1 files changed, 125 insertions, 0 deletions
diff --git a/rand/rand_os/src/wasm32_bindgen.rs b/rand/rand_os/src/wasm32_bindgen.rs
new file mode 100644
index 0000000..8e7c979
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+++ b/rand/rand_os/src/wasm32_bindgen.rs
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+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Implementation for WASM via wasm-bindgen
+
+use rand_core::{Error, ErrorKind};
+use super::OsRngImpl;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+extern "C" {
+    pub type Function;
+    #[wasm_bindgen(constructor)]
+    pub fn new(s: &str) -> Function;
+    #[wasm_bindgen(method)]
+    pub fn call(this: &Function, self_: &JsValue) -> JsValue;
+
+    pub type This;
+    #[wasm_bindgen(method, getter, structural, js_name = self)]
+    pub fn self_(me: &This) -> JsValue;
+    #[wasm_bindgen(method, getter, structural)]
+    pub fn crypto(me: &This) -> JsValue;
+
+    #[derive(Clone, Debug)]
+    pub type BrowserCrypto;
+
+    // TODO: these `structural` annotations here ideally wouldn't be here to
+    // avoid a JS shim, but for now with feature detection they're
+    // unavoidable.
+    #[wasm_bindgen(method, js_name = getRandomValues, structural, getter)]
+    pub fn get_random_values_fn(me: &BrowserCrypto) -> JsValue;
+    #[wasm_bindgen(method, js_name = getRandomValues, structural)]
+    pub fn get_random_values(me: &BrowserCrypto, buf: &mut [u8]);
+
+    #[wasm_bindgen(js_name = require)]
+    pub fn node_require(s: &str) -> NodeCrypto;
+
+    #[derive(Clone, Debug)]
+    pub type NodeCrypto;
+
+    #[wasm_bindgen(method, js_name = randomFillSync, structural)]
+    pub fn random_fill_sync(me: &NodeCrypto, buf: &mut [u8]);
+}
+
+#[derive(Clone, Debug)]
+pub enum OsRng {
+    Node(NodeCrypto),
+    Browser(BrowserCrypto),
+}
+
+impl OsRngImpl for OsRng {
+    fn new() -> Result<OsRng, Error> {
+        // First up we need to detect if we're running in node.js or a
+        // browser. To do this we get ahold of the `this` object (in a bit
+        // of a roundabout fashion).
+        //
+        // Once we have `this` we look at its `self` property, which is
+        // only defined on the web (either a main window or web worker).
+        let this = Function::new("return this").call(&JsValue::undefined());
+        assert!(this != JsValue::undefined());
+        let this = This::from(this);
+        let is_browser = this.self_() != JsValue::undefined();
+
+        if !is_browser {
+            return Ok(OsRng::Node(node_require("crypto")))
+        }
+
+        // If `self` is defined then we're in a browser somehow (main window
+        // or web worker). Here we want to try to use
+        // `crypto.getRandomValues`, but if `crypto` isn't defined we assume
+        // we're in an older web browser and the OS RNG isn't available.
+        let crypto = this.crypto();
+        if crypto.is_undefined() {
+            let msg = "self.crypto is undefined";
+            return Err(Error::new(ErrorKind::Unavailable, msg))
+        }
+
+        // Test if `crypto.getRandomValues` is undefined as well
+        let crypto: BrowserCrypto = crypto.into();
+        if crypto.get_random_values_fn().is_undefined() {
+            let msg = "crypto.getRandomValues is undefined";
+            return Err(Error::new(ErrorKind::Unavailable, msg))
+        }
+
+        // Ok! `self.crypto.getRandomValues` is a defined value, so let's
+        // assume we can do browser crypto.
+        Ok(OsRng::Browser(crypto))
+    }
+
+    fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        match *self {
+            OsRng::Node(ref n) => n.random_fill_sync(dest),
+            OsRng::Browser(ref n) => n.get_random_values(dest),
+        }
+        Ok(())
+    }
+
+    fn max_chunk_size(&self) -> usize {
+        match *self {
+            OsRng::Node(_) => usize::max_value(),
+            OsRng::Browser(_) => {
+                // see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
+                //
+                // where it says:
+                //
+                // > A QuotaExceededError DOMException is thrown if the
+                // > requested length is greater than 65536 bytes.
+                65536
+            }
+        }
+    }
+
+    fn method_str(&self) -> &'static str {
+        match *self {
+            OsRng::Node(_) => "crypto.randomFillSync",
+            OsRng::Browser(_) => "crypto.getRandomValues",
+        }
+    }
+}