jextract: Move Foundation support into a common package with code generation

.licenseignore

@@ -52,3 +52,7 @@ Samples/JavaDependencySampleApp/gradle
 Sources/_Subprocess/**
 Sources/_SubprocessCShims/**
 Samples/gradle
+Sources/SwiftJavaRuntimeSupport/Foundation/*
+Sources/SwiftRuntimeFunctions/Foundation/*
+SwiftKitCore/src/main/java/org/swift/swiftkit/core/foundation/*
+SwiftKitFFM/src/main/java/org/swift/swiftkit/ffm/foundation/*

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

@@ -14,10 +14,10 @@
 
 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;
+import org.swift.swiftkit.ffm.foundation.Data;
 
 import java.lang.foreign.MemorySegment;
 import java.lang.foreign.ValueLayout;
@@ -79,7 +79,7 @@ public ByteBuffer ffm_data_withUnsafeBytes_asByteBuffer() {
       });
       return buf.value;
     }
-    
+
     @Benchmark
     public byte[] ffm_data_withUnsafeBytes_toArray() {
       Holder<byte[]> buf = new Holder<>();

Samples/SwiftJavaExtractFFMSampleApp/src/main/java/com/example/swift/HelloJava2Swift.java

@@ -22,6 +22,7 @@
 import org.swift.swiftkit.core.SwiftLibraries;
 import org.swift.swiftkit.ffm.AllocatingSwiftArena;
 import org.swift.swiftkit.ffm.SwiftRuntime;
+import org.swift.swiftkit.ffm.foundation.Data;
 
 import java.util.Optional;
 import java.util.OptionalLong;
@@ -85,7 +86,7 @@ static void examples() {
             var origBytes = arena.allocateFrom("foobar");
             var origDat = Data.init(origBytes, origBytes.byteSize(), arena);
             CallTraces.trace("origDat.count = " + origDat.getCount());
-            
+
             var retDat = MySwiftLibrary.globalReceiveReturnData(origDat, arena);
             retDat.withUnsafeBytes((retBytes) -> {
                 var str = retBytes.getString(0);

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;

Samples/SwiftJavaExtractJNISampleApp/src/jmh/java/com/example/swift/JNIDataBenchmark.java

@@ -18,6 +18,7 @@
 import org.openjdk.jmh.infra.Blackhole;
 import org.swift.swiftkit.core.ClosableSwiftArena;
 import org.swift.swiftkit.core.SwiftArena;
+import org.swift.swiftkit.core.foundation.Data;
 
 import java.util.concurrent.TimeUnit;
 

Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift/DataTest.java

@@ -16,6 +16,7 @@
 
 import org.junit.jupiter.api.Test;
 import org.swift.swiftkit.core.SwiftArena;
+import org.swift.swiftkit.core.foundation.Data;
 
 import static org.junit.jupiter.api.Assertions.*;
 

Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift/DateTest.java

@@ -16,6 +16,7 @@
 
 import org.junit.jupiter.api.Test;
 import org.swift.swiftkit.core.SwiftArena;
+import org.swift.swiftkit.core.foundation.Date;
 
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
@@ -59,4 +60,4 @@ void date_timeIntervalSince1970() {
             assertEquals(1000, date.getTimeIntervalSince1970());
         }
     }
-}
+}

Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift/OptionalsTest.java

@@ -14,9 +14,10 @@
 
 package com.example.swift;
 
-import com.example.swift.MySwiftLibrary;
 import org.junit.jupiter.api.Test;
 import org.swift.swiftkit.core.SwiftArena;
+import org.swift.swiftkit.core.foundation.Data;
+import org.swift.swiftkit.core.foundation.Date;
 
 import java.time.Instant;
 import java.util.Optional;
@@ -143,4 +144,4 @@ void optionalThrows() {
             assertEquals("swiftError", exception.getMessage());
         }
     }
-}
+}

Sources/FakeFoundation/Data.swift

@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+public struct Data: DataProtocol {
+  public init(bytes: UnsafeRawPointer, count: Int)
+  public init(_ bytes: [UInt8])
+  public var count: Int { get }
+  public func withUnsafeBytes(_ body: (UnsafeRawBufferPointer) -> Void)
+}

