1 files changed, 72 insertions, 0 deletions
diff --git a/vendor/getrandom/src/backends/wasm_js.rs b/vendor/getrandom/src/backends/wasm_js.rs
new file mode 100644
index 00000000..1320d9fc
--- /dev/null
+++ b/vendor/getrandom/src/backends/wasm_js.rs
@@ -0,0 +1,72 @@
+//! Implementation for WASM based on Web and Node.js
+use crate::Error;
+use core::mem::MaybeUninit;
+
+pub use crate::util::{inner_u32, inner_u64};
+
+#[cfg(not(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "none"))))]
+compile_error!("`wasm_js` backend can be enabled only for OS-less WASM targets!");
+
+use wasm_bindgen::{prelude::wasm_bindgen, JsValue};
+
+// Maximum buffer size allowed in `Crypto.getRandomValuesSize` is 65536 bytes.
+// See https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
+const MAX_BUFFER_SIZE: usize = 65536;
+
+#[cfg(not(target_feature = "atomics"))]
+#[inline]
+pub fn fill_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
+    for chunk in dest.chunks_mut(MAX_BUFFER_SIZE) {
+        if get_random_values(chunk).is_err() {
+            return Err(Error::WEB_CRYPTO);
+        }
+    }
+    Ok(())
+}
+
+#[cfg(target_feature = "atomics")]
+pub fn fill_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
+    // getRandomValues does not work with all types of WASM memory,
+    // so we initially write to browser memory to avoid exceptions.
+    let buf_len = usize::min(dest.len(), MAX_BUFFER_SIZE);
+    let buf_len_u32 = buf_len
+        .try_into()
+        .expect("buffer length is bounded by MAX_BUFFER_SIZE");
+    let buf = js_sys::Uint8Array::new_with_length(buf_len_u32);
+    for chunk in dest.chunks_mut(buf_len) {
+        let chunk_len = chunk
+            .len()
+            .try_into()
+            .expect("chunk length is bounded by MAX_BUFFER_SIZE");
+        // The chunk can be smaller than buf's length, so we call to
+        // JS to create a smaller view of buf without allocation.
+        let sub_buf = if chunk_len == buf_len_u32 {
+            &buf
+        } else {
+            &buf.subarray(0, chunk_len)
+        };
+
+        if get_random_values(sub_buf).is_err() {
+            return Err(Error::WEB_CRYPTO);
+        }
+
+        sub_buf.copy_to_uninit(chunk);
+    }
+    Ok(())
+}
+
+#[wasm_bindgen]
+extern "C" {
+    // Crypto.getRandomValues()
+    #[cfg(not(target_feature = "atomics"))]
+    #[wasm_bindgen(js_namespace = ["globalThis", "crypto"], js_name = getRandomValues, catch)]
+    fn get_random_values(buf: &mut [MaybeUninit<u8>]) -> Result<(), JsValue>;
+    #[cfg(target_feature = "atomics")]
+    #[wasm_bindgen(js_namespace = ["globalThis", "crypto"], js_name = getRandomValues, catch)]
+    fn get_random_values(buf: &js_sys::Uint8Array) -> Result<(), JsValue>;
+}
+
+impl Error {
+    /// The environment does not support the Web Crypto API.
+    pub(crate) const WEB_CRYPTO: Error = Self::new_internal(10);
+}