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2785 lines (2341 loc) · 92.3 KB
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# SOME DESCRIPTIVE TITLE.
# Copyright (C) 2001-2022, Python Software Foundation
# This file is distributed under the same license as the Python package.
#
# Translators:
msgid ""
msgstr ""
"Project-Id-Version: Python 3.12\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2023-08-20 15:45+0000\n"
"PO-Revision-Date: 2023-04-26 02:59+0800\n"
"Last-Translator: Adrian Liaw <adrianliaw2000@gmail.com>\n"
"Language-Team: Chinese - TAIWAN (https://github.com/python/python-docs-zh-"
"tw)\n"
"Language: zh_TW\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Plural-Forms: nplurals=1; plural=0;\n"
"X-Generator: Poedit 3.2.2\n"
#: ../../library/ctypes.rst:2
msgid ":mod:`ctypes` --- A foreign function library for Python"
msgstr ""
#: ../../library/ctypes.rst:9
msgid "**Source code:** :source:`Lib/ctypes`"
msgstr "**原始碼：**\\ :source:`Lib/ctypes`"
#: ../../library/ctypes.rst:13
msgid ""
":mod:`ctypes` is a foreign function library for Python. It provides C "
"compatible data types, and allows calling functions in DLLs or shared "
"libraries. It can be used to wrap these libraries in pure Python."
msgstr ""
#: ../../library/ctypes.rst:21
msgid "ctypes tutorial"
msgstr ""
#: ../../library/ctypes.rst:23
msgid ""
"Note: The code samples in this tutorial use :mod:`doctest` to make sure that "
"they actually work. Since some code samples behave differently under Linux, "
"Windows, or macOS, they contain doctest directives in comments."
msgstr ""
#: ../../library/ctypes.rst:27
msgid ""
"Note: Some code samples reference the ctypes :class:`c_int` type. On "
"platforms where ``sizeof(long) == sizeof(int)`` it is an alias to :class:"
"`c_long`. So, you should not be confused if :class:`c_long` is printed if "
"you would expect :class:`c_int` --- they are actually the same type."
msgstr ""
#: ../../library/ctypes.rst:35
msgid "Loading dynamic link libraries"
msgstr ""
#: ../../library/ctypes.rst:37
msgid ""
":mod:`ctypes` exports the *cdll*, and on Windows *windll* and *oledll* "
"objects, for loading dynamic link libraries."
msgstr ""
#: ../../library/ctypes.rst:40
msgid ""
"You load libraries by accessing them as attributes of these objects. *cdll* "
"loads libraries which export functions using the standard ``cdecl`` calling "
"convention, while *windll* libraries call functions using the ``stdcall`` "
"calling convention. *oledll* also uses the ``stdcall`` calling convention, "
"and assumes the functions return a Windows :c:type:`!HRESULT` error code. "
"The error code is used to automatically raise an :class:`OSError` exception "
"when the function call fails."
msgstr ""
#: ../../library/ctypes.rst:48
msgid ""
"Windows errors used to raise :exc:`WindowsError`, which is now an alias of :"
"exc:`OSError`."
msgstr ""
#: ../../library/ctypes.rst:53
msgid ""
"Here are some examples for Windows. Note that ``msvcrt`` is the MS standard "
"C library containing most standard C functions, and uses the cdecl calling "
"convention::"
msgstr ""
#: ../../library/ctypes.rst:65
msgid "Windows appends the usual ``.dll`` file suffix automatically."
msgstr ""
#: ../../library/ctypes.rst:68
msgid ""
"Accessing the standard C library through ``cdll.msvcrt`` will use an "
"outdated version of the library that may be incompatible with the one being "
"used by Python. Where possible, use native Python functionality, or else "
"import and use the ``msvcrt`` module."
