mirror of
https://github.com/pocketpy/pocketpy
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107 lines
3.1 KiB
Markdown
107 lines
3.1 KiB
Markdown
---
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icon: dot
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label: 'Bind native function'
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order: 60
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---
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pkpy allows to wrap a function pointer as a python function or method that can be called in python code.
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This function pointer has the following signature:
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```cpp
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typedef PyObject* (*NativeFuncC)(VM*, ArgsView);
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```
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+ The first argument is the pointer of `VM` instance.
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+ The second argument is an array-like object indicates the arguments list. You can use `[]` operator to get the element.
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+ The return value is a `PyObject*`, which should not be `nullptr`. If there is no return value, return `vm->None`.
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## Bind a function or method
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Use `vm->bind` to bind a function or method.
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+ `PyObject* bind(PyObject*, const char* sig, NativeFuncC)`
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+ `PyObject* bind(PyObject*, const char* sig, const char* docstring, NativeFuncC)`
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```cpp
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vm->bind(obj, "add(a: int, b: int) -> int", [](VM* vm, ArgsView args){
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int a = CAST(int, args[0]);
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int b = CAST(int, args[1]);
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return VAR(a + b);
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});
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// or you can provide a docstring
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vm->bind(obj,
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"add(a: int, b: int) -> int",
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"add two integers", [](VM* vm, ArgsView args){
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int a = CAST(int, args[0]);
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int b = CAST(int, args[1]);
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return VAR(a + b);
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});
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```
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### Bind a magic method
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For some magic methods, we provide specialized binding function.
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They do not take universal function pointer as argument.
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You need to provide the detailed `Type` object and the corresponding function pointer.
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```cpp
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PyObject* __add__(PyObject* lhs, PyObject* rhs){
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int a = CAST(int, lhs);
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int b = CAST(int, rhs);
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return VAR(a + b);
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}
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Type type = vm->tp_int;
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vm->bind__add__(type, __add__);
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```
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This specialized binding function has optimizations and result in better performance when calling from python code.
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For example, `vm->bind__add__` is preferred over `vm->bind_method<1>(type, "__add__", ...)`.
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### Bind a property
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a property is a python's `property` that attached to a type instance with a getter and an optional setter. It is a data descriptor. A property redirects attribute access to specific functions.
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You can use `@property` to create python property or use `vm->property` to create native property.
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Use `vm->bind_property()`, the new style property binding function.
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```cpp
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struct Point {
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PY_CLASS(Point, test, Point);
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int x;
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int y;
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Point(int x, int y) : x(x), y(y) {}
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static void _register(VM *vm, auto mod, auto type) {
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vm->bind_constructor<3>(type, [](VM *vm, auto args) {
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auto x = CAST(i64, args[1]);
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auto y = CAST(i64, args[2]);
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return VAR_T(Point, x, y);
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});
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// getter and setter of property `x`
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vm->bind_property(type, "x: int",
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[](VM* vm, ArgsView args){
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Point& self = CAST(Point&, args[0]);
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return VAR(self.x);
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},
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[](VM* vm, ArgsView args){
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Point& self = CAST(Point&, args[0]);
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self.x = CAST(int, args[1]);
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return vm->None;
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});
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}
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};
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```
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### Old style binding
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You may see somewhere in the code that `vm->bind_method<>` or `vm->bind_func<>` is used.
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They are old style binding functions and are deprecated.
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You should use `vm->bind` instead. |