1 files changed, 90 insertions, 0 deletions
diff --git a/third_party/rust/cc/src/parallel/stderr.rs b/third_party/rust/cc/src/parallel/stderr.rs
new file mode 100644
index 0000000000..47fa085dba
--- /dev/null
+++ b/third_party/rust/cc/src/parallel/stderr.rs
@@ -0,0 +1,90 @@
+/// Helpers functions for [ChildStderr].
+use std::{convert::TryInto, process::ChildStderr};
+
+use crate::{Error, ErrorKind};
+
+#[cfg(all(not(unix), not(windows)))]
+compile_error!("Only unix and windows support non-blocking pipes! For other OSes, disable the parallel feature.");
+
+#[cfg(unix)]
+fn get_flags(fd: std::os::unix::io::RawFd) -> Result<i32, Error> {
+    let flags = unsafe { libc::fcntl(fd, libc::F_GETFL, 0) };
+    if flags == -1 {
+        Err(Error::new(
+            ErrorKind::IOError,
+            format!(
+                "Failed to get flags for pipe {}: {}",
+                fd,
+                std::io::Error::last_os_error()
+            ),
+        ))
+    } else {
+        Ok(flags)
+    }
+}
+
+#[cfg(unix)]
+fn set_flags(fd: std::os::unix::io::RawFd, flags: std::os::raw::c_int) -> Result<(), Error> {
+    if unsafe { libc::fcntl(fd, libc::F_SETFL, flags) } == -1 {
+        Err(Error::new(
+            ErrorKind::IOError,
+            format!(
+                "Failed to set flags for pipe {}: {}",
+                fd,
+                std::io::Error::last_os_error()
+            ),
+        ))
+    } else {
+        Ok(())
+    }
+}
+
+#[cfg(unix)]
+pub fn set_non_blocking(pipe: &impl std::os::unix::io::AsRawFd) -> Result<(), Error> {
+    // On Unix, switch the pipe to non-blocking mode.
+    // On Windows, we have a different way to be non-blocking.
+    let fd = pipe.as_raw_fd();
+
+    let flags = get_flags(fd)?;
+    set_flags(fd, flags | libc::O_NONBLOCK)
+}
+
+pub fn bytes_available(stderr: &mut ChildStderr) -> Result<usize, Error> {
+    let mut bytes_available = 0;
+    #[cfg(windows)]
+    {
+        use crate::windows::windows_sys::PeekNamedPipe;
+        use std::os::windows::io::AsRawHandle;
+        use std::ptr::null_mut;
+        if unsafe {
+            PeekNamedPipe(
+                stderr.as_raw_handle(),
+                null_mut(),
+                0,
+                null_mut(),
+                &mut bytes_available,
+                null_mut(),
+            )
+        } == 0
+        {
+            return Err(Error::new(
+                ErrorKind::IOError,
+                format!(
+                    "PeekNamedPipe failed with {}",
+                    std::io::Error::last_os_error()
+                ),
+            ));
+        }
+    }
+    #[cfg(unix)]
+    {
+        use std::os::unix::io::AsRawFd;
+        if unsafe { libc::ioctl(stderr.as_raw_fd(), libc::FIONREAD, &mut bytes_available) } != 0 {
+            return Err(Error::new(
+                ErrorKind::IOError,
+                format!("ioctl failed with {}", std::io::Error::last_os_error()),
+            ));
+        }
+    }
+    Ok(bytes_available.try_into().unwrap())
+}