convert to typescript

src/decoders/chunk.ts

@@ -0,0 +1,23 @@
+export interface Chunk {
+  id?: number;
+  has_subchunks?: boolean;
+  data_len?: number;
+  chunk_data?: Buffer;
+}
+
+export default (buffer: Buffer, dataDecoder: Function): Chunk => {
+  let offset = 0;
+  const chunk: Chunk = {};
+  chunk.id = buffer.readUInt16LE(offset);
+  offset += 2;
+
+  // NOTE(jwetzell): this data is split up as 1 bit for has_subchunks and 15 bits for the data_len
+  const combinedLengthAndFlag = buffer.readUInt16LE(offset);
+  chunk.has_subchunks = combinedLengthAndFlag > 32768;
+  chunk.data_len = chunk.has_subchunks ? combinedLengthAndFlag - 32768 : combinedLengthAndFlag;
+  offset += 2;
+  chunk.chunk_data = buffer.subarray(offset, offset + chunk.data_len);
+
+  dataDecoder(chunk);
+  return chunk;
+};