
Data marshalling support
************************

These routines allow C code to work with serialized objects using the
same data format as the ``marshal`` module.  There are functions to
write data into the serialization format, and additional functions
that can be used to read the data back.  Files used to store
marshalled data must be opened in binary mode.

Numeric values are stored with the least significant byte first.

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.

   Changed in version 2.4: *version* indicates the file format.

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

   Marshal a Python object, *value*, to *file*.

   Changed in version 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*.

   Changed in version 2.4: *version* indicates the file format.

The following functions allow marshalled values to be read back in.

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)

   Return a C ``long`` from the data stream in a ``FILE*`` opened for
   reading.  Only a 32-bit value can be read in using this function,
   regardless of the native size of ``long``.

int PyMarshal_ReadShortFromFile(FILE *file)

   Return a C ``short`` from the data stream in a ``FILE*`` opened for
   reading.  Only a 16-bit value can be read in using this function,
   regardless of the native size of ``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*.

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