From 490b56705b114f118311621a1f4833fbcb07ea42 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Fri, 31 Mar 2023 13:29:18 +0200
Subject: [PATCH 01/19] unsafe impl<'a> BufMut for ReadBuf<'a>

---
 tokio/src/io/read_buf.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index 0dc595a87dd..de84fa56eeb 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -1,5 +1,9 @@
 use std::fmt;
 use std::mem::MaybeUninit;
+use bytes::{
+    BufMut, 
+    buf::UninitSlice,
+};
 
 /// A wrapper around a byte buffer that is incrementally filled and initialized.
 ///
@@ -270,6 +274,22 @@ impl<'a> ReadBuf<'a> {
     }
 }
 
+unsafe impl<'a> BufMut for ReadBuf<'a> {
+    fn remaining_mut(&self) -> usize { 
+        self.remaining() 
+    }
+    
+    unsafe fn advance_mut(&mut self, cnt: usize) {
+        self.advance(cnt);
+    }
+    
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
+        unsafe {
+            UninitSlice::from_raw_parts_mut(10 as *mut u8, 10)
+        }
+    }
+}
+
 impl fmt::Debug for ReadBuf<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("ReadBuf")

From fc7e30bcc6d8af39036b15dbf9acf0bdb31551a7 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Fri, 31 Mar 2023 13:37:17 +0200
Subject: [PATCH 02/19] rustfmt

---
 tokio/src/io/read_buf.rs | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index de84fa56eeb..8dbf743ef4d 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -1,9 +1,6 @@
+use bytes::{buf::UninitSlice, BufMut};
 use std::fmt;
 use std::mem::MaybeUninit;
-use bytes::{
-    BufMut, 
-    buf::UninitSlice,
-};
 
 /// A wrapper around a byte buffer that is incrementally filled and initialized.
 ///
@@ -275,18 +272,16 @@ impl<'a> ReadBuf<'a> {
 }
 
 unsafe impl<'a> BufMut for ReadBuf<'a> {
-    fn remaining_mut(&self) -> usize { 
-        self.remaining() 
+    fn remaining_mut(&self) -> usize {
+        self.remaining()
     }
-    
+
     unsafe fn advance_mut(&mut self, cnt: usize) {
         self.advance(cnt);
     }
-    
+
     fn chunk_mut(&mut self) -> &mut UninitSlice {
-        unsafe {
-            UninitSlice::from_raw_parts_mut(10 as *mut u8, 10)
-        }
+        unsafe { UninitSlice::from_raw_parts_mut(10 as *mut u8, 10) }
     }
 }
 

From bad061b152c79b9ff0180456456fabd3ab778222 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Fri, 31 Mar 2023 13:42:24 +0200
Subject: [PATCH 03/19] Add feature gate

---
 tokio/src/io/read_buf.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index 8dbf743ef4d..b00118fed9e 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -1,4 +1,6 @@
+#[cfg(feature = "bytes")]
 use bytes::{buf::UninitSlice, BufMut};
+
 use std::fmt;
 use std::mem::MaybeUninit;
 
@@ -271,6 +273,7 @@ impl<'a> ReadBuf<'a> {
     }
 }
 
+#[cfg(feature = "bytes")]
 unsafe impl<'a> BufMut for ReadBuf<'a> {
     fn remaining_mut(&self) -> usize {
         self.remaining()

From ec629ee1e54b428f0ca197d6840f78409e98d17b Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Fri, 31 Mar 2023 14:09:57 +0200
Subject: [PATCH 04/19] Add len to from_raw_parts_mut(ptr, len)

---
 tokio/src/io/read_buf.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index b00118fed9e..605fb1ccf64 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -284,7 +284,10 @@ unsafe impl<'a> BufMut for ReadBuf<'a> {
     }
 
     fn chunk_mut(&mut self) -> &mut UninitSlice {
-        unsafe { UninitSlice::from_raw_parts_mut(10 as *mut u8, 10) }
+        let ptr = 10 as *mut u8; // any ideas?
+        let len = self.filled().len();
+        unsafe { UninitSlice::from_raw_parts_mut(ptr, len) }
+
     }
 }
 

From d56a3e20e055a04c060bed8a026a215adceef72f Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Fri, 31 Mar 2023 16:25:01 +0200
Subject: [PATCH 05/19] Fix chunk_mut

