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# Suporte a marshalling de dados

Essas rotinas permitem que o código C trabalhe com objetos serializados usando o mesmo formato de dados que o módulo `marshal`. Existem funções para gravar dados no formato de serialização e funções adicionais que podem ser usadas para ler os dados novamente. Os arquivos usados para armazenar dados empacotados devem ser abertos no modo binário.

Os valores numéricos são armazenados primeiro com o byte menos significativo.

The module supports two versions of the data format: version `0` is the historical version, version `1` (new in Python 2.4) shares interned strings in the file, and upon unmarshalling. Version 2 (new in Python 2.5) uses a binary format for floating point numbers. Py_MARSHAL_VERSION indicates the current file format (currently 2).

void `PyMarshal_WriteLongToFile`(long value, FILE *file, int version)

  Marshal a `long` integer, value, to file. This will only write the least-significant 32 bits of value; regardless of the size of the native `long` type.

  Alterado na versão 2.4: version indicates the file format.

void `PyMarshal_WriteObjectToFile`(PyObject *value, FILE *file, int version)

  Marshal a Python object, value, to file.

  Alterado na versão 2.4: version indicates the file format.

PyObject* `PyMarshal_WriteObjectToString`(PyObject *value, int version)
  Return value: New reference.

  Return a string object containing the marshalled representation of value.

  Alterado na versão 2.4: version indicates the file format.

As seguintes funções permitem que os valores pós-marshalling sejam lidos novamente.

XXX What about error detection? It appears that reading past the end of the file will always result in a negative numeric value (where that’s relevant), but it’s not clear that negative values won’t be handled properly when there’s no error. What’s the right way to tell? Should only non-negative values be written using these routines?

long `PyMarshal_ReadLongFromFile`(FILE *file)

  Retorna um `long` C do fluxo de dados em um `FILE*` aberto para leitura. Somente um valor de 32 bits pode ser lido usando essa função, independentemente do tamanho nativo de `long`.

int `PyMarshal_ReadShortFromFile`(FILE *file)

  Retorna um `short` C do fluxo de dados em um `FILE*` aberto para leitura. Somente um valor de 16 bits pode ser lido usando essa função, independentemente do tamanho nativo de `short`.

PyObject* `PyMarshal_ReadObjectFromFile`(FILE *file)
  Return value: New reference.

  Return a Python object from the data stream in a `FILE*` opened for reading. On error, sets the appropriate exception (`EOFError` or `TypeError`) and returns NULL.

PyObject* `PyMarshal_ReadLastObjectFromFile`(FILE *file)
  Return value: New reference.

  Return a Python object from the data stream in a `FILE*` opened for reading. Unlike `PyMarshal_ReadObjectFromFile()`, this function assumes that no further objects will be read from the file, allowing it to aggressively load file data into memory so that the de-serialization can operate from data in memory rather than reading a byte at a time from the file. Only use these variant if you are certain that you won’t be reading anything else from the file. On error, sets the appropriate exception (`EOFError` or `TypeError`) and returns NULL.

PyObject* `PyMarshal_ReadObjectFromString`(char *string, Py_ssize_t len)
  Return value: New reference.

  Return a Python object from the data stream in a character buffer containing len bytes pointed to by string. On error, sets the appropriate exception (`EOFError` or `TypeError`) and returns NULL.

  Alterado na versão 2.5: This function used an `int` type for len. This might require changes in your code for properly supporting 64-bit systems.