Message encoder/decoder (#1664)

Sources/GRPCCore/Coding/Coding.swift

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+/*
+ * Copyright 2023, gRPC Authors 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.
+ */
+
+/// Serializes a message into a sequence of bytes.
+///
+/// Message serializers convert an input message to a sequence of bytes. Serializers are used to
+/// convert messages into a form which is suitable for sending over a network. The reverse
+/// operation, deserialization, is performed by a ``MessageDeserializer``.
+///
+/// Serializers are used frequently and implementations should take care to ensure that
+/// serialization is as cheap as possible.
+public protocol MessageSerializer<Message>: Sendable {
+  /// The type of message this serializer can serialize.
+  associatedtype Message
+
+  /// Serializes a ``Message`` into a sequence of bytes.
+  ///
+  /// - Parameter message: The message to serialize.
+  /// - Returns: The serialized bytes of a message.
+  func serialize(_ message: Message) throws -> [UInt8]
+}
+
+/// Deserializes a sequence of bytes into a message.
+///
+/// Message deserializers convert a sequence of bytes into a message. Deserializers are used to
+/// convert bytes received from the network into an application specific message. The reverse
+/// operation, serialization, is performed by a ``MessageSerializer``.
+///
+/// Deserializers are used frequently and implementations should take care to ensure that
+/// deserialization is as cheap as possible.
+public protocol MessageDeserializer<Message>: Sendable {
+  /// The type of message this deserializer can deserialize.
+  associatedtype Message
+
+  /// Deserializes a sequence of bytes into a ``Message``.
+  ///
+  /// - Parameter serializedMessageBytes: The bytes to deserialize.
+  /// - Returns: The deserialized message.
+  func deserialize(_ serializedMessageBytes: [UInt8]) throws -> Message
+}

Tests/GRPCCoreTests/Coding/CodingTests.swift

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+/*
+ * Copyright 2023, gRPC Authors 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.
+ */
+import GRPCCore
+import XCTest
+
+final class CodingTests: XCTestCase {
+  func testJSONRoundtrip() throws {
+    // This test just demonstrates that the API is suitable.
+
+    struct Message: Codable, Hashable {
+      var foo: String
+      var bar: Int
+      var baz: Baz
+
+      struct Baz: Codable, Hashable {
+        var bazzy: Double
+      }
+    }
+
+    let message = Message(foo: "foo", bar: 42, baz: .init(bazzy: 3.1415))
+
+    let serializer = JSONSerializer<Message>()
+    let deserializer = JSONDeserializer<Message>()
+
+    let bytes = try serializer.serialize(message)
+    let roundTrip = try deserializer.deserialize(bytes)
+    XCTAssertEqual(roundTrip, message)
+  }
+}

Tests/GRPCCoreTests/Test Utilities/Coding+JSON.swift

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+/*
+ * Copyright 2023, gRPC Authors 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.
+ */
+import GRPCCore
+
+import struct Foundation.Data
+import class Foundation.JSONDecoder
+import class Foundation.JSONEncoder
+
+private let jsonEncoder = JSONEncoder()
+private let jsonDecoder = JSONDecoder()
+
+struct JSONSerializer<Message: Codable>: MessageSerializer {
+  func serialize(_ message: Message) throws -> [UInt8] {
+    do {
+      return try Array(jsonEncoder.encode(message))
+    } catch {
+      throw RPCError(code: .internalError, message: "Can't serialize message to JSON. \(error)")
+    }
+  }
+}
+
+struct JSONDeserializer<Message: Codable>: MessageDeserializer {
+  func deserialize(_ serializedMessageBytes: [UInt8]) throws -> Message {
+    do {
+      return try jsonDecoder.decode(Message.self, from: Data(serializedMessageBytes))
+    } catch {
+      throw RPCError(code: .internalError, message: "Can't deserialze message from JSON. \(error)")
+    }
+  }
+}