Array of structures as an attribute of the Perl 6 NativeCall structure

Question

I am trying to encapsulate a C structure, one of which is an array of pointers to structures, and I am having trouble figuring out how to do this.

Let's say the C code looks like this:

struct foo { unsigned char a; }; struct bar { struct foo *f[5]; }; 

This kind of code works:

 use NativeCall; class foo is repr('CStruct') { has uint8 $.a; } class bar is repr('CStruct') { has foo $.f1; has foo $.f2; has foo $.f3; has foo $.f4; has foo $.f5; } 

but it is terrible.

A CArray is useless here because it is just a pointer to an array, not an array of pointers; I cannot use something like has A @.a because repr('CStruct') does not handle this attribute.

Any clues?

Answer 1

I am writing code for this. Side C:

 struct bar* create_bar_ptr(unsigned char a) { printf("GET A CHAR => %#0x = %c\n", a, a); struct bar* bar = (struct bar*)malloc(sizeof(struct bar)); for (size_t i = 0;i < 5;i ++) { struct foo* tf = (struct foo*)malloc(sizeof(struct foo)); tf->a = a + i; bar->f[i] = tf; } printf("CREATE BAR PTR OK\n"); return bar; } 

Since Rakudo does not support getting the stack variable from the C side, you should use malloc to place the struct bar on the heap.

Then compile the code with gcc, for example gcc -shared -fPIC -o libshasa.so xxx.c

And this is the side of Perl6:

 use NativeCall; class foo is repr('CStruct') { has uint8 $.a; } class bar is repr('CStruct') { # Here you should use !!HAS!!, not has HAS Pointer[foo] $.f1; HAS Pointer[foo] $.f2; HAS Pointer[foo] $.f3; HAS Pointer[foo] $.f4; HAS Pointer[foo] $.f5; } sub create_bar_ptr(uint8) returns Pointer[bar] is native('./libshasa.so') { * } my Pointer[bar] $p = create_bar_ptr(uint8.new(97)); say $p.deref."f{$_}"().deref.a for 1 .. 5; 

It is output:

 GET A CHAR => 0x61 = a CREATE BAR PTR OK 97 98 99 100 101