Adds mediapipe_core package

Makefile

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+# Runs unit tests for `mediapipe_core`
+test_core:
+	cd packages/mediapipe-core && dart test
+
+# Runs the utility to pull in all header files from `google/mediapipe`
+headers:
+	cd packages/build_cmd && dart bin/main.dart headers
+
+# Runs `ffigen` for `mediapipe_core`
+generate_core:
+	cd packages/mediapipe-core && dart run ffigen --config=ffigen.yaml
+
+# Runs `ffigen` for `mediapipe_text`
+generate_text:
+	cd packages/mediapipe-task-text && dart run ffigen --config=ffigen.yaml
+
+# Runs `ffigen` for all packages
+generate: generate_core generate_text
+
+# Compiles the faked C artifacts for testing
+compile_fake_text:
+	# Builds standalone executable
+	cd packages/mediapipe-task-text/test/c && gcc fake_text_classifier.c -o fake_text_classifier
+	# Builds what Flutter needs
+	cd packages/mediapipe-task-text/test/c && gcc -static -c -fPIC *.c -o fake_text_classifier.o
+	cd packages/mediapipe-task-text/test/c && gcc -shared -o fake_text_classifier.dylib fake_text_classifier.o 
+
+# Runs all text tests
+test_text_only:
+	cd packages/mediapipe-task-text && flutter test
+
+# Runs `ffigen` for `mediapipe_text` and all text tests
+test_text: compile_fake_text test_text_only
+
+# Runs `ffigen` for all packages, compiles the faked C artifacts, and runs all tests
+test: generate_text test_text generate_core test_core
+
+# Runs `ffigen` for all packages and all tests for all packages
+test_only: test_core test_text
+

packages/mediapipe-core/.gitignore

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+# https://dart.dev/guides/libraries/private-files
+# Created by `dart pub`
+.dart_tool/
+
+# Avoid committing pubspec.lock for library packages; see
+# https://dart.dev/guides/libraries/private-files#pubspeclock.
+pubspec.lock

packages/mediapipe-core/CHANGELOG.md

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+## 1.0.0
+
+- Initial version.

packages/mediapipe-core/README.md

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+<!-- 
+This README describes the package. If you publish this package to pub.dev,
+this README's contents appear on the landing page for your package.
+
+For information about how to write a good package README, see the guide for
+[writing package pages](https://dart.dev/guides/libraries/writing-package-pages). 
+
+For general information about developing packages, see the Dart guide for
+[creating packages](https://dart.dev/guides/libraries/create-library-packages)
+and the Flutter guide for
+[developing packages and plugins](https://flutter.dev/developing-packages). 
+-->
+
+TODO: Put a short description of the package here that helps potential users
+know whether this package might be useful for them.
+
+## Features
+
+TODO: List what your package can do. Maybe include images, gifs, or videos.
+
+## Getting started
+
+TODO: List prerequisites and provide or point to information on how to
+start using the package.
+
+## Usage
+
+TODO: Include short and useful examples for package users. Add longer examples
+to `/example` folder. 
+
+```dart
+const like = 'sample';
+```
+
+## Additional information
+
+TODO: Tell users more about the package: where to find more information, how to 
+contribute to the package, how to file issues, what response they can expect 
+from the package authors, and more.

packages/mediapipe-core/analysis_options.yaml

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+# Specify analysis options.
+
+include: package:lints/recommended.yaml
+
+analyzer:
+  exclude:
+    - "lib/src/mediapipe_common_bindings.dart"

packages/mediapipe-core/ffigen.yaml

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+name: "MediaPipeCommonBindings"
+description: "Bindings for shared MediaPipe structs common across many tasks"
+output:
+  bindings: "lib/src/mediapipe_common_bindings.dart"
+  symbol-file:
+    output: "package:mediapipe_core/generated/core_symbols.yaml"
+    import-path: "package:mediapipe_core/src/mediapipe_common_bindings.dart"
+headers:
+  entry-points:
+    - "third_party/mediapipe/tasks/c/core/base_options.h"
+    - "third_party/mediapipe/tasks/c/components/containers/category.h"
+    - "third_party/mediapipe/tasks/c/components/containers/classification_result.h"
+    - "third_party/mediapipe/tasks/c/components/processors/classifier_options.h"

packages/mediapipe-core/lib/generated/core_symbols.yaml

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+format_version: 1.0.0
+files:
+  package:mediapipe_core/src/mediapipe_common_bindings.dart:
+    used-config:
+      ffi-native: false
+    symbols:
+      c:@S@BaseOptions:
+        name: BaseOptions
+      c:@S@Category:
+        name: Category
+      c:@S@ClassificationResult:
+        name: ClassificationResult
+      c:@S@Classifications:
+        name: Classifications
+      c:@S@ClassifierOptions:
+        name: ClassifierOptions
+      c:@S@__darwin_pthread_handler_rec:
+        name: __darwin_pthread_handler_rec
+      c:@S@_opaque_pthread_attr_t:
+        name: _opaque_pthread_attr_t
+      c:@S@_opaque_pthread_cond_t:
+        name: _opaque_pthread_cond_t
+      c:@S@_opaque_pthread_condattr_t:
+        name: _opaque_pthread_condattr_t
+      c:@S@_opaque_pthread_mutex_t:
+        name: _opaque_pthread_mutex_t
+      c:@S@_opaque_pthread_mutexattr_t:
+        name: _opaque_pthread_mutexattr_t
+      c:@S@_opaque_pthread_once_t:
+        name: _opaque_pthread_once_t
+      c:@S@_opaque_pthread_rwlock_t:
+        name: _opaque_pthread_rwlock_t
+      c:@S@_opaque_pthread_rwlockattr_t:
+        name: _opaque_pthread_rwlockattr_t
+      c:@S@_opaque_pthread_t:
+        name: _opaque_pthread_t
+      c:@UA@__mbstate_t:
+        name: __mbstate_t

