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Diffstat (limited to 'Doc/c-api/marshal.rst')
| -rw-r--r-- | Doc/c-api/marshal.rst | 66 |
1 files changed, 36 insertions, 30 deletions
diff --git a/Doc/c-api/marshal.rst b/Doc/c-api/marshal.rst index 6d9879c..16c9fc3 100644 --- a/Doc/c-api/marshal.rst +++ b/Doc/c-api/marshal.rst @@ -5,24 +5,25 @@ 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 shares interned strings in the file, and upon unmarshalling. -Version 2 uses a binary format for floating point numbers. +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). .. 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. *version* indicates the file format. + 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. *version* indicates the file format. .. cfunction:: void PyMarshal_WriteObjectToFile(PyObject *value, FILE *file, int version) @@ -40,24 +41,24 @@ Version 2 uses a binary format for 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) @@ -70,17 +71,22 @@ 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*. + + .. versionchanged:: 2.5 + This function used an :ctype:`int` type for *len*. This might require + changes in your code for properly supporting 64-bit systems. |