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Jeroen Ruigrok van der Werven 2009-04-25 20:40:10 +00:00
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Doc/c-api/marshal.rst
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@ -5,25 +5,26 @@
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.
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 (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).
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).
.. cfunction:: void PyMarshal_WriteLongToFile(long value, FILE *file, int version)
Marshal a :ctype:`long` integer, *value*, to *file*. This will only write the
least-significant 32 bits of *value*; regardless of the size of the native
:ctype:`long` type.
Marshal a :ctype:`long` integer, *value*, to *file*. This will only write
the least-significant 32 bits of *value*; regardless of the size of the
native :ctype:`long` type.
.. versionchanged:: 2.4
*version* indicates the file format.
@ -48,24 +49,24 @@ floating point numbers.
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?
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?
.. cfunction:: long PyMarshal_ReadLongFromFile(FILE *file)
Return a C :ctype:`long` from the data stream in a :ctype:`FILE\*` opened for
reading. Only a 32-bit value can be read in using this function, regardless of
the native size of :ctype:`long`.
Return a C :ctype:`long` from the data stream in a :ctype:`FILE\*` opened
for reading. Only a 32-bit value can be read in using this function,
regardless of the native size of :ctype:`long`.
.. cfunction:: int PyMarshal_ReadShortFromFile(FILE *file)
Return a C :ctype:`short` from the data stream in a :ctype:`FILE\*` opened for
reading. Only a 16-bit value can be read in using this function, regardless of
the native size of :ctype:`short`.
Return a C :ctype:`short` from the data stream in a :ctype:`FILE\*` opened
for reading. Only a 16-bit value can be read in using this function,
regardless of the native size of :ctype:`short`.
.. cfunction:: PyObject* PyMarshal_ReadObjectFromFile(FILE *file)
@ -78,17 +79,18 @@ using these routines?
.. cfunction:: PyObject* PyMarshal_ReadLastObjectFromFile(FILE *file)
Return a Python object from the data stream in a :ctype:`FILE\*` opened for
reading. Unlike :cfunc:`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` or
:exc:`TypeError`) and returns *NULL*.
reading. Unlike :cfunc:`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` or :exc:`TypeError`) and returns *NULL*.
.. cfunction:: PyObject* PyMarshal_ReadObjectFromString(char *string, Py_ssize_t len)
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
(:exc:`EOFError` or :exc:`TypeError`) and returns *NULL*.
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 (:exc:`EOFError` or :exc:`TypeError`) and returns
*NULL*.