msgstr ""
#: ../../library/ctypes.rst:73
msgid ""
"On Linux, it is required to specify the filename *including* the extension "
"to load a library, so attribute access can not be used to load libraries. "
"Either the :meth:`~LibraryLoader.LoadLibrary` method of the dll loaders "
"should be used, or you should load the library by creating an instance of "
"CDLL by calling the constructor::"
msgstr ""
#: ../../library/ctypes.rst:92
msgid "Accessing functions from loaded dlls"
msgstr ""
#: ../../library/ctypes.rst:94
msgid "Functions are accessed as attributes of dll objects::"
msgstr ""
#: ../../library/ctypes.rst:109
msgid ""
"Note that win32 system dlls like ``kernel32`` and ``user32`` often export "
"ANSI as well as UNICODE versions of a function. The UNICODE version is "
"exported with an ``W`` appended to the name, while the ANSI version is "
"exported with an ``A`` appended to the name. The win32 ``GetModuleHandle`` "
"function, which returns a *module handle* for a given module name, has the "
"following C prototype, and a macro is used to expose one of them as "
"``GetModuleHandle`` depending on whether UNICODE is defined or not::"
msgstr ""
#: ../../library/ctypes.rst:122
msgid ""
"*windll* does not try to select one of them by magic, you must access the "
"version you need by specifying ``GetModuleHandleA`` or ``GetModuleHandleW`` "
"explicitly, and then call it with bytes or string objects respectively."
msgstr ""
#: ../../library/ctypes.rst:126
msgid ""
"Sometimes, dlls export functions with names which aren't valid Python "
"identifiers, like ``\"??2@YAPAXI@Z\"``. In this case you have to use :func:"
"`getattr` to retrieve the function::"
msgstr ""
#: ../../library/ctypes.rst:134
msgid ""
"On Windows, some dlls export functions not by name but by ordinal. These "
"functions can be accessed by indexing the dll object with the ordinal "
"number::"
msgstr ""
#: ../../library/ctypes.rst:151
msgid "Calling functions"
msgstr ""
#: ../../library/ctypes.rst:153
msgid ""
"You can call these functions like any other Python callable. This example "
"uses the ``rand()`` function, which takes no arguments and returns a pseudo-"
"random integer::"
msgstr ""
#: ../../library/ctypes.rst:159
msgid ""
"On Windows, you can call the ``GetModuleHandleA()`` function, which returns "
"a win32 module handle (passing ``None`` as single argument to call it with a "
"``NULL`` pointer)::"
msgstr ""
#: ../../library/ctypes.rst:166
msgid ""
":exc:`ValueError` is raised when you call an ``stdcall`` function with the "
"``cdecl`` calling convention, or vice versa::"
msgstr ""
#: ../../library/ctypes.rst:181
msgid ""
"To find out the correct calling convention you have to look into the C "
"header file or the documentation for the function you want to call."
msgstr ""
#: ../../library/ctypes.rst:184
msgid ""
"On Windows, :mod:`ctypes` uses win32 structured exception handling to "
"prevent crashes from general protection faults when functions are called "
"with invalid argument values::"
msgstr ""
#: ../../library/ctypes.rst:194
msgid ""
"There are, however, enough ways to crash Python with :mod:`ctypes`, so you "
"should be careful anyway. The :mod:`faulthandler` module can be helpful in "
"debugging crashes (e.g. from segmentation faults produced by erroneous C "
"library calls)."
msgstr ""
#: ../../library/ctypes.rst:199
msgid ""
"``None``, integers, bytes objects and (unicode) strings are the only native "
"Python objects that can directly be used as parameters in these function "
"calls. ``None`` is passed as a C ``NULL`` pointer, bytes objects and strings "
"are passed as pointer to the memory block that contains their data (:c:expr:"
"`char *` or :c:expr:`wchar_t *`). Python integers are passed as the "
"platforms default C :c:expr:`int` type, their value is masked to fit into "
"the C type."
msgstr ""
#: ../../library/ctypes.rst:206
msgid ""
"Before we move on calling functions with other parameter types, we have to "
"learn more about :mod:`ctypes` data types."
