Add hwysum example

examples/hwysum.rs

@@ -0,0 +1,25 @@
+use highway::HighwayHash;
+
+// This is a simple example of how to hash data from stdin using a
+// HighwayHasher. Analagous to `shasum` and `md5sum` but using HighwayHash.
+//
+// ```bash
+// cargo run --release --example hwysum < README.md
+// ```
+#[cfg(feature = "std")]
+fn main() {
+    let stdin = std::io::stdin();
+    let mut lock = stdin.lock();
+    let mut hasher = highway::HighwayHasher::new(highway::Key::default());
+    let _ = std::io::copy(&mut lock, &mut hasher);
+    let hash = hasher.finalize256();
+    println!(
+        "{:016x}{:016x}{:016x}{:016x}",
+        hash[0], hash[1], hash[2], hash[3]
+    );
+}
+
+#[cfg(not(feature = "std"))]
+fn main() {
+    println!("This example requires the 'std' feature to be enabled.");
+}