FFI bindings for function with ***item argument

[Maarten Boekhold]

I'm trying to write FFI bindings to a C library that has a function that uses ***Struct as one of its parameters:

typedef struct {

    char *name;

    char *value;

} Item;
extern void getItems(Item ***items);

which should be called, and the result used, as:

const Item **items;

getItems(&items);
for (int i = 0; items[i]; i++) {
    Item *item = items[i];
    printf("name: %s, value %s\n", item->name, item->value);
}

I'm very close to making this work, but I'm still stuck at accessing the individual members of Item. When I try to access item->value, the code actually seems to access item->name. Since both name & value are *char, I suspect that item->name and item->value actually resolve just as *item...

class Item extends Struct {
    external Pointer<Utf8> name;

    external Pointer<Utf8> value;

}

late int Function(Pointer<Pointer<Pointer<Item>>>) getItems; 

typedef getItemsNative_t =

    Int32 Function(Pointer<Pointer<Pointer<Item>>>);

getItems = library

    .lookup<NativeFunction<getItemsNative_t ('get_items')

    .asFunction();

Pointer<Pointer<Pointer<Item>>> pppItem = calloc(); getItems(pppItem);

Pointer<Pointer<Item>> ppItem = pppItem.value;

int idx = 0;

Pointer<Item> pItem = ppItem.elementAt(idx).value; // *item

while (pItem != nullptr) {

    Item item = pItem.ref; // IS THIS CORRECT?

    print('name = ${item.name.toDartString()}');

    print('value = ${item.value.toDartString()}');

    pItem = ppItem.elementAt(++idx).value;

}

calloc.free(pppItem);

This almost works. It 'gets to' every Item, except that each member access returns the value for 'name', not 'value', .e.g if the original C code returns:

name = Brad

value = Quarterback

name = John

value = Pitcher

my Dart code returns:

name = Brad

value = Brad

name = John

value = John

I must be doing something wrong at the line with the 'IS THIS CORRECT' comment, but I can't figure out what it is. I've tried various combinations of 'value', 'ref' and 'elementAt()', but the above is the only one that doesn't throw any errors inside my IntelliJ IDE / dart analyzer.

Anybody has any idea/suggestion?

[Maarten Boekhold]

I am so embarrassed. My real code is a bit more complicated than I showed above, and it turns out my test case was incorrect (too much copy/paste).

So, the above all works.