Started `sys/pipe`: Interfacing with raw `pipe()` created streams.

Fortune for comfork's current commit: Middle blessing − 中吉

src/ext/macros.rs

@@ -46,3 +46,13 @@ fn _debug_if_test()
 	}
     }
 }
+
+/// Do not compile the code in this block
+#[macro_export] macro_rules! remove {
+    ($($tt:tt)*) => {
+	const _:() = {
+	    $($tt)*
+	    ()
+	};
+    }
+}

src/sys/errno.rs

@@ -41,7 +41,7 @@ fn get_message(raw: RawError) -> String
 }
 
 /// A raw C error
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct Errno
 {
     errno: NonZeroI32,
@@ -115,7 +115,80 @@ impl fmt::Display for Errno
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
     {
-	write!(f, "{}", self.message())
+	write!(f, "{} ({})", self.message(), self.errno.get())
     }
 }
 
+remove! {
+    /// Wrapping of errno around another Rust error type.
+    #[derive(Debug)]
+    pub struct ErrnoWrap<T: ?Sized>
+    {
+	error: Errno,
+	inner: T,
+    }
+
+    impl<T: error::Error + 'static> error::Error for ErrnoWrap<T>
+    {
+	fn source(&self) -> Option<&(dyn error::Error + 'static)> {
+	    Some(&self.inner)
+	}
+    }
+
+    impl<T: fmt::Display> fmt::Display for ErrnoWrap<T>
+    {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+	{
+	    write!(f, "{}: {}", self.inner, self.error)
+	}
+    }
+
+    impl<T> ErrnoWrap<T>
+    {
+	pub fn into_inner(self) -> T
+	{
+	    self.inner
+	}
+
+	pub fn map_inner<F, U>(self, map: F) -> ErrnoWrap<U>
+	where F: FnOnce(T) -> U,
+	      U: error::Error + 'static
+	{
+	    ErrnoWrap {
+		error: self.error,
+		inner: map(self.inner)
+	    }
+	}
+    }
+
+    impl<T: ?Sized> ErrnoWrap<T>
+    {
+	pub fn errno(&self) -> &Errno
+	{
+	    &self.error
+	}
+	pub fn inner(&self) -> &T
+	{
+	    &self.inner
+	}
+    }
+
+    impl<T: error::Error + 'static> ErrnoWrap<T>
+    {
+	pub fn with_errno(error: T, errno: Errno) -> Self
+	{
+	    Self {
+		error: errno,
+		inner: error
+	    }
+	}
+
+	pub fn last(error: T) -> Result<(), Self>
+	{
+	    Err(Self::with_errno(error, match Errno::last() {
+		Ok(()) => return Ok(()),
+		Err(e) => e, 
+	    }))
+	}
+    }
+}

src/sys/mod.rs

@@ -2,3 +2,5 @@
 use super::*;
 
 pub mod errno;
+
+pub mod pipe;

src/sys/pipe.rs

@@ -0,0 +1,137 @@
+//! Wrapper around internal pipes fds.
+//!
+//! These pipe fds are valid across forks, and can be used for IPC between parent and non-exec()d child process forks.
+use super::*;
+use errno::Errno;
+use std::{error, fmt};
+
+/// Kind of pipe error
+#[derive(Debug)]
+#[non_exhaustive]
+pub enum ErrorKind
+{
+    /// Failed to create pipes
+    Create,
+    /// Unknown error
+    Unknown,
+}
+
+/// A raw unix pipe
+pub type RawPipe = i32;
+
+/// Create a raw pipe pair.
+pub(crate) fn unix_pipe() -> Result<(i32, i32), Error>
+{
+    use libc::pipe;
+    let mut pipe_fds: [libc::c_int; 2] = [-1;2];
+    if unsafe{pipe(pipe_fds.as_mut_ptr())} == 0 {
+	Ok((i32::from(pipe_fds[0]), i32::from(pipe_fds[1])))
+    } else {
+	Err(ErrorKind::Create.into_error())
+    }
+}
+
+impl fmt::Display for ErrorKind
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	match self {
+	    Self::Create => write!(f, "failed to create raw pipes"),
+	    _ => write!(f, "unknown error"),
+	}
+    }
+}
+
+/// An error on a pipe operation
+#[derive(Debug)]
+pub struct Error(ErrorKind, Errno);
+
+impl ErrorKind
+{
+    /// Consume into `Error` using the last `errno` value, if it's not set then return `val`.
+    #[inline] pub(crate) fn try_into_error_or<T>(self, val: T) -> Result<T, Error>
+    {
+	Error::or_last(self, val)
+    }    
+    /// Consume into `Error` using the last `errno` value, if it's not set then return the result of `fun`.
+    #[inline] pub(crate) fn try_into_error_or_with<F, T>(self, fun: F) -> Result<T, Error>
+	where F: FnOnce() -> T
+    {
+	Error::or_last_with(self, fun)
+    }
+    /// Consume into `Error` using the last `errno` value.
+    pub(crate) fn try_into_error(self) -> Result<(), Error>
+    {
+	Error::last(self)
+    }
+
+    /// Consume into an `Error` using the last `errno` value.
+    ///
+    /// # Panics
+    /// If `errno` was success.
+    #[inline] pub(crate) fn into_error(self) -> Error
+    {
+	Self::try_into_error(self).expect_err("Expected an error to be set in errno")
+    }
+}
+
+impl Error
+{
+    /// Create a new error of this kind from the last set errno if it's not success.
+    /// If it is, return `val`.
+    #[inline] pub(crate) fn or_last<T>(err: ErrorKind, val: T) -> Result<T, Self>
+    {
+	Self::or_last_with(err, move || val)
+    }
+    /// Create a new error of this kind from the last set errno if it's not success.
+    /// If it is, return the result of `fun`.
+    pub(crate) fn or_last_with<F, T>(err: ErrorKind, fun: F) -> Result<T, Self>
+    where F: FnOnce() -> T
+    {
+	Err(Self(err, match Errno::or_last_with(fun) {
+	    Ok(v) => return Ok(v),
+	    Err(e) => e,
+	}))
+    }
+    /// Create a new error of this kind from the last set errno (if it's not success.)
+    pub(crate) fn last(err: ErrorKind) -> Result<(), Self>
+    {
+	Err(Self(err, match Errno::last() {
+	    Ok(()) => return Ok(()),
+	    Err(e) => e,
+	}))
+    }
+
+    /// Create a new error of this kind with this errno value
+    #[inline] pub fn new(kind: ErrorKind, err: Errno) -> Self
+    {
+	Self(kind, err)
+    }
+
+    /// The kind of pipe error
+    #[inline] pub fn kind(&self) -> &ErrorKind
+    {
+	&self.0
+    }
+
+    /// The errno value
+    #[inline] pub fn error(&self) -> &Errno
+    {
+	&self.1
+    }
+}
+
+impl error::Error for Error
+{
+    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
+	Some(&self.1)
+    }
+}
+impl fmt::Display for Error
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	write!(f, "{}: {}", self.0, self.1)
+    }
+}
+