feat(blob): add bindings and api

lib/src/blob.dart

@@ -0,0 +1,61 @@
+import 'dart:ffi';
+import 'bindings/libgit2_bindings.dart';
+import 'bindings/blob.dart' as bindings;
+import 'oid.dart';
+import 'repository.dart';
+
+class Blob {
+  /// Initializes a new instance of [Blob] class from provided
+  /// [Repository] and [Oid] objects.
+  ///
+  /// Should be freed with `free()` to release allocated memory.
+  Blob.lookup(Repository repo, Oid oid) {
+    _blobPointer = bindings.lookup(repo.pointer, oid.pointer);
+  }
+
+  late final Pointer<git_blob> _blobPointer;
+
+  /// Pointer to memory address for allocated blob object.
+  Pointer<git_blob> get pointer => _blobPointer;
+
+  /// Creates a new blob from a [content] string and writes it to ODB.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  static Oid create(Repository repo, String content) {
+    return Oid(bindings.create(repo.pointer, content, content.length));
+  }
+
+  /// Creates a new blob from the file in working directory of a repository and writes
+  /// it to the ODB. Provided [relativePath] should be relative to the working directory.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  static Oid createFromWorkdir(Repository repo, String relativePath) {
+    return Oid(bindings.createFromWorkdir(repo.pointer, relativePath));
+  }
+
+  /// Creates a new blob from the file in filesystem and writes it to the ODB.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  static Oid createFromDisk(Repository repo, String path) {
+    return Oid(bindings.createFromDisk(repo.pointer, path));
+  }
+
+  /// Returns the Oid of the blob.
+  Oid get id => Oid(bindings.id(_blobPointer));
+
+  /// Determines if the blob content is most certainly binary or not.
+  ///
+  /// The heuristic used to guess if a file is binary is taken from core git:
+  /// Searching for NUL bytes and looking for a reasonable ratio of printable to
+  /// non-printable characters among the first 8000 bytes.
+  bool get isBinary => bindings.isBinary(_blobPointer);
+
+  /// Returns a read-only buffer with the raw content of a blob.
+  String get content => bindings.content(_blobPointer);
+
+  /// Returns the size in bytes of the contents of a blob.
+  int get size => bindings.size(_blobPointer);
+
+  /// Releases memory allocated for blob object.
+  void free() => bindings.free(_blobPointer);
+}