updates to inference and example

Author: craiglabenz

packages/mediapipe-core/lib/src/interface/task_options.dart

@@ -6,9 +6,12 @@ import 'dart:typed_data';
 
 import 'package:equatable/equatable.dart';
 
-/// {@template TaskOptions}
+/// {@template BaseOptions}
 /// Root class for options classes for MediaPipe tasks.
-///
+/// {@endtemplate}
+abstract class Options extends Equatable {}
+
+/// {@template TaskOptions}
 /// Implementing classes will contain two [BaseInnerTaskOptions] subclasses,
 /// including a descendent of the universal options struct, [BaseBaseOptions].
 /// The second field will be task-specific.
@@ -17,7 +20,7 @@ import 'package:equatable/equatable.dart';
 /// This implementation is not immutable to track whether `dispose` has been
 /// called. All values used by pkg:equatable are in fact immutable.
 // ignore: must_be_immutable
-abstract class BaseTaskOptions extends Equatable {
+abstract class BaseTaskOptions extends Options {
   /// {@macro TaskOptions}
   BaseTaskOptions();
 

packages/mediapipe-core/lib/src/io/ffi_utils.dart

@@ -69,11 +69,12 @@ extension DartAwareChars on Pointer<Char> {
   ///
   /// See also:
   ///  * [toDartStrings]
-  String toDartString({int? length}) {
+  String toDartString({int? length, bool copy = false}) {
     if (isNullPointer) {
       throw Exception('Unexpectedly called `toDartString` on nullptr');
     }
-    return cast<Utf8>().toDartString(length: length);
+    final value = cast<Utf8>().toDartString(length: length);
+    return copy ? String.fromCharCodes(List<int>.from(value.codeUnits)) : value;
   }
 
   /// Releases all native memory.
@@ -90,14 +91,14 @@ extension DartAwarePointerChars on Pointer<Pointer<Char>> {
   ///
   /// See also:
   ///  * [toDartString], for a non-list equivalent.
-  List<String?> toDartStrings(int length) {
+  List<String> toDartStrings(int length, {bool copy = false}) {
     if (isNullPointer) {
       throw Exception('Unexpectedly called `toDartStrings` on nullptr');
     }
-    final dartStrings = <String?>[];
+    final dartStrings = <String>[];
     int counter = 0;
     while (counter < length) {
-      dartStrings.add(this[counter].toDartString());
+      dartStrings.add(this[counter].toDartString(copy: copy));
       counter++;
     }
     return dartStrings;

packages/mediapipe-core/lib/src/io/task_options.dart

@@ -15,7 +15,7 @@ import 'third_party/mediapipe/generated/mediapipe_common_bindings.dart'
 /// should manage their [InnerTaskOptions] fields. The two suggested methods are
 /// [copyToNative] and [dispose].
 /// {@endtemplate}
-mixin TaskOptions<T extends Struct> on BaseTaskOptions {
+mixin TaskOptions<T extends Struct> on Options {
   /// {@template TaskOptions.copyToNative}
   /// Copies these task options into native memory. Any fields of type
   /// [InnerTaskOptions] should have their `assignToStruct` method called.

packages/mediapipe-core/test/io/task_options_test.dart

@@ -86,13 +86,17 @@ void main() {
         expect(ptr.ref.score_threshold, lessThan(0.90001));
         expect(ptr.ref.category_allowlist_count, 3);
         expect(
-          ptr.ref.category_allowlist.toDartStrings(3),
+          ptr.ref.category_allowlist.toDartStrings(
+            3,
+          ),
           ['good', 'great', 'best'],
         );
 
         expect(ptr.ref.category_denylist_count, 4);
         expect(
-          ptr.ref.category_denylist.toDartStrings(4),
+          ptr.ref.category_denylist.toDartStrings(
+            4,
+          ),
           ['bad', 'terrible', 'worst', 'honestly come on'],
         );
       });