packages/mediapipe-core/lib/mediapipe_core.dart

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+library;
+
+export 'src/containers.dart' show Category, Classifications;
+export 'src/ffi_utils.dart';
+export 'src/task_options.dart' show BaseOptions, ClassifierOptions;

packages/mediapipe-core/lib/src/containers.dart

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+import 'dart:ffi';
+import 'package:ffi/ffi.dart';
+import 'package:mediapipe_core/mediapipe_core.dart';
+import 'mediapipe_common_bindings.dart' as bindings;
+
+class Category {
+  const Category({
+    required this.index,
+    required this.score,
+    required this.categoryName,
+    required this.displayName,
+  });
+  final int index;
+  final double score;
+  final String? categoryName;
+  final String? displayName;
+
+  static List<Category> fromStructs(
+    Pointer<bindings.Category> structs,
+    int count,
+  ) {
+    final categories = <Category>[];
+    for (int i = 0; i < count; i++) {
+      categories.add(fromStruct(structs[i]));
+    }
+    return categories;
+  }
+
+  static Category fromStruct(bindings.Category struct) {
+    return Category(
+      index: struct.index,
+      score: struct.score,
+      categoryName: toDartString(struct.category_name),
+      displayName: toDartString(struct.display_name),
+    );
+  }
+
+  static void freeStructs(Pointer<bindings.Category> structs, int count) {
+    int index = 0;
+    while (index < count) {
+      bindings.Category obj = structs[index];
+      calloc.free(obj.category_name);
+      calloc.free(obj.display_name);
+      index++;
+    }
+    calloc.free(structs);
+  }
+
+  @override
+  String toString() => 'Category(index=$index, score=$score, '
+      'categoryName=$categoryName, displayName=$displayName)';
+}
+
+class Classifications {
+  const Classifications({
+    required this.categories,
+    required this.headIndex,
+    required this.headName,
+  });
+  final List<Category> categories;
+  final int headIndex;
+  final String? headName;
+
+  static List<Classifications> fromStructs(
+    Pointer<bindings.Classifications> structs,
+    int count,
+  ) {
+    final classifications = <Classifications>[];
+    for (int i = 0; i < count; i++) {
+      classifications.add(fromStruct(structs[i]));
+    }
+    return classifications;
+  }
+
+  static Classifications fromStruct(bindings.Classifications struct) {
+    return Classifications(
+      categories: Category.fromStructs(
+        struct.categories,
+        struct.categories_count,
+      ),
+      headIndex: struct.head_index,
+      headName: toDartString(struct.head_name),
+    );
+  }
+
+  static void freeStructs(
+    Pointer<bindings.Classifications> structs,
+    int count,
+  ) {
+    int index = 0;
+    while (index < count) {
+      bindings.Classifications obj = structs[index];
+      Category.freeStructs(obj.categories, obj.categories_count);
+      calloc.free(obj.head_name);
+      index++;
+    }
+    calloc.free(structs);
+  }
+
+  Category? get firstCategory =>
+      categories.isNotEmpty ? categories.first : null;
+
+  @override
+  String toString() {
+    final categoryStrings = categories.map((cat) => cat.toString()).join(', ');
+    return 'Classification(categories=[$categoryStrings], '
+        'headIndex=$headIndex, headName=$headName)';
+  }
+}

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

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+import 'dart:ffi';
+import 'dart:typed_data';
+import 'package:ffi/ffi.dart';
+
+Pointer<Pointer<Char>> prepareListOfStrings(List<String> values) {
+  final ptrArray = calloc<Pointer<Char>>(values.length);
+  for (var i = 0; i < values.length; i++) {
+    ptrArray[i] = values[i].toNativeUtf8().cast<Char>();
+  }
+  return ptrArray;
+}
+
+Pointer<Char> prepareString(String val) => val.toNativeUtf8().cast<Char>();
+
+String? toDartString(Pointer<Char> val) {
+  if (val == nullptr) return null;
+  return val.cast<Utf8>().toDartString();
+}
+
+List<String?> toDartStrings(Pointer<Pointer<Char>> val, int length) {
+  final dartStrings = <String?>[];
+  int counter = 0;
+  while (counter < length) {
+    dartStrings.add(toDartString(val[counter]));
+    counter++;
+  }
+  return dartStrings;
+}
+
+Pointer<Char> prepareUint8List(Uint8List ints) {
+  final Pointer<Uint8> ptr = calloc<Uint8>(ints.length);
+  ptr.asTypedList(ints.length).setAll(0, ints);
+  return ptr.cast();
+}
+
+Uint8List toUint8List(Pointer<Char> val, {int? length}) {
+  final codeUnits = val.cast<Uint8>();
+  if (length != null) {
+    RangeError.checkNotNegative(length, 'length');
+  } else {
+    length = _length(codeUnits);
+  }
+  return codeUnits.asTypedList(length);
+}
+
+int _length(Pointer<Uint8> codeUnits) {
+  var length = 0;
+  while (codeUnits[length] != 0) {
+    length++;
+  }
+  return length;
+}