From 41829f3e2bd0b1c3af8b508dfafb1b5a17fe59b6 Mon Sep 17 00:00:00 2001
From: Max Graey <maxgraey@gmail.com>
Date: Tue, 22 Jan 2019 05:56:35 +0200
Subject: fix possible range issues for copyBytes in io/util
 (denoland/deno_std#146)

Original: https://github.com/denoland/deno_std/commit/2081f03a0748dac0cf0ab7e6e2d7e427841aca22
---
 io/util.ts      |  1 +
 io/util_test.ts | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)
 create mode 100644 io/util_test.ts

(limited to 'io')

diff --git a/io/util.ts b/io/util.ts
index 3266e5018..185732b36 100644
--- a/io/util.ts
+++ b/io/util.ts
@@ -4,6 +4,7 @@ import { Buffer, Reader } from "deno";
 // from `src`.
 // Returns the number of bytes copied.
 export function copyBytes(dst: Uint8Array, src: Uint8Array, off = 0): number {
+  off = Math.max(0, Math.min(off, dst.byteLength));
   const r = dst.byteLength - off;
   if (src.byteLength > r) {
     src = src.subarray(0, r);
diff --git a/io/util_test.ts b/io/util_test.ts
new file mode 100644
index 000000000..7318d887c
--- /dev/null
+++ b/io/util_test.ts
@@ -0,0 +1,36 @@
+import { test, assert } from "../testing/mod.ts";
+import { copyBytes } from "./util.ts";
+
+test(function testCopyBytes() {
+  let dst = new Uint8Array(4);
+
+  dst.fill(0);
+  let src = Uint8Array.of(1, 2);
+  let len = copyBytes(dst, src, 0);
+  assert(len === 2);
+  assert.equal(dst, Uint8Array.of(1, 2, 0, 0));
+
+  dst.fill(0);
+  src = Uint8Array.of(1, 2);
+  len = copyBytes(dst, src, 1);
+  assert(len === 2);
+  assert.equal(dst, Uint8Array.of(0, 1, 2, 0));
+
+  dst.fill(0);
+  src = Uint8Array.of(1, 2, 3, 4, 5);
+  len = copyBytes(dst, src);
+  assert(len === 4);
+  assert.equal(dst, Uint8Array.of(1, 2, 3, 4));
+
+  dst.fill(0);
+  src = Uint8Array.of(1, 2);
+  len = copyBytes(dst, src, 100);
+  assert(len === 0);
+  assert.equal(dst, Uint8Array.of(0, 0, 0, 0));
+
+  dst.fill(0);
+  src = Uint8Array.of(3, 4);
+  len = copyBytes(dst, src, -2);
+  assert(len === 2);
+  assert.equal(dst, Uint8Array.of(3, 4, 0, 0));
+});
-- 
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