msgstr ""
#: ../../library/ctypes.rst:213 ../../library/ctypes.rst:2201
msgid "Fundamental data types"
msgstr ""
#: ../../library/ctypes.rst:215
msgid ":mod:`ctypes` defines a number of primitive C compatible data types:"
msgstr ""
#: ../../library/ctypes.rst:218
msgid "ctypes type"
msgstr ""
#: ../../library/ctypes.rst:218
msgid "C type"
msgstr ""
#: ../../library/ctypes.rst:218
msgid "Python type"
msgstr ""
#: ../../library/ctypes.rst:220
msgid ":class:`c_bool`"
msgstr ":class:`c_bool`"
#: ../../library/ctypes.rst:220
msgid ":c:expr:`_Bool`"
msgstr ":c:expr:`_Bool`"
#: ../../library/ctypes.rst:220
msgid "bool (1)"
msgstr "bool (1)"
#: ../../library/ctypes.rst:222
msgid ":class:`c_char`"
msgstr ":class:`c_char`"
#: ../../library/ctypes.rst:222 ../../library/ctypes.rst:226
msgid ":c:expr:`char`"
msgstr ":c:expr:`char`"
#: ../../library/ctypes.rst:222
msgid "1-character bytes object"
msgstr ""
#: ../../library/ctypes.rst:224
msgid ":class:`c_wchar`"
msgstr ":class:`c_wchar`"
#: ../../library/ctypes.rst:224
msgid ":c:type:`wchar_t`"
msgstr ":c:type:`wchar_t`"
#: ../../library/ctypes.rst:224
msgid "1-character string"
msgstr ""
#: ../../library/ctypes.rst:226
msgid ":class:`c_byte`"
msgstr ":class:`c_byte`"
#: ../../library/ctypes.rst:226 ../../library/ctypes.rst:228
#: ../../library/ctypes.rst:230 ../../library/ctypes.rst:232
#: ../../library/ctypes.rst:234 ../../library/ctypes.rst:236
#: ../../library/ctypes.rst:238 ../../library/ctypes.rst:240
#: ../../library/ctypes.rst:242 ../../library/ctypes.rst:244
#: ../../library/ctypes.rst:247 ../../library/ctypes.rst:249
#: ../../library/ctypes.rst:252
msgid "int"
msgstr "int"
#: ../../library/ctypes.rst:228
msgid ":class:`c_ubyte`"
msgstr ":class:`c_ubyte`"
#: ../../library/ctypes.rst:228
msgid ":c:expr:`unsigned char`"
msgstr ":c:expr:`unsigned char`"
#: ../../library/ctypes.rst:230
msgid ":class:`c_short`"
msgstr ":class:`c_short`"
#: ../../library/ctypes.rst:230
msgid ":c:expr:`short`"
msgstr ":c:expr:`short`"
#: ../../library/ctypes.rst:232
msgid ":class:`c_ushort`"
msgstr ":class:`c_ushort`"
#: ../../library/ctypes.rst:232
msgid ":c:expr:`unsigned short`"
msgstr ":c:expr:`unsigned short`"
#: ../../library/ctypes.rst:234
msgid ":class:`c_int`"
msgstr ":class:`c_int`"
#: ../../library/ctypes.rst:234
msgid ":c:expr:`int`"
msgstr ":c:expr:`int`"
#: ../../library/ctypes.rst:236
msgid ":class:`c_uint`"
msgstr ":class:`c_uint`"
#: ../../library/ctypes.rst:236
msgid ":c:expr:`unsigned int`"
msgstr ":c:expr:`unsigned int`"
#: ../../library/ctypes.rst:238
msgid ":class:`c_long`"
msgstr ":class:`c_long`"
#: ../../library/ctypes.rst:238
msgid ":c:expr:`long`"
msgstr ":c:expr:`long`"
#: ../../library/ctypes.rst:240
msgid ":class:`c_ulong`"
msgstr ":class:`c_ulong`"
#: ../../library/ctypes.rst:240
msgid ":c:expr:`unsigned long`"
msgstr ":c:expr:`unsigned long`"
#: ../../library/ctypes.rst:242
msgid ":class:`c_longlong`"
msgstr ":class:`c_longlong`"
#: ../../library/ctypes.rst:242
msgid ":c:expr:`__int64` or :c:expr:`long long`"
msgstr ":c:expr:`__int64` 或 :c:expr:`long long`"
#: ../../library/ctypes.rst:244
msgid ":class:`c_ulonglong`"
msgstr ":class:`c_ulonglong`"
#: ../../library/ctypes.rst:244
msgid ":c:expr:`unsigned __int64` or :c:expr:`unsigned long long`"
msgstr ":c:expr:`unsigned __int64` 或 :c:expr:`unsigned long long`"
#: ../../library/ctypes.rst:247
msgid ":class:`c_size_t`"
msgstr ":class:`c_size_t`"
#: ../../library/ctypes.rst:247
msgid ":c:type:`size_t`"
msgstr ":c:type:`size_t`"
#: ../../library/ctypes.rst:249
msgid ":class:`c_ssize_t`"
msgstr ":class:`c_ssize_t`"
#: ../../library/ctypes.rst:249
msgid ":c:type:`ssize_t` or :c:expr:`Py_ssize_t`"
msgstr ":c:type:`ssize_t` 或 :c:expr:`Py_ssize_t`"
#: ../../library/ctypes.rst:252
msgid ":class:`c_time_t`"
msgstr ":class:`c_time_t`"
#: ../../library/ctypes.rst:252
msgid ":c:type:`time_t`"
msgstr ":c:type:`time_t`"
#: ../../library/ctypes.rst:254
