Implement an Arithmetic Request supporting increment and decrement operations

Sources/SwiftMemcache/Extensions/ByteBuffer+SwiftMemcache.swift

@@ -53,6 +53,9 @@ extension ByteBuffer {
  /// - parameters:
  /// - flags: An instance of MemcachedFlags that holds the flags intended to be serialized and written to the ByteBuffer.
  mutating func writeMemcachedFlags(flags: MemcachedFlags) {
+ // Ensure that both storageMode and arithmeticMode aren't set at the same time.
+ precondition(!(flags.storageMode != nil && flags.arithmeticMode != nil), "Cannot specify both a storage and arithmetic mode.")
+
  if let shouldReturnValue = flags.shouldReturnValue, shouldReturnValue {
  self.writeInteger(UInt8.whitespace)
  self.writeInteger(UInt8.v)
@@ -101,6 +104,23 @@ extension ByteBuffer {
  self.writeInteger(UInt8.R)
  }
  }
+
+ if let arithmeticMode = flags.arithmeticMode {
+ self.writeInteger(UInt8.whitespace)
+ self.writeInteger(UInt8.M)
+ switch arithmeticMode {
+ case .decrement(let delta):
+ self.writeInteger(UInt8.decrement)
+ self.writeInteger(UInt8.whitespace)
+ self.writeInteger(UInt8.D)
+ self.writeIntegerAsASCII(delta)
+ case .increment(let delta):
+ self.writeInteger(UInt8.increment)
+ self.writeInteger(UInt8.whitespace)
+ self.writeInteger(UInt8.D)
+ self.writeIntegerAsASCII(delta)
+ }
+ }
  }
 }
 

Sources/SwiftMemcache/Extensions/UInt8+Characters.swift

@@ -20,13 +20,17 @@ extension UInt8 {
  static var s: UInt8 = .init(ascii: "s")
  static var g: UInt8 = .init(ascii: "g")
  static var d: UInt8 = .init(ascii: "d")
+ static var a: UInt8 = .init(ascii: "a")
  static var v: UInt8 = .init(ascii: "v")
  static var T: UInt8 = .init(ascii: "T")
  static var M: UInt8 = .init(ascii: "M")
  static var P: UInt8 = .init(ascii: "P")
  static var A: UInt8 = .init(ascii: "A")
  static var E: UInt8 = .init(ascii: "E")
  static var R: UInt8 = .init(ascii: "R")
+ static var D: UInt8 = .init(ascii: "D")
  static var zero: UInt8 = .init(ascii: "0")
  static var nine: UInt8 = .init(ascii: "9")
+ static var increment: UInt8 = .init(ascii: "+")
+ static var decrement: UInt8 = .init(ascii: "-")
 }

Sources/SwiftMemcache/MemcachedConnection.swift

@@ -424,4 +424,62 @@ public actor MemcachedConnection {
  throw MemcachedConnectionError.connectionShutdown
  }
  }
+
+ // MARK: - Increment a Value
+
+ /// Increment the value for an existing key in the Memcache server by a specified amount.
+ ///
+ /// - Parameters:
+ /// - key: The key for the value to increment.
+ /// - amount: The `Int` amount to increment the value by. Must be larger than 0.
+ /// - Throws: A `MemcachedConnectionError` if the connection to the Memcached server is shut down.
+ public func increment(_ key: String, amount: Int) async throws {
+ // Ensure the amount is greater than 0
+ precondition(amount > 0, "Amount to increment should be larger than 0")
+
+ switch self.state {
+ case .initial(_, _, _, _),
+ .running:
+
+ var flags = MemcachedFlags()
+ flags.arithmeticMode = .increment(amount)
+
+ let command = MemcachedRequest.ArithmeticCommand(key: key, flags: flags)
+ let request = MemcachedRequest.arithmetic(command)
+
+ _ = try await self.sendRequest(request)
+
+ case .finished:
+ throw MemcachedConnectionError.connectionShutdown
+ }
+ }
+
+ // MARK: - Decrement a Value
+
+ /// Decrement the value for an existing key in the Memcache server by a specified amount.
+ ///
+ /// - Parameters:
+ /// - key: The key for the value to decrement.
+ /// - amount: The `Int` amount to decrement the value by. Must be larger than 0.
+ /// - Throws: A `MemcachedConnectionError` if the connection to the Memcached server is shut down.
+ public func decrement(_ key: String, amount: Int) async throws {
+ // Ensure the amount is greater than 0
+ precondition(amount > 0, "Amount to decrement should be larger than 0")
+
+ switch self.state {
+ case .initial(_, _, _, _),
+ .running:
+
+ var flags = MemcachedFlags()
+ flags.arithmeticMode = .decrement(amount)
+
+ let command = MemcachedRequest.ArithmeticCommand(key: key, flags: flags)
+ let request = MemcachedRequest.arithmetic(command)
+
+ _ = try await self.sendRequest(request)
+
+ case .finished:
+ throw MemcachedConnectionError.connectionShutdown
+ }
+ }
 }

