如何在 Perl 6 中声明固定大小的本机数组? [英] How to declare native array of fixed size in Perl 6?

问题描述

我正在尝试在 Perl 6 中声明以下 C 结构:

I'm am trying to declare the following C struct in Perl 6:

struct myStruct
{
    int A[2]; //<---NEED to declare this
    int B;
    int C;
};

我的问题是我不知道如何使用内置的 NativeCall api 声明 int A[2]; 部分.

My problem is that I don't know how to declare the int A[2]; part using the built in NativeCall api.

所以我所拥有的是:

class myStruct is repr('CStruct') {
    has CArray[int32] $.A;
    has int32 $.B;
    has int32 $.C;
};

但是，我知道 有 CArray[int32] $.A; 部分是错误的，因为它没有在我的结构中声明仅占用 2 个 int32 尺寸.

However, I know that the has CArray[int32] $.A; part is wrong as it does not declare a part in my struct that takes up ONLY 2 int32 sizes.

推荐答案

更新 2:事实证明这在我第一次发布此答案时不起作用，因此发表评论.我仍然尚未对其进行测试，但它肯定可以根据 Tobias 对 使用 NativeCall 将 CStruct 中的内联 CArray 传递到共享库.\o/

Update 2: It turned out that this didn't work at the time I first posted this answer, hence the comments. I still haven't tested it but it must surely work per Tobias's answer to Passing an inlined CArray in a CStruct to a shared library using NativeCall. \o/

我还没有测试过这个，但是在使用 Rakudo 编译器 2018.05 版时应该可以工作:

I haven't tested this, but this should work when using Rakudo compiler release 2018.05:

use NativeCall;
class myStruct is repr('CStruct') {
    HAS int32 @.A[2] is CArray;
    has int32 $.B;
    has int32 $.C;
}

• HAS 而不是 has 导致属性内联而不是指针；

  • HAS instead of has causes the attribute to be inline rather than a pointer;

    int32 而不是 int 是因为 Perl 6 int 类型与 C 的 int 类型，但特定于平台(通常为 64 位)；

    int32 instead of int is because the Perl 6 int type isn't the same as C's int type but is instead platform specific (and usually 64 bit);

    @ 而不是 $ 将属性标记为 Positional(支持按索引查找值")而不是标量(被视为单一事物)；

    @ instead of $ marks the attribute as being Positional ("supports looking up values by index") instead of scalar (which gets treated as a single thing);

    [2] 将位置数据整形"为具有 2 个元素；

    [2] "shapes" the Positional data to have 2 elements;

    is CArray绑定一个CArray作为Positional数据的容器逻辑；

    is CArray binds a CArray as the Positional data's container logic;

    今年 4 月的提交连接了 是 repr('CStruct') 使用声明的属性信息来适当分配内存.

    This commit from April this year wired up the is repr('CStruct') to use the declared attribute information to appropriately allocate memory.

    Fwiw 我从 搜索 CArray 的 #perl6 日志，发现它已经从 搜索 Rakudo 提交以获取提交消息标题.

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