Sources/FakeFoundation/DataProtocol.swift

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+public protocol DataProtocol {}

Sources/FakeFoundation/Date.swift

@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+public struct Date {
+  /// The interval between the date object and 00:00:00 UTC on 1 January 1970.
+  public var timeIntervalSince1970: Double { get }
+
+  /// Returns a `Date` initialized relative to 00:00:00 UTC on 1 January 1970 by a given number of seconds.
+  public init(timeIntervalSince1970: Double)
+}

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -456,6 +456,8 @@ extension FFMSwift2JavaGenerator {
       let arena =
         if let className = type.className,
           analysis.importedTypes[className] != nil
+            || type == .swiftkitFFMFoundationData
+            || type == .swiftkitFFMFoundationDataProtocol
         {
           // Use passed-in 'SwiftArena' for 'SwiftValue'.
           "swiftArena"
@@ -619,7 +621,9 @@ extension FFMSwift2JavaGenerator {
   func renderMemoryLayoutValue(for javaType: JavaType) -> String {
     if let layout = ForeignValueLayout(javaType: javaType) {
       return layout.description
-    } else if case .class(package: _, name: let customClass, _) = javaType {
+    } else if case .class(.some(let package), name: let customClass, _) = javaType {
+      return ForeignValueLayout(customType: "\(package).\(customClass)").description
+    } else if case .class(.none, name: let customClass, _) = javaType {
       return ForeignValueLayout(customType: customClass).description
     } else {
       fatalError("renderMemoryLayoutValue not supported for \(javaType)")
@@ -776,7 +780,7 @@ extension FFMSwift2JavaGenerator.JavaConversionStep {
 
     case .wrapMemoryAddressUnsafe(let inner, let javaType):
       let inner = inner.render(&printer, placeholder, placeholderForDowncall: placeholderForDowncall)
-      return "\(javaType.className!).wrapMemoryAddressUnsafe(\(inner), swiftArena)"
+      return "\(javaType).wrapMemoryAddressUnsafe(\(inner), swiftArena)"
 
     case .construct(let inner, let javaType):
       let inner = inner.render(&printer, placeholder, placeholderForDowncall: placeholderForDowncall)

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator+JavaTranslation.swift

@@ -464,7 +464,15 @@ extension FFMSwift2JavaGenerator {
             )
 
           case .foundationData, .essentialsData:
-            break
+            return TranslatedParameter(
+              javaParameters: [
+                JavaParameter(
+                  name: parameterName,
+                  type: .swiftkitFFMFoundationData
+                )
+              ],
+              conversion: .swiftValueSelfSegment(.placeholder)
+            )
 
           case .swiftJavaError:
             // SwiftJavaError is a class — treat as arbitrary nominal type below
@@ -635,10 +643,26 @@ extension FFMSwift2JavaGenerator {
       case .nominal(let nominal):
         if let knownType = nominal.nominalTypeDecl.knownTypeKind {
           switch knownType {
-          case .foundationData, .foundationDataProtocol:
-            break
-          case .essentialsData, .essentialsDataProtocol:
-            break
+          case .foundationData, .essentialsData:
+            return TranslatedParameter(
+              javaParameters: [
+                JavaParameter(
+                  name: parameterName,
+                  type: .optional(.swiftkitFFMFoundationData)
+                )
+              ],
+              conversion: .call(.placeholder, function: "SwiftRuntime.toOptionalSegmentInstance", withArena: false)
+            )
+          case .foundationDataProtocol, .essentialsDataProtocol:
+            return TranslatedParameter(
+              javaParameters: [
+                JavaParameter(
+                  name: parameterName,
+                  type: .optional(.swiftkitFFMFoundationDataProtocol)
+                )
+              ],
+              conversion: .call(.placeholder, function: "SwiftRuntime.toOptionalSegmentInstance", withArena: false)
+            )
           default:
             throw JavaTranslationError.unhandledType(known: .optional(swiftType))
           }
@@ -647,7 +671,7 @@ extension FFMSwift2JavaGenerator {
         let translatedTy = try self.translate(swiftType: swiftType)
         return TranslatedParameter(
           javaParameters: [
-            JavaParameter(name: parameterName, type: JavaType(className: "Optional<\(translatedTy.description)>"))
+            JavaParameter(name: parameterName, type: .optional(translatedTy))
           ],
           conversion: .call(.placeholder, function: "SwiftRuntime.toOptionalSegmentInstance", withArena: false)
         )
@@ -750,7 +774,15 @@ extension FFMSwift2JavaGenerator {
             )
 
