将结构数组传递给 Perl 6 NativeCall 函数 [英] Passing an array of structures to a Perl 6 NativeCall function

问题描述

我正在尝试使用 NativeCall 与一些 C 函数进行交互.

I'm trying to use NativeCall to interact with some C functions.

我有一个简单的 C 结构体和一个需要它们的数组的函数.

I have a simple C struct, and a function that wants an array of them.

struct foo {
    int x;
    char *s;
};

struct foo foo_array[3];

foo_array[0].x = 12;
foo_array[0].s = "foo";
foo_array[1].x = 27;
foo_array[1].s = "bar";
foo_array[2].x = -1;

void somefunc(foo_array);

我尝试了很多方法，但似乎无法完全正确.

I've tried a bunch of ways, but can't seem to get it quite right.

class foo is repr('CStruct') {
    has int32 $.x;
    has Str $.s
};

sub somefunc(CArray[foo]) is native { * }

my @foo-array := CArray[foo].new;

@foo-array[0] = ???
@foo-array[1] = ???
@foo-array[2] = ???

somefunc(@foo-array);

如何正确创建 foo 类的对象并设置它们的值，以及如何制作适合传递的数组?

How do I properly create an object of class foo and set their values, and how do I make an array of them suitable for passing?

推荐答案

据我所知，没有内置的方法可以做到这一点.但是，有足够的绳子可以上吊自己 建立一个解决方法:

As far as I'm aware, there's no built-in way to do this. However, there's enough rope to hang yourself build a workaround:

role StructArray[Mu:U \T where .REPR eq 'CStruct'] does Positional[T] {
    has $.bytes;
    has $.elems;

    method new(UInt \n) {
        self.bless(bytes => buf8.allocate(n * nativesizeof T), elems => n);
    }

    method AT-POS(UInt \i where ^$!elems) {
        nativecast(T, Pointer.new(nativecast(Pointer, $!bytes) + i * nativesizeof T));
    }

    method pointer {
        nativecast(Pointer[T], $!bytes);
    }
}

这应该允许以下工作:

my @foo-array := StructArray[foo].new(10); # 'array' with 10 elements
@foo-array[0].x = 42;

通过将 @foo-array.pointer 传递给 Pointer[foo] 类型的参数，可以与 C 函数进行交互.由于结构也是通过指针传递的，您也可以将 @foo-array[0] 传递给 foo 类型的参数以获得相同的效果.

Interaction with C functions is possible by passing @foo-array.pointer to a parameter of type Pointer[foo]. As structures are passed by pointer as well, you could also pass @foo-array[0] to a parameter of type foo for the same effect.

这篇关于将结构数组传递给 Perl 6 NativeCall 函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！