1 files changed, 18 insertions, 0 deletions
diff --git a/third_party/rust/getrandom/src/emscripten.rs b/third_party/rust/getrandom/src/emscripten.rs
new file mode 100644
index 0000000000..a50372f566
--- /dev/null
+++ b/third_party/rust/getrandom/src/emscripten.rs
@@ -0,0 +1,18 @@
+//! Implementation for Emscripten
+use crate::{util_libc::last_os_error, Error};
+use core::mem::MaybeUninit;
+
+// Not yet defined in libc crate.
+extern "C" {
+    fn getentropy(buffer: *mut libc::c_void, length: usize) -> libc::c_int;
+}
+
+pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
+    // Emscripten 2.0.5 added getentropy, so we can use it unconditionally.
+    // Unlike other getentropy implementations, there is no max buffer length.
+    let ret = unsafe { getentropy(dest.as_mut_ptr() as *mut libc::c_void, dest.len()) };
+    if ret < 0 {
+        return Err(last_os_error());
+    }
+    Ok(())
+}