implement randomness

crates/wasi-c2/src/random.rs

@@ -0,0 +1,37 @@
+use crate::Error;
+use std::cell::RefCell;
+
+pub trait WasiRandom {
+    fn get(&self, buf: &mut [u8]) -> Result<(), Error>;
+}
+
+pub struct GetRandom;
+
+impl WasiRandom for GetRandom {
+    fn get(&self, buf: &mut [u8]) -> Result<(), Error> {
+        getrandom::getrandom(buf)?;
+        Ok(())
+    }
+}
+
+pub struct Deterministic {
+    sequence: RefCell<std::iter::Cycle<std::vec::IntoIter<u8>>>,
+}
+
+impl Deterministic {
+    pub fn new(bytes: Vec<u8>) -> Self {
+        Deterministic {
+            sequence: RefCell::new(bytes.into_iter().cycle()),
+        }
+    }
+}
+
+impl WasiRandom for Deterministic {
+    fn get(&self, buf: &mut [u8]) -> Result<(), Error> {
+        let mut s = self.sequence.borrow_mut();
+        for b in buf.iter_mut() {
+            *b = s.next().expect("infinite sequence");
+        }
+        Ok(())
+    }
+}