native implementation and fix test import

Author: sidepelican

Samples/SwiftJavaExtractFFMSampleApp/src/jmh/java/org/swift/swiftkit/ffm/FFMDataBenchmark.java

@@ -14,7 +14,6 @@
 
 package org.swift.swiftkit.ffm;
 
-import com.example.swift.Data;
 import com.example.swift.MySwiftLibrary;
 import org.openjdk.jmh.annotations.*;
 import org.openjdk.jmh.infra.Blackhole;
@@ -79,7 +78,7 @@ public ByteBuffer ffm_data_withUnsafeBytes_asByteBuffer() {
       });
       return buf.value;
     }
-    
+
     @Benchmark
     public byte[] ffm_data_withUnsafeBytes_toArray() {
       Holder<byte[]> buf = new Holder<>();

Samples/SwiftJavaExtractFFMSampleApp/src/test/java/com/example/swift/DataImportTest.java

@@ -16,6 +16,7 @@
 
 import org.junit.jupiter.api.Test;
 import org.swift.swiftkit.ffm.AllocatingSwiftArena;
+import org.swift.swiftkit.ffm.foundation.Data;
 
 import java.lang.foreign.ValueLayout;
 
@@ -134,7 +135,7 @@ void test_Data_toByteBuffer_emptyData() {
             byte[] original = new byte[0];
             var data = Data.fromByteArray(original, arena);
             var buffer = data.toByteBuffer(arena);
-            
+
             assertEquals(0, buffer.capacity());
         }
     }

Samples/SwiftJavaExtractFFMSampleApp/src/test/java/com/example/swift/OptionalImportTest.java

@@ -16,6 +16,7 @@
 
 import org.junit.jupiter.api.Test;
 import org.swift.swiftkit.ffm.AllocatingSwiftArena;
+import org.swift.swiftkit.ffm.foundation.Data;
 
 import java.util.Optional;
 import java.util.OptionalLong;

Sources/SwiftRuntimeFunctions/foundation/Data+FFM.swift

@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
+import Foundation
+#endif
+
+
+// ==== --------------------------------------------------
+// Thunks for Data
+
+@_cdecl("swiftjava_getType_SwiftRuntimeFunctions_Data")
+public func swiftjava_getType_SwiftRuntimeFunctions_Data() -> UnsafeMutableRawPointer /* Any.Type */ {
+  return unsafeBitCast(Data.self, to: UnsafeMutableRawPointer.self)
+}
+
+@_cdecl("swiftjava_SwiftRuntimeFunctions_Data_init_bytes_count")
+public func swiftjava_SwiftRuntimeFunctions_Data_init_bytes_count(_ bytes: UnsafeRawPointer, _ count: Int, _ _result: UnsafeMutableRawPointer) {
+  _result.assumingMemoryBound(to: Data.self).initialize(to: Data(bytes: bytes, count: count))
+}
+
+@_cdecl("swiftjava_SwiftRuntimeFunctions_Data_init__")
+public func swiftjava_SwiftRuntimeFunctions_Data_init__(_ bytes_pointer: UnsafeRawPointer, _ bytes_count: Int, _ _result: UnsafeMutableRawPointer) {
+  _result.assumingMemoryBound(to: Data.self).initialize(to: Data([UInt8](UnsafeRawBufferPointer(start: bytes_pointer, count: bytes_count))))
+}
+
+@_cdecl("swiftjava_SwiftRuntimeFunctions_Data_count$get")
+public func swiftjava_SwiftRuntimeFunctions_Data_count$get(_ self: UnsafeRawPointer) -> Int {
+  return self.assumingMemoryBound(to: Data.self).pointee.count
+}
+
+@_cdecl("swiftjava_SwiftRuntimeFunctions_Data_withUnsafeBytes__")
+public func swiftjava_SwiftRuntimeFunctions_Data_withUnsafeBytes__(_ body: @convention(c) (UnsafeRawPointer?, Int) -> Void, _ self: UnsafeRawPointer) {
+  self.assumingMemoryBound(to: Data.self).pointee.withUnsafeBytes({ (_0) in
+    return body(_0.baseAddress, _0.count)
+  })
+}
+
+@_cdecl("swiftjava_SwiftRuntimeFunctions_Data_copyBytes__")
+public func swiftjava_SwiftRuntimeFunctions_Data_copyBytes__(
+  selfPointer: UnsafeRawPointer,
+  destinationPointer: UnsafeMutableRawPointer,
+  count: Int
+) {
+  let data = selfPointer.assumingMemoryBound(to: Data.self).pointee
+  data.withUnsafeBytes { buffer in
+    destinationPointer.copyMemory(from: buffer.baseAddress!, byteCount: count)
+  }
+}
+
+// ==== --------------------------------------------------
+// Thunks for DataProtocol
+
+@_cdecl("swiftjava_getType_SwiftRuntimeFunctions_DataProtocol")
+public func swiftjava_getType_SwiftRuntimeFunctions_DataProtocol() -> UnsafeMutableRawPointer /* Any.Type */ {
+  return unsafeBitCast((any DataProtocol).self, to: UnsafeMutableRawPointer.self)
+}