feat(commit): add base bindings and api

lib/src/signature.dart

@@ -0,0 +1,71 @@
+import 'dart:ffi';
+import 'package:ffi/ffi.dart';
+import 'bindings/libgit2_bindings.dart';
+import 'bindings/signature.dart' as bindings;
+import 'util.dart';
+
+class Signature {
+  /// Initializes a new instance of [Signature] class from provided pointer to
+  /// signature object in memory.
+  ///
+  /// Should be freed with `free()` to release allocated memory.
+  Signature(this._signaturePointer) {
+    libgit2.git_libgit2_init();
+  }
+
+  /// Initializes a new instance of [Signature] class from provided [name], [email],
+  /// and optional [time] in seconds from epoch and [offset] in minutes.
+  ///
+  /// If [time] isn't provided [Signature] will be created with a timestamp of 'now'.
+  ///
+  /// Should be freed with `free()` to release allocated memory.
+  Signature.create({
+    required String name,
+    required String email,
+    int? time,
+    int offset = 0,
+  }) {
+    libgit2.git_libgit2_init();
+
+    if (time == null) {
+      _signaturePointer = bindings.now(name, email);
+    } else {
+      _signaturePointer = bindings.create(name, email, time, offset);
+    }
+  }
+
+  /// Pointer to memory address for allocated signature object.
+  late final Pointer<git_signature> _signaturePointer;
+
+  /// Returns full name of the author.
+  String get name => _signaturePointer.ref.name.cast<Utf8>().toDartString();
+
+  /// Returns email of the author.
+  String get email => _signaturePointer.ref.email.cast<Utf8>().toDartString();
+
+  /// Returns time in seconds from epoch.
+  int get time => _signaturePointer.ref.when.time;
+
+  /// Returns timezone offset in minutes.
+  int get offset => _signaturePointer.ref.when.offset;
+
+  @override
+  bool operator ==(other) {
+    return (other is Signature) &&
+        (name == other.name) &&
+        (email == other.email) &&
+        (time == other.time) &&
+        (offset == other.offset) &&
+        (_signaturePointer.ref.when.sign ==
+            other._signaturePointer.ref.when.sign);
+  }
+
+  @override
+  int get hashCode => _signaturePointer.address.hashCode;
+
+  /// Releases memory allocated for signature object.
+  void free() {
+    bindings.free(_signaturePointer);
+    libgit2.git_libgit2_shutdown();
+  }
+}