feat: first step

tests/decoder.spec.ts

@@ -0,0 +1,135 @@
+import { assert, describe, it } from 'vitest';
+import {
+  EbmlTagPosition,
+  EbmlElementType,
+  EbmlStreamDecoder as Decoder,
+  EbmlDataTag,
+  type EbmlTagTrait,
+} from 'konoebml';
+
+const bufFrom = (data: Uint8Array | readonly number[]): ArrayBuffer =>
+  new Uint8Array(data).buffer;
+
+const getDecoderWithNullSink = () => {
+  const decoder = new Decoder();
+  decoder.readable.pipeTo(new WritableStream({}));
+  return decoder;
+};
+
+async function collectTags(decoder: Decoder): Promise<EbmlTagTrait[]> {
+  const tags: EbmlTagTrait[] = [];
+  await decoder.readable.pipeTo(
+    new WritableStream({
+      write: (tag) => {
+        tags.push(tag);
+      },
+    })
+  );
+  return tags;
+}
+
+describe('EbmlStreamDecoder', () => {
+  it('should wait for more data if a tag is longer than the buffer', async () => {
+    const decoder = getDecoderWithNullSink();
+    const writer = decoder.writable.getWriter();
+    await writer.write(bufFrom([0x1a, 0x45]));
+
+    assert.strictEqual(decoder.transformer.getBuffer().byteLength, 2);
+  });
+
+  it('should clear the buffer after a full tag is written in one chunk', async () => {
+    const decoder = getDecoderWithNullSink();
+    const writer = decoder.writable.getWriter();
+    await writer.write(bufFrom([0x42, 0x86, 0x81, 0x01]));
+
+    assert.strictEqual(decoder.transformer.getBuffer().byteLength, 0);
+  });
+
+  it('should clear the buffer after a full tag is written in multiple chunks', async () => {
+    const decoder = getDecoderWithNullSink();
+    const writer = decoder.writable.getWriter();
+
+    await writer.write(bufFrom([0x42, 0x86]));
+    await writer.write(bufFrom([0x81, 0x01]));
+
+    assert.strictEqual(decoder.transformer.getBuffer().byteLength, 0);
+  });
+
+  it('should increment the cursor on each step', async () => {
+    const decoder = getDecoderWithNullSink();
+    const writer = decoder.writable.getWriter();
+
+    await writer.write(bufFrom([0x42])); // 4
+
+    assert.strictEqual(decoder.transformer.getBuffer().byteLength, 1);
+
+    await writer.write(bufFrom([0x86])); // 5
+
+    assert.strictEqual(decoder.transformer.getBuffer().byteLength, 2);
+
+    await writer.write(bufFrom([0x81])); // 6 & 7
+
+    assert.strictEqual(decoder.transformer.getBuffer().byteLength, 0);
+
+    await writer.write(bufFrom([0x01])); // 6 & 7
+
+    assert.strictEqual(decoder.transformer.getBuffer().byteLength, 0);
+  });
+
+  it('should emit correct tag events for simple data', async () => {
+    const decoder = new Decoder();
+    const writer = decoder.writable.getWriter();
+
+    const tags = collectTags(decoder);
+
+    await writer.write(bufFrom([0x42, 0x86, 0x81, 0x01]));
+    await writer.close();
+
+    const [tag] = await tags;
+
+    assert.strictEqual(tag.position, EbmlTagPosition.Content);
+    assert.strictEqual(tag.id.toString(16), '4286');
+    assert.strictEqual(tag.contentLength, 0x01);
+    assert.strictEqual(tag.type, EbmlElementType.UnsignedInt);
+    assert.ok(tag instanceof EbmlDataTag);
+    assert.deepStrictEqual(tag.data, 1);
+  });
+
+  it('should emit correct EBML tag events for master tags', async () => {
+    const decoder = new Decoder();
+    const writer = decoder.writable.getWriter();
+
+    writer.write(bufFrom([0x1a, 0x45, 0xdf, 0xa3, 0x80]));
+    writer.close();
+
+    const [tag] = await collectTags(decoder);
+
+    assert.strictEqual(tag.position, EbmlTagPosition.Start);
+    assert.strictEqual(tag.id.toString(16), '1a45dfa3');
+    assert.strictEqual(tag.contentLength, 0);
+    assert.strictEqual(tag.type, EbmlElementType.Master);
+    assert.ok(!(tag instanceof EbmlDataTag));
+    assert.ok(!('data' in tag));
+  });
+
+  it('should emit correct EBML:end events for master tags', async () => {
+    const decoder = new Decoder();
+    const writer = decoder.writable.getWriter();
+
+    writer.write(bufFrom([0x1a, 0x45, 0xdf, 0xa3]));
+    writer.write(bufFrom([0x84, 0x42, 0x86, 0x81, 0x00]));
+    writer.close();
+
+    const tags = await collectTags(decoder);
+
+    assert.strictEqual(tags.length, 3);
+
+    const firstEndTag = tags.find((t) => t.position === EbmlTagPosition.End)!;
+
+    assert.strictEqual(firstEndTag.id.toString(16), '1a45dfa3');
+    assert.strictEqual(firstEndTag.contentLength, 4);
+    assert.strictEqual(firstEndTag.type, EbmlElementType.Master);
+    assert.ok(!(firstEndTag instanceof EbmlDataTag));
+    assert.ok(!('data' in firstEndTag));
+  });
+});