Use std::io::Initializer instead of our own Initializer

Author: taiki-e

futures-io/src/lib.rs

@@ -8,6 +8,8 @@
 //! All items of this library are only available when the `std` feature of this
 //! library is activated, and it is activated by default.
 
+#![cfg_attr(feature = "read_initializer", feature(read_initializer))]
+
 #![cfg_attr(not(feature = "std"), no_std)]
 
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms, unreachable_pub)]
@@ -28,8 +30,6 @@ mod if_std {
     use std::io;
     use std::ops::DerefMut;
     use std::pin::Pin;
-    #[cfg(feature = "read_initializer")]
-    use std::ptr;
     use std::task::{Context, Poll};
 
     // Re-export some types from `std::io` so that users don't have to deal
@@ -44,47 +44,9 @@ mod if_std {
         SeekFrom as SeekFrom,
     };
 
-    /// A type used to conditionally initialize buffers passed to `AsyncRead`
-    /// methods, modeled after `std`.
-    #[cfg(feature = "read_initializer")]
-    #[derive(Debug)]
-    pub struct Initializer(bool);
-
     #[cfg(feature = "read_initializer")]
-    impl Initializer {
-        /// Returns a new `Initializer` which will zero out buffers.
-        #[inline]
-        pub fn zeroing() -> Initializer {
-            Initializer(true)
-        }
-
-        /// Returns a new `Initializer` which will not zero out buffers.
-        ///
-        /// # Safety
-        ///
-        /// This method may only be called by `AsyncRead`ers which guarantee
-        /// that they will not read from the buffers passed to `AsyncRead`
-        /// methods, and that the return value of the method accurately reflects
-        /// the number of bytes that have been written to the head of the buffer.
-        #[inline]
-        pub unsafe fn nop() -> Initializer {
-            Initializer(false)
-        }
-
-        /// Indicates if a buffer should be initialized.
-        #[inline]
-        pub fn should_initialize(&self) -> bool {
-            self.0
-        }
-
-        /// Initializes a buffer if necessary.
-        #[inline]
-        pub fn initialize(&self, buf: &mut [u8]) {
-            if self.should_initialize() {
-                unsafe { ptr::write_bytes(buf.as_mut_ptr(), 0, buf.len()) }
-            }
-        }
-    }
+    #[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
+    pub use io::Initializer as Initializer;
 
     /// Read bytes asynchronously.
     ///

futures-util/src/lib.rs

@@ -2,6 +2,7 @@
 //! and the `AsyncRead` and `AsyncWrite` traits.
 
 #![cfg_attr(feature = "cfg-target-has-atomic", feature(cfg_target_has_atomic))]
+#![cfg_attr(feature = "read_initializer", feature(read_initializer))]
 
 #![cfg_attr(not(feature = "std"), no_std)]
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms, unreachable_pub)]

futures/src/lib.rs

@@ -22,6 +22,7 @@
 //! completion, but *do not block* the thread running them.
 
 #![cfg_attr(feature = "cfg-target-has-atomic", feature(cfg_target_has_atomic))]
+#![cfg_attr(feature = "read_initializer", feature(read_initializer))]
 
 #![cfg_attr(not(feature = "std"), no_std)]