Add encoding function that returns Data. Fixes #94

Package.swift

@@ -22,13 +22,16 @@ let package = Package(
             dependencies: [
                 .product(name: "NIO", package: "swift-nio"),
                 .product(name: "NIOHTTP1", package: "swift-nio"),
+                .product(name: "NIOFoundationCompat", package: "swift-nio"),
                 .product(name: "Collections", package: "swift-collections"),
             ]
         ),
         .testTarget(
             name: "MultipartKitTests",
             dependencies: [
                 .target(name: "MultipartKit"),
+            ], resources: [
+                .copy("Utilities/image.jpeg"),
             ]
         ),
     ]

Package@swift-5.9.swift

@@ -22,6 +22,7 @@ let package = Package(
             dependencies: [
                 .product(name: "NIO", package: "swift-nio"),
                 .product(name: "NIOHTTP1", package: "swift-nio"),
+                .product(name: "NIOFoundationCompat", package: "swift-nio"),
                 .product(name: "Collections", package: "swift-collections"),
             ],
             swiftSettings: [
@@ -32,6 +33,8 @@ let package = Package(
             name: "MultipartKitTests",
             dependencies: [
                 .target(name: "MultipartKit"),
+            ], resources: [
+                .copy("Utilities/image.jpeg"),
             ],
             swiftSettings: [
                 .enableExperimentalFeature("StrictConcurrency=complete"),

Sources/MultipartKit/FormDataDecoder/FormDataDecoder.swift

@@ -1,5 +1,7 @@
+import Foundation
 import NIOCore
 import NIOHTTP1
+import NIOFoundationCompat
 
 /// Decodes `Decodable` types from `multipart/form-data` encoded `Data`.
 ///
@@ -28,23 +30,37 @@ public struct FormDataDecoder: Sendable {
     ///     let foo = try FormDataDecoder().decode(Foo.self, from: "...", boundary: "123")
     ///
     /// - Parameters:
-    ///   - decodable: Generic `Decodable` type.
+    ///   - decodable: A `Decodable` item.
     ///   - data: String to decode.
-    ///   - boundary: Multipart boundary to used in the decoding.
+    ///   - boundary: The multipart boundary to use for decoding. This string must not appear in the decoded data.
     /// - Throws: Any errors decoding the model with `Codable` or parsing the data.
     /// - Returns: An instance of the decoded type `D`.
     public func decode<D: Decodable>(_ decodable: D.Type, from data: String, boundary: String) throws -> D {
         try decode(D.self, from: ByteBuffer(string: data), boundary: boundary)
     }
 
+    /// Decodes a `Decodable` item from `Data` using the supplied boundary.
+    ///
+    ///     let foo = try FormDataDecoder().decode(Foo.self, from: Data(), boundary: "123")
+    ///
+    /// - Parameters:
+    ///   - decodable: A `Decodable` item.
+    ///   - data: String to decode.
+    ///   - boundary: The multipart boundary to use for decoding. This string must not appear in the decoded data.
+    /// - Throws: Any errors decoding the model with `Codable` or parsing the data.
+    /// - Returns: An instance of the decoded type `D`.
+    public func decode<D: Decodable>(_ decodable: D.Type, from data: Data, boundary: String) throws -> D {
+        try decode(D.self, from: ByteBuffer(data: data), boundary: boundary)
+    }
+
     /// Decodes a `Decodable` item from `Data` using the supplied boundary.
     ///
     ///     let foo = try FormDataDecoder().decode(Foo.self, from: data, boundary: "123")
     ///
     /// - Parameters:
-    ///   - decodable: Generic `Decodable` type.
+    ///   - decodable: A `Decodable` item.
     ///   - data: Data to decode.
-    ///   - boundary: Multipart boundary to used in the decoding.
+    ///   - boundary: The multipart boundary to use for decoding. This string must not appear in the decoded data.
     /// - Throws: Any errors decoding the model with `Codable` or parsing the data.
     /// - Returns: An instance of the decoded type `D`.
     public func decode<D: Decodable>(_ decodable: D.Type, from data: [UInt8], boundary: String) throws -> D {
@@ -56,9 +72,9 @@ public struct FormDataDecoder: Sendable {
     ///     let foo = try FormDataDecoder().decode(Foo.self, from: data, boundary: "123")
     ///
     /// - Parameters:
-    ///   - decodable: Generic `Decodable` type.
+    ///   - decodable: A `Decodable` item.
     ///   - data: Data to decode.
-    ///   - boundary: Multipart boundary to used in the decoding.
+    ///   - boundary: The multipart boundary to use for decoding. This string must not appear in the decoded data.
     /// - Throws: Any errors decoding the model with `Codable` or parsing the data.
     /// - Returns: An instance of the decoded type `D`.
     public func decode<D: Decodable>(_ decodable: D.Type, from buffer: ByteBuffer, boundary: String) throws -> D {

