# Capsule 对象

有关使用这些对象的更多信息请参阅 给扩展模块提供C API。

3.1 新版功能.

`PyCapsule`

  这个 `PyObject` 的子类型代表一个隐藏的值，适用于需要将隐藏值（作为 `void*` 指针）通过 Python 代码传递到其他 C 代码的 C 扩展模块。 它常常被用来让在一个模块中定义的 C 函数指针在其他模块中可用，这样就可以使用常规导入机制来访问在动态加载的模块中定义的 C API。

`PyCapsule_Destructor`

  Capsule 的析构器回调的类型。 定义如下：

      typedef void (*PyCapsule_Destructor)(PyObject *);

  参阅 `PyCapsule_New()` 来获取 PyCapsule_Destructor 返回值的语义。

int `PyCapsule_CheckExact`(PyObject *p)

  如果参数是一个 `PyCapsule` 则返回 True

PyObject* `PyCapsule_New`(void *pointer, const char *name, PyCapsule_Destructor destructor)
  Return value: New reference.

  创建一个封装了 pointer 的 `PyCapsule`。 pointer 参考可以不为 `NULL`。

  在失败时设置一个异常并返回 `NULL`。

  The name string may either be `NULL` or a pointer to a valid C string. If non-`NULL`, this string must outlive the capsule. (Though it is permitted to free it inside the destructor.)

  If the destructor argument is not `NULL`, it will be called with the capsule as its argument when it is destroyed.

  If this capsule will be stored as an attribute of a module, the name should be specified as `modulename.attributename`. This will enable other modules to import the capsule using `PyCapsule_Import()`.

void* `PyCapsule_GetPointer`(PyObject *capsule, const char *name)

  Retrieve the pointer stored in the capsule. On failure, set an exception and return `NULL`.

  The name parameter must compare exactly to the name stored in the capsule. If the name stored in the capsule is `NULL`, the name passed in must also be `NULL`. Python uses the C function `strcmp()` to compare capsule names.

PyCapsule_Destructor `PyCapsule_GetDestructor`(PyObject *capsule)

  Return the current destructor stored in the capsule. On failure, set an exception and return `NULL`.

  It is legal for a capsule to have a `NULL` destructor. This makes a `NULL` return code somewhat ambiguous; use `PyCapsule_IsValid()` or `PyErr_Occurred()` to disambiguate.

void* `PyCapsule_GetContext`(PyObject *capsule)

  Return the current context stored in the capsule. On failure, set an exception and return `NULL`.

  It is legal for a capsule to have a `NULL` context. This makes a `NULL` return code somewhat ambiguous; use `PyCapsule_IsValid()` or `PyErr_Occurred()` to disambiguate.

const char* `PyCapsule_GetName`(PyObject *capsule)

  Return the current name stored in the capsule. On failure, set an exception and return `NULL`.

  It is legal for a capsule to have a `NULL` name. This makes a `NULL` return code somewhat ambiguous; use `PyCapsule_IsValid()` or `PyErr_Occurred()` to disambiguate.

void* `PyCapsule_Import`(const char *name, int no_block)

  Import a pointer to a C object from a capsule attribute in a module. The name parameter should specify the full name to the attribute, as in `module.attribute`. The name stored in the capsule must match this string exactly. If no_block is true, import the module without blocking (using `PyImport_ImportModuleNoBlock()`). If no_block is false, import the module conventionally (using `PyImport_ImportModule()`).

  Return the capsule's internal pointer on success. On failure, set an exception and return `NULL`.

int `PyCapsule_IsValid`(PyObject *capsule, const char *name)

  Determines whether or not capsule is a valid capsule. A valid capsule is non-`NULL`, passes `PyCapsule_CheckExact()`, has a non-`NULL` pointer stored in it, and its internal name matches the name parameter. (See `PyCapsule_GetPointer()` for information on how capsule names are compared.)

  In other words, if `PyCapsule_IsValid()` returns a true value, calls to any of the accessors (any function starting with `PyCapsule_Get()`) are guaranteed to succeed.

  Return a nonzero value if the object is valid and matches the name passed in. Return `0` otherwise. This function will not fail.

int `PyCapsule_SetContext`(PyObject *capsule, void *context)

  Set the context pointer inside capsule to context.

  Return `0` on success. Return nonzero and set an exception on failure.

int `PyCapsule_SetDestructor`(PyObject *capsule, PyCapsule_Destructor destructor)

  Set the destructor inside capsule to destructor.

  Return `0` on success. Return nonzero and set an exception on failure.

int `PyCapsule_SetName`(PyObject *capsule, const char *name)

  Set the name inside capsule to name. If non-`NULL`, the name must outlive the capsule. If the previous name stored in the capsule was not `NULL`, no attempt is made to free it.

  Return `0` on success. Return nonzero and set an exception on failure.

int `PyCapsule_SetPointer`(PyObject *capsule, void *pointer)

  Set the void pointer inside capsule to pointer. The pointer may not be `NULL`.

  Return `0` on success. Return nonzero and set an exception on failure.