peekFirstResultSetPayload static method

Uint8List? peekFirstResultSetPayload(Uint8List data)

Returns a zero-copy view of the first result-set payload without decoding cell data. Skips leading row-count items. Returns null when no result-set item is present.

Used by typed-columnar decode to avoid rematerializing a columnar v2 first result set through QueryResult.

Implementation

static Uint8List? peekFirstResultSetPayload(Uint8List data) {
  late final int offset;
  late final int itemCount;
  final byteData = ByteData.sublistView(data);

  if (data.length >= 4 &&
      byteData.getUint32(0, _littleEndian) == multiResultMagic) {
    if (data.length < _headerV2Len) {
      throw const FormatException(
        'Buffer too small for multi-result v2 header',
      );
    }
    final version = byteData.getUint16(4, _littleEndian);
    if (version != multiResultVersionV2) {
      throw FormatException(
        'Unsupported multi-result version: $version '
        '(expected $multiResultVersionV2)',
      );
    }
    itemCount = byteData.getUint32(8, _littleEndian);
    offset = _headerV2Len;
  } else {
    if (data.length < headerSize) {
      throw const FormatException(
        'Buffer too small for multi-result header',
      );
    }
    itemCount = byteData.getUint32(0, _littleEndian);
    offset = headerSize;
  }

  var cursor = offset;
  for (var i = 0; i < itemCount; i++) {
    if (cursor + itemHeaderSize > data.length) {
      throw const FormatException(
        'Multi-result buffer truncated at item header',
      );
    }
    final tag = data[cursor];
    cursor += 1;
    final length = byteData.getUint32(cursor, _littleEndian);
    cursor += 4;
    if (cursor + length > data.length) {
      throw const FormatException(
        'Multi-result buffer truncated at item payload',
      );
    }
    if (tag == tagResultSet || tag == tagResultSetBatch) {
      return Uint8List.sublistView(data, cursor, cursor + length);
    }
    cursor += length;
  }
  return null;
}