--- /dev/null
+'use strict';
+
+/**
+ * Merges an array of buffers into a new buffer.
+ *
+ * @param {Buffer[]} list The array of buffers to concat
+ * @param {Number} totalLength The total length of buffers in the list
+ * @return {Buffer} The resulting buffer
+ * @public
+ */
+function concat (list, totalLength) {
+ const target = Buffer.allocUnsafe(totalLength);
+ var offset = 0;
+
+ for (var i = 0; i < list.length; i++) {
+ const buf = list[i];
+ buf.copy(target, offset);
+ offset += buf.length;
+ }
+
+ return target;
+}
+
+/**
+ * Masks a buffer using the given mask.
+ *
+ * @param {Buffer} source The buffer to mask
+ * @param {Buffer} mask The mask to use
+ * @param {Buffer} output The buffer where to store the result
+ * @param {Number} offset The offset at which to start writing
+ * @param {Number} length The number of bytes to mask.
+ * @public
+ */
+function _mask (source, mask, output, offset, length) {
+ for (var i = 0; i < length; i++) {
+ output[offset + i] = source[i] ^ mask[i & 3];
+ }
+}
+
+/**
+ * Unmasks a buffer using the given mask.
+ *
+ * @param {Buffer} buffer The buffer to unmask
+ * @param {Buffer} mask The mask to use
+ * @public
+ */
+function _unmask (buffer, mask) {
+ // Required until https://github.com/nodejs/node/issues/9006 is resolved.
+ const length = buffer.length;
+ for (var i = 0; i < length; i++) {
+ buffer[i] ^= mask[i & 3];
+ }
+}
+
+try {
+ const bufferUtil = require('bufferutil');
+ const bu = bufferUtil.BufferUtil || bufferUtil;
+
+ module.exports = {
+ mask (source, mask, output, offset, length) {
+ if (length < 48) _mask(source, mask, output, offset, length);
+ else bu.mask(source, mask, output, offset, length);
+ },
+ unmask (buffer, mask) {
+ if (buffer.length < 32) _unmask(buffer, mask);
+ else bu.unmask(buffer, mask);
+ },
+ concat
+ };
+} catch (e) /* istanbul ignore next */ {
+ module.exports = { concat, mask: _mask, unmask: _unmask };
+}