| package kotlinx.coroutines.internal |
| |
| import java.io.* |
| import java.net.* |
| import java.util.* |
| import java.util.jar.* |
| import java.util.zip.* |
| |
| /** |
| * A simplified version of [ServiceLoader]. |
| * FastServiceLoader locates and instantiates all service providers named in configuration |
