[JExtract] Add support for JNI member methods (#305)

Author: madsodgaard

Samples/JExtractJNISampleApp/Sources/MySwiftLibrary/MySwiftClass.swift

@@ -34,4 +34,20 @@ public class MySwiftClass {
   deinit {
     p("deinit called!")
   }
+
+  public func sum() -> Int64 {
+    return x + y
+  }
+
+  public func xMultiplied(by z: Int64) -> Int64 {
+    return x * z;
+  }
+
+  enum MySwiftClassError: Error {
+    case swiftError
+  }
+
+  public func throwingFunction() throws {
+    throw MySwiftClassError.swiftError
+  }
 }

Samples/JExtractJNISampleApp/src/main/java/com/example/swift/HelloJava2SwiftJNI.java

@@ -44,6 +44,12 @@ static void examples() {
         try (var arena = new ConfinedSwiftMemorySession(Thread.currentThread())) {
             MySwiftClass myClass = MySwiftClass.init(10, 5, arena);
             MySwiftClass myClass2 = MySwiftClass.init(arena);
+
+            try {
+                myClass.throwingFunction();
+            } catch (Exception e) {
+                System.out.println("Caught exception: " + e.getMessage());
+            }
         }
 
         System.out.println("DONE.");

Samples/JExtractJNISampleApp/src/test/java/com/example/swift/MySwiftClassTest.java

@@ -35,4 +35,30 @@ void init_withParameters() {
             assertNotNull(c);
         }
     }
+
+    @Test
+    void sum() {
+        try (var arena = new ConfinedSwiftMemorySession(Thread.currentThread())) {
+            MySwiftClass c = MySwiftClass.init(20, 10, arena);
+            assertEquals(30, c.sum());
+        }
+    }
+
+    @Test
+    void xMultiplied() {
+        try (var arena = new ConfinedSwiftMemorySession(Thread.currentThread())) {
+            MySwiftClass c = MySwiftClass.init(20, 10, arena);
+            assertEquals(200, c.xMultiplied(10));
+        }
+    }
+
+    @Test
+    void throwingFunction() {
+        try (var arena = new ConfinedSwiftMemorySession(Thread.currentThread())) {
+            MySwiftClass c = MySwiftClass.init(20, 10, arena);
+            Exception exception = assertThrows(Exception.class, () -> c.throwingFunction());
+
+            assertEquals("swiftError", exception.getMessage());
+        }
+    }
 }

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -164,12 +164,49 @@ extension JNISwift2JavaGenerator {
   }
 
   private func printFunctionBinding(_ printer: inout CodePrinter, _ decl: ImportedFunc) {
+    if decl.isStatic || decl.isInitializer || !decl.hasParent {
+      printStaticFunctionBinding(&printer, decl)
+    } else {
+      printMemberMethodBindings(&printer, decl)
+    }
+  }
+
+  private func printStaticFunctionBinding(_ printer: inout CodePrinter, _ decl: ImportedFunc) {
     printDeclDocumentation(&printer, decl)
     printer.print(
       "public static native \(renderFunctionSignature(decl));"
     )
   }
 
+  /// Renders Java bindings for member methods
+  ///
+  /// Member methods are generated as a function that extracts the `selfPointer`
+  /// and passes it down to another native function along with the arguments
+  /// to call the Swift implementation.
+  private func printMemberMethodBindings(_ printer: inout CodePrinter, _ decl: ImportedFunc) {
+    let translatedDecl = translatedDecl(for: decl)
+
+    printDeclDocumentation(&printer, decl)
+    printer.printBraceBlock("public \(renderFunctionSignature(decl))") { printer in
+      var arguments = translatedDecl.translatedFunctionSignature.parameters.map(\.name)
+      arguments.append("selfPointer")
+
+      let returnKeyword = translatedDecl.translatedFunctionSignature.resultType.isVoid ? "" : "return "
+
+      printer.print(
+        """
+        long selfPointer = this.pointer();
+        \(returnKeyword)\(translatedDecl.parentName).$\(translatedDecl.name)(\(arguments.joined(separator: ", ")));
+        """
+      )
+    }
+
+    let returnType = translatedDecl.translatedFunctionSignature.resultType
+    var parameters = translatedDecl.translatedFunctionSignature.parameters.map(\.asParameter)
+    parameters.append("long selfPointer")
+    printer.print("private static native \(returnType) $\(translatedDecl.name)(\(parameters.joined(separator: ", ")));")
+  }
+
   private func printInitializerBindings(_ printer: inout CodePrinter, _ decl: ImportedFunc, type: ImportedNominalType) {
     let translatedDecl = translatedDecl(for: decl)
 

