Always return copy of data from socket

We don't know how long the caller will hang on to this data, so we need
to be safe by default and assume it will kept indefinitely. That means
we can't return a reference to the internal buffer, as that will get
overwritten with future messages.

We want to avoid unnecessary copying in performance critical code,
though. So allow code to explicitly ask for a shared buffer, assuming
they know the data needs to be consumed immediately.

tests/test.websock.js

@@ -101,6 +101,12 @@ describe('Websock', function () {
                 expect(shifted).to.array.equal(new Uint8Array(RQ_TEMPLATE.buffer, befRQi, 3));
                 expect(sock._rQlen - sock._rQi).to.equal(befLen - 3);
             });
+            it('should return a shared array if requested', function () {
+                const befRQi = sock._rQi;
+                const shifted = sock.rQshiftBytes(3, false);
+                expect(shifted).to.array.equal(new Uint8Array(RQ_TEMPLATE.buffer, befRQi, 3));
+                expect(shifted.buffer.byteLength).to.not.equal(shifted.length);
+            });
         });
 
         describe('rQpeekBytes', function () {
@@ -124,6 +130,12 @@ describe('Websock', function () {
                 sock._rQi = 1;
                 expect(sock.rQpeekBytes(2)).to.array.equal(new Uint8Array(RQ_TEMPLATE.buffer, 1, 2));
             });
+
+            it('should return a shared array if requested', function () {
+                const sl = sock.rQpeekBytes(2, false);
+                expect(sl).to.array.equal(new Uint8Array(RQ_TEMPLATE.buffer, 0, 2));
+                expect(sl.buffer.byteLength).to.not.equal(sl.length);
+            });
         });
 
         describe('rQwait', function () {