msgid ":class:`c_float`"
msgstr ":class:`c_float`"
#: ../../library/ctypes.rst:254
msgid ":c:expr:`float`"
msgstr ":c:expr:`float`"
#: ../../library/ctypes.rst:254 ../../library/ctypes.rst:256
#: ../../library/ctypes.rst:258
msgid "float"
msgstr "float"
#: ../../library/ctypes.rst:256
msgid ":class:`c_double`"
msgstr ":class:`c_double`"
#: ../../library/ctypes.rst:256
msgid ":c:expr:`double`"
msgstr ":c:expr:`double`"
#: ../../library/ctypes.rst:258
msgid ":class:`c_longdouble`"
msgstr ":class:`c_longdouble`"
#: ../../library/ctypes.rst:258
msgid ":c:expr:`long double`"
msgstr ":c:expr:`long double`"
#: ../../library/ctypes.rst:260
msgid ":class:`c_char_p`"
msgstr ":class:`c_char_p`"
#: ../../library/ctypes.rst:260
msgid ":c:expr:`char *` (NUL terminated)"
msgstr ""
#: ../../library/ctypes.rst:260
msgid "bytes object or ``None``"
msgstr ""
#: ../../library/ctypes.rst:262
msgid ":class:`c_wchar_p`"
msgstr ":class:`c_wchar_p`"
#: ../../library/ctypes.rst:262
msgid ":c:expr:`wchar_t *` (NUL terminated)"
msgstr ""
#: ../../library/ctypes.rst:262
msgid "string or ``None``"
msgstr "字串或 ``None``"
#: ../../library/ctypes.rst:264
msgid ":class:`c_void_p`"
msgstr ":class:`c_void_p`"
#: ../../library/ctypes.rst:264
msgid ":c:expr:`void *`"
msgstr ":c:expr:`void *`"
#: ../../library/ctypes.rst:264
msgid "int or ``None``"
msgstr ""
#: ../../library/ctypes.rst:268
msgid "The constructor accepts any object with a truth value."
msgstr ""
#: ../../library/ctypes.rst:270
msgid ""
"All these types can be created by calling them with an optional initializer "
"of the correct type and value::"
msgstr ""
#: ../../library/ctypes.rst:281
msgid ""
"Since these types are mutable, their value can also be changed afterwards::"
msgstr ""
#: ../../library/ctypes.rst:293
msgid ""
"Assigning a new value to instances of the pointer types :class:`c_char_p`, :"
"class:`c_wchar_p`, and :class:`c_void_p` changes the *memory location* they "
"point to, *not the contents* of the memory block (of course not, because "
"Python bytes objects are immutable)::"
msgstr ""
#: ../../library/ctypes.rst:313
msgid ""
"You should be careful, however, not to pass them to functions expecting "
"pointers to mutable memory. If you need mutable memory blocks, ctypes has a :"
"func:`create_string_buffer` function which creates these in various ways. "
"The current memory block contents can be accessed (or changed) with the "
"``raw`` property; if you want to access it as NUL terminated string, use the "
"``value`` property::"
msgstr ""
#: ../../library/ctypes.rst:337
msgid ""
"The :func:`create_string_buffer` function replaces the old :func:`!c_buffer` "
"function (which is still available as an alias). To create a mutable memory "
"block containing unicode characters of the C type :c:type:`wchar_t`, use "
"the :func:`create_unicode_buffer` function."
msgstr ""
#: ../../library/ctypes.rst:346
msgid "Calling functions, continued"
msgstr ""
#: ../../library/ctypes.rst:348
msgid ""
"Note that printf prints to the real standard output channel, *not* to :data:"
"`sys.stdout`, so these examples will only work at the console prompt, not "
"from within *IDLE* or *PythonWin*::"
msgstr ""
#: ../../library/ctypes.rst:368
msgid ""
"As has been mentioned before, all Python types except integers, strings, and "
"bytes objects have to be wrapped in their corresponding :mod:`ctypes` type, "
"so that they can be converted to the required C data type::"
msgstr ""
#: ../../library/ctypes.rst:380
msgid "Calling variadic functions"
msgstr ""
#: ../../library/ctypes.rst:382
msgid ""
"On a lot of platforms calling variadic functions through ctypes is exactly "
"the same as calling functions with a fixed number of parameters. On some "
"platforms, and in particular ARM64 for Apple Platforms, the calling "
"convention for variadic functions is different than that for regular "
"functions."
