From 642961436a727d51930e5839e3dbfee04ba4af95 Mon Sep 17 00:00:00 2001
From: Joel Galenson <jgalenson@google.com>
Date: Tue, 17 Aug 2021 08:33:38 -0700
Subject: Upgrade rust/crates/tokio to 1.10.0

Test: make
Change-Id: I4ec984178af20297aae0ed51f0b1c6410876a51b
---
 src/io/util/fill_buf.rs | 52 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 src/io/util/fill_buf.rs

(limited to 'src/io/util/fill_buf.rs')

diff --git a/src/io/util/fill_buf.rs b/src/io/util/fill_buf.rs
new file mode 100644
index 0000000..98ae2ea
--- /dev/null
+++ b/src/io/util/fill_buf.rs
@@ -0,0 +1,52 @@
+use crate::io::AsyncBufRead;
+
+use pin_project_lite::pin_project;
+use std::future::Future;
+use std::io;
+use std::marker::PhantomPinned;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+pin_project! {
+    /// Future for the [`fill_buf`](crate::io::AsyncBufReadExt::fill_buf) method.
+    #[derive(Debug)]
+    #[must_use = "futures do nothing unless you `.await` or poll them"]
+    pub struct FillBuf<'a, R: ?Sized> {
+        reader: Option<&'a mut R>,
+        #[pin]
+        _pin: PhantomPinned,
+    }
+}
+
+pub(crate) fn fill_buf<R>(reader: &mut R) -> FillBuf<'_, R>
+where
+    R: AsyncBufRead + ?Sized + Unpin,
+{
+    FillBuf {
+        reader: Some(reader),
+        _pin: PhantomPinned,
+    }
+}
+
+impl<'a, R: AsyncBufRead + ?Sized + Unpin> Future for FillBuf<'a, R> {
+    type Output = io::Result<&'a [u8]>;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let me = self.project();
+
+        // Due to a limitation in the borrow-checker, we cannot return the value
+        // directly on Ready. Once Rust starts using the polonius borrow checker,
+        // this can be simplified.
+        let reader = me.reader.take().expect("Polled after completion.");
+        match Pin::new(&mut *reader).poll_fill_buf(cx) {
+            Poll::Ready(_) => match Pin::new(reader).poll_fill_buf(cx) {
+                Poll::Ready(slice) => Poll::Ready(slice),
+                Poll::Pending => panic!("poll_fill_buf returned Pending while having data"),
+            },
+            Poll::Pending => {
+                *me.reader = Some(reader);
+                Poll::Pending
+            }
+        }
+    }
+}
-- 
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