add swift flatbuffers

flatbuffers/String+extension.swift

@@ -0,0 +1,113 @@
+/*
+ * 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
+
+extension String: Verifiable {
+
+  /// Verifies that the current value is which the bounds of the buffer, and if
+  /// the current `Value` is aligned properly
+  /// - Parameters:
+  ///   - verifier: Verifier that hosts the buffer
+  ///   - position: Current position within the buffer
+  ///   - type: The type of the object to be verified
+  /// - Throws: Errors coming from `inBuffer`, `missingNullTerminator` and `outOfBounds`
+  public static func verify<T>(
+    _ verifier: inout Verifier,
+    at position: Int,
+    of type: T.Type) throws where T: Verifiable
+  {
+
+    let range = try String.verifyRange(&verifier, at: position, of: UInt8.self)
+    /// Safe &+ since we already check for overflow in verify range
+    let stringLen = range.start &+ range.count
+
+    if stringLen >= verifier.capacity {
+      throw FlatbuffersErrors.outOfBounds(
+        position: UInt(clamping: stringLen.magnitude),
+        end: verifier.capacity)
+    }
+
+    let isNullTerminated = verifier._buffer.read(
+      def: UInt8.self,
+      position: stringLen) == 0
+
+    if !verifier._options._ignoreMissingNullTerminators && !isNullTerminated {
+      let str = verifier._buffer.readString(at: range.start, count: range.count)
+      throw FlatbuffersErrors.missingNullTerminator(
+        position: position,
+        str: str)
+    }
+  }
+}
+
+extension String: FlatbuffersInitializable {
+
+  /// Initailizes a string from a Flatbuffers ByteBuffer
+  /// - Parameters:
+  ///   - bb: ByteBuffer containing the readable string
+  ///   - o: Current position
+  public init(_ bb: ByteBuffer, o: Int32) {
+    let v = Int(o)
+    let count = bb.read(def: Int32.self, position: v)
+    self = bb.readString(
+      at: MemoryLayout<Int32>.size + v,
+      count: Int(count)) ?? ""
+  }
+}
+
+extension String: ObjectAPIPacker {
+
+  public static func pack(
+    _ builder: inout FlatBufferBuilder,
+    obj: inout String?) -> Offset
+  {
+    guard var obj = obj else { return Offset() }
+    return pack(&builder, obj: &obj)
+  }
+
+  public static func pack(
+    _ builder: inout FlatBufferBuilder,
+    obj: inout String) -> Offset
+  {
+    builder.create(string: obj)
+  }
+
+  public mutating func unpack() -> String {
+    self
+  }
+
+}
+
+extension String: NativeObject {
+
+  public func serialize<T: ObjectAPIPacker>(type: T.Type) -> ByteBuffer
+    where T.T == Self
+  {
+    fatalError("serialize should never be called from string directly")
+  }
+
+  public func serialize<T: ObjectAPIPacker>(
+    builder: inout FlatBufferBuilder,
+    type: T.Type) -> ByteBuffer where T.T == Self
+  {
+    fatalError("serialize should never be called from string directly")
+  }
+}