add swift flatbuffers

flatbuffers/Message.swift

@@ -0,0 +1,69 @@
+/*
+ * 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
+
+/// FlatBufferGRPCMessage protocol that should allow us to invoke
+/// initializers directly from the GRPC generated code
+public protocol FlatBufferGRPCMessage {
+
+  /// Raw pointer which would be pointing to the beginning of the readable bytes
+  var rawPointer: UnsafeMutableRawPointer { get }
+
+  /// Size of readable bytes in the buffer
+  var size: Int { get }
+
+  init(byteBuffer: ByteBuffer)
+}
+
+/// Message is a wrapper around Buffers to to able to send Flatbuffers `Buffers` through the
+/// GRPC library
+public struct Message<T: FlatBufferObject>: FlatBufferGRPCMessage {
+  internal var buffer: ByteBuffer
+
+  /// Returns the an object of type T that would be  read from the buffer
+  public var object: T {
+    T.init(
+      buffer,
+      o: Int32(buffer.read(def: UOffset.self, position: buffer.reader)) +
+        Int32(buffer.reader))
+  }
+
+  public var rawPointer: UnsafeMutableRawPointer {
+    buffer.memory.advanced(by: buffer.reader) }
+
+  public var size: Int { Int(buffer.size) }
+
+  /// Initializes the message with the type Flatbuffer.Bytebuffer that is transmitted over
+  /// GRPC
+  /// - Parameter byteBuffer: Flatbuffer ByteBuffer object
+  public init(byteBuffer: ByteBuffer) {
+    buffer = byteBuffer
+  }
+
+  /// Initializes the message by copying the buffer to the message to be sent.
+  /// from the builder
+  /// - Parameter builder: FlatbufferBuilder that has the bytes created in
+  /// - Note: Use  `builder.finish(offset)` before passing the builder without prefixing anything to it
+  public init(builder: inout FlatBufferBuilder) {
+    buffer = builder.sizedBuffer
+    builder.clear()
+  }
+}