MySQLColumnDefinitionPacket.decode constructor

MySQLColumnDefinitionPacket.decode(Uint8List buffer)

Decodifica um Uint8List recebido do servidor MySQL e constrói um objeto MySQLColumnDefinitionPacket.

A sequência de leitura segue a especificação do protocolo MySQL:

1. catalog (length-encoded string)
2. schema (length-encoded string)
3. table (length-encoded string)
4. org_table (length-encoded string)
5. name (length-encoded string)
6. org_name (length-encoded string)
7. lengthOfFixedLengthFields (length-encoded integer; geralmente 0x0c)
8. charset (2 bytes, little-endian)
9. column_length (4 bytes, little-endian)
10. type (1 byte)
11. flags (2 bytes, little-endian)
12. decimals (1 byte)
13. filler (2 bytes, geralmente 0x00 0x00)

Ao final, retorna uma instância de MySQLColumnDefinitionPacket.

Implementation

factory MySQLColumnDefinitionPacket.decode(Uint8List buffer) {
  final byteData = ByteData.sublistView(buffer);
  int offset = 0;

  // 1) Lê catalog (length-encoded string)
  final catalogLE = buffer.getUtf8LengthEncodedString(offset);
  offset += catalogLE.item2;

  // 2) Lê schema (length-encoded string)
  final schemaLE = buffer.getUtf8LengthEncodedString(offset);
  offset += schemaLE.item2;

  // 3) Lê table (length-encoded string)
  final tableLE = buffer.getUtf8LengthEncodedString(offset);
  offset += tableLE.item2;

  // 4) Lê org_table (length-encoded string)
  final orgTableLE = buffer.getUtf8LengthEncodedString(offset);
  offset += orgTableLE.item2;

  // 5) Lê name (length-encoded string)
  final nameLE = buffer.getUtf8LengthEncodedString(offset);
  offset += nameLE.item2;

  // 6) Lê org_name (length-encoded string)
  final orgNameLE = buffer.getUtf8LengthEncodedString(offset);
  offset += orgNameLE.item2;

  // 7) Lê lengthOfFixedLengthFields (geralmente 0x0c)
  final lengthOfFixedLengthFields = byteData.getVariableEncInt(offset);
  offset += lengthOfFixedLengthFields.item2;

  // 8) Lê charset (2 bytes, little-endian)
  final charset = byteData.getUint16(offset, Endian.little);
  offset += 2;

  // 9) Lê column_length (4 bytes, little-endian)
  final columnLength = byteData.getUint32(offset, Endian.little);
  offset += 4;

  // 10) Lê type (1 byte)
  final colType = byteData.getUint8(offset);
  offset += 1;

  // 11) Lê flags (2 bytes, little-endian)
  final flags = byteData.getUint16(offset, Endian.little);
  offset += 2;

  // 12) Lê o número de decimais (1 byte)
  final decimals = byteData.getUint8(offset);
  offset += 1;

  // 13) Pula 2 bytes de filler (geralmente 0x00 0x00)
  offset += 2;

  // Retorna a instância
  return MySQLColumnDefinitionPacket(
    catalog: catalogLE.item1,
    schema: schemaLE.item1,
    table: tableLE.item1,
    orgTable: orgTableLE.item1,
    name: nameLE.item1,
    orgName: orgNameLE.item1,
    charset: charset,
    columnLength: columnLength,
    type: MySQLColumnType.create(colType),
    flags: flags,
    decimals: decimals,
  );
}