feat(rand): add rand crate integration

Signed-off-by: Roman Volosatovs <[email protected]>

Author: rvolosatovs

Cargo.toml

@@ -19,6 +19,9 @@ compiler_builtins = { version = "0.1", optional = true }
 core = { version = "1.0", optional = true, package = "rustc-std-workspace-core" }
 rustc-std-workspace-alloc = { version = "1.0", optional = true }
 
+# When built with `rand` crate integration
+rand = { version = "0.8.5", default-features = false, optional = true }
+
 [features]
 default = ["std"]
 std = []
@@ -32,3 +35,7 @@ crate-type = ["cdylib"]
 [[example]]
 name = "http-proxy"
 crate-type = ["cdylib"]
+
+[[example]]
+name = "rand"
+required-features = ["rand"]

examples/rand.rs

@@ -0,0 +1,20 @@
+use std::io::Write as _;
+
+use wasi::ext::rand::rand::Rng as _;
+use wasi::ext::rand::{HostInsecureRng, HostRng};
+
+fn main() {
+    let mut stdout = wasi::cli::stdout::get_stdout();
+
+    let r: u64 = HostRng.gen();
+    stdout
+        .write_all(format!("Cryptographically-secure random u64 is {r}\n").as_bytes())
+        .unwrap();
+
+    let r: u64 = HostInsecureRng.gen();
+    stdout
+        .write_all(format!("Pseudo-random u64 is {r}\n").as_bytes())
+        .unwrap();
+
+    stdout.flush().unwrap();
+}

src/ext/mod.rs

@@ -1,6 +1,9 @@
 #[cfg(feature = "std")]
 mod std;
 
+#[cfg(feature = "rand")]
+pub mod rand;
+
 impl core::fmt::Display for crate::io::error::Error {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
         f.write_str(&self.to_debug_string())

src/ext/rand.rs

@@ -0,0 +1,71 @@
+pub use rand;
+
+use rand::{CryptoRng, RngCore};
+
+/// The secure interface for cryptographically-secure random numbers
+pub struct HostRng;
+
+impl CryptoRng for HostRng {}
+
+impl RngCore for HostRng {
+    #[inline]
+    fn next_u32(&mut self) -> u32 {
+        crate::random::random::get_random_u64() as _
+    }
+
+    #[inline]
+    fn next_u64(&mut self) -> u64 {
+        crate::random::random::get_random_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        let n = dest.len();
+        if usize::BITS <= u64::BITS || n <= u64::MAX as _ {
+            dest.copy_from_slice(&crate::random::random::get_random_bytes(n as _));
+        } else {
+            let (head, tail) = dest.split_at_mut(u64::MAX as _);
+            head.copy_from_slice(&crate::random::random::get_random_bytes(u64::MAX));
+            self.fill_bytes(tail);
+        }
+    }
+
+    #[inline]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand::Error> {
+        self.fill_bytes(dest);
+        Ok(())
+    }
+}
+
+/// The insecure interface for insecure pseudo-random numbers
+pub struct HostInsecureRng;
+
+impl RngCore for HostInsecureRng {
+    #[inline]
+    fn next_u32(&mut self) -> u32 {
+        crate::random::insecure::get_insecure_random_u64() as _
+    }
+
+    #[inline]
+    fn next_u64(&mut self) -> u64 {
+        crate::random::insecure::get_insecure_random_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        let n = dest.len();
+        if usize::BITS <= u64::BITS || n <= u64::MAX as _ {
+            dest.copy_from_slice(&crate::random::insecure::get_insecure_random_bytes(n as _));
+        } else {
+            let (head, tail) = dest.split_at_mut(u64::MAX as _);
+            head.copy_from_slice(&crate::random::insecure::get_insecure_random_bytes(
+                u64::MAX,
+            ));
+            self.fill_bytes(tail);
+        }
+    }
+
+    #[inline]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand::Error> {
+        self.fill_bytes(dest);
+        Ok(())
+    }
+}

src/lib.rs

@@ -179,7 +179,7 @@
 #[cfg(feature = "std")]
 extern crate std;
 
-mod ext;
+pub mod ext;
 
 // These modules are all auto-generated by `./ci/regenerate.sh`
 mod bindings;