From 5a13041ed7033c9dab6e2adafd08b6af20cd33fb Mon Sep 17 00:00:00 2001
From: Anthony Ramine <123095+nox@users.noreply.github.com>
Date: Mon, 15 Jul 2024 20:25:49 +0200
Subject: [PATCH] feat(rt): add `ReadBufCursor` methods `remaining()` and
 `put_slice()` (#3700)

There is currently no way to write to ReadBufCursor without
unsafe code, even though writing a slice to it like one would
do to a Buf shouldn't require unsafe code.
---
 src/rt/io.rs | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/rt/io.rs b/src/rt/io.rs
index fbe9ecc901..e8f6ed9994 100644
--- a/src/rt/io.rs
+++ b/src/rt/io.rs
@@ -244,19 +244,29 @@ impl<'data> ReadBufCursor<'data> {
         self.buf.init = self.buf.filled.max(self.buf.init);
     }
 
+    /// Returns the number of bytes that can be written from the current
+    /// position until the end of the buffer is reached.
+    ///
+    /// This value is equal to the length of the slice returned by `as_mut()``.
     #[inline]
-    pub(crate) fn remaining(&self) -> usize {
+    pub fn remaining(&self) -> usize {
         self.buf.remaining()
     }
 
+    /// Transfer bytes into `self`` from `src` and advance the cursor
+    /// by the number of bytes written.
+    ///
+    /// # Panics
+    ///
+    /// `self` must have enough remaining capacity to contain all of `src`.
     #[inline]
-    pub(crate) fn put_slice(&mut self, buf: &[u8]) {
+    pub fn put_slice(&mut self, src: &[u8]) {
         assert!(
-            self.buf.remaining() >= buf.len(),
-            "buf.len() must fit in remaining()"
+            self.buf.remaining() >= src.len(),
+            "src.len() must fit in remaining()"
         );
 
-        let amt = buf.len();
+        let amt = src.len();
         // Cannot overflow, asserted above
         let end = self.buf.filled + amt;
 
@@ -265,7 +275,7 @@ impl<'data> ReadBufCursor<'data> {
             self.buf.raw[self.buf.filled..end]
                 .as_mut_ptr()
                 .cast::<u8>()
-                .copy_from_nonoverlapping(buf.as_ptr(), amt);
+                .copy_from_nonoverlapping(src.as_ptr(), amt);
         }
 
         if self.buf.init < end {