msgstr ""
#: ../../library/ctypes.rst:387
msgid ""
"On those platforms it is required to specify the :attr:`~_FuncPtr.argtypes` "
"attribute for the regular, non-variadic, function arguments:"
msgstr ""
#: ../../library/ctypes.rst:394
msgid ""
"Because specifying the attribute does not inhibit portability it is advised "
"to always specify :attr:`~_FuncPtr.argtypes` for all variadic functions."
msgstr ""
#: ../../library/ctypes.rst:401
msgid "Calling functions with your own custom data types"
msgstr ""
#: ../../library/ctypes.rst:403
msgid ""
"You can also customize :mod:`ctypes` argument conversion to allow instances "
"of your own classes be used as function arguments. :mod:`ctypes` looks for "
"an :attr:`!_as_parameter_` attribute and uses this as the function argument. "
"The attribute must be an integer, string, bytes, a :mod:`ctypes` instance, "
"or an object with an :attr:`!_as_parameter_` attribute::"
msgstr ""
#: ../../library/ctypes.rst:419
msgid ""
"If you don't want to store the instance's data in the :attr:`!"
"_as_parameter_` instance variable, you could define a :class:`property` "
"which makes the attribute available on request."
msgstr ""
#: ../../library/ctypes.rst:427
msgid "Specifying the required argument types (function prototypes)"
msgstr ""
#: ../../library/ctypes.rst:429
msgid ""
"It is possible to specify the required argument types of functions exported "
"from DLLs by setting the :attr:`~_FuncPtr.argtypes` attribute."
msgstr ""
#: ../../library/ctypes.rst:432
msgid ""
":attr:`~_FuncPtr.argtypes` must be a sequence of C data types (the :func:`!"
"printf` function is probably not a good example here, because it takes a "
"variable number and different types of parameters depending on the format "
"string, on the other hand this is quite handy to experiment with this "
"feature)::"
msgstr ""
#: ../../library/ctypes.rst:443
msgid ""
"Specifying a format protects against incompatible argument types (just as a "
"prototype for a C function), and tries to convert the arguments to valid "
"types::"
msgstr ""
#: ../../library/ctypes.rst:455
msgid ""
"If you have defined your own classes which you pass to function calls, you "
"have to implement a :meth:`~_CData.from_param` class method for them to be "
"able to use them in the :attr:`~_FuncPtr.argtypes` sequence. The :meth:"
"`~_CData.from_param` class method receives the Python object passed to the "
"function call, it should do a typecheck or whatever is needed to make sure "
"this object is acceptable, and then return the object itself, its :attr:`!"
"_as_parameter_` attribute, or whatever you want to pass as the C function "
"argument in this case. Again, the result should be an integer, string, "
"bytes, a :mod:`ctypes` instance, or an object with an :attr:`!"
"_as_parameter_` attribute."
msgstr ""
#: ../../library/ctypes.rst:469
msgid "Return types"
msgstr ""
#: ../../library/ctypes.rst:479
msgid ""
"By default functions are assumed to return the C :c:expr:`int` type. Other "
"return types can be specified by setting the :attr:`~_FuncPtr.restype` "
"attribute of the function object."
msgstr ""
#: ../../library/ctypes.rst:483
msgid ""
"The C prototype of :c:func:`time` is ``time_t time(time_t *)``. Because :c:"
"type:`time_t` might be of a different type than the default return type :c:"
"expr:`int`, you should specify the :attr:`!restype` attribute::"
msgstr ""
#: ../../library/ctypes.rst:489
msgid "The argument types can be specified using :attr:`~_FuncPtr.argtypes`::"
msgstr ""
#: ../../library/ctypes.rst:493
msgid ""
"To call the function with a ``NULL`` pointer as first argument, use "
"``None``::"
msgstr ""
#: ../../library/ctypes.rst:498
msgid ""
"Here is a more advanced example, it uses the :func:`!strchr` function, which "
"expects a string pointer and a char, and returns a pointer to a string::"
msgstr ""
#: ../../library/ctypes.rst:511
msgid ""
"If you want to avoid the :func:`ord(\"x\") <ord>` calls above, you can set "
"the :attr:`~_FuncPtr.argtypes` attribute, and the second argument will be "
"converted from a single character Python bytes object into a C char:"
msgstr ""
#: ../../library/ctypes.rst:530
msgid ""
"You can also use a callable Python object (a function or a class for "
"example) as the :attr:`~_FuncPtr.restype` attribute, if the foreign function "
"returns an integer. The callable will be called with the *integer* the C "
"function returns, and the result of this call will be used as the result of "
"your function call. This is useful to check for error return values and "
"automatically raise an exception::"
msgstr ""
#: ../../library/ctypes.rst:553
msgid ""
"``WinError`` is a function which will call Windows ``FormatMessage()`` api "
"to get the string representation of an error code, and *returns* an "
"exception. ``WinError`` takes an optional error code parameter, if no one is "
"used, it calls :func:`GetLastError` to retrieve it."
