From be5cd35fbeff23956711b0a7096bf881efb90644 Mon Sep 17 00:00:00 2001
From: jkkang <jkkang@smartauth.kr>
Date: Wed, 4 Nov 2020 19:31:35 +0900
Subject: [PATCH] add length check

---
 index.js        | 14 +++++++++-----
 test/methods.js |  7 +++++++
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/index.js b/index.js
index ba68f7b..94c71ea 100644
--- a/index.js
+++ b/index.js
@@ -409,11 +409,15 @@ Buffer.concat = function concat (list, length) {
   for (i = 0; i < list.length; ++i) {
     const buf = list[i]
     if (isInstance(buf, Uint8Array)) {
-      Uint8Array.prototype.set.call(
-        buffer,
-        buf,
-        pos
-      )
+      if (pos + buf.length > buffer.length) {
+        Buffer.from(buf).copy(buffer, pos)
+      } else {
+        Uint8Array.prototype.set.call(
+          buffer,
+          buf,
+          pos
+        )
+      }
     } else if (!Buffer.isBuffer(buf)) {
       throw new TypeError('"list" argument must be an Array of Buffers')
     } else {
diff --git a/test/methods.js b/test/methods.js
index 20f445c..b1bf75b 100644
--- a/test/methods.js
+++ b/test/methods.js
@@ -67,6 +67,13 @@ test('concat() works on Uint8Array instances', function (t) {
   t.end()
 })
 
+test('concat() works on Uint8Array instances for smaller provided totalLength', function (t) {
+  const result = B.concat([new Uint8Array([1, 2]), new Uint8Array([3, 4])], 3)
+  const expected = B.from([1, 2, 3])
+  t.deepEqual(result, expected)
+  t.end()
+})
+
 test('fill', function (t) {
   const b = new B(10)
   b.fill(2)
-- 
2.34.1