Sources/SwiftMemcache/MemcachedFlags.swift

@@ -37,6 +37,11 @@ struct MemcachedFlags {
  /// The default mode is 'set'.
  var storageMode: StorageMode?
 
+ /// Flag 'M' for the 'ma' (meta arithmetic) command.
+ ///
+ /// Represents the mode of the 'ma' command, which determines the behavior of the arithmetic operation.
+ var arithmeticMode: ArithmeticMode?
+
  init() {}
 }
 
@@ -60,4 +65,12 @@ enum StorageMode: Equatable, Hashable {
  case replace
 }
 
+/// Enum representing the mode for the 'ma' (meta arithmetic) command in Memcached (corresponding to the 'M' flag).
+enum ArithmeticMode: Equatable, Hashable {
+ /// 'increment' command. If applied, it increases the numerical value of the item.
+ case increment(Int)
+ /// 'decrement' command. If applied, it decreases the numerical value of the item.
+ case decrement(Int)
+}
+
 extension MemcachedFlags: Hashable {}

Sources/SwiftMemcache/MemcachedRequest.swift

@@ -29,7 +29,13 @@ enum MemcachedRequest {
  let key: String
  }
 
+ struct ArithmeticCommand {
+ let key: String
+ var flags: MemcachedFlags
+ }
+
  case set(SetCommand)
  case get(GetCommand)
  case delete(DeleteCommand)
+ case arithmetic(ArithmeticCommand)
 }

Sources/SwiftMemcache/MemcachedRequestEncoder.swift

@@ -73,6 +73,22 @@ struct MemcachedRequestEncoder: MessageToByteEncoder {
  out.writeInteger(UInt8.whitespace)
  out.writeBytes(command.key.utf8)
 
+ // write separator
+ out.writeInteger(UInt8.carriageReturn)
+ out.writeInteger(UInt8.newline)
+
+ case .arithmetic(let command):
+ precondition(!command.key.isEmpty, "Key must not be empty")
+
+ // write command and key
+ out.writeInteger(UInt8.m)
+ out.writeInteger(UInt8.a)
+ out.writeInteger(UInt8.whitespace)
+ out.writeBytes(command.key.utf8)
+
+ // write flags if there are any
+ out.writeMemcachedFlags(flags: command.flags)
+
  // write separator
  out.writeInteger(UInt8.carriageReturn)
  out.writeInteger(UInt8.newline)

Sources/SwiftMemcache/MemcachedValue.swift

@@ -33,14 +33,14 @@ extension MemcachedValue where Self: FixedWidthInteger {
  ///
  /// - Parameter buffer: The ByteBuffer to which the integer should be written.
  public func writeToBuffer(_ buffer: inout ByteBuffer) {
- buffer.writeInteger(self)
+ buffer.writeIntegerAsASCII(self)
  }
 
  /// Reads a FixedWidthInteger from a ByteBuffer.
  ///
  /// - Parameter buffer: The ByteBuffer from which the value should be read.
  public static func readFromBuffer(_ buffer: inout ByteBuffer) -> Self? {
- return buffer.readInteger()
+ return buffer.readIntegerFromASCII()
  }
 }
 