---
 tokio/src/io/read_buf.rs | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index 605fb1ccf64..d3d49a31e5a 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -284,10 +284,9 @@ unsafe impl<'a> BufMut for ReadBuf<'a> {
     }
 
     fn chunk_mut(&mut self) -> &mut UninitSlice {
-        let ptr = 10 as *mut u8; // any ideas?
         let len = self.filled().len();
-        unsafe { UninitSlice::from_raw_parts_mut(ptr, len) }
-
+        let ptr = unsafe { self.unfilled_mut().as_mut_ptr() };
+        unsafe { UninitSlice::from_raw_parts_mut(ptr as *mut u8, len) }
     }
 }
 

From afe2501597e7447814f2a9990a8eb39dad491ffc Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Sat, 1 Apr 2023 18:35:13 +0200
Subject: [PATCH 06/19] Length of remaining part, not the filled part

---
 tokio/src/io/read_buf.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index d3d49a31e5a..b332f30fd2e 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -284,9 +284,11 @@ unsafe impl<'a> BufMut for ReadBuf<'a> {
     }
 
     fn chunk_mut(&mut self) -> &mut UninitSlice {
-        let len = self.filled().len();
-        let ptr = unsafe { self.unfilled_mut().as_mut_ptr() };
-        unsafe { UninitSlice::from_raw_parts_mut(ptr as *mut u8, len) }
+        unsafe {
+            let len = self.unfilled_mut().len();
+            let ptr = self.unfilled_mut().as_mut_ptr();
+            UninitSlice::from_raw_parts_mut(ptr as *mut u8, len)
+        }
     }
 }
 

From 214226e25cdc0ce074aba7527fd32605585b55ab Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 11:07:52 +0200
Subject: [PATCH 07/19] Apply feedback

---
 tokio/src/io/read_buf.rs   | 12 +++++-------
 tokio/tests/io_read_buf.rs | 39 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index b332f30fd2e..b11caa48904 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -1,6 +1,3 @@
-#[cfg(feature = "bytes")]
-use bytes::{buf::UninitSlice, BufMut};
-
 use std::fmt;
 use std::mem::MaybeUninit;
 
@@ -273,8 +270,9 @@ impl<'a> ReadBuf<'a> {
     }
 }
 
-#[cfg(feature = "bytes")]
-unsafe impl<'a> BufMut for ReadBuf<'a> {
+#[cfg(feature = "io-util")]
+#[cfg_attr(docsrs, doc(cfg(feature = "io-util")))]
+unsafe impl<'a> bytes::BufMut for ReadBuf<'a> {
     fn remaining_mut(&self) -> usize {
         self.remaining()
     }
@@ -283,11 +281,11 @@ unsafe impl<'a> BufMut for ReadBuf<'a> {
         self.advance(cnt);
     }
 
-    fn chunk_mut(&mut self) -> &mut UninitSlice {
+    fn chunk_mut(&mut self) -> &mut bytes::buf::UninitSlice {
         unsafe {
             let len = self.unfilled_mut().len();
             let ptr = self.unfilled_mut().as_mut_ptr();
-            UninitSlice::from_raw_parts_mut(ptr as *mut u8, len)
+            bytes::buf::UninitSlice::from_raw_parts_mut(ptr as *mut u8, len)
         }
     }
 }
diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index 0328168d7ab..62ee7c9527e 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -34,3 +34,42 @@ async fn read_buf() {
     assert_eq!(n, 11);
     assert_eq!(buf[..], b"hello world"[..]);
 }
+
+#[tokio::test]
+#[cfg(feature = "io-util")]
+#[cfg_attr(docsrs, doc(cfg(feature = "io-util")))]
+async fn issue_5588() {
+    use bytes::BufMut;
+
+    // steps to zero
+    let mut buf = [0; 8];
+    let mut read_buf = ReadBuf::new(&mut buf);
+    assert_eq!(read_buf.remaining_mut(), 8);
+    assert_eq!(read_buf.remaining_mut(), 8);
+    unsafe {
+        read_buf.advance_mut(1);
+    }
+    assert_eq!(read_buf.remaining_mut(), 7);
+    assert_eq!(read_buf.remaining_mut(), 7);
+    unsafe {
+        read_buf.advance_mut(5);
+    }
+    assert_eq!(read_buf.remaining_mut(), 2);
+    assert_eq!(read_buf.remaining_mut(), 2);
+    unsafe {
+        read_buf.advance_mut(2);
+    }
+    assert_eq!(read_buf.remaining_mut(), 0);
+    assert_eq!(read_buf.remaining_mut(), 0);
+
+    // directly to zero
+    let mut buf = [0; 8];
+    let mut read_buf = ReadBuf::new(&mut buf);
+    assert_eq!(read_buf.remaining_mut(), 8);
+    assert_eq!(read_buf.chunk_mut().len(), 8);
+    unsafe {
+        read_buf.advance_mut(8);
+    }
+    assert_eq!(read_buf.remaining_mut(), 0);
+    assert_eq!(read_buf.chunk_mut().len(), 0);
+}
\ No newline at end of file

