Function createFrameReader

src/daemon/framing.ts:18–51

(
  onMessage: (msg: unknown) => void,
  onError?: (err: Error) => void,
)

 * Returns a function to be used as the 'data' event handler.
 */
export function createFrameReader(
  onMessage: (msg: unknown) => void,
  onError?: (err: Error) => void,
): (chunk: Buffer) => void {
  let buffer = Buffer.alloc(0);

  return (chunk: Buffer) => {
    buffer = Buffer.concat([buffer, chunk]);

    while (buffer.length >= 4) {
      const len = buffer.readUInt32BE(0);

      if (len > 100 * 1024 * 1024) {
        onError?.(new Error(`Message too large: ${len} bytes`));
        buffer = Buffer.alloc(0);
        return;
      }

      if (buffer.length < 4 + len) {
        return;
      }

      const payload = buffer.subarray(4, 4 + len);
      buffer = buffer.subarray(4 + len);

      try {
        const msg = JSON.parse(payload.toString('utf8')) as unknown;
        onMessage(msg);
      } catch (err) {
        onError?.(err instanceof Error ? err : new Error(String(err)));
      }
    }
  };
}