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2265 lines (1831 loc) · 74.5 KB
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# SOME DESCRIPTIVE TITLE.
# Copyright (C) 2001-2026, Python Software Foundation
# This file is distributed under the same license as the Python package.
# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
#
# Translators:
# python-doc bot, 2025
#
#, fuzzy
msgid ""
msgstr ""
"Project-Id-Version: Python 3.10\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2026-10-01 23:56+0000\n"
"PO-Revision-Date: 2025-09-22 15:57+0000\n"
"Last-Translator: python-doc bot, 2025\n"
"Language-Team: Polish (https://app.transifex.com/python-doc/teams/5390/pl/)\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Language: pl\n"
"Plural-Forms: nplurals=4; plural=(n==1 ? 0 : (n%10>=2 && n%10<=4) && "
"(n%100<12 || n%100>14) ? 1 : n!=1 && (n%10>=0 && n%10<=1) || (n%10>=5 && "
"n%10<=9) || (n%100>=12 && n%100<=14) ? 2 : 3);\n"
msgid ":mod:`ctypes` --- A foreign function library for Python"
msgstr ""
msgid "**Source code:** :source:`Lib/ctypes`"
msgstr "**Kod źródłowy:** :source:`Lib/ctypes`"
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 ""
msgid "ctypes tutorial"
msgstr ""
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 ""
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 ""
msgid "Loading dynamic link libraries"
msgstr ""
msgid ""
":mod:`ctypes` exports the *cdll*, and on Windows *windll* and *oledll* "
"objects, for loading dynamic link libraries."
msgstr ""
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 ""
msgid ""
"Windows errors used to raise :exc:`WindowsError`, which is now an alias "
"of :exc:`OSError`."
msgstr ""
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 ""
msgid "Windows appends the usual ``.dll`` file suffix automatically."
msgstr ""
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 ""
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:`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 ""
msgid "Accessing functions from loaded dlls"
msgstr ""
msgid "Functions are accessed as attributes of dll objects::"
msgstr ""
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 ""
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 ""
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 ""
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 ""
msgid "Calling functions"
msgstr ""
msgid ""
"You can call these functions like any other Python callable. This example "
"uses the ``time()`` function, which returns system time in seconds since the "
"Unix epoch, and the ``GetModuleHandleA()`` function, which returns a win32 "
"module handle."
msgstr ""
msgid ""
"This example calls both functions with a ``NULL`` pointer (``None`` should "
"be used as the ``NULL`` pointer)::"
msgstr ""
msgid ""
":exc:`ValueError` is raised when you call an ``stdcall`` function with the "
"``cdecl`` calling convention, or vice versa::"
msgstr ""
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 ""
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 ""
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 ""
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 ""
msgid ""
"Before we move on calling functions with other parameter types, we have to "
"learn more about :mod:`ctypes` data types."