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -136,67 +136,97 @@ extension JNISwift2JavaGenerator {
     _ printer: inout CodePrinter,
     _ decl: ImportedFunc
   ) {
+    // Free functions does not have a parent
+    if decl.isStatic || !decl.hasParent {
+      self.printSwiftStaticFunctionThunk(&printer, decl)
+    } else {
+      self.printSwiftMemberFunctionThunk(&printer, decl)
+    }
+  }
+
+  private func printSwiftStaticFunctionThunk(_ printer: inout CodePrinter, _ decl: ImportedFunc) {
     let translatedDecl = self.translatedDecl(for: decl)
-    let parentName = translatedDecl.parentName
-    let swiftReturnType = decl.functionSignature.result.type
 
-    printCDecl(&printer, decl) { printer in
-      let downcallParameters = renderDowncallArguments(
-        swiftFunctionSignature: decl.functionSignature,
-        translatedFunctionSignature: translatedDecl.translatedFunctionSignature
+    printCDecl(
+      &printer,
+      javaMethodName: translatedDecl.name,
+      parentName: translatedDecl.parentName,
+      parameters: translatedDecl.translatedFunctionSignature.parameters,
+      isStatic: true,
+      resultType: translatedDecl.translatedFunctionSignature.resultType
+    ) { printer in
+      // For free functions the parent is the Swift module
+      let parentName = decl.parentType?.asNominalTypeDeclaration?.qualifiedName ?? swiftModuleName
+      self.printFunctionDowncall(&printer, decl, calleeName: parentName)
+    }
+  }
+
+  private func printSwiftMemberFunctionThunk(_ printer: inout CodePrinter, _ decl: ImportedFunc) {
+    let translatedDecl = self.translatedDecl(for: decl)
+    let swiftParentName = decl.parentType!.asNominalTypeDeclaration!.qualifiedName
+
+    printCDecl(
+      &printer,
+      javaMethodName: "$\(translatedDecl.name)",
+      parentName: translatedDecl.parentName,
+      parameters: translatedDecl.translatedFunctionSignature.parameters + [
+        JavaParameter(name: "selfPointer", type: .long)
+      ],
+      isStatic: true,
+      resultType: translatedDecl.translatedFunctionSignature.resultType
+    ) { printer in
+      printer.print(
+        """
+        let self$ = UnsafeMutablePointer<\(swiftParentName)>(bitPattern: Int(Int64(fromJNI: selfPointer, in: environment!)))!
+        """
       )
-      let tryClause: String = decl.isThrowing ? "try " : ""
-      let functionDowncall =
-        "\(tryClause)\(parentName).\(decl.name)(\(downcallParameters))"
-
-      let innerBody =
-        if swiftReturnType.isVoid {
-          functionDowncall
-        } else {
-          """
-          let result = \(functionDowncall)
-          return result.getJNIValue(in: environment)
-          """
-        }
+      self.printFunctionDowncall(&printer, decl, calleeName: "self$.pointee")
+    }
+  }
+
+  private func printFunctionDowncall(
+    _ printer: inout CodePrinter,
+    _ decl: ImportedFunc,
+    calleeName: String
+  ) {
+    let translatedDecl = self.translatedDecl(for: decl)
+    let swiftReturnType = decl.functionSignature.result.type
+
+    let downcallParameters = renderDowncallArguments(
+      swiftFunctionSignature: decl.functionSignature,
+      translatedFunctionSignature: translatedDecl.translatedFunctionSignature
+    )
+    let tryClause: String = decl.isThrowing ? "try " : ""
+    let functionDowncall = "\(tryClause)\(calleeName).\(decl.name)(\(downcallParameters))"
+
+    let returnStatement =
+    if swiftReturnType.isVoid {
+      functionDowncall
+    } else {
+      """
+      let result = \(functionDowncall)
+      return result.getJNIValue(in: environment)
+      """
+    }
 
