Add Dart API for keyword spotter (#1162)

flutter/sherpa_onnx/lib/src/keyword_spotter.dart

@@ -0,0 +1,164 @@
+// Copyright (c)  2024  Xiaomi Corporation
+import 'dart:convert';
+import 'dart:ffi';
+
+import 'package:ffi/ffi.dart';
+
+import './feature_config.dart';
+import './online_stream.dart';
+import './online_recognizer.dart';
+import './sherpa_onnx_bindings.dart';
+import './utils.dart';
+
+class KeywordSpotterConfig {
+  const KeywordSpotterConfig({
+    this.feat = const FeatureConfig(),
+    required this.model,
+    this.maxActivePaths = 4,
+    this.numTrailingBlanks = 1,
+    this.keywordsScore = 1.0,
+    this.keywordsThreshold = 0.25,
+    this.keywordsFile = '',
+  });
+
+  @override
+  String toString() {
+    return 'KeywordSpotterConfig(feat: $feat, model: $model, maxActivePaths: $maxActivePaths, numTrailingBlanks: $numTrailingBlanks, keywordsScore: $keywordsScore, keywordsThreshold: $keywordsThreshold, keywordsFile: $keywordsFile)';
+  }
+
+  final FeatureConfig feat;
+  final OnlineModelConfig model;
+
+  final int maxActivePaths;
+  final int numTrailingBlanks;
+
+  final double keywordsScore;
+  final double keywordsThreshold;
+  final String keywordsFile;
+}
+
+class KeywordResult {
+  KeywordResult({required this.keyword});
+
+  @override
+  String toString() {
+    return 'KeywordResult(keyword: $keyword)';
+  }
+
+  final String keyword;
+}
+
+class KeywordSpotter {
+  KeywordSpotter._({required this.ptr, required this.config});
+
+  /// The user is responsible to call the OnlineRecognizer.free()
+  /// method of the returned instance to avoid memory leak.
+  factory KeywordSpotter(KeywordSpotterConfig config) {
+    final c = calloc<SherpaOnnxKeywordSpotterConfig>();
+    c.ref.feat.sampleRate = config.feat.sampleRate;
+    c.ref.feat.featureDim = config.feat.featureDim;
+
+    // transducer
+    c.ref.model.transducer.encoder =
+        config.model.transducer.encoder.toNativeUtf8();
+    c.ref.model.transducer.decoder =
+        config.model.transducer.decoder.toNativeUtf8();
+    c.ref.model.transducer.joiner =
+        config.model.transducer.joiner.toNativeUtf8();
+
+    // paraformer
+    c.ref.model.paraformer.encoder =
+        config.model.paraformer.encoder.toNativeUtf8();
+    c.ref.model.paraformer.decoder =
+        config.model.paraformer.decoder.toNativeUtf8();
+
+    // zipformer2Ctc
+    c.ref.model.zipformer2Ctc.model =
+        config.model.zipformer2Ctc.model.toNativeUtf8();
+
+    c.ref.model.tokens = config.model.tokens.toNativeUtf8();
+    c.ref.model.numThreads = config.model.numThreads;
+    c.ref.model.provider = config.model.provider.toNativeUtf8();
+    c.ref.model.debug = config.model.debug ? 1 : 0;
+    c.ref.model.modelType = config.model.modelType.toNativeUtf8();
+    c.ref.model.modelingUnit = config.model.modelingUnit.toNativeUtf8();
+    c.ref.model.bpeVocab = config.model.bpeVocab.toNativeUtf8();
+
+    c.ref.maxActivePaths = config.maxActivePaths;
+    c.ref.numTrailingBlanks = config.numTrailingBlanks;
+    c.ref.keywordsScore = config.keywordsScore;
+    c.ref.keywordsThreshold = config.keywordsThreshold;
+    c.ref.keywordsFile = config.keywordsFile.toNativeUtf8();
+
+    final ptr = SherpaOnnxBindings.createKeywordSpotter?.call(c) ?? nullptr;
+
+    calloc.free(c.ref.keywordsFile);
+    calloc.free(c.ref.model.bpeVocab);
+    calloc.free(c.ref.model.modelingUnit);
+    calloc.free(c.ref.model.modelType);
+    calloc.free(c.ref.model.provider);
+    calloc.free(c.ref.model.tokens);
+    calloc.free(c.ref.model.zipformer2Ctc.model);
+    calloc.free(c.ref.model.paraformer.encoder);
+    calloc.free(c.ref.model.paraformer.decoder);
+
+    calloc.free(c.ref.model.transducer.encoder);
+    calloc.free(c.ref.model.transducer.decoder);
+    calloc.free(c.ref.model.transducer.joiner);
+    calloc.free(c);
+
+    return KeywordSpotter._(ptr: ptr, config: config);
+  }
+
+  void free() {
+    SherpaOnnxBindings.destroyKeywordSpotter?.call(ptr);
+    ptr = nullptr;
+  }
+
+  /// The user has to invoke stream.free() on the returned instance
+  /// to avoid memory leak
+  OnlineStream createStream({String keywords = ''}) {
+    if (keywords == '') {
+      final p = SherpaOnnxBindings.createKeywordStream?.call(ptr) ?? nullptr;
+      return OnlineStream(ptr: p);
+    }
+
+    final utf8 = keywords.toNativeUtf8();
+    final p =
+        SherpaOnnxBindings.createKeywordStreamWithKeywords?.call(ptr, utf8) ??
+            nullptr;
+    calloc.free(utf8);
+    return OnlineStream(ptr: p);
+  }
+
+  bool isReady(OnlineStream stream) {
+    int ready =
+        SherpaOnnxBindings.isKeywordStreamReady?.call(ptr, stream.ptr) ?? 0;
+
+    return ready == 1;
+  }
+
+  KeywordResult getResult(OnlineStream stream) {
+    final json =
+        SherpaOnnxBindings.getKeywordResultAsJson?.call(ptr, stream.ptr) ??
+            nullptr;
+    if (json == nullptr) {
+      return KeywordResult(keyword: '');
+    }
+
+    final parsedJson = jsonDecode(toDartString(json));
+
+    SherpaOnnxBindings.freeKeywordResultJson?.call(json);
+
+    return KeywordResult(
+      keyword: parsedJson['keyword'],
+    );
+  }
+
+  void decode(OnlineStream stream) {
+    SherpaOnnxBindings.decodeKeywordStream?.call(ptr, stream.ptr);
+  }
+
+  Pointer<SherpaOnnxKeywordSpotter> ptr;
+  KeywordSpotterConfig config;
+}