From 87ffd8b862f53d575ccee63a953489c038bc9940 Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jackpot51@gmail.com>
Date: Mon, 28 Feb 2022 15:03:51 -0700
Subject: [PATCH] 0.2.11 - add daemon abstraction

---
 Cargo.toml    |  2 +-
 src/daemon.rs | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs    |  5 +++++
 3 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 src/daemon.rs

diff --git a/Cargo.toml b/Cargo.toml
index bedfb1a..856cab8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "redox_syscall"
-version = "0.2.10"
+version = "0.2.11"
 description = "A Rust library to access raw Redox system calls"
 license = "MIT"
 authors = ["Jeremy Soller <jackpot51@gmail.com>"]
diff --git a/src/daemon.rs b/src/daemon.rs
new file mode 100644
index 0000000..11a97ca
--- /dev/null
+++ b/src/daemon.rs
@@ -0,0 +1,58 @@
+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) -> !>(f: F) -> Result<!> {
+        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,
+            });
+        } 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))
+        }
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 60c0c60..0af87b3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,5 +1,6 @@
 #![feature(asm)]
 #![feature(llvm_asm)]
+#![feature(never_type)]
 #![cfg_attr(not(test), no_std)]
 
 #[cfg(test)]
@@ -7,6 +8,7 @@ extern crate core;
 
 pub use self::arch::*;
 pub use self::call::*;
+pub use self::daemon::*;
 pub use self::data::*;
 pub use self::error::*;
 pub use self::flag::*;
@@ -44,6 +46,9 @@ pub mod call;
 /// Complex structures that are used for some system calls
 pub mod data;
 
+/// Wrapper to make daemons easier to write
+pub mod daemon;
+
 /// All errors that can be generated by a system call
 pub mod error;