Add ByteValued::{write_all_to,read_exact_from}

Suggested-by: Paolo Bonzini <[email protected]>
Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

src/bytes.rs

@@ -11,6 +11,7 @@
 //! Define the `ByteValued` trait to mark that it is safe to instantiate the struct with random
 //! data.
 
+use std::io::{Read, Write};
 use std::mem::{size_of, MaybeUninit};
 use std::result::Result;
 use std::slice::{from_raw_parts, from_raw_parts_mut};
@@ -116,6 +117,20 @@ pub unsafe trait ByteValued: Copy + Send + Sync {
     fn as_bytes(&mut self) -> VolatileSlice {
         VolatileSlice::from(self.as_mut_slice())
     }
+
+    /// Writes this [`ByteValued`]'s byte representation to the given [`Write`] impl.
+    fn write_all_to<W: Write>(&self, mut writer: W) -> Result<(), std::io::Error> {
+        writer.write_all(self.as_slice())
+    }
+
+    /// Constructs an instance of this [`ByteValued`] by reading from the given [`Read`] impl.
+    fn read_exact_from<R: Read>(mut reader: R) -> Result<Self, std::io::Error> {
+        // SAFETY: ByteValued objects must be assignable from arbitrary byte
+        // sequences and are mandated to be packed.
+        // Hence, zeroed memory is a fine initialization.
+        let mut result: Self = unsafe { MaybeUninit::<Self>::zeroed().assume_init() };
+        reader.read_exact(result.as_mut_slice()).map(|_| result)
+    }
 }
 
 macro_rules! byte_valued_array {