feat(random): add opt start/end for randomBytes()

thi-ng · Jan 13, 2021 · 4d095da · 4d095da
1 parent d6205d7
commit 4d095da
Showing 1 changed file with 18 additions and 4 deletions.
diff --git a/packages/random/src/random-bytes.ts b/packages/random/src/random-bytes.ts
@@ -8,9 +8,16 @@ import { SYSTEM } from "./system";
  *
  * @param rnd -
  * @param buf -
+ * @param start -
+ * @param end -
  */
-export const randomBytesFrom = (rnd: IRandom, buf: Uint8Array) => {
-    for (let i = buf.length; --i >= 0; ) {
+export const randomBytesFrom = (
+    rnd: IRandom,
+    buf: Uint8Array,
+    start = 0,
+    end = buf.length
+) => {
+    for (let i = end; --i >= start; ) {
         buf[i] = rnd.int() & 0xff;
     }
     return buf;
@@ -20,7 +27,14 @@ export const randomBytesFrom = (rnd: IRandom, buf: Uint8Array) => {
  * 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.
+ *
+ * @param buf -
+ * @param start -
+ * @param end -
  */
 export const randomBytes = hasCrypto()
-    ? (buf: Uint8Array) => window.crypto.getRandomValues(buf)
-    : (buf: Uint8Array) => randomBytesFrom(SYSTEM, buf);
+    ? (buf: Uint8Array, start = 0, end = buf.length) => (
+          window.crypto.getRandomValues(buf.subarray(start, end)), buf
+      )
+    : (buf: Uint8Array, start?: number, end?: number) =>
+          randomBytesFrom(SYSTEM, buf, start, end);