Tests/SwiftMemcacheTests/IntegrationTest/MemcachedIntegrationTests.swift

@@ -434,6 +434,62 @@ final class MemcachedIntegrationTest: XCTestCase {
  }
  }
 
+ func testIncrementValue() async throws {
+ let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+ defer {
+ XCTAssertNoThrow(try! group.syncShutdownGracefully())
+ }
+ let memcachedConnection = MemcachedConnection(host: "memcached", port: 11211, eventLoopGroup: group)
+
+ try await withThrowingTaskGroup(of: Void.self) { group in
+ group.addTask { try await memcachedConnection.run() }
+
+ // Set key and initial value
+ let initialValue = 1
+ try await memcachedConnection.set("increment", value: initialValue)
+
+ // Increment value
+ let incrementAmount = 100
+ try await memcachedConnection.increment("increment", amount: incrementAmount)
+
+ // Get new value
+ let newValue: Int? = try await memcachedConnection.get("increment")
+
+ // Check if new value is equal to initial value plus increment amount
+ XCTAssertEqual(newValue, initialValue + incrementAmount, "Incremented value is incorrect")
+
+ group.cancelAll()
+ }
+ }
+
+ func testDecrementValue() async throws {
+ let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+ defer {
+ XCTAssertNoThrow(try! group.syncShutdownGracefully())
+ }
+ let memcachedConnection = MemcachedConnection(host: "memcached", port: 11211, eventLoopGroup: group)
+
+ try await withThrowingTaskGroup(of: Void.self) { group in
+ group.addTask { try await memcachedConnection.run() }
+
+ // Set key and initial value
+ let initialValue = 100
+ try await memcachedConnection.set("decrement", value: initialValue)
+
+ // Increment value
+ let decrementAmount = 10
+ try await memcachedConnection.decrement("decrement", amount: decrementAmount)
+
+ // Get new value
+ let newValue: Int? = try await memcachedConnection.get("decrement")
+
+ // Check if new value is equal to initial value plus increment amount
+ XCTAssertEqual(newValue, initialValue - decrementAmount, "Incremented value is incorrect")
+
+ group.cancelAll()
+ }
+ }
+
  func testMemcachedConnectionWithUInt() async throws {
  let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
  defer {

Tests/SwiftMemcacheTests/UnitTest/MemcachedRequestEncoderTests.swift

@@ -169,4 +169,32 @@ final class MemcachedRequestEncoderTests: XCTestCase {
  let expectedEncodedData = "md foo\r\n"
  XCTAssertEqual(outBuffer.getString(at: 0, length: outBuffer.readableBytes), expectedEncodedData)
  }
+
+ func testEncodeIncrementRequest() {
+ // Prepare a MemcachedRequest
+ var flags = MemcachedFlags()
+ flags.arithmeticMode = .increment(100)
+ let command = MemcachedRequest.ArithmeticCommand(key: "foo", flags: flags)
+ let request = MemcachedRequest.arithmetic(command)
+
+ // pass our request through the encoder
+ let outBuffer = self.encodeRequest(request)
+
+ let expectedEncodedData = "ma foo M+ D100\r\n"
+ XCTAssertEqual(outBuffer.getString(at: 0, length: outBuffer.readableBytes), expectedEncodedData)
+ }
+
+ func testEncodeDecrementRequest() {
+ // Prepare a MemcachedRequest
+ var flags = MemcachedFlags()
+ flags.arithmeticMode = .decrement(100)
+ let command = MemcachedRequest.ArithmeticCommand(key: "foo", flags: flags)
+ let request = MemcachedRequest.arithmetic(command)
+
+ // pass our request through the encoder
+ let outBuffer = self.encodeRequest(request)
+
+ let expectedEncodedData = "ma foo M- D100\r\n"
+ XCTAssertEqual(outBuffer.getString(at: 0, length: outBuffer.readableBytes), expectedEncodedData)
+ }
 }