Add protobuf mirror

Author: Pouya Yarandi

Sources/SwiftProtobuf/CMakeLists.txt

@@ -58,6 +58,7 @@ add_library(SwiftProtobuf
   NameMap.swift
   ProtobufAPIVersionCheck.swift
   ProtobufMap.swift
+  ProtobufMirror.swift
   ProtoNameProviding.swift
   SelectiveVisitor.swift
   SimpleExtensionMap.swift

Sources/SwiftProtobuf/ProtobufMirror.swift

@@ -0,0 +1,134 @@
+// Sources/SwiftProtobuf/ProtobufMirror.swift - Reflection
+//
+// Copyright (c) 2014 - 2016 Apple Inc. and the project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See LICENSE.txt for license information:
+// https://github.com/apple/swift-protobuf/blob/main/LICENSE.txt
+//
+// -----------------------------------------------------------------------------
+///
+/// Enables reflection for protobuf Message.
+///
+// -----------------------------------------------------------------------------
+
+import Foundation
+
+/// ProtobufMirror is for mirroring a protobuf Message type.
+/// 
+/// By using this object, a Message is being mirrored and it enables us to
+/// get all its children by their fieldNumber and value. Notice that it is not
+/// type safe and it should be used only in cases you need to get values
+/// by protobuf model indices.
+/// It also provides a field of unknownBytes for fields that could not be
+/// decoded by Message protobuf structure.
+public struct ProtobufMirror {
+
+  public typealias Child = (fieldNumber: Int, value: Any)
+
+  private var _children: [Int: Any] = [:]
+  private var _unknownBytes: [Data] = []
+
+  internal mutating func set(_ value: Any, for fieldNumber: Int) {
+    _children[fieldNumber] = value
+  }
+
+  internal mutating func recordUnknown(_ bytes: Data) {
+    _unknownBytes.append(bytes)
+  }
+
+  /// Children of a protobuf Message, which refers to all of its fields.
+  /// The fieldNumber of children is unique across the list.
+  public var children: [Child] {
+    _children.map { entry in
+      (fieldNumber: entry.key, value: entry.value)
+    }
+  }
+
+  /// A list of bytes that could not be decoded by protobuf Message structure.
+  public var unknownBytes: [Data] {
+    _unknownBytes
+  }
+
+}
+
+struct ReflectionVisitor: Visitor {
+
+  private(set) var mirror: ProtobufMirror = .init()
+
+  internal init() {}
+
+  mutating func visitSingularDoubleField(value: Double, fieldNumber: Int) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitSingularInt64Field(value: Int64, fieldNumber: Int) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitSingularUInt64Field(value: UInt64, fieldNumber: Int) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitSingularBoolField(value: Bool, fieldNumber: Int) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitSingularStringField(value: String, fieldNumber: Int) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitSingularBytesField(value: Data, fieldNumber: Int) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitSingularEnumField<E>(value: E, fieldNumber: Int) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitSingularMessageField<M>(value: M, fieldNumber: Int) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitMapField<KeyType, ValueType>(
+    fieldType: _ProtobufMap<KeyType, ValueType>.Type,
+    value: _ProtobufMap<KeyType, ValueType>.BaseType,
+    fieldNumber: Int
+  ) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitMapField<KeyType, ValueType>(
+    fieldType: _ProtobufEnumMap<KeyType, ValueType>.Type,
+    value: _ProtobufEnumMap<KeyType, ValueType>.BaseType,
+    fieldNumber: Int
+  ) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitMapField<KeyType, ValueType>(
+    fieldType: _ProtobufMessageMap<KeyType, ValueType>.Type,
+    value: _ProtobufMessageMap<KeyType, ValueType>.BaseType,
+    fieldNumber: Int
+  ) throws {
+    mirror.set(value, for: fieldNumber)
+  }
+
+  mutating func visitUnknown(bytes: Data) throws {
+    mirror.recordUnknown(bytes)
+  }
+
+}
+
+public extension ProtobufMirror {
+
+  /// Throwing init which initiates a ProtobutMirror for reflecting a protobuf
+  /// Message type.
+  /// - Parameter message: protobuf Message to be reflected.
+  init(reflecting message: Message) throws {
+    var visitor = ReflectionVisitor()
+    try message.traverse(visitor: &visitor)
+    self = visitor.mirror
+  }
+
+}