msgstr ""
#: ../../library/ctypes.rst:558
msgid ""
"Please note that a much more powerful error checking mechanism is available "
"through the :attr:`~_FuncPtr.errcheck` attribute; see the reference manual "
"for details."
msgstr ""
#: ../../library/ctypes.rst:566
msgid "Passing pointers (or: passing parameters by reference)"
msgstr ""
#: ../../library/ctypes.rst:568
msgid ""
"Sometimes a C api function expects a *pointer* to a data type as parameter, "
"probably to write into the corresponding location, or if the data is too "
"large to be passed by value. This is also known as *passing parameters by "
"reference*."
msgstr ""
#: ../../library/ctypes.rst:572
msgid ""
":mod:`ctypes` exports the :func:`byref` function which is used to pass "
"parameters by reference. The same effect can be achieved with the :func:"
"`pointer` function, although :func:`pointer` does a lot more work since it "
"constructs a real pointer object, so it is faster to use :func:`byref` if "
"you don't need the pointer object in Python itself::"
msgstr ""
#: ../../library/ctypes.rst:594
msgid "Structures and unions"
msgstr ""
#: ../../library/ctypes.rst:596
msgid ""
"Structures and unions must derive from the :class:`Structure` and :class:"
"`Union` base classes which are defined in the :mod:`ctypes` module. Each "
"subclass must define a :attr:`~Structure._fields_` attribute. :attr:`!"
"_fields_` must be a list of *2-tuples*, containing a *field name* and a "
"*field type*."
msgstr ""
#: ../../library/ctypes.rst:601
msgid ""
"The field type must be a :mod:`ctypes` type like :class:`c_int`, or any "
"other derived :mod:`ctypes` type: structure, union, array, pointer."
msgstr ""
#: ../../library/ctypes.rst:604
msgid ""
"Here is a simple example of a POINT structure, which contains two integers "
"named *x* and *y*, and also shows how to initialize a structure in the "
"constructor::"
msgstr ""
#: ../../library/ctypes.rst:624
msgid ""
"You can, however, build much more complicated structures. A structure can "
"itself contain other structures by using a structure as a field type."
msgstr ""
#: ../../library/ctypes.rst:627
msgid ""
"Here is a RECT structure which contains two POINTs named *upperleft* and "
"*lowerright*::"
msgstr ""
#: ../../library/ctypes.rst:641
msgid ""
"Nested structures can also be initialized in the constructor in several "
"ways::"
msgstr ""
#: ../../library/ctypes.rst:646
msgid ""
"Field :term:`descriptor`\\s can be retrieved from the *class*, they are "
"useful for debugging because they can provide useful information::"
msgstr ""
#: ../../library/ctypes.rst:660
msgid ""
":mod:`ctypes` does not support passing unions or structures with bit-fields "
"to functions by value. While this may work on 32-bit x86, it's not "
"guaranteed by the library to work in the general case. Unions and "
"structures with bit-fields should always be passed to functions by pointer."
msgstr ""
#: ../../library/ctypes.rst:666
msgid "Structure/union alignment and byte order"
msgstr ""
#: ../../library/ctypes.rst:668
msgid ""
"By default, Structure and Union fields are aligned in the same way the C "
"compiler does it. It is possible to override this behavior by specifying a :"
"attr:`~Structure._pack_` class attribute in the subclass definition. This "
"must be set to a positive integer and specifies the maximum alignment for "
"the fields. This is what ``#pragma pack(n)`` also does in MSVC."