msgstr ""
msgid "Fundamental data types"
msgstr ""
msgid ":mod:`ctypes` defines a number of primitive C compatible data types:"
msgstr ""
msgid "ctypes type"
msgstr ""
msgid "C type"
msgstr ""
msgid "Python type"
msgstr ""
msgid ":class:`c_bool`"
msgstr ":class:`c_bool`"
msgid ":c:expr:`_Bool`"
msgstr ":c:expr:`_Bool`"
msgid "bool (1)"
msgstr ""
msgid ":class:`c_char`"
msgstr ":class:`c_char`"
msgid ":c:expr:`char`"
msgstr ":c:expr:`char`"
msgid "1-character bytes object"
msgstr ""
msgid ":class:`c_wchar`"
msgstr ":class:`c_wchar`"
msgid ":c:expr:`wchar_t`"
msgstr ""
msgid "1-character string"
msgstr ""
msgid ":class:`c_byte`"
msgstr ":class:`c_byte`"
msgid "int"
msgstr "int"
msgid ":class:`c_ubyte`"
msgstr ":class:`c_ubyte`"
msgid ":c:expr:`unsigned char`"
msgstr ":c:expr:`unsigned char`"
msgid ":class:`c_short`"
msgstr ":class:`c_short`"
msgid ":c:expr:`short`"
msgstr ":c:expr:`short`"
msgid ":class:`c_ushort`"
msgstr ":class:`c_ushort`"
msgid ":c:expr:`unsigned short`"
msgstr ":c:expr:`unsigned short`"
msgid ":class:`c_int`"
msgstr ":class:`c_int`"
msgid ":c:expr:`int`"
msgstr ":c:expr:`int`"
msgid ":class:`c_uint`"
msgstr ":class:`c_uint`"
msgid ":c:expr:`unsigned int`"
msgstr ":c:expr:`unsigned int`"
msgid ":class:`c_long`"
msgstr ":class:`c_long`"
msgid ":c:expr:`long`"
msgstr ":c:expr:`long`"
msgid ":class:`c_ulong`"
msgstr ":class:`c_ulong`"
msgid ":c:expr:`unsigned long`"
msgstr ":c:expr:`unsigned long`"
msgid ":class:`c_longlong`"
msgstr ":class:`c_longlong`"
msgid ":c:expr:`__int64` or :c:expr:`long long`"
msgstr ""
msgid ":class:`c_ulonglong`"
msgstr ":class:`c_ulonglong`"
msgid ":c:expr:`unsigned __int64` or :c:expr:`unsigned long long`"
msgstr ""
msgid ":class:`c_size_t`"
msgstr ":class:`c_size_t`"
msgid ":c:expr:`size_t`"
msgstr ""
msgid ":class:`c_ssize_t`"
msgstr ":class:`c_ssize_t`"
msgid ":c:expr:`ssize_t` or :c:expr:`Py_ssize_t`"
msgstr ""
msgid ":class:`c_float`"
msgstr ":class:`c_float`"
msgid ":c:expr:`float`"
msgstr ":c:expr:`float`"
msgid "float"
msgstr "typ (float) zmiennoprzecinkowy pojedynczej precyzji"
msgid ":class:`c_double`"
msgstr ":class:`c_double`"
msgid ":c:expr:`double`"
msgstr ":c:expr:`double`"
msgid ":class:`c_longdouble`"
msgstr ":class:`c_longdouble`"
msgid ":c:expr:`long double`"
msgstr ":c:expr:`long double`"
msgid ":class:`c_char_p`"
msgstr ":class:`c_char_p`"
msgid ":c:expr:`char *` (NUL terminated)"
msgstr ""
msgid "bytes object or ``None``"
msgstr ""
msgid ":class:`c_wchar_p`"
msgstr ":class:`c_wchar_p`"
msgid ":c:expr:`wchar_t *` (NUL terminated)"
msgstr ""
msgid "string or ``None``"
msgstr ""
msgid ":class:`c_void_p`"
msgstr ":class:`c_void_p`"
msgid ":c:expr:`void *`"
msgstr ":c:expr:`void *`"
msgid "int or ``None``"
msgstr ""
msgid "The constructor accepts any object with a truth value."
msgstr ""
msgid ""
"All these types can be created by calling them with an optional initializer "
"of the correct type and value::"
msgstr ""
msgid ""
"Since these types are mutable, their value can also be changed afterwards::"
msgstr ""
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 ""
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 ""
msgid ""
"The :func:`create_string_buffer` function replaces the :func:`c_buffer` "
"function (which is still available as an alias), as well as "
"the :func:`c_string` function from earlier ctypes releases. To create a "
"mutable memory block containing unicode characters of the C "
"type :c:expr:`wchar_t` use the :func:`create_unicode_buffer` function."
msgstr ""
msgid "Calling functions, continued"
msgstr ""
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 ""
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 ""
msgid "Calling variadic functions"
msgstr ""
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 ""
msgid ""
"On those platforms it is required to specify the *argtypes* attribute for "
"the regular, non-variadic, function arguments:"
msgstr ""
msgid ""
"Because specifying the attribute does inhibit portability it is advised to "
"always specify ``argtypes`` for all variadic functions."
