Python C-API对象分配

我想使用new和delete运算符来创建和销毁我的对象.

I want to use the new and delete operators for creating and destroying my objects.

问题是python似乎将其分为几个阶段. tp_new，tp_init和tp_alloc用于创建，tp_del，tp_free和tp_dealloc用于销毁.然而，c ++只是具有新的功能，它可以分配并完全构造对象，而删除的对象则可以破坏并取消分配对象.

The problem is python seems to break it into several stages. tp_new, tp_init and tp_alloc for creation and tp_del, tp_free and tp_dealloc for destruction. However c++ just has new which allocates and fully constructs the object and delete which destructs and deallocates the object.

我需要提供哪些python tp_ *方法，它们必须做什么?

Which of the python tp_* methods do I need to provide and what must they do?

我还希望能够直接在c ++中创建对象，例如"PyObject * obj = new MyExtensionObject(args);"我是否还需要以某种方式使新操作符过载以支持此操作?

Also I want to be able to create the object directly in c++ eg "PyObject *obj = new MyExtensionObject(args);" Will I also need to overload the new operator in some way to support this?

我还希望能够在python中扩展我的扩展类型，我需要做些特别的事情来支持它吗?

I also would like to be able to subclass my extension types in python, is there anything special I need to do to support this?

我正在使用python 3.0.1.

I'm using python 3.0.1.

好的，tp_init似乎使对象对于我正在做的事情太易变(例如，获取一个Texture对象，在创建后更改内容是可以的，但是更改其基本方面，例如大小，位分隔等会破坏很多假设这些东西是固定的现有c ++东西).如果我不实现它，它将仅仅阻止人们在其构造之后调用__init__(或至少像tuple那样忽略该调用).或者如果在同一对象上多次调用tp_init，我是否应该有一些引发异常或异常的标志?

ok, tp_init seems to make objects a bit too mutable for what I'm doing (eg take a Texture object, changing the contents after creation is fine, but change fundamental aspects of it such as, size, bitdept, etc will break lots of existing c++ stuff that assumes those sort of things are fixed). If I dont implement it will it simply stop people calling __init__ AFTER its constructed (or at least ignore the call, like tuple does). Or should I have some flag that throws an exception or somthing if tp_init is called more than once on the same object?

除此之外，我认为我把剩下的大部分都整理了.

Apart from that I think ive got most of the rest sorted.

extern "C"
{
    //creation + destruction
    PyObject* global_alloc(PyTypeObject *type, Py_ssize_t items)
    {
        return (PyObject*)new char[type->tp_basicsize + items*type->tp_itemsize];
    }
    void global_free(void *mem)
    {
        delete[] (char*)mem;
    }
}
template<class T> class ExtensionType
{
    PyTypeObject *t;
    ExtensionType()
    {
        t = new PyTypeObject();//not sure on this one, what is the "correct" way to create an empty type object
        memset((void*)t, 0, sizeof(PyTypeObject));
        static PyVarObject init = {PyObject_HEAD_INIT, 0};
        *((PyObject*)t) = init;

        t->tp_basicsize = sizeof(T);
        t->tp_itemsize  = 0;

        t->tp_name = "unknown";

        t->tp_alloc   = (allocfunc) global_alloc;
        t->tp_free    = (freefunc)  global_free;
        t->tp_new     = (newfunc)   T::obj_new;
        t->tp_dealloc = (destructor)T::obj_dealloc;
        ...
    }
    ...bunch of methods for changing stuff...
    PyObject *Finalise()
    {
    ...
    }
};
template <class T> PyObjectExtension : public PyObject
{
...
    extern "C" static PyObject* obj_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds)
    {
        void *mem = (void*)subtype->tp_alloc(subtype, 0);
        return (PyObject*)new(mem) T(args, kwds)
    }
    extern "C" static void obj_dealloc(PyObject *obj)
    {
        ~T();
        obj->ob_type->tp_free(obj);//most of the time this is global_free(obj)
    }
...
};
class MyObject : PyObjectExtension<MyObject>
{
public:
    static PyObject* InitType()
    {
        ExtensionType<MyObject> extType();
        ...sets other stuff...
        return extType.Finalise();
    }
    ...
};