Initial implementation of anonymous_pipe

Co-authored-by: Alphyr <47725341+a1phyr@users.noreply.github.com>
Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>
Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

library/std/src/sys/anonymous_pipe/unix.rs

@@ -0,0 +1,103 @@
+use crate::{
+    io,
+    os::fd::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd},
+    pipe::{PipeReader, PipeWriter},
+    process::Stdio,
+    sys::{fd::FileDesc, pipe::anon_pipe},
+    sys_common::{FromInner, IntoInner},
+};
+
+pub(crate) type AnonPipe = FileDesc;
+
+#[inline]
+pub(crate) fn pipe() -> io::Result<(AnonPipe, AnonPipe)> {
+    anon_pipe().map(|(rx, wx)| (rx.into_inner(), wx.into_inner()))
+}
+
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl AsFd for PipeReader {
+    fn as_fd(&self) -> BorrowedFd<'_> {
+        self.0.as_fd()
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl AsRawFd for PipeReader {
+    fn as_raw_fd(&self) -> RawFd {
+        self.0.as_raw_fd()
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl From<PipeReader> for OwnedFd {
+    fn from(pipe: PipeReader) -> Self {
+        FileDesc::into_inner(pipe.0)
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl FromRawFd for PipeReader {
+    unsafe fn from_raw_fd(raw_fd: RawFd) -> Self {
+        Self(FileDesc::from_raw_fd(raw_fd))
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl IntoRawFd for PipeReader {
+    fn into_raw_fd(self) -> RawFd {
+        self.0.into_raw_fd()
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl From<PipeReader> for Stdio {
+    fn from(pipe: PipeReader) -> Self {
+        Self::from(OwnedFd::from(pipe))
+    }
+}
+
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl AsFd for PipeWriter {
+    fn as_fd(&self) -> BorrowedFd<'_> {
+        self.0.as_fd()
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl AsRawFd for PipeWriter {
+    fn as_raw_fd(&self) -> RawFd {
+        self.0.as_raw_fd()
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl From<PipeWriter> for OwnedFd {
+    fn from(pipe: PipeWriter) -> Self {
+        FileDesc::into_inner(pipe.0)
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl FromRawFd for PipeWriter {
+    unsafe fn from_raw_fd(raw_fd: RawFd) -> Self {
+        Self(FileDesc::from_raw_fd(raw_fd))
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl IntoRawFd for PipeWriter {
+    fn into_raw_fd(self) -> RawFd {
+        self.0.into_raw_fd()
+    }
+}
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl From<PipeWriter> for Stdio {
+    fn from(pipe: PipeWriter) -> Self {
+        Self::from(OwnedFd::from(pipe))
+    }
+}
+
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl From<OwnedFd> for PipeReader {
+    fn from(owned_fd: OwnedFd) -> Self {
+        Self(FileDesc::from_inner(owned_fd))
+    }
+}
+
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl From<OwnedFd> for PipeWriter {
+    fn from(owned_fd: OwnedFd) -> Self {
+        Self(FileDesc::from_inner(owned_fd))
+    }
+}