add length check

feross · Nov 4, 2020 · be5cd35 · be5cd35
1 parent f44c2f2
commit be5cd35
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Showing 2 changed files with 16 additions and 5 deletions.
diff --git 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
@@ -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)