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madsodgaardktoso
madsodgaard
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ktoso
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Add JExtract JNI sample app (#295)
Co-authored-by: Konrad `ktoso` Malawski <[email protected]>
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‎.github/workflows/pull_request.yml‎

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@@ -78,6 +78,7 @@ jobs:
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'JavaSieve',
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'SwiftAndJavaJarSampleLib',
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'SwiftKitSampleApp',
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'JExtractJNISampleApp'
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]
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container:
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image: ${{ (contains(matrix.swift_version, 'nightly') && 'swiftlang/swift') || 'swift' }}:${{ matrix.swift_version }}-${{ matrix.os_version }}

‎Samples/JExtractJNISampleApp/Package.swift‎

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// swift-tools-version: 6.0
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// The swift-tools-version declares the minimum version of Swift required to build this package.
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import CompilerPluginSupport
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import PackageDescription
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import class Foundation.FileManager
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import class Foundation.ProcessInfo
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// Note: the JAVA_HOME environment variable must be set to point to where
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// Java is installed, e.g.,
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// Library/Java/JavaVirtualMachines/openjdk-21.jdk/Contents/Home.
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func findJavaHome() -> String {
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if let home = ProcessInfo.processInfo.environment["JAVA_HOME"] {
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return home
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}
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// This is a workaround for envs (some IDEs) which have trouble with
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// picking up env variables during the build process
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let path = "\(FileManager.default.homeDirectoryForCurrentUser.path()).java_home"
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if let home = try? String(contentsOfFile: path, encoding: .utf8) {
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if let lastChar = home.last, lastChar.isNewline {
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return String(home.dropLast())
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}
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return home
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}
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fatalError("Please set the JAVA_HOME environment variable to point to where Java is installed.")
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}
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let javaHome = findJavaHome()
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let javaIncludePath = "\(javaHome)/include"
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#if os(Linux)
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let javaPlatformIncludePath = "\(javaIncludePath)/linux"
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#elseif os(macOS)
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let javaPlatformIncludePath = "\(javaIncludePath)/darwin"
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#else
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// TODO: Handle windows as well
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#error("Currently only macOS and Linux platforms are supported, this may change in the future.")
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#endif
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let package = Package(
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name: "JExtractJNISampleApp",
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platforms: [
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.macOS(.v15)
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],
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products: [
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.library(
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name: "MySwiftLibrary",
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type: .dynamic,
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targets: ["MySwiftLibrary"]
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)
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],
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dependencies: [
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.package(name: "swift-java", path: "../../")
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],
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targets: [
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.target(
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name: "MySwiftLibrary",
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dependencies: [
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.product(name: "JavaKit", package: "swift-java"),
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.product(name: "JavaRuntime", package: "swift-java"),
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.product(name: "SwiftKitSwift", package: "swift-java"),
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],
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exclude: [
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"swift-java.config"
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],
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swiftSettings: [
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.swiftLanguageMode(.v5),
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.unsafeFlags(["-I\(javaIncludePath)", "-I\(javaPlatformIncludePath)"]),
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],
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plugins: [
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.plugin(name: "JExtractSwiftPlugin", package: "swift-java")
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]
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)
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]
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)

‎Samples/JExtractJNISampleApp/Sources/MySwiftLibrary/MySwiftLibrary.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of Swift.org project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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// This is a "plain Swift" file containing various types of declarations,
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// that is exported to Java by using the `jextract-swift` tool.
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//
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// No annotations are necessary on the Swift side to perform the export.
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#if os(Linux)
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import Glibc
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#else
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import Darwin.C
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#endif
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public func helloWorld() {
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p("\(#function)")
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}
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public func globalTakeInt(i: Int64) {
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p("i:\(i)")
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}
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public func globalMakeInt() -> Int64 {
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return 42
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}
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public func globalWriteString(string: String) -> Int64 {
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return Int64(string.count)
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}
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public func globalTakeIntInt(i: Int64, j: Int64) {
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p("i:\(i), j:\(j)")
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}
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// ==== Internal helpers
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func p(_ msg: String, file: String = #fileID, line: UInt = #line, function: String = #function) {
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print("[swift][\(file):\(line)](\(function)) \(msg)")
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fflush(stdout)
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}
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#if os(Linux)
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// FIXME: why do we need this workaround?
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@_silgen_name("_objc_autoreleaseReturnValue")
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public func _objc_autoreleaseReturnValue(a: Any) {}
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@_silgen_name("objc_autoreleaseReturnValue")
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public func objc_autoreleaseReturnValue(a: Any) {}
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#endif

‎Samples/JExtractJNISampleApp/Sources/MySwiftLibrary/swift-java.config‎

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{
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"javaPackage": "com.example.swift",
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"mode": "jni"
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}

