在Perl 6 NativeCall CStruct中声明一个数组 [英] Declaring an array inside a Perl 6 NativeCall CStruct

问题描述

是否可以在CStruct中声明对象数组？

Is there any way to declare an array of objects inside a CStruct?

struct my_struct {
    int foo;
    int bar;
    char somestring[80];
};

class My::Struct is repr('CStruct') {
    has int32 $.foo;
    has int32 $.bar;
    ???
}

A CArray [uint8] 将是一个 char * 指针，而不是实际上在结构内部保留空间。

A CArray[uint8] would be a char * pointer, not actually reserving space inside the struct.

而不是 My :: Struct.new ，我可能自己做一个记忆（而不是 My :: Struct.new（），我使用 buf8.allocate（xxx）并保留一个句柄，以使GC不会收获它， nativecast 可以My :: Struct），然后我必须使用指针数学在结构内查找字符串，等等。但是似乎应该有一种更简单的方法。

Instead of My::Struct.new, I could probably make the memory myself (instead of My::Struct.new(), I use a buf8.allocate(xxx) and keep a handle so the GC doesn't reap it, nativecast it to My::Struct), then I have to use pointer math to find the string inside the struct, etc. but it seems like there should be an easier way.

甚至如果尚未完全实现，则说在此处放置80个字节，这是它的指针的简单方法将非常好。

Even if it wasn't fully implemented, a simple way to say "Put 80 bytes here and here's a Pointer to it" would be very nice.

推荐答案

这是我的丑陋解决方法：

Here is my ugly work-around:

class My::Struct is repr('CStruct') {
    has int32 $.foo is rw;
    has int32 $.bar is rw;
    has int64 $.h0; # 10 int64s = 80 bytes
    has int64 $.h1;
    has int64 $.h2;
    has int64 $.h3;
    has int64 $.h4;
    has int64 $.h5;
    has int64 $.h6;
    has int64 $.h7;
    has int64 $.h8;
    has int64 $.h9;

    method somestring {
        nativecast(Str, Pointer.new(nativecast(Pointer, self)+8))
    }

    sub strcpy(Pointer, Blob, --> Pointer) is native {}

    method set-somestring(Str:D $s) {
        my $buf = "$s\0".encode;
        die "too long" if $buf.bytes > 80;            
        strcpy(Pointer.new(nativecast(Pointer, self)+8), $buf);
    }
}

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