msgstr ""
#: ../../library/ctypes.rst:674
msgid ""
":mod:`ctypes` uses the native byte order for Structures and Unions. To "
"build structures with non-native byte order, you can use one of the :class:"
"`BigEndianStructure`, :class:`LittleEndianStructure`, :class:"
"`BigEndianUnion`, and :class:`LittleEndianUnion` base classes. These "
"classes cannot contain pointer fields."
msgstr ""
#: ../../library/ctypes.rst:684
msgid "Bit fields in structures and unions"
msgstr ""
#: ../../library/ctypes.rst:686
msgid ""
"It is possible to create structures and unions containing bit fields. Bit "
"fields are only possible for integer fields, the bit width is specified as "
"the third item in the :attr:`~Structure._fields_` tuples::"
msgstr ""
#: ../../library/ctypes.rst:704
msgid "Arrays"
msgstr ""
#: ../../library/ctypes.rst:706
msgid ""
"Arrays are sequences, containing a fixed number of instances of the same "
"type."
msgstr ""
#: ../../library/ctypes.rst:708
msgid ""
"The recommended way to create array types is by multiplying a data type with "
"a positive integer::"
msgstr ""
#: ../../library/ctypes.rst:713
msgid ""
"Here is an example of a somewhat artificial data type, a structure "
"containing 4 POINTs among other stuff::"
msgstr ""
#: ../../library/ctypes.rst:729
msgid "Instances are created in the usual way, by calling the class::"
msgstr ""
#: ../../library/ctypes.rst:735
msgid ""
"The above code print a series of ``0 0`` lines, because the array contents "
"is initialized to zeros."
msgstr ""
#: ../../library/ctypes.rst:738
msgid "Initializers of the correct type can also be specified::"
msgstr ""
#: ../../library/ctypes.rst:754
msgid "Pointers"
msgstr ""
#: ../../library/ctypes.rst:756
msgid ""
"Pointer instances are created by calling the :func:`pointer` function on a :"
"mod:`ctypes` type::"
msgstr ""
#: ../../library/ctypes.rst:764
msgid ""
"Pointer instances have a :attr:`~_Pointer.contents` attribute which returns "
"the object to which the pointer points, the ``i`` object above::"
msgstr ""
#: ../../library/ctypes.rst:771
msgid ""
"Note that :mod:`ctypes` does not have OOR (original object return), it "
"constructs a new, equivalent object each time you retrieve an attribute::"
msgstr ""
#: ../../library/ctypes.rst:780
msgid ""
"Assigning another :class:`c_int` instance to the pointer's contents "
"attribute would cause the pointer to point to the memory location where this "
"is stored::"
msgstr ""
#: ../../library/ctypes.rst:792
msgid "Pointer instances can also be indexed with integers::"
msgstr ""
#: ../../library/ctypes.rst:798
msgid "Assigning to an integer index changes the pointed to value::"
msgstr ""
#: ../../library/ctypes.rst:807
msgid ""
"It is also possible to use indexes different from 0, but you must know what "
"you're doing, just as in C: You can access or change arbitrary memory "
"locations. Generally you only use this feature if you receive a pointer from "
"a C function, and you *know* that the pointer actually points to an array "
"instead of a single item."
msgstr ""
#: ../../library/ctypes.rst:813
msgid ""
"Behind the scenes, the :func:`pointer` function does more than simply create "
"pointer instances, it has to create pointer *types* first. This is done with "
"the :func:`POINTER` function, which accepts any :mod:`ctypes` type, and "
"returns a new type::"
msgstr ""
#: ../../library/ctypes.rst:829
msgid ""
"Calling the pointer type without an argument creates a ``NULL`` pointer. "
"``NULL`` pointers have a ``False`` boolean value::"
msgstr ""
#: ../../library/ctypes.rst:837
msgid ""
":mod:`ctypes` checks for ``NULL`` when dereferencing pointers (but "
"dereferencing invalid non-\\ ``NULL`` pointers would crash Python)::"
msgstr ""
#: ../../library/ctypes.rst:856
msgid "Type conversions"
msgstr ""
#: ../../library/ctypes.rst:858
msgid ""
"Usually, ctypes does strict type checking. This means, if you have "
"``POINTER(c_int)`` in the :attr:`~_FuncPtr.argtypes` list of a function or "
"as the type of a member field in a structure definition, only instances of "
"exactly the same type are accepted. There are some exceptions to this rule, "
"where ctypes accepts other objects. For example, you can pass compatible "
"array instances instead of pointer types. So, for ``POINTER(c_int)``, "
"ctypes accepts an array of c_int::"
msgstr ""
#: ../../library/ctypes.rst:879
msgid ""
"In addition, if a function argument is explicitly declared to be a pointer "
"type (such as ``POINTER(c_int)``) in :attr:`~_FuncPtr.argtypes`, an object "
"of the pointed type (``c_int`` in this case) can be passed to the function. "
"ctypes will apply the required :func:`byref` conversion in this case "
"automatically."