Sources/MultipartKit/FormDataEncoder/FormDataEncoder.swift

@@ -1,3 +1,4 @@
+import Foundation
 import NIOCore
 
 /// Encodes `Encodable` items to `multipart/form-data` encoded `Data`.
@@ -18,31 +19,45 @@ public struct FormDataEncoder: Sendable {
     ///     let a = Foo(string: "a", int: 42, double: 3.14, array: [1, 2, 3])
     ///     let data = try FormDataEncoder().encode(a, boundary: "123")
     ///
-    /// - parameters:
-    ///     - encodable: Generic `Encodable` item.
-    ///     - boundary: Multipart boundary to use for encoding. This must not appear anywhere in the encoded data.
-    /// - throws: Any errors encoding the model with `Codable` or serializing the data.
-    /// - returns: `multipart/form-data`-encoded `String`.
-    public func encode<E: Encodable>(_ encodable: E, boundary: String) throws -> String {
+    /// - Parameters:
+    ///     - encodable: An `Encodable` item.
+    ///     - boundary: The multipart boundary to use for encoding. This string must not appear in the encoded data.
+    /// - Throws: Any errors encoding the model with `Codable` or serializing the data.
+    /// - Returns: A `multipart/form-data`-encoded `String`.
+    public func encode(_ encodable: some Encodable, boundary: String) throws -> String {
         try MultipartSerializer().serialize(parts: parts(from: encodable), boundary: boundary)
     }
+
+    /// Encodes an `Encodable` item to `Data` using the supplied boundary.
+    ///
+    ///     let a = Foo(string: "a", int: 42, double: 3.14, array: [1, 2, 3])
+    ///     let data = try FormDataEncoder().encodeToData(a, boundary: "123")
+    ///
+    /// - Parameters:
+    ///     - encodable: An `Encodable` item.
+    ///     - boundary: The multipart boundary to use for encoding. This string must not appear in the encoded data.
+    /// - Throws: Any errors encoding the model or serializing the data.
+    /// - Returns: A `multipart/form-data`-encoded `String`.
+    public func encodeToData(_ encodable: some Encodable, boundary: String) throws -> Data {
+        try MultipartSerializer().serializeToData(parts: parts(from: encodable), boundary: boundary)
+    }
 
     /// Encodes an `Encodable` item into a `ByteBuffer` using the supplied boundary.
     ///
     ///     let a = Foo(string: "a", int: 42, double: 3.14, array: [1, 2, 3])
     ///     var buffer = ByteBuffer()
     ///     let data = try FormDataEncoder().encode(a, boundary: "123", into: &buffer)
     ///
-    /// - parameters:
-    ///     - encodable: Generic `Encodable` item.
-    ///     - boundary: Multipart boundary to use for encoding. This must not appear anywhere in the encoded data.
+    /// - Parameters:
+    ///     - encodable: An `Encodable` item.
+    ///     - boundary: The multipart boundary to use for encoding. This string must not appear in the encoded data.
     ///     - buffer: Buffer to write to.
-    /// - throws: Any errors encoding the model with `Codable` or serializing the data.
-    public func encode<E: Encodable>(_ encodable: E, boundary: String, into buffer: inout ByteBuffer) throws {
+    /// - Throws: Any errors encoding the model with `Codable` or serializing the data.
+    public func encode(_ encodable: some Encodable, boundary: String, into buffer: inout ByteBuffer) throws {
         try MultipartSerializer().serialize(parts: parts(from: encodable), boundary: boundary, into: &buffer)
     }
 
-    private func parts<E: Encodable>(from encodable: E) throws -> [MultipartPart] {
+    private func parts(from encodable: some Encodable) throws -> [MultipartPart] {
         let encoder = Encoder(codingPath: [], userInfo: userInfo)
         try encodable.encode(to: encoder)
         return encoder.storage.data?.namedParts() ?? []