           case .foundationData, .essentialsData:
-            break // Implemented as wrapper
+            let javaType: JavaType = .swiftkitFFMFoundationData
+            return TranslatedResult(
+              javaResultType: javaType,
+              annotations: resultAnnotations,
+              outParameters: [
+                JavaParameter(name: "", type: javaType)
+              ],
+              conversion: .wrapMemoryAddressUnsafe(.placeholder, javaType)
+            )
 
           case .unsafePointer, .unsafeMutablePointer:
             // FIXME: Implement

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -71,6 +71,7 @@ extension FFMSwift2JavaGenerator {
     // === All types
     // We have to write all types to their corresponding output file that matches the file they were declared in,
     // because otherwise SwiftPM plugins will not pick up files apropriately -- we expect 1 output +SwiftJava.swift file for every input.
+
     let filteredTypes: [String: ImportedNominalType]
     if let singleType = config.singleType {
       filteredTypes = self.analysis.importedTypes.filter { $0.key == singleType }
@@ -92,14 +93,13 @@ extension FFMSwift2JavaGenerator {
       let filename = "\(inputFileName)".replacing(".swift", with: "+SwiftJava.swift")
 
       // Print file header before all type thunks
-      printer.print(
-        """
-        // Generated by swift-java
-
-        import SwiftRuntimeFunctions
+      printer.print("// Generated by swift-java")
+      printer.println()
+      if !group.value.allSatisfy({ $0.value.swiftNominal.moduleName == "SwiftRuntimeFunctions" }) {
+        printer.print("import SwiftRuntimeFunctions")
+      }
+      printer.println()
 
-        """
-      )
       self.lookupContext.symbolTable.printImportedModules(&printer)
 
       for ty in importedTypesForThisFile {
@@ -263,16 +263,15 @@ struct SwiftThunkTranslator {
 
   /// Render special thunks for known types like Foundation.Data
   func renderSpecificTypeThunks(_ nominal: ImportedNominalType) -> [DeclSyntax] {
-    guard let knownType = nominal.swiftNominal.knownTypeKind else {
-      return []
-    }
-
-    switch knownType {
-    case .foundationData, .essentialsData:
-      return renderFoundationDataThunks(nominal)
-    default:
-      return []
+    if nominal.swiftNominal.moduleName == "SwiftRuntimeFunctions" {
+      switch nominal.swiftNominal.qualifiedName {
+      case "Data":
+        return renderFoundationDataThunks(nominal)
+      default:
+        break
+      }
     }
+    return []
   }
 
   /// Render Swift thunks for Foundation.Data helper methods

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator.swift

@@ -448,7 +448,7 @@ extension FFMSwift2JavaGenerator {
 
       printer.print(
         """
-        static MemorySegment findOrThrow(String symbol) {
+        public static MemorySegment findOrThrow(String symbol) {
             return SYMBOL_LOOKUP.find(symbol)
                     .orElseThrow(() -> new UnsatisfiedLinkError("unresolved symbol: %s".formatted(symbol)));
         }
@@ -557,15 +557,13 @@ extension FFMSwift2JavaGenerator {
 
   /// Print special helper methods for known types like Foundation.Data
   func printSpecificTypeHelpers(_ printer: inout CodePrinter, _ decl: ImportedNominalType) {
-    guard let knownType = decl.swiftNominal.knownTypeKind else {
-      return
-    }
-
-    switch knownType {
-    case .foundationData, .essentialsData:
-      printFoundationDataHelpers(&printer, decl)
-    default:
-      break
+    if decl.swiftNominal.moduleName == "SwiftRuntimeFunctions" {
+      switch decl.swiftNominal.qualifiedName {
+      case "Data":
+        printFoundationDataHelpers(&printer, decl)
+      default:
+        break
+      }
     }
   }