msgstr ""
msgid "Calling functions with your own custom data types"
msgstr ""
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. "
"Of course, it must be one of integer, string, or bytes::"
msgstr ""
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 ""
msgid "Specifying the required argument types (function prototypes)"
msgstr ""
msgid ""
"It is possible to specify the required argument types of functions exported "
"from DLLs by setting the :attr:`argtypes` attribute."
msgstr ""
msgid ""
":attr:`argtypes` must be a sequence of C data types (the ``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 ""
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 ""
msgid ""
"If you have defined your own classes which you pass to function calls, you "
"have to implement a :meth:`from_param` class method for them to be able to "
"use them in the :attr:`argtypes` sequence. The :meth:`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 ""
msgid "Return types"
msgstr ""
msgid ""
"By default functions are assumed to return the C :c:expr:`int` type. Other "
"return types can be specified by setting the :attr:`restype` attribute of "
"the function object."
msgstr ""
msgid ""
"Here is a more advanced example, it uses the ``strchr`` function, which "
"expects a string pointer and a char, and returns a pointer to a string::"
msgstr ""
msgid ""
"If you want to avoid the ``ord(\"x\")`` calls above, you can set "
"the :attr:`argtypes` attribute, and the second argument will be converted "
"from a single character Python bytes object into a C char::"
msgstr ""
msgid ""
"You can also use a callable Python object (a function or a class for "
"example) as the :attr:`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 ""
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 ""
msgid ""
"Please note that a much more powerful error checking mechanism is available "
"through the :attr:`errcheck` attribute; see the reference manual for details."
msgstr ""
msgid "Passing pointers (or: passing parameters by reference)"
msgstr ""
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 ""
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 ""
msgid "Structures and unions"
msgstr ""
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:`_fields_` "
"attribute. :attr:`_fields_` must be a list of *2-tuples*, containing a "
"*field name* and a *field type*."
msgstr ""
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 ""
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 ""
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 ""
msgid ""
"Here is a RECT structure which contains two POINTs named *upperleft* and "
"*lowerright*::"
msgstr ""
msgid ""
"Nested structures can also be initialized in the constructor in several "
"ways::"
msgstr ""
msgid ""
"Field :term:`descriptor`\\s can be retrieved from the *class*, they are "
"useful for debugging because they can provide useful information::"
msgstr ""
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 ""
msgid "Structure/union alignment and byte order"
msgstr ""
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:`_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 ""
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 ""
msgid "Bit fields in structures and unions"
msgstr ""
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:`_fields_` tuples::"
msgstr ""
msgid "Arrays"
msgstr ""
msgid ""
"Arrays are sequences, containing a fixed number of instances of the same "
"type."
msgstr ""
msgid ""
"The recommended way to create array types is by multiplying a data type with "
"a positive integer::"
msgstr ""
msgid ""
"Here is an example of a somewhat artificial data type, a structure "
"containing 4 POINTs among other stuff::"
msgstr ""
msgid "Instances are created in the usual way, by calling the class::"
msgstr ""
msgid ""
"The above code print a series of ``0 0`` lines, because the array contents "
"is initialized to zeros."
