output swift thunk for JNI

Author: madsodgaard

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator.swift

@@ -14,7 +14,7 @@
 
 import JavaTypes
 
-struct JNISwift2JavaGenerator: Swift2JavaGenerator {
+class JNISwift2JavaGenerator: Swift2JavaGenerator {
   let analysis: AnalysisResult
   let swiftModuleName: String
   let javaPackage: String
@@ -26,6 +26,8 @@ struct JNISwift2JavaGenerator: Swift2JavaGenerator {
     javaPackage.replacingOccurrences(of: ".", with: "/")
   }
 
+  var thunkNameRegistry = ThunkNameRegistry()
+
   init(
     translator: Swift2JavaTranslator,
     javaPackage: String,
@@ -41,6 +43,7 @@ struct JNISwift2JavaGenerator: Swift2JavaGenerator {
   }
 
   func generate() throws {
+    try writeSwiftThunkSources()
     try writeExportedJavaSources()
   }
 }
@@ -61,6 +64,84 @@ extension JNISwift2JavaGenerator {
       logger.info("[swift-java] Generated: \(self.swiftModuleName).java (at \(outputFile))")
     }
   }
+
+  func writeSwiftThunkSources() throws {
+    var printer = CodePrinter()
+
+    let moduleFilenameBase = "\(self.swiftModuleName)Module+SwiftJava"
+    let moduleFilename = "\(moduleFilenameBase).swift"
+
+    logger.trace("Printing swift module class: \(moduleFilename)")
+
+    try printGlobalSwiftThunkSources(&printer)
+
+    if let outputFile = try printer.writeContents(
+      outputDirectory: self.swiftOutputDirectory,
+      javaPackagePath: nil,
+      filename: moduleFilename)
+    {
+      print("[swift-java] Generated: \(moduleFilenameBase.bold).swift (at \(outputFile)")
+    }
+  }
+}
+
+extension JNISwift2JavaGenerator {
+  private func printGlobalSwiftThunkSources(_ printer: inout CodePrinter) throws {
+    printer.print(
+      """
+      // Generated by swift-java
+
+      import JavaKit
+
+      """)
+
+    for decl in analysis.importedGlobalFuncs {
+      printSwiftFunctionThunk(&printer, decl)
+      printer.println()
+    }
+  }
+
+  private func printSwiftFunctionThunk(_ printer: inout CodePrinter, _ decl: ImportedFunc) {
+    // TODO: Replace swiftModuleName with class name if non-global
+    let cName = "Java_" + self.javaPackage.replacingOccurrences(of: ".", with: "_") + "_\(swiftModuleName)_" + decl.name
+    let thunkName = thunkNameRegistry.functionThunkName(decl: decl)
+    let translatedParameters = decl.functionSignature.parameters.enumerated().map { idx, param in
+      (param.parameterName ?? "arg\(idx)", param.type.javaType)
+    }
+
+    let thunkParameters = [
+      "environment: UnsafeMutablePointer<JNIEnv?>!",
+      "thisClass: jclass"
+    ] + translatedParameters.map { "\($0.0): \($0.1.jniTypeName)"}
+    let swiftReturnType = decl.functionSignature.result.type
+
+    let thunkReturnType = !swiftReturnType.isVoid ? " -> \(swiftReturnType.javaType.jniTypeName)" : ""
+
+    printer.printBraceBlock(
+      """
+      @_cdecl("\(cName)")
+      func \(thunkName)(\(thunkParameters.joined(separator: ", ")))\(thunkReturnType)
+      """
+    ) { printer in
+      let downcallParameters = zip(decl.functionSignature.parameters, translatedParameters).map { originalParam, translatedParam in
+        let label = originalParam.argumentLabel ?? originalParam.parameterName ?? ""
+        return "\(label)\(!label.isEmpty ? ": " : "")\(translatedParam.0)"
+      }
+      let functionDowncall = "\(swiftModuleName).\(decl.name)(\(downcallParameters.joined(separator: ", ")))"
+      printer.print("\(functionDowncall)")
+
+      if swiftReturnType.isVoid {
+        printer.print(functionDowncall)
+      } else {
+        printer.print(
+          """
+          let result = \(functionDowncall)
+          return result.getJNIValue(in: environment)")
+          """
+        )
+      }
+    }
+  }
 }
 
 extension JNISwift2JavaGenerator {
@@ -72,6 +153,7 @@ extension JNISwift2JavaGenerator {
       for decl in analysis.importedGlobalFuncs {
         self.logger.trace("Print global function: \(decl)")
         printFunctionBinding(&printer, decl)
+        printer.println()
       }
     }
   }
@@ -103,10 +185,20 @@ extension JNISwift2JavaGenerator {
 
   private func printFunctionBinding(_ printer: inout CodePrinter, _ decl: ImportedFunc) {
     let returnType = decl.functionSignature.result.type.javaType
-    let params = decl.functionSignature.parameters.map {
-      "\($0.type.javaType) \($0.parameterName!)"
+    let params = decl.functionSignature.parameters.enumerated().map { idx, param in
+      "\(param.type.javaType) \(param.parameterName ?? "arg\(idx))")"
     }
 
+    printer.print(
+      """
+      /**
+      * Downcall to Swift:
+      * {@snippet lang=swift :
+      * \(decl.signatureString)
+      * }
+      */
+      """
+    )
     printer.print("public static native \(returnType) \(decl.name)(\(params.joined(separator: ", ")));")
   }
 }
@@ -128,7 +220,7 @@ extension SwiftType {
       return .void
 
     case .metatype, .optional, .tuple, .function:
-      fatalError("unsupported")
+      fatalError("unsupported type: \(self)")
     }
   }
 }

Sources/JavaTypes/JavaType+JNI.swift

@@ -14,7 +14,7 @@
 
 extension JavaType {
   /// Map this Java type to the appropriate JNI type name.
-  var jniTypeName: String {
+  package var jniTypeName: String {
     switch self {
     case .boolean: "jboolean"
     case .float: "jfloat"