feat: first step

src/models/tag-block.ts

@@ -0,0 +1,123 @@
+import { type CreateEbmlDataTagOptions, EbmlDataTag } from './tag-data';
+import { EbmlBlockLacing } from './enums';
+import {
+  dataViewSlice,
+  dataViewSliceToBuf,
+  readSigned,
+  readVint,
+  writeSigned,
+  writeVint,
+} from '../tools';
+import {
+  type EbmlBlockTagIdType,
+  type EbmlSimpleBlockTagIdType,
+  EbmlTagIdEnum,
+} from './enums';
+import { EbmlElementType } from './enums';
+import type { FileDataViewController } from '../adapters';
+
+export interface CreateEbmlBlockTagOptions
+  extends Omit<CreateEbmlDataTagOptions, 'id' | 'type'> {
+  id?: EbmlBlockTagIdType | EbmlSimpleBlockTagIdType;
+}
+
+export class EbmlBlockTag extends EbmlDataTag {
+  payload = new Uint8Array(0);
+  track: number | bigint = 0;
+  value = 0;
+
+  invisible: boolean | undefined;
+  lacing: EbmlBlockLacing | undefined;
+
+  constructor(options: CreateEbmlBlockTagOptions) {
+    super({
+      ...options,
+      id: options.id ?? EbmlTagIdEnum.Block,
+      type: EbmlElementType.Binary,
+    });
+  }
+
+  protected writeTrackBuffer(): Uint8Array {
+    return writeVint(this.track);
+  }
+
+  protected writeValueBuffer(): Uint8Array {
+    return writeSigned(this.value, 2);
+  }
+
+  protected writeFlagsBuffer(): Uint8Array {
+    let flags = 0x00;
+    if (this.invisible) {
+      flags |= 0x10;
+    }
+
+    switch (this.lacing) {
+      case EbmlBlockLacing.None:
+        break;
+      case EbmlBlockLacing.Xiph:
+        flags |= 0x04;
+        break;
+      case EbmlBlockLacing.EBML:
+        flags |= 0x08;
+        break;
+      case EbmlBlockLacing.FixedSize:
+        flags |= 0x0c;
+        break;
+      default:
+    }
+
+    return new Uint8Array([flags % 256]);
+  }
+
+  *encodeContent(): Generator<Uint8Array, void, unknown> {
+    yield this.writeTrackBuffer();
+    yield this.writeValueBuffer();
+    yield this.writeFlagsBuffer();
+    yield this.payload;
+  }
+
+  // biome-ignore lint/correctness/useYield: <explanation>
+  async *decodeContentImpl(controller: FileDataViewController) {
+    const offset = controller.getOffset();
+    const view = await controller.read(offset, this.contentLength, true);
+    const track = readVint(view)!;
+    this.track = track.value;
+    this.value = Number(
+      readSigned(dataViewSlice(view, track.length, track.length + 2))
+    );
+    const flags: number = view.getUint8(track.length + 2);
+    this.invisible = Boolean(flags & 0x10);
+    switch (flags & 0x0c) {
+      case 0x00:
+        this.lacing = EbmlBlockLacing.None;
+        break;
+
+      case 0x04:
+        this.lacing = EbmlBlockLacing.Xiph;
+        break;
+
+      case 0x08:
+        this.lacing = EbmlBlockLacing.EBML;
+        break;
+
+      case 0x0c:
+        this.lacing = EbmlBlockLacing.FixedSize;
+        break;
+      default:
+    }
+    this.payload = dataViewSliceToBuf(view, track.length + 3, undefined);
+    await controller.seek(offset + view.byteLength);
+  }
+
+  override toDebugRecord() {
+    const s = super.toDebugRecord();
+    return {
+      ...s,
+      payload: this.payload,
+      track: this.track,
+      value: this.value,
+      invisible: this.invisible,
+      lacing: EbmlBlockLacing[this.lacing!] || this.lacing,
+    };
+  }
+}