From 8a94073ac37cc466181da9cfb2145db453cc7521 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 11:12:10 +0200
Subject: [PATCH 08/19] Apply feedback

---
 tokio/tests/io_read_buf.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index 62ee7c9527e..2e43dd55bab 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -72,4 +72,4 @@ async fn issue_5588() {
     }
     assert_eq!(read_buf.remaining_mut(), 0);
     assert_eq!(read_buf.chunk_mut().len(), 0);
-}
\ No newline at end of file
+}

From 7ea22e5be1fef2c3355f7e671b861e84de229ee4 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 11:15:32 +0200
Subject: [PATCH 09/19] remove docs from test

---
 tokio/tests/io_read_buf.rs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index 2e43dd55bab..275057b64fd 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -37,7 +37,6 @@ async fn read_buf() {
 
 #[tokio::test]
 #[cfg(feature = "io-util")]
-#[cfg_attr(docsrs, doc(cfg(feature = "io-util")))]
 async fn issue_5588() {
     use bytes::BufMut;
 

From c3cf522e5f1e49e6b863f172e336e7740f94c2d4 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 12:00:02 +0200
Subject: [PATCH 10/19] Isolate unsafety, add comments

---
 tokio/src/io/read_buf.rs | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index b11caa48904..3210bde6021 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -282,10 +282,17 @@ unsafe impl<'a> bytes::BufMut for ReadBuf<'a> {
     }
 
     fn chunk_mut(&mut self) -> &mut bytes::buf::UninitSlice {
+        // SAFETY: No region of `unfilled` will be deinitialized because it is
+        // exposed as an `UninitSlice`, whose API guarantees that the memory is
+        // never deinitialized.
+        let unfilled = unsafe { self.unfilled_mut() };
+        let len = unfilled.len();
+        let ptr = unfilled.as_mut_ptr() as *mut u8;
+        
+        // SAFETY: The pointer is valid for `len` bytes because it comes from a
+        // slice of that length.
         unsafe {
-            let len = self.unfilled_mut().len();
-            let ptr = self.unfilled_mut().as_mut_ptr();
-            bytes::buf::UninitSlice::from_raw_parts_mut(ptr as *mut u8, len)
+            bytes::buf::UninitSlice::from_raw_parts_mut(ptr, len)
         }
     }
 }

From 5cdd398e0c4115722568cd4b2c8c3642c476d756 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 12:25:26 +0200
Subject: [PATCH 11/19] fmt

---
 tokio/src/io/read_buf.rs | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index 3210bde6021..85041ccefa1 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -288,12 +288,10 @@ unsafe impl<'a> bytes::BufMut for ReadBuf<'a> {
         let unfilled = unsafe { self.unfilled_mut() };
         let len = unfilled.len();
         let ptr = unfilled.as_mut_ptr() as *mut u8;
-        
+
         // SAFETY: The pointer is valid for `len` bytes because it comes from a
         // slice of that length.
-        unsafe {
-            bytes::buf::UninitSlice::from_raw_parts_mut(ptr, len)
-        }
+        unsafe { bytes::buf::UninitSlice::from_raw_parts_mut(ptr, len) }
     }
 }
 

From a1af08ed9a140928b4b91d82e18a70978d9d7c27 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 13:22:44 +0200
Subject: [PATCH 12/19] improve test

