2 files changed, 170 insertions, 0 deletions
diff --git a/std/bytes/mod.ts b/std/bytes/mod.ts
new file mode 100644
index 000000000..a42eaffd2
--- /dev/null
+++ b/std/bytes/mod.ts
@@ -0,0 +1,96 @@
+// 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 findIndex(a: Uint8Array, pat: Uint8Array): number {
+  const s = pat[0];
+  for (let i = 0; i < a.length; i++) {
+    if (a[i] !== s) continue;
+    const pin = i;
+    let matched = 1,
+      j = i;
+    while (matched < pat.length) {
+      j++;
+      if (a[j] !== pat[j - pin]) {
+        break;
+      }
+      matched++;
+    }
+    if (matched === pat.length) {
+      return pin;
+    }
+  }
+  return -1;
+}
+
+/** Find last index of binary pattern from a. If not found, then return -1 **/
+export function findLastIndex(a: Uint8Array, pat: Uint8Array): number {
+  const e = pat[pat.length - 1];
+  for (let i = a.length - 1; i >= 0; i--) {
+    if (a[i] !== e) continue;
+    const pin = i;
+    let matched = 1,
+      j = i;
+    while (matched < pat.length) {
+      j--;
+      if (a[j] !== pat[pat.length - 1 - (pin - j)]) {
+        break;
+      }
+      matched++;
+    }
+    if (matched === pat.length) {
+      return pin - pat.length + 1;
+    }
+  }
+  return -1;
+}
+
+/** Check whether binary arrays are equal to each other **/
+export function equal(a: Uint8Array, match: Uint8Array): boolean {
+  if (a.length !== match.length) return false;
+  for (let i = 0; i < match.length; i++) {
+    if (a[i] !== match[i]) return false;
+  }
+  return true;
+}
+
+/** Check whether binary array has binary prefix  **/
+export function hasPrefix(a: Uint8Array, prefix: Uint8Array): boolean {
+  for (let i = 0, max = prefix.length; i < max; i++) {
+    if (a[i] !== prefix[i]) return false;
+  }
+  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 repeat(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;
+}
diff --git a/std/bytes/test.ts b/std/bytes/test.ts
new file mode 100644
index 000000000..0a779dd3d
--- /dev/null
+++ b/std/bytes/test.ts
@@ -0,0 +1,74 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+
+import { findIndex, findLastIndex, equal, hasPrefix, repeat } from "./mod.ts";
+import { test } from "../testing/mod.ts";
+import { assertEquals, assertThrows } from "../testing/asserts.ts";
+
+test(function bytesfindIndex1(): void {
+  const i = findIndex(
+    new Uint8Array([1, 2, 0, 1, 2, 0, 1, 2, 0, 1, 3]),
+    new Uint8Array([0, 1, 2])
+  );
+  assertEquals(i, 2);
+});
+
+test(function bytesfindIndex2(): void {
+  const i = findIndex(new Uint8Array([0, 0, 1]), new Uint8Array([0, 1]));
+  assertEquals(i, 1);
+});
+
+test(function bytesfindLastIndex1(): void {
+  const i = findLastIndex(
+    new Uint8Array([0, 1, 2, 0, 1, 2, 0, 1, 3]),
+    new Uint8Array([0, 1, 2])
+  );
+  assertEquals(i, 3);
+});
+
+test(function bytesfindLastIndex2(): void {
+  const i = findLastIndex(new Uint8Array([0, 1, 1]), new Uint8Array([0, 1]));
+  assertEquals(i, 0);
+});
+
+test(function bytesBytesequal(): void {
+  const v = equal(new Uint8Array([0, 1, 2, 3]), new Uint8Array([0, 1, 2, 3]));
+  assertEquals(v, true);
+});
+
+test(function byteshasPrefix(): void {
+  const v = hasPrefix(new Uint8Array([0, 1, 2]), new Uint8Array([0, 1]));
+  assertEquals(v, true);
+});
+
+test(function bytesrepeat(): void {
+  // input / output / count / error message
+  const repeatTestCase = [
+    ["", "", 0],
+    ["", "", 1],
+    ["", "", 1.1, "bytes: repeat count must be an integer"],
+    ["", "", 2],
+    ["", "", 0],
+    ["-", "", 0],
+    ["-", "-", -1, "bytes: negative repeat count"],
+    ["-", "----------", 10],
+    ["abc ", "abc abc abc ", 3]
+  ];
+  for (const [input, output, count, errMsg] of repeatTestCase) {
+    if (errMsg) {
+      assertThrows(
+        (): void => {
+          repeat(new TextEncoder().encode(input as string), count as number);
+        },
+        Error,
+        errMsg as string
+      );
+    } else {
+      const newBytes = repeat(
+        new TextEncoder().encode(input as string),
+        count as number
+      );
+
+      assertEquals(new TextDecoder().decode(newBytes), output);
+    }
+  }
+});