rand for WASIp3 (#157)

* rand for WASIp3

* only include module under wasi

Author: adamrk

src/lib.rs

@@ -65,7 +65,7 @@ pub mod io;
 pub mod iter;
 #[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod net;
-#[cfg(all(target_os = "wasi", target_env = "p2"))]
+#[cfg(target_os = "wasi")]
 pub mod rand;
 #[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod runtime;

src/rand/mod.rs

@@ -1,6 +1,9 @@
 //! Random number generation.
 
+#[cfg(target_env = "p2")]
 use wasip2::random;
+#[cfg(target_env = "p3")]
+use wasip3::random;
 
 /// Fill the slice with cryptographically secure random bytes.
 pub fn get_random_bytes(buf: &mut [u8]) {

tests/rand.rs

@@ -0,0 +1,14 @@
+/// Check that the rand interface works with empty and non-empty buffers.
+#[wstd::test]
+async fn fills_random_bytes() {
+    let mut secure = [0; 32];
+    wstd::rand::get_random_bytes(&mut secure);
+    assert!(secure.iter().any(|byte| *byte != 0));
+
+    let mut insecure = [0; 32];
+    wstd::rand::get_insecure_random_bytes(&mut insecure);
+    assert!(insecure.iter().any(|byte| *byte != 0));
+
+    wstd::rand::get_random_bytes(&mut []);
+    wstd::rand::get_insecure_random_bytes(&mut []);
+}