Sources/MultipartKit/MultipartSerializer.swift

@@ -1,4 +1,6 @@
+import Foundation
 import NIOCore
+import NIOFoundationCompat
 
 /// Serializes `MultipartForm`s to `Data`.
 ///
@@ -13,15 +15,31 @@ public final class MultipartSerializer: Sendable {
     ///     let data = try MultipartSerializer().serialize(parts: [part], boundary: "123")
     ///     print(data) // multipart-encoded
     ///
-    /// - parameters:
-    ///     - parts: One or more `MultipartPart`s to serialize into `Data`.
-    ///     - boundary: Multipart boundary to use for encoding. This must not appear anywhere in the encoded data.
-    /// - throws: Any errors that may occur during serialization.
-    /// - returns: `multipart`-encoded `Data`.
+    /// - Parameters:
+    ///     - parts: One or more `MultipartPart`s to serialize into `String`.
+    ///     - boundary: The multipart boundary to use for encoding. This string must not appear in the encoded data.
+    /// - Throws: Any errors that may occur during serialization.
+    /// - Returns: A `multipart`-encoded `Data`.
     public func serialize(parts: [MultipartPart], boundary: String) throws -> String {
         var buffer = ByteBufferAllocator().buffer(capacity: 0)
         try self.serialize(parts: parts, boundary: boundary, into: &buffer)
-        return String(decoding: buffer.readableBytesView, as: UTF8.self)
+        return String(buffer: buffer)
+    }
+
+    /// Serializes the `MultipartForm` to data.
+    ///
+    ///     let data = try MultipartSerializer().serializeToData(parts: [part], boundary: "123")
+    ///     print(data) // multipart-encoded
+    ///
+    /// - Parameters:
+    ///     - parts: One or more `MultipartPart`s to serialize into `Data`.
+    ///     - boundary: The multipart boundary to use for encoding. This string must not appear in the encoded data.
+    /// - Throws: Any errors that may occur during serialization.
+    /// - Returns: A `multipart`-encoded `Data`.
+    public func serializeToData(parts: [MultipartPart], boundary: String) throws -> Data {
+        var buffer = ByteBufferAllocator().buffer(capacity: 0)
+        try self.serialize(parts: parts, boundary: boundary, into: &buffer)
+        return Data(buffer: buffer, byteTransferStrategy: .automatic)
     }
 
     /// Serializes the `MultipartForm` into a `ByteBuffer`.
@@ -30,11 +48,11 @@ public final class MultipartSerializer: Sendable {
     ///     try MultipartSerializer().serialize(parts: [part], boundary: "123", into: &buffer)
     ///     print(String(buffer: buffer)) // multipart-encoded
     ///
-    /// - parameters:
+    /// - Parameters:
     ///     - parts: One or more `MultipartPart`s to serialize into `Data`.
-    ///     - boundary: Multipart boundary to use for encoding. This must not appear anywhere in the encoded data.
+    ///     - boundary: The multipart boundary to use for encoding. This string must not appear in the encoded data.
     ///     - buffer: Buffer to write to.
-    /// - throws: Any errors that may occur during serialization.
+    /// - Throws: Any errors that may occur during serialization.
     public func serialize(parts: [MultipartPart], boundary: String, into buffer: inout ByteBuffer) throws {
         for part in parts {
             buffer.writeString("--")

Tests/MultipartKitTests/MultipartTests.swift

@@ -141,6 +141,46 @@ class MultipartTests: XCTestCase {
         }
     }
 
+    func testFormDataCodingToFromStringWithJPEG() throws {
+        guard let resourceURL = Bundle.module.url(forResource: "image", withExtension: "jpeg") else {
+            XCTFail("image.jpeg file missing from package resource")
+            return
+        }
+        let originalData = try Data(contentsOf: resourceURL)
+
+        struct ObjectToEncode: Codable {
+            let data: Data
+        }
+
+        let object = ObjectToEncode(data: originalData)
+        let boundary = UUID().uuidString
+
+        let encoded = try FormDataEncoder().encode(object, boundary: boundary)
+        let decoded = try FormDataDecoder().decode(ObjectToEncode.self, from: encoded, boundary: boundary)
+
+        XCTAssertEqual(originalData, decoded.data)
+    }
+
+    func testFormDataCodingToFromDataWithJPEG() throws {
+        guard let resourceURL = Bundle.module.url(forResource: "image", withExtension: "jpeg") else {
+            XCTFail("image.jpeg file missing from package resource")
+            return
+        }
+        let originalData = try Data(contentsOf: resourceURL)
+
+        struct ObjectToEncode: Codable {
+            let data: Data
+        }
+
+        let object = ObjectToEncode(data: originalData)
+        let boundary = UUID().uuidString
+
+        let encoded = try FormDataEncoder().encodeToData(object, boundary: boundary)
+        let decoded = try FormDataDecoder().decode(ObjectToEncode.self, from: encoded, boundary: boundary)
+
+        XCTAssertEqual(originalData, decoded.data)
+    }
+
     func testDocBlocks() throws {
         do {
             /// Content-Type: multipart/form-data; boundary=123