Add FromBytes::read_from_io and IntoBytes::write_to_io

Makes progress on #158.

src/lib.rs

@@ -359,12 +359,16 @@ use core::{
     slice,
 };
 
+#[cfg(feature = "std")]
+use std::io;
+
 use crate::pointer::{invariant, BecauseExclusive};
 
 #[cfg(any(feature = "alloc", test))]
 extern crate alloc;
 #[cfg(any(feature = "alloc", test))]
 use alloc::{boxed::Box, vec::Vec};
+use pointer::invariant::Initialized;
 
 #[cfg(any(feature = "alloc", test, kani))]
 use core::alloc::Layout;
@@ -4525,6 +4529,24 @@ pub unsafe trait FromBytes: FromZeros {
         }
     }
 
+    /// TODO
+    #[cfg(feature = "std")]
+    #[inline(always)]
+    fn read_from_io(source: &mut impl io::Read) -> io::Result<Self>
+    where
+        Self: Sized,
+    {
+        let mut buffer = MaybeUninit::<Self>::zeroed();
+        let ptr = Ptr::from_mut(&mut buffer);
+        // SAFETY: `buffer` consists entirely of initialized, zeroed bytes.
+        let ptr = unsafe { ptr.assume_validity::<Initialized>() };
+        let ptr = ptr.as_bytes::<BecauseExclusive>();
+        source.read_exact(ptr.as_mut())?;
+        // SAFETY: `buffer` consists entirely of initialized bytes, and `Self`
+        // is `FromBytes`.
+        Ok(unsafe { buffer.assume_init() })
+    }
+
     #[deprecated(since = "0.8.0", note = "renamed to `FromBytes::ref_from_bytes`")]
     #[doc(hidden)]
     #[must_use = "has no side effects"]
@@ -5188,6 +5210,16 @@ pub unsafe trait IntoBytes {
         Ok(())
     }
 
+    /// TODO
+    #[cfg(feature = "std")]
+    #[inline(always)]
+    fn write_to_io(&self, dst: &mut impl io::Write) -> io::Result<()>
+    where
+        Self: Immutable,
+    {
+        dst.write_all(self.as_bytes())
+    }
+
     #[deprecated(since = "0.8.0", note = "`IntoBytes::as_bytes_mut` was renamed to `as_mut_bytes`")]
     #[doc(hidden)]
     #[inline]