dart ffi: dealing with Pointer<Void> parameter

[Maarten Boekhold]

Following up on my previous post (which I resolved), I'm stuck on another native function in this library for which I cannot figure out how to do the binding:

typedef Handle void;

Handle handle

int res = getHandle("myDevice", &handle);

My dart code looks like:

typedef Handle = Void;

typedef getHandle_native_t = Int32 Function(Pointer<Utf8> name, Pointer<Void> handle);

late int Function(Pointer<Utf8> name, Pointer<Void> handle) getHandle;

getHandle = library

    .lookup<NativeFunction<getHandle_native_t>>('getHandle')

    .asFunction();

// Here I'm stuck, how do I get an initialized "handle'?

Pointer<Handle> handlePointer = calloc(); // this compiles

String name = "myDevice";

int res = getHandle(name.toNativeUtf8(), handlePointer);

Handle handle = handlePointer.value; // compile error, no such property 'value'. "ref" doesn't exist either as a property...

How do I get to the "void" value? I need this value to pass to subsequent function calls...

Maarten

[Daco Harkes]

Dear Maarten,

One can't dereference a void* in C, nor can one get the value of a Pointer<Void> in Dart.

What are you trying to accomplish? Do you have a link to your code somewhere? Is it an existing C API or one you are writing?

Kind regards,

 •  Daco Harkes
 •  Software Engineer
 •  dacoh...@google.com 
 •  🔵 Blue Dot Ally

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[Maarten Boekhold]

Hi Daco, your response prompted me to compose a very detailed description of what I'm (trying) to do, which had me jump into the source code of the library I'm trying to create bindings for. This proved very useful as it led me to discover my mistake: I need to deal with a **void, not *void. So in Dart, "Pointer<Pointer<Void>> handle = calloc();". I have much progressed now. Thanks for responding to my query,

Maarten