impl AsyncWrite for Hasher

Cargo.toml

@@ -87,6 +87,9 @@ no_avx2 = []
 no_avx512 = []
 no_neon = []
 
+# This feature enables the tokio AsyncWrite implementation for the hashers.
+tokio = ["dep:tokio", "std"]
+
 [package.metadata.docs.rs]
 # Document the rayon/mmap methods and the Zeroize impls on docs.rs.
 features = ["mmap", "rayon", "zeroize"]
@@ -100,6 +103,7 @@ cfg-if = "1.0.0"
 digest = { version = "0.10.1", features = [ "mac" ], optional = true }
 zeroize = { version = "1", default-features = false, features = ["zeroize_derive"], optional = true }
 memmap2 = { version = "0.7.1", optional = true }
+tokio = { version = "1", default-features = false, features = [], optional = true }
 
 [dev-dependencies]
 hmac = "0.12.0"

src/lib.rs

@@ -1516,6 +1516,44 @@ impl std::io::Write for Hasher {
     }
 }
 
+#[cfg(feature = "tokio")]
+impl tokio::io::AsyncWrite for Hasher {
+    fn poll_write(
+        self: std::pin::Pin<&mut Self>,
+        _: &mut std::task::Context<'_>,
+        buf: &[u8],
+    ) -> std::task::Poll<Result<usize, std::io::Error>> {
+        self.get_mut().update(buf);
+        std::task::Poll::Ready(Ok(buf.len()))
+    }
+
+    fn poll_flush(
+        self: std::pin::Pin<&mut Self>,
+        _: &mut std::task::Context<'_>,
+    ) -> std::task::Poll<Result<(), std::io::Error>> {
+        std::task::Poll::Ready(Ok(()))
+    }
+
+    fn poll_shutdown(
+        self: std::pin::Pin<&mut Self>,
+        _: &mut std::task::Context<'_>,
+    ) -> std::task::Poll<Result<(), std::io::Error>> {
+        std::task::Poll::Ready(Ok(()))
+    }
+
+    fn poll_write_vectored(
+        mut self: std::pin::Pin<&mut Self>,
+        _: &mut std::task::Context<'_>,
+        bufs: &[std::io::IoSlice<'_>],
+    ) -> std::task::Poll<Result<usize, std::io::Error>> {
+        std::task::Poll::Ready(std::io::Write::write_vectored(&mut *self, bufs))
+    }
+
+    fn is_write_vectored(&self) -> bool {
+        true
+    }
+}
+
 /// An incremental reader for extended output, returned by
 /// [`Hasher::finalize_xof`](struct.Hasher.html#method.finalize_xof).
 ///