feat(random): add randomBytes() wrapper

thi-ng · Jan 26, 2020 · c536bcd · c536bcd
1 parent df87b7c
commit c536bcd
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diff --git a/packages/random/src/index.ts b/packages/random/src/index.ts
@@ -5,5 +5,6 @@ export * from "./xorshift128";
 export * from "./xorwow";
 export * from "./xsadd";
 
+export * from "./random-bytes";
 export * from "./random-id";
 export * from "./weighted-random";
diff --git a/packages/random/src/random-bytes.ts b/packages/random/src/random-bytes.ts
@@ -0,0 +1,17 @@
+import { hasCrypto } from "@thi.ng/checks";
+import { SYSTEM } from "./system";
+
+/**
+ * Fills given byte array with random values. Wrapper for
+ * `crypto.getRandomValues()` with automatic fallback to using
+ * `Math.random` if platform doesn't provide global crypto instance.
+ */
+export const randomBytes = hasCrypto()
+    ? (buf: Uint8Array) => window.crypto.getRandomValues(buf)
+    : (buf: Uint8Array) => {
+          const n = buf.length;
+          for (let i = 0; i < n; i++) {
+              buf[i] = SYSTEM.int() & 0xff;
+          }
+          return buf;
+      };