feat: add examples gcd, memory

__wasm/wasmtime/examples/gcd.rs

@@ -0,0 +1,46 @@
+use anyhow::Result;
+use wasmtime::*;
+
+// https://docs.wasmtime.dev/examples-rust-gcd.html
+fn main() -> Result<()> {
+    // Load our WebAssembly (parsed WAT in our case), and then load it into a
+    // `Module` which is attached to a `Store` cache. After we've got that we
+    // can instantiate it.
+    let mut store = Store::<()>::default();
+    let module = Module::new(store.engine(), r#"
+    (module
+      (func $gcd (param i32 i32) (result i32)
+        (local i32)
+        block  ;; label = @1
+          block  ;; label = @2
+            local.get 0
+            br_if 0 (;@2;)
+            local.get 1
+            local.set 2
+            br 1 (;@1;)
+          end
+          loop  ;; label = @2
+            local.get 1
+            local.get 0
+            local.tee 2
+            i32.rem_u
+            local.set 0
+            local.get 2
+            local.set 1
+            local.get 0
+            br_if 0 (;@2;)
+          end
+        end
+        local.get 2
+      )
+      (export "gcd" (func $gcd))
+    )
+    "#)?;
+    let instance = Instance::new(&mut store, &module, &[])?;
+
+    // Invoke `gcd` export
+    let gcd = instance.get_typed_func::<(i32, i32), i32>(&mut store, "gcd")?;
+
+    println!("gcd(6, 27) = {}", gcd.call(&mut store, (6, 27))?);
+    Ok(())
+}