From a372405e851e2f1c59a17ec0681326d82d28ee64 Mon Sep 17 00:00:00 2001
From: Thalia Archibald <thalia@archibald.dev>
Date: Tue, 4 Feb 2025 19:53:14 -0800
Subject: [PATCH] Implement read_buf for Hermit

---
 library/std/src/sys/fs/hermit.rs     |  2 +-
 library/std/src/sys/pal/hermit/fd.rs | 14 +++++++++++++-
 library/std/src/sys/stdio/unix.rs    |  5 +----
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/library/std/src/sys/fs/hermit.rs b/library/std/src/sys/fs/hermit.rs
index e9339ff261c99..d83a204709e9b 100644
--- a/library/std/src/sys/fs/hermit.rs
+++ b/library/std/src/sys/fs/hermit.rs
@@ -396,7 +396,7 @@ impl File {
     }
 
     pub fn read_buf(&self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
-        crate::io::default_read_buf(|buf| self.read(buf), cursor)
+        self.0.read_buf(cursor)
     }
 
     pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
diff --git a/library/std/src/sys/pal/hermit/fd.rs b/library/std/src/sys/pal/hermit/fd.rs
index 79fc13bd4a87f..13a7d14da5f05 100644
--- a/library/std/src/sys/pal/hermit/fd.rs
+++ b/library/std/src/sys/pal/hermit/fd.rs
@@ -2,7 +2,7 @@
 
 use super::hermit_abi;
 use crate::cmp;
-use crate::io::{self, IoSlice, IoSliceMut, Read};
+use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut, Read};
 use crate::os::hermit::io::{FromRawFd, OwnedFd, RawFd, *};
 use crate::sys::{cvt, unsupported};
 use crate::sys_common::{AsInner, FromInner, IntoInner};
@@ -23,6 +23,18 @@ impl FileDesc {
         Ok(result as usize)
     }
 
+    pub fn read_buf(&self, mut buf: BorrowedCursor<'_>) -> io::Result<()> {
+        let result = cvt(unsafe {
+            hermit_abi::read(
+                self.fd.as_raw_fd(),
+                buf.as_mut().as_mut_ptr() as *mut u8,
+                buf.capacity(),
+            )
+        })?;
+        unsafe { buf.advance_unchecked(result as usize) };
+        Ok(())
+    }
+
     pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
         let ret = cvt(unsafe {
             hermit_abi::readv(
diff --git a/library/std/src/sys/stdio/unix.rs b/library/std/src/sys/stdio/unix.rs
index 8d133857c596d..08a06e0da9f34 100644
--- a/library/std/src/sys/stdio/unix.rs
+++ b/library/std/src/sys/stdio/unix.rs
@@ -3,9 +3,7 @@ use hermit_abi::{EBADF, STDERR_FILENO, STDIN_FILENO, STDOUT_FILENO};
 #[cfg(target_family = "unix")]
 use libc::{EBADF, STDERR_FILENO, STDIN_FILENO, STDOUT_FILENO};
 
-#[cfg(target_family = "unix")]
-use crate::io::BorrowedCursor;
-use crate::io::{self, IoSlice, IoSliceMut};
+use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::mem::ManuallyDrop;
 #[cfg(target_os = "hermit")]
 use crate::os::hermit::io::FromRawFd;
@@ -28,7 +26,6 @@ impl io::Read for Stdin {
         unsafe { ManuallyDrop::new(FileDesc::from_raw_fd(STDIN_FILENO)).read(buf) }
     }
 
-    #[cfg(not(target_os = "hermit"))]
     fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> io::Result<()> {
         unsafe { ManuallyDrop::new(FileDesc::from_raw_fd(STDIN_FILENO)).read_buf(buf) }
     }