-      if decl.isThrowing {
-        let dummyReturn =
-          !swiftReturnType.isVoid ? "return \(swiftReturnType).jniPlaceholderValue" : ""
-        printer.print(
+    if decl.isThrowing {
+      let dummyReturn =
+      !swiftReturnType.isVoid ? "return \(swiftReturnType).jniPlaceholderValue" : ""
+      printer.print(
           """
           do {
-            \(innerBody)
+            \(returnStatement)
           } catch {
             environment.throwAsException(error)
             \(dummyReturn)
           }
           """
-        )
-      } else {
-        printer.print(innerBody)
-      }
+      )
+    } else {
+      printer.print(returnStatement)
     }
   }
 
-  private func printCDecl(
-    _ printer: inout CodePrinter,
-    _ decl: ImportedFunc,
-    _ body: (inout CodePrinter) -> Void
-  ) {
-    let translatedDecl = translatedDecl(for: decl)
-    let parentName = translatedDecl.parentName
-
-    printCDecl(
-      &printer,
-      javaMethodName: translatedDecl.name,
-      parentName: parentName,
-      parameters: translatedDecl.translatedFunctionSignature.parameters,
-      isStatic: decl.isStatic || decl.isInitializer || !decl.hasParent,
-      resultType: translatedDecl.translatedFunctionSignature.resultType,
-      body
-    )
-  }
-
   private func printCDecl(
     _ printer: inout CodePrinter,
     javaMethodName: String,

Sources/JavaKit/Exceptions/ExceptionHandling.swift

@@ -39,7 +39,7 @@ extension JNIEnvironment {
     }
 
     // Otherwise, create a exception with a message.
-    _ = try! JavaClass<Exception>.withJNIClass(in: self) { exceptionClass in
+    _ = try! Exception.withJNIClass(in: self) { exceptionClass in
       interface.ThrowNew(self, exceptionClass, String(describing: error))
     }
   }

Tests/JExtractSwiftTests/JNI/JNIClassTests.swift

@@ -33,6 +33,8 @@ struct JNIClassTests {
         self.x = 0
         self.y = 0
       }
+  
+      public func doSomething(x: Int64) {}
     }
   """
 
@@ -206,4 +208,49 @@ struct JNIClassTests {
       ]
     )
   }
+
+  @Test
+  func memberMethod_javaBindings() throws {
+    try assertOutput(
+      input: source,
+      .jni,
+      .java,
+      expectedChunks: [
+        """
+        /**
+          * Downcall to Swift:
+          * {@snippet lang=swift :
+          * public func doSomething(x: Int64)
+          * }
+          */
+        public void doSomething(long x) {
+          long selfPointer = this.pointer();
+          MyClass.$doSomething(x, selfPointer);
+        }
+        """,
+        """
+        private static native void $doSomething(long x, long selfPointer);
+        """
+      ]
+    )
+  }
+
+  @Test
+  func memberMethod_swiftThunks() throws {
+    try assertOutput(
+      input: source,
+      .jni,
+      .swift,
+      detectChunkByInitialLines: 1,
+      expectedChunks: [
+        """
+        @_cdecl("Java_com_example_swift_MyClass__00024doSomething__JJ")
+        func Java_com_example_swift_MyClass__00024doSomething__JJ(environment: UnsafeMutablePointer<JNIEnv?>!, thisClass: jclass, x: jlong, selfPointer: jlong) {
+          let self$ = UnsafeMutablePointer<MyClass>(bitPattern: Int(Int64(fromJNI: selfPointer, in: environment!)))!
+          self$.pointee.doSomething(x: Int64(fromJNI: x, in: environment!))
+        }
+        """,
+      ]
+    )
+  }
 }