‎Samples/JExtractJNISampleApp/build.gradle‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2024 Apple Inc. and the Swift.org project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of Swift.org project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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import groovy.json.JsonSlurper
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import org.swift.swiftkit.gradle.BuildUtils
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import java.nio.file.*
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import kotlinx.serialization.json.*
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plugins {
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id("build-logic.java-application-conventions")
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id("me.champeau.jmh") version "0.7.2"
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}
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group = "org.swift.swiftkit"
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version = "1.0-SNAPSHOT"
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repositories {
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mavenCentral()
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}
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java {
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toolchain {
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languageVersion.set(JavaLanguageVersion.of(24))
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}
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}
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def swiftProductsWithJExtractPlugin() {
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def stdout = new ByteArrayOutputStream()
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def stderr = new ByteArrayOutputStream()
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def result = exec {
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commandLine 'swift', 'package', 'describe', '--type', 'json'
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standardOutput = stdout
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errorOutput = stderr
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ignoreExitValue = true
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}
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def jsonOutput = stdout.toString()
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if (result.exitValue == 0) {
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def json = new JsonSlurper().parseText(jsonOutput)
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def products = json.targets
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.findAll { target ->
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target.product_dependencies?.contains("JExtractSwiftPlugin")
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}
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.collectMany { target ->
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target.product_memberships ?: []
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}
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return products
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} else {
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logger.warn("Command failed: ${stderr.toString()}")
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return []
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}
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}
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def swiftCheckValid = tasks.register("swift-check-valid", Exec) {
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commandLine "swift"
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args("-version")
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}
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def jextract = tasks.register("jextract", Exec) {
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description = "Generate Java wrappers for swift target"
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dependsOn swiftCheckValid
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// only because we depend on "live developing" the plugin while using this project to test it
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inputs.file(new File(rootDir, "Package.swift"))
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inputs.dir(new File(rootDir, "Sources"))
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// If the package description changes, we should execute jextract again, maybe we added jextract to new targets
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inputs.file(new File(projectDir, "Package.swift"))
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// monitor all targets/products which depend on the JExtract plugin
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swiftProductsWithJExtractPlugin().each {
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logger.info("[swift-java:jextract (Gradle)] Swift input target: ${it}")
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inputs.dir(new File(layout.projectDirectory.asFile, "Sources/${it}".toString()))
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}
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outputs.dir(layout.buildDirectory.dir("../.build/plugins/outputs/${layout.projectDirectory.asFile.getName().toLowerCase()}"))
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File baseSwiftPluginOutputsDir = layout.buildDirectory.dir("../.build/plugins/outputs/").get().asFile
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if (!baseSwiftPluginOutputsDir.exists()) {
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baseSwiftPluginOutputsDir.mkdirs()
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}
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Files.walk(layout.buildDirectory.dir("../.build/plugins/outputs/").get().asFile.toPath()).each {
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// Add any Java sources generated by the plugin to our sourceSet
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if (it.endsWith("JExtractSwiftPlugin/src/generated/java")) {
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outputs.dir(it)
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}
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}
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workingDir = layout.projectDirectory
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commandLine "swift"
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args("build") // since Swift targets which need to be jextract-ed have the jextract build plugin, we just need to build
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// If we wanted to execute a specific subcommand, we can like this:
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// args("run",/*
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// "swift-java", "jextract",
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// "--swift-module", "MySwiftLibrary",
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// // java.package is obtained from the swift-java.config in the swift module
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// "--output-java", "${layout.buildDirectory.dir(".build/plugins/outputs/${layout.projectDirectory.asFile.getName().toLowerCase()}/JExtractSwiftPlugin/src/generated/java").get()}",
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// "--output-swift", "${layout.buildDirectory.dir(".build/plugins/outputs/${layout.projectDirectory.asFile.getName().toLowerCase()}/JExtractSwiftPlugin/Sources").get()}",
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// "--log-level", (logging.level <= LogLevel.INFO ? "debug" : */"info")
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// )
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}
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// Add the java-swift generated Java sources
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sourceSets {
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main {
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java {
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srcDir(jextract)
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}
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}
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test {
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java {
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srcDir(jextract)
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}
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}
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jmh {
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java {
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srcDir(jextract)
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}
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}
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}
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tasks.build {
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dependsOn("jextract")
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}
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def cleanSwift = tasks.register("cleanSwift", Exec) {
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workingDir = layout.projectDirectory
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commandLine "swift"
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args("package", "clean")
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}
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tasks.clean {
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dependsOn("cleanSwift")
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}
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dependencies {
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implementation(project(':SwiftKit'))
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testImplementation(platform("org.junit:junit-bom:5.10.0"))
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testImplementation("org.junit.jupiter:junit-jupiter")
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}
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tasks.named('test', Test) {
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useJUnitPlatform()
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}
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application {
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mainClass = "com.example.swift.HelloJava2SwiftJNI"
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applicationDefaultJvmArgs = [
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"--enable-native-access=ALL-UNNAMED",
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// Include the library paths where our dylibs are that we want to load and call
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"-Djava.library.path=" +
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(BuildUtils.javaLibraryPaths(rootDir) +
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BuildUtils.javaLibraryPaths(project.projectDir)).join(":"),
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// Enable tracing downcalls (to Swift)
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"-Djextract.trace.downcalls=true"
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]
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}
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String jmhIncludes = findProperty("jmhIncludes")
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jmh {
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if (jmhIncludes != null) {
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includes = [jmhIncludes]
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}
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jvmArgsAppend = [
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"--enable-native-access=ALL-UNNAMED",
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"-Djava.library.path=" +
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(BuildUtils.javaLibraryPaths(rootDir) +
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BuildUtils.javaLibraryPaths(project.projectDir)).join(":"),
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// Enable tracing downcalls (to Swift)
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"-Djextract.trace.downcalls=false"
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]
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}

‎Samples/JExtractJNISampleApp/ci-validate.sh‎

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#!/bin/bash
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set -x
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set -e
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./gradlew run

‎Samples/JExtractJNISampleApp/gradlew‎

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../../gradlew

‎Samples/JExtractJNISampleApp/gradlew.bat‎

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../../gradlew.bat

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