Add encoding function that returns Data. Fixes #94

Package.swift

@@ -29,6 +29,8 @@ let package = Package(
             name: "MultipartKitTests",
             dependencies: [
                 .target(name: "MultipartKit"),
+            ], resources: [
+                .copy("Utilities/image.jpeg"),
             ]
         ),
     ]

Sources/MultipartKit/FormDataDecoder/FormDataDecoder.swift

@@ -1,3 +1,4 @@
+import Foundation
 import NIOCore
 import NIOHTTP1
 
@@ -37,6 +38,22 @@ public struct FormDataDecoder: Sendable {
         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: "...", boundary: "123")
+    ///
+    /// - Parameters:
+    ///   - decodable: Generic `Decodable` type.
+    ///   - data: String to decode.
+    ///   - boundary: Multipart boundary to used in the decoding.
+    /// - 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 {
+        var buffer = ByteBufferAllocator().buffer(capacity: data.count)
+        buffer.writeBytes(data)
+        return try decode(D.self, from: buffer, boundary: boundary)
+    }
+
     /// Decodes a `Decodable` item from `Data` using the supplied boundary.
     ///
     ///     let foo = try FormDataDecoder().decode(Foo.self, from: data, boundary: "123")

Sources/MultipartKit/FormDataEncoder/FormDataEncoder.swift

@@ -1,3 +1,4 @@
+import Foundation
 import NIOCore
 
 /// Encodes `Encodable` items to `multipart/form-data` encoded `Data`.
@@ -26,6 +27,20 @@ public struct FormDataEncoder: Sendable {
     public func encode<E: Encodable>(_ encodable: E, 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: 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 encodeToData<E: Encodable>(_ encodable: E, boundary: String) throws -> Data {
+        try MultipartSerializer().serializeToData(parts: parts(from: encodable), boundary: boundary)
+    }
 
     /// Encodes an `Encodable` item into a `ByteBuffer` using the supplied boundary.
     ///

Sources/MultipartKit/MultipartSerializer.swift

@@ -1,3 +1,4 @@
+import Foundation
 import NIOCore
 
 /// Serializes `MultipartForm`s to `Data`.
@@ -14,7 +15,7 @@ public final class MultipartSerializer: Sendable {
     ///     print(data) // multipart-encoded
     ///
     /// - parameters:
-    ///     - parts: One or more `MultipartPart`s to serialize into `Data`.
+    ///     - parts: One or more `MultipartPart`s to serialize into `String`.
     ///     - 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`.
@@ -23,6 +24,22 @@ public final class MultipartSerializer: Sendable {
         try self.serialize(parts: parts, boundary: boundary, into: &buffer)
         return String(decoding: buffer.readableBytesView, as: UTF8.self)
     }
+
+    /// 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: 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`.
+    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.readableBytesView)
+    }
 
     /// Serializes the `MultipartForm` into a `ByteBuffer`.
     ///

Tests/MultipartKitTests/MultipartTests.swift

@@ -141,6 +141,42 @@ class MultipartTests: XCTestCase {
         }
     }
 
+    func testFormDataCodingToFromStringWithJPEG() throws {
+        let folder = #filePath.split(separator: "/").dropLast().joined(separator: "/")
+        let path = "/" + folder + "/Utilities/image.jpeg"
+        let originalData = try Data(contentsOf: URL(fileURLWithPath: path))
+
+        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 {
+        let folder = #filePath.split(separator: "/").dropLast().joined(separator: "/")
+        let path = "/" + folder + "/Utilities/image.jpeg"
+        let originalData = try Data(contentsOf: URL(fileURLWithPath: path))
+
+        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