Re: C-binding external array.

[Ali Çehreli via Digitalmars-d-learn]

On 08/09/2016 11:46 AM, ciechowoj wrote:
> On Tuesday, 9 August 2016 at 15:41:08 UTC, Steven Schveighoffer wrote:
>> @property int* tabp() { return tab.ptr; }
>>
>> tabp[elem];
>
> This is nice. The best would be to have it with the same name as
> original symbol, but I can't imagine how it could be done.
Well, C's array symbol is used as a pointer to the first element and D 
allows array indexing for pointers as well.

Here is the C code:

// c.c
#include "stdio.h"

int tab[64];

int *get() {
    return tab;    // or &tab[0]
}

void info() {
    printf("%p\n", tab);
}

void write_at(int i, int value) {
    tab[i] = value;
}

int read_at(int i) {
    return tab[i];
}

The D code uses the array as a pointer and then makes a slice at the 
very end:

// d.d
import std.stdio;

extern (C) {
    int *get();
    void info();
    void write_at(int i, int value);
    int read_at(int i);
}

void main() {
    int *tab = get();
    info();
    writefln("0x%s", tab);

    // make sure we can see what C writes
    write_at(7, 77);
    assert(tab[7] == 77);

    // make sure C can read what we write
    tab[42] = 42;
    assert(read_at(42) == 42);

    // If you know the size, use as a D array
    int[] tab_D = tab[0..64];
    writeln(tab_D);
}

Ali