---
 tokio/tests/io_read_buf.rs | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index 275057b64fd..4672c6892e7 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -44,22 +44,22 @@ async fn issue_5588() {
     let mut buf = [0; 8];
     let mut read_buf = ReadBuf::new(&mut buf);
     assert_eq!(read_buf.remaining_mut(), 8);
-    assert_eq!(read_buf.remaining_mut(), 8);
+    assert_eq!(read_buf.chunk_mut().len(), 8);
     unsafe {
         read_buf.advance_mut(1);
     }
     assert_eq!(read_buf.remaining_mut(), 7);
-    assert_eq!(read_buf.remaining_mut(), 7);
+    assert_eq!(read_buf.chunk_mut().len(), 7);
     unsafe {
         read_buf.advance_mut(5);
     }
     assert_eq!(read_buf.remaining_mut(), 2);
-    assert_eq!(read_buf.remaining_mut(), 2);
+    assert_eq!(read_buf.chunk_mut().len(), 2);
     unsafe {
         read_buf.advance_mut(2);
     }
     assert_eq!(read_buf.remaining_mut(), 0);
-    assert_eq!(read_buf.remaining_mut(), 0);
+    assert_eq!(read_buf.chunk_mut().len(), 0);
 
     // directly to zero
     let mut buf = [0; 8];
@@ -71,4 +71,10 @@ async fn issue_5588() {
     }
     assert_eq!(read_buf.remaining_mut(), 0);
     assert_eq!(read_buf.chunk_mut().len(), 0);
+
+    // uninit
+    let mut buf = [std::mem::MaybeUninit::new(1); 8];
+    let mut uninit = ReadBuf::uninit(&mut buf);
+    assert_eq!(read_buf.remaining_mut(), 0);
+    assert_eq!(uninit.chunk_mut().len(), 8);
 }

From 43fe36b8efd357ac6040a61d18ce14e58e2897e9 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 15:17:51 +0200
Subject: [PATCH 13/19] debug uninit.advance_mut(1000000)

---
 tokio/src/io/read_buf.rs   | 4 +++-
 tokio/tests/io_read_buf.rs | 8 ++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index 85041ccefa1..2fe2f8e1ade 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -278,7 +278,9 @@ unsafe impl<'a> bytes::BufMut for ReadBuf<'a> {
     }
 
     unsafe fn advance_mut(&mut self, cnt: usize) {
-        self.advance(cnt);
+        if self.initialized > 0 {
+            self.advance(cnt);
+        }
     }
 
     fn chunk_mut(&mut self) -> &mut bytes::buf::UninitSlice {
diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index 4672c6892e7..6657e2d9be2 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -71,10 +71,14 @@ async fn issue_5588() {
     }
     assert_eq!(read_buf.remaining_mut(), 0);
     assert_eq!(read_buf.chunk_mut().len(), 0);
-
+    
     // uninit
     let mut buf = [std::mem::MaybeUninit::new(1); 8];
     let mut uninit = ReadBuf::uninit(&mut buf);
-    assert_eq!(read_buf.remaining_mut(), 0);
+    assert_eq!(uninit.remaining_mut(), 8);
     assert_eq!(uninit.chunk_mut().len(), 8);
+    
+    let mut buf = [std::mem::MaybeUninit::uninit(); 8];
+    let mut uninit = ReadBuf::uninit(&mut buf);
+    unsafe { uninit.advance_mut(100000); } // should be effectively no-op
 }

From 90762ac79de8e52fac1ba6233b8344c30f12c0f0 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 15:19:01 +0200
Subject: [PATCH 14/19] fmt

---
 tokio/tests/io_read_buf.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index 6657e2d9be2..41b745bc3e8 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -71,14 +71,16 @@ async fn issue_5588() {
     }
     assert_eq!(read_buf.remaining_mut(), 0);
     assert_eq!(read_buf.chunk_mut().len(), 0);
-    
+
     // uninit
     let mut buf = [std::mem::MaybeUninit::new(1); 8];
     let mut uninit = ReadBuf::uninit(&mut buf);
     assert_eq!(uninit.remaining_mut(), 8);
     assert_eq!(uninit.chunk_mut().len(), 8);
-    
+
     let mut buf = [std::mem::MaybeUninit::uninit(); 8];
     let mut uninit = ReadBuf::uninit(&mut buf);
-    unsafe { uninit.advance_mut(100000); } // should be effectively no-op
+    unsafe {
+        uninit.advance_mut(100000);
+    } // should be effectively no-op
 }

From 65682946fa595b019e96bea7e56dfb5cefc5e613 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 15:25:33 +0200
Subject: [PATCH 15/19] Add remaining_mut() and check_mut().len() to uninit
 test

