible>(f: F) -> Result<Infallible> {
+        let mut pipes = [0; 2];
+        pipe2(&mut pipes, 0)?;
+
+        let [read_pipe, write_pipe] = pipes;
+
+        if unsafe { clone(CloneFlags::empty())? } == 0 {
+            let _ = close(read_pipe);
+
+            f(Daemon {
+                write_pipe,
+            });
+            // TODO: Replace Infallible with the never type once it is stabilized.
+            unreachable!();
+        } else {
+            let _ = close(write_pipe);
+
+            let mut data = [0];
+            let res = read(read_pipe, &mut data);
+            let _ = close(read_pipe);
+
+            if res? == 1 {
+                exit(data[0] as usize)?;
+                unreachable!();
+            } else {
+                Err(Error::new(EIO))
+            }
+        }
+    }
+
+    pub fn ready(self) -> Result<()> {
+        let res = write(self.write_pipe, &[0]);
+        let _ = close(self.write_pipe);
+
+        if res? == 1 {
+            Ok(())
+        } else {
+            Err(Error::new(EIO))
+        }
+    }
+}