test(DirectStream): add new 4kb and 4mb encode tests

After other implementations of this, it was determined that expect(4mb).toEqual(4mb) took around 30 seconds
to run, so we only really check (and care about) the first three bytes.

.vscode/settings.json

@@ -1,3 +1,3 @@
 {
-    "cSpell.words": ["TCPIO"]
+    "cSpell.words": ["bufncmp", "TCPIO"]
 }

src/tests/stream/DirectStream.test.ts

@@ -20,6 +20,16 @@ import { kb, mb } from "../../lib/sizeHelpers";
 import { ControlCharacters } from "../../stream/controlCharacters";
 import DirectStream, { DirectStreamEvents } from "../../stream/DirectStream";
 
+/** Like C's memncmp() for buffers. Used in the large-buffer tests to avoid long test times */
+function bufncmp(n: number, left: Buffer, right: Buffer): number {
+    const len = Math.min(left.length, right.length, n);
+    for (let i = 0; i < len; i++) {
+        if (left[i] < right[i]) return -1;
+        if (left[i] > right[i]) return 1;
+    }
+    return 0;
+}
+
 /** Makes a new {@link DirectStream} and attaches listeners. */
 function makeNewStream(): { stream: DirectStream; onRead: jest.Mock; onPacket: jest.Mock; onReset: jest.Mock } {
     const stream = new DirectStream();
@@ -317,7 +327,22 @@ describe("Stream", () => {
                 0xff
             ])
         );
-        // TODO: more?
+        it("4kb", () => {
+            const stream = new DirectStream();
+
+            const expected = Buffer.concat([Buffer.from([ControlCharacters.ReadKB, 0x00]), Buffer.alloc(kb(4))]);
+
+            // Running .toEqual is extremely slow on huge buffers, so we use a custom bufncmp function
+            expect(bufncmp(3, stream.encode(expected.subarray(2)), expected)).toBe(0);
+        });
+        it("4mb", () => {
+            const stream = new DirectStream();
+
+            const expected = Buffer.concat([Buffer.from([ControlCharacters.ReadMB, 0x00]), Buffer.alloc(mb(4))]);
+
+            // See above
+            expect(bufncmp(3, stream.encode(expected.subarray(2)), expected)).toBe(0);
+        });
     });
 
     it("fails for unsupported read sizes", () => {