msgstr ""
msgid "Initializers of the correct type can also be specified::"
msgstr ""
msgid "Pointers"
msgstr ""
msgid ""
"Pointer instances are created by calling the :func:`pointer` function on "
"a :mod:`ctypes` type::"
msgstr ""
msgid ""
"Pointer instances have a :attr:`~_Pointer.contents` attribute which returns "
"the object to which the pointer points, the ``i`` object above::"
msgstr ""
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 ""
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 ""
msgid "Pointer instances can also be indexed with integers::"
msgstr ""
msgid "Assigning to an integer index changes the pointed to value::"
msgstr ""
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 ""
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 ""
msgid ""
"Calling the pointer type without an argument creates a ``NULL`` pointer. "
"``NULL`` pointers have a ``False`` boolean value::"
msgstr ""
msgid ""
":mod:`ctypes` checks for ``NULL`` when dereferencing pointers (but "
"dereferencing invalid non-\\ ``NULL`` pointers would crash Python)::"
msgstr ""
msgid "Type conversions"
msgstr ""
msgid ""
"Usually, ctypes does strict type checking. This means, if you have "
"``POINTER(c_int)`` in the :attr:`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 ""
msgid ""
"In addition, if a function argument is explicitly declared to be a pointer "
"type (such as ``POINTER(c_int)``) in :attr:`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 ""
msgid "To set a POINTER type field to ``NULL``, you can assign ``None``::"
msgstr ""
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 ""
msgid "For these cases, the :func:`cast` function is handy."
msgstr ""
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 ""
msgid ""
"So, :func:`cast` can be used to assign to the ``values`` field of ``Bar`` "
"the structure::"
msgstr ""
msgid "Incomplete Types"
msgstr ""
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 ""
msgid ""
"The straightforward translation into ctypes code would be this, but it does "
"not work::"
msgstr ""
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:`_fields_` attribute later, after the class statement::"
msgstr ""
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 ""
msgid "Callback functions"
msgstr ""
msgid ""
":mod:`ctypes` allows creating C callable function pointers from Python "
"callables. These are sometimes called *callback functions*."
msgstr ""
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 ""
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 ""
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 ""
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 ""
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."
msgstr ""
msgid ""
"So our callback function receives pointers to integers, and must return an "
"integer. First we create the ``type`` for the callback function::"
msgstr ""
msgid ""
"To get started, here is a simple callback that shows the values it gets "
"passed::"
msgstr ""
msgid "The result::"
msgstr "Wynik::"
msgid "Now we can actually compare the two items and return a useful result::"
msgstr ""
msgid "As we can easily check, our array is sorted now::"
msgstr ""
msgid ""
"The function factories can be used as decorator factories, so we may as well "
"write::"
msgstr ""
msgid ""
"Make sure you keep references to :func:`CFUNCTYPE` objects as long as they "
"are used from C code. :mod:`ctypes` doesn't, and if you don't, they may be "
"garbage collected, crashing your program when a callback is made."
msgstr ""
msgid ""
"Also, note that if the callback function is called in a thread created "
"outside of Python's control (e.g. by the foreign code that calls the "
"callback), ctypes creates a new dummy Python thread on every invocation. "
"This behavior is correct for most purposes, but it means that values stored "
"with :class:`threading.local` will *not* survive across different callbacks, "
"even when those calls are made from the same C thread."
msgstr ""
msgid "Accessing values exported from dlls"
msgstr ""
msgid ""
"Some shared libraries not only export functions, they also export variables. "
"An example in the Python library itself is the :c:data:`Py_OptimizeFlag`, an "
"integer set to 0, 1, or 2, depending on the :option:`-O` or :option:`-OO` "
"flag given on startup."
msgstr ""
msgid ""
":mod:`ctypes` can access values like this with the :meth:`in_dll` class "
"methods of the type. *pythonapi* is a predefined symbol giving access to "
"the Python C api::"
msgstr ""
msgid ""
"If the interpreter would have been started with :option:`-O`, the sample "
"would have printed ``c_long(1)``, or ``c_long(2)`` if :option:`-OO` would "
"have been specified."
msgstr ""
msgid ""
"An extended example which also demonstrates the use of pointers accesses "
"the :c:data:`PyImport_FrozenModules` pointer exported by Python."
msgstr ""
msgid "Quoting the docs for that value:"
msgstr ""
msgid ""
"This pointer is initialized to point to an array of :c:struct:`_frozen` "
"records, terminated by one whose members are all ``NULL`` or zero. When a "
"frozen module is imported, it is searched in this table. Third-party code "
"could play tricks with this to provide a dynamically created collection of "
"frozen modules."