---
 tokio/tests/io_read_buf.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index 41b745bc3e8..cc95ae322e7 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -83,4 +83,7 @@ async fn issue_5588() {
     unsafe {
         uninit.advance_mut(100000);
     } // should be effectively no-op
+    assert_eq!(uninit.remaining_mut(), 8);
+    assert_eq!(uninit.chunk_mut().len(), 8);
+    
 }

From e8e58f1789328a7df037cef069fcd73c5919d32c Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Mon, 3 Apr 2023 15:44:32 +0200
Subject: [PATCH 16/19] fmt

---
 tokio/tests/io_read_buf.rs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index cc95ae322e7..c7edd4d83a4 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -85,5 +85,4 @@ async fn issue_5588() {
     } // should be effectively no-op
     assert_eq!(uninit.remaining_mut(), 8);
     assert_eq!(uninit.chunk_mut().len(), 8);
-    
 }

From 6c264c2b4147e52d077f299bf73f468839491e4e Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Tue, 4 Apr 2023 05:24:37 +0200
Subject: [PATCH 17/19] Improve advance_mut

---
 tokio/src/io/read_buf.rs   | 6 +++---
 tokio/tests/io_read_buf.rs | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tokio/src/io/read_buf.rs b/tokio/src/io/read_buf.rs
index 2fe2f8e1ade..283d96e3095 100644
--- a/tokio/src/io/read_buf.rs
+++ b/tokio/src/io/read_buf.rs
@@ -277,10 +277,10 @@ unsafe impl<'a> bytes::BufMut for ReadBuf<'a> {
         self.remaining()
     }
 
+    // SAFETY: The caller guarantees that at least `cnt` unfilled bytes have been initialized.
     unsafe fn advance_mut(&mut self, cnt: usize) {
-        if self.initialized > 0 {
-            self.advance(cnt);
-        }
+        self.assume_init(cnt);
+        self.advance(cnt);
     }
 
     fn chunk_mut(&mut self) -> &mut bytes::buf::UninitSlice {
diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index c7edd4d83a4..d3e8b426bd5 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -82,7 +82,7 @@ async fn issue_5588() {
     let mut uninit = ReadBuf::uninit(&mut buf);
     unsafe {
         uninit.advance_mut(100000);
-    } // should be effectively no-op
+    }
     assert_eq!(uninit.remaining_mut(), 8);
     assert_eq!(uninit.chunk_mut().len(), 8);
 }

From 93c360c0d11ed00eb462f17e2c3a8a3bbe7bdce6 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Tue, 4 Apr 2023 05:47:17 +0200
Subject: [PATCH 18/19] Pass the test

---
 tokio/tests/io_read_buf.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index d3e8b426bd5..42d933d48f5 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -81,8 +81,8 @@ async fn issue_5588() {
     let mut buf = [std::mem::MaybeUninit::uninit(); 8];
     let mut uninit = ReadBuf::uninit(&mut buf);
     unsafe {
-        uninit.advance_mut(100000);
+        uninit.advance_mut(8);
     }
-    assert_eq!(uninit.remaining_mut(), 8);
-    assert_eq!(uninit.chunk_mut().len(), 8);
+    assert_eq!(uninit.remaining_mut(), 0);
+    assert_eq!(uninit.chunk_mut().len(), 0);
 }

From a1d66843301dde7888aa2b1af13c88b9b7680487 Mon Sep 17 00:00:00 2001
From: amab8901 <amab8901@protonmail.com>
Date: Tue, 4 Apr 2023 16:09:54 +0200
Subject: [PATCH 19/19] Add write to test

---
 tokio/tests/io_read_buf.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
index 42d933d48f5..49a4f86f8ad 100644
--- a/tokio/tests/io_read_buf.rs
+++ b/tokio/tests/io_read_buf.rs
@@ -81,8 +81,14 @@ async fn issue_5588() {
     let mut buf = [std::mem::MaybeUninit::uninit(); 8];
     let mut uninit = ReadBuf::uninit(&mut buf);
     unsafe {
-        uninit.advance_mut(8);
+        uninit.advance_mut(4);
     }
+    assert_eq!(uninit.remaining_mut(), 4);
+    assert_eq!(uninit.chunk_mut().len(), 4);
+    uninit.put_u8(1);
+    assert_eq!(uninit.remaining_mut(), 3);
+    assert_eq!(uninit.chunk_mut().len(), 3);
+    uninit.put_slice(&[1, 2, 3]);
     assert_eq!(uninit.remaining_mut(), 0);
     assert_eq!(uninit.chunk_mut().len(), 0);
 }