From 2efe6b0d3d1cca5b0b360ff760f08cb7d647878a Mon Sep 17 00:00:00 2001
From: Dan Gohman <dev@sunfishcode.online>
Date: Mon, 22 Aug 2022 12:14:35 -0700
Subject: [PATCH] Add `AsFd` implementations for stdio types on WASI.

This mirrors the implementations on Unix platforms, and also mirrors the
existing `AsRawFd` impls.
---
 library/std/src/sys/wasi/stdio.rs | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/library/std/src/sys/wasi/stdio.rs b/library/std/src/sys/wasi/stdio.rs
index 4cc0e4ed5a4..d2081771b6e 100644
--- a/library/std/src/sys/wasi/stdio.rs
+++ b/library/std/src/sys/wasi/stdio.rs
@@ -4,7 +4,7 @@
 use crate::io::{self, IoSlice, IoSliceMut};
 use crate::mem::ManuallyDrop;
 use crate::os::raw;
-use crate::os::wasi::io::{AsRawFd, FromRawFd};
+use crate::os::wasi::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd};
 
 pub struct Stdin;
 pub struct Stdout;
@@ -23,6 +23,13 @@ fn as_raw_fd(&self) -> raw::c_int {
     }
 }
 
+impl AsFd for Stdin {
+    #[inline]
+    fn as_fd(&self) -> BorrowedFd<'_> {
+        unsafe { BorrowedFd::borrow_raw(0) }
+    }
+}
+
 impl io::Read for Stdin {
     fn read(&mut self, data: &mut [u8]) -> io::Result<usize> {
         self.read_vectored(&mut [IoSliceMut::new(data)])
@@ -51,6 +58,13 @@ fn as_raw_fd(&self) -> raw::c_int {
     }
 }
 
+impl AsFd for Stdout {
+    #[inline]
+    fn as_fd(&self) -> BorrowedFd<'_> {
+        unsafe { BorrowedFd::borrow_raw(1) }
+    }
+}
+
 impl io::Write for Stdout {
     fn write(&mut self, data: &[u8]) -> io::Result<usize> {
         self.write_vectored(&[IoSlice::new(data)])
@@ -82,6 +96,13 @@ fn as_raw_fd(&self) -> raw::c_int {
     }
 }
 
+impl AsFd for Stderr {
+    #[inline]
+    fn as_fd(&self) -> BorrowedFd<'_> {
+        unsafe { BorrowedFd::borrow_raw(2) }
+    }
+}
+
 impl io::Write for Stderr {
     fn write(&mut self, data: &[u8]) -> io::Result<usize> {
         self.write_vectored(&[IoSlice::new(data)])