msgstr ""
#: ../../library/ctypes.rst:884
msgid "To set a POINTER type field to ``NULL``, you can assign ``None``::"
msgstr ""
#: ../../library/ctypes.rst:891
msgid ""
"Sometimes you have instances of incompatible types. In C, you can cast one "
"type into another type. :mod:`ctypes` provides a :func:`cast` function "
"which can be used in the same way. The ``Bar`` structure defined above "
"accepts ``POINTER(c_int)`` pointers or :class:`c_int` arrays for its "
"``values`` field, but not instances of other types::"
msgstr ""
#: ../../library/ctypes.rst:903
msgid "For these cases, the :func:`cast` function is handy."
msgstr ""
#: ../../library/ctypes.rst:905
msgid ""
"The :func:`cast` function can be used to cast a ctypes instance into a "
"pointer to a different ctypes data type. :func:`cast` takes two parameters, "
"a ctypes object that is or can be converted to a pointer of some kind, and a "
"ctypes pointer type. It returns an instance of the second argument, which "
"references the same memory block as the first argument::"
msgstr ""
#: ../../library/ctypes.rst:916
msgid ""
"So, :func:`cast` can be used to assign to the ``values`` field of ``Bar`` "
"the structure::"
msgstr ""
#: ../../library/ctypes.rst:929
msgid "Incomplete Types"
msgstr ""
#: ../../library/ctypes.rst:931
msgid ""
"*Incomplete Types* are structures, unions or arrays whose members are not "
"yet specified. In C, they are specified by forward declarations, which are "
"defined later::"
msgstr ""
#: ../../library/ctypes.rst:942
msgid ""
"The straightforward translation into ctypes code would be this, but it does "
"not work::"
msgstr ""
#: ../../library/ctypes.rst:955
msgid ""
"because the new ``class cell`` is not available in the class statement "
"itself. In :mod:`ctypes`, we can define the ``cell`` class and set the :attr:"
"`~Structure._fields_` attribute later, after the class statement::"
msgstr ""
#: ../../library/ctypes.rst:967
msgid ""
"Let's try it. We create two instances of ``cell``, and let them point to "
"each other, and finally follow the pointer chain a few times::"
msgstr ""
#: ../../library/ctypes.rst:988
msgid "Callback functions"
msgstr ""
#: ../../library/ctypes.rst:990
msgid ""
":mod:`ctypes` allows creating C callable function pointers from Python "
"callables. These are sometimes called *callback functions*."
msgstr ""
#: ../../library/ctypes.rst:993
msgid ""
"First, you must create a class for the callback function. The class knows "
"the calling convention, the return type, and the number and types of "
"arguments this function will receive."
msgstr ""
#: ../../library/ctypes.rst:997
msgid ""
"The :func:`CFUNCTYPE` factory function creates types for callback functions "
"using the ``cdecl`` calling convention. On Windows, the :func:`WINFUNCTYPE` "
"factory function creates types for callback functions using the ``stdcall`` "
"calling convention."
msgstr ""
#: ../../library/ctypes.rst:1002
msgid ""
"Both of these factory functions are called with the result type as first "
"argument, and the callback functions expected argument types as the "
"remaining arguments."
msgstr ""
#: ../../library/ctypes.rst:1006
msgid ""
"I will present an example here which uses the standard C library's :c:func:`!"
"qsort` function, that is used to sort items with the help of a callback "
"function. :c:func:`!qsort` will be used to sort an array of integers::"
msgstr ""
#: ../../library/ctypes.rst:1016
msgid ""
":func:`!qsort` must be called with a pointer to the data to sort, the number "
"of items in the data array, the size of one item, and a pointer to the "
"comparison function, the callback. The callback will then be called with two "
"pointers to items, and it must return a negative integer if the first item "
"is smaller than the second, a zero if they are equal, and a positive integer "
"otherwise."