add swift flatbuffers

flatbuffers/Struct.swift

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2023 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#if !os(WASI)
+import Foundation
+#else
+import SwiftOverlayShims
+#endif
+
+/// Struct is a representation of a mutable `Flatbuffers` struct
+/// since native structs are value types and cant be mutated
+@frozen
+public struct Struct {
+
+  /// Hosting Bytebuffer
+  public private(set) var bb: ByteBuffer
+  /// Current position of the struct
+  public private(set) var postion: Int32
+
+  /// Initializer for a mutable flatbuffers struct
+  /// - Parameters:
+  ///   - bb: Current hosting Bytebuffer
+  ///   - position: Current position for the struct in the ByteBuffer
+  public init(bb: ByteBuffer, position: Int32 = 0) {
+    self.bb = bb
+    postion = position
+  }
+
+  /// Reads data from the buffer directly at offset O
+  /// - Parameters:
+  ///   - type: Type of data to be read
+  ///   - o: Current offset of the data
+  /// - Returns: Data of Type T that conforms to type Scalar
+  public func readBuffer<T: Scalar>(of type: T.Type, at o: Int32) -> T {
+    let r = bb.read(def: T.self, position: Int(o + postion))
+    return r
+  }
+}