Enable bytes tests and add bytesRepeat (denoland/deno_std#446)

Original: https://github.com/denoland/deno_std/commit/bd46d60ded3197d93a52ede92eba7302df9b4713

1 files changed, 34 insertions, 0 deletions

diff --git a/bytes/bytes.ts b/bytes/bytes.ts
index a79a9ed56..127dad1c2 100644
--- a/bytes/bytes.ts
+++ b/bytes/bytes.ts
@@ -1,4 +1,5 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import { copyBytes } from "../io/util.ts";
 
 /** Find first index of binary pattern from a. If not found, then return -1 **/
 export function bytesFindIndex(a: Uint8Array, pat: Uint8Array): number {
@@ -60,3 +61,36 @@ export function bytesHasPrefix(a: Uint8Array, prefix: Uint8Array): boolean {
   }
   return true;
 }
+
+/**
+ * Repeat bytes. returns a new byte slice consisting of `count` copies of `b`.
+ * @param b The origin bytes
+ * @param count The count you want to repeat.
+ */
+export function bytesRepeat(b: Uint8Array, count: number): Uint8Array {
+  if (count === 0) {
+    return new Uint8Array();
+  }
+
+  if (count < 0) {
+    throw new Error("bytes: negative repeat count");
+  } else if ((b.length * count) / count !== b.length) {
+    throw new Error("bytes: repeat count causes overflow");
+  }
+
+  const int = Math.floor(count);
+
+  if (int !== count) {
+    throw new Error("bytes: repeat count must be an integer");
+  }
+
+  const nb = new Uint8Array(b.length * count);
+
+  let bp = copyBytes(nb, b);
+
+  for (; bp < nb.length; bp *= 2) {
+    copyBytes(nb, nb.slice(0, bp), bp);
+  }
+
+  return nb;
+}