mirror of
https://github.com/python/cpython.git
synced 2025-11-03 03:22:27 +00:00
98 lines
3.7 KiB
ReStructuredText
98 lines
3.7 KiB
ReStructuredText
.. highlight:: c
|
|
|
|
.. _marshalling-utils:
|
|
|
|
Data marshalling support
|
|
========================
|
|
|
|
These routines allow C code to work with serialized objects using the same
|
|
data format as the :mod:`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 shares interned strings in the file, and upon
|
|
unmarshalling. Version 2 uses a binary format for floating point numbers.
|
|
``Py_MARSHAL_VERSION`` indicates the current file format (currently 2).
|
|
|
|
|
|
.. c:function:: void PyMarshal_WriteLongToFile(long value, FILE *file, int version)
|
|
|
|
Marshal a :c:expr:`long` integer, *value*, to *file*. This will only write
|
|
the least-significant 32 bits of *value*; regardless of the size of the
|
|
native :c:expr:`long` type. *version* indicates the file format.
|
|
|
|
This function can fail, in which case it sets the error indicator.
|
|
Use :c:func:`PyErr_Occurred` to check for that.
|
|
|
|
.. c:function:: void PyMarshal_WriteObjectToFile(PyObject *value, FILE *file, int version)
|
|
|
|
Marshal a Python object, *value*, to *file*.
|
|
*version* indicates the file format.
|
|
|
|
This function can fail, in which case it sets the error indicator.
|
|
Use :c:func:`PyErr_Occurred` to check for that.
|
|
|
|
.. c:function:: PyObject* PyMarshal_WriteObjectToString(PyObject *value, int version)
|
|
|
|
Return a bytes object containing the marshalled representation of *value*.
|
|
*version* indicates the file format.
|
|
|
|
|
|
The following functions allow marshalled values to be read back in.
|
|
|
|
|
|
.. c:function:: long PyMarshal_ReadLongFromFile(FILE *file)
|
|
|
|
Return a C :c:expr:`long` from the data stream in a :c:expr:`FILE*` opened
|
|
for reading. Only a 32-bit value can be read in using this function,
|
|
regardless of the native size of :c:expr:`long`.
|
|
|
|
On error, sets the appropriate exception (:exc:`EOFError`) and returns
|
|
``-1``.
|
|
|
|
|
|
.. c:function:: int PyMarshal_ReadShortFromFile(FILE *file)
|
|
|
|
Return a C :c:expr:`short` from the data stream in a :c:expr:`FILE*` opened
|
|
for reading. Only a 16-bit value can be read in using this function,
|
|
regardless of the native size of :c:expr:`short`.
|
|
|
|
On error, sets the appropriate exception (:exc:`EOFError`) and returns
|
|
``-1``.
|
|
|
|
|
|
.. c:function:: PyObject* PyMarshal_ReadObjectFromFile(FILE *file)
|
|
|
|
Return a Python object from the data stream in a :c:expr:`FILE*` opened for
|
|
reading.
|
|
|
|
On error, sets the appropriate exception (:exc:`EOFError`, :exc:`ValueError`
|
|
or :exc:`TypeError`) and returns ``NULL``.
|
|
|
|
|
|
.. c:function:: PyObject* PyMarshal_ReadLastObjectFromFile(FILE *file)
|
|
|
|
Return a Python object from the data stream in a :c:expr:`FILE*` opened for
|
|
reading. Unlike :c:func:`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 (:exc:`EOFError`, :exc:`ValueError`
|
|
or :exc:`TypeError`) and returns ``NULL``.
|
|
|
|
|
|
.. c:function:: PyObject* PyMarshal_ReadObjectFromString(const char *data, Py_ssize_t len)
|
|
|
|
Return a Python object from the data stream in a byte buffer
|
|
containing *len* bytes pointed to by *data*.
|
|
|
|
On error, sets the appropriate exception (:exc:`EOFError`, :exc:`ValueError`
|
|
or :exc:`TypeError`) and returns ``NULL``.
|
|
|