Function encodeEventStreamFrame

src/aws-event-stream.ts:56–90

(headers: Record<string, string>, payload: Buffer)

 * payload buffer.
 */
export function encodeEventStreamFrame(headers: Record<string, string>, payload: Buffer): Buffer {
  const headersBuffer = encodeHeaders(headers);
  const headersLength = headersBuffer.length;

  // prelude (8) + prelude_crc (4) + headers + payload + message_crc (4)
  const totalLength = 4 + 4 + 4 + headersLength + payload.length + 4;

  const frame = Buffer.alloc(totalLength);
  let offset = 0;

  // Prelude
  frame.writeUInt32BE(totalLength, offset);
  offset += 4;
  frame.writeUInt32BE(headersLength, offset);
  offset += 4;

  // Prelude CRC32 (covers first 8 bytes)
  const preludeCrc = crc32(frame.subarray(0, 8));
  frame.writeUInt32BE(preludeCrc >>> 0, offset);
  offset += 4;

  // Headers
  headersBuffer.copy(frame, offset);
  offset += headersLength;

  // Payload
  payload.copy(frame, offset);
  offset += payload.length;

  // Message CRC32 (covers entire frame minus last 4 bytes)
  const messageCrc = crc32(frame.subarray(0, totalLength - 4));
  frame.writeUInt32BE(messageCrc >>> 0, offset);

  return frame;
}

// ─── Convenience wrappers ───────────────────────────────────────────────────