msgstr ""
msgid ""
"So manipulating this pointer could even prove useful. To restrict the "
"example size, we show only how this table can be read with :mod:`ctypes`::"
msgstr ""
msgid ""
"We have defined the :c:struct:`_frozen` data type, so we can get the pointer "
"to the table::"
msgstr ""
msgid ""
"Since ``table`` is a ``pointer`` to the array of ``struct_frozen`` records, "
"we can iterate over it, but we just have to make sure that our loop "
"terminates, because pointers have no size. Sooner or later it would probably "
"crash with an access violation or whatever, so it's better to break out of "
"the loop when we hit the ``NULL`` entry::"
msgstr ""
msgid ""
"The fact that standard Python has a frozen module and a frozen package "
"(indicated by the negative ``size`` member) is not well known, it is only "
"used for testing. Try it out with ``import __hello__`` for example."
msgstr ""
msgid "Surprises"
msgstr ""
msgid ""
"There are some edges in :mod:`ctypes` where you might expect something other "
"than what actually happens."
msgstr ""
msgid "Consider the following example::"
msgstr ""
msgid ""
"Hm. We certainly expected the last statement to print ``3 4 1 2``. What "
"happened? Here are the steps of the ``rc.a, rc.b = rc.b, rc.a`` line above::"
msgstr ""
msgid ""
"Note that ``temp0`` and ``temp1`` are objects still using the internal "
"buffer of the ``rc`` object above. So executing ``rc.a = temp0`` copies the "
"buffer contents of ``temp0`` into ``rc`` 's buffer. This, in turn, changes "
"the contents of ``temp1``. So, the last assignment ``rc.b = temp1``, doesn't "
"have the expected effect."
msgstr ""
msgid ""
"Keep in mind that retrieving sub-objects from Structure, Unions, and Arrays "
"doesn't *copy* the sub-object, instead it retrieves a wrapper object "
"accessing the root-object's underlying buffer."
msgstr ""
msgid ""
"Another example that may behave differently from what one would expect is "
"this::"
msgstr ""
msgid ""
"Objects instantiated from :class:`c_char_p` can only have their value set to "
"bytes or integers."
msgstr ""
msgid ""
"Why is it printing ``False``? ctypes instances are objects containing a "
"memory block plus some :term:`descriptor`\\s accessing the contents of the "
"memory. Storing a Python object in the memory block does not store the "
"object itself, instead the ``contents`` of the object is stored. Accessing "
"the contents again constructs a new Python object each time!"
msgstr ""
msgid "Variable-sized data types"
msgstr ""
msgid ""
":mod:`ctypes` provides some support for variable-sized arrays and structures."
msgstr ""
msgid ""
"The :func:`resize` function can be used to resize the memory buffer of an "
"existing ctypes object. The function takes the object as first argument, "
"and the requested size in bytes as the second argument. The memory block "
"cannot be made smaller than the natural memory block specified by the "
"objects type, a :exc:`ValueError` is raised if this is tried::"
msgstr ""
msgid ""
"This is nice and fine, but how would one access the additional elements "
"contained in this array? Since the type still only knows about 4 elements, "
"we get errors accessing other elements::"
msgstr ""
msgid ""
"Another way to use variable-sized data types with :mod:`ctypes` is to use "
"the dynamic nature of Python, and (re-)define the data type after the "
"required size is already known, on a case by case basis."
msgstr ""
msgid "ctypes reference"
msgstr ""
msgid "Finding shared libraries"
msgstr ""
msgid ""
"When programming in a compiled language, shared libraries are accessed when "
"compiling/linking a program, and when the program is run."
msgstr ""
msgid ""
"The purpose of the :func:`find_library` function is to locate a library in a "
"way similar to what the compiler or runtime loader does (on platforms with "
"several versions of a shared library the most recent should be loaded), "
"while the ctypes library loaders act like when a program is run, and call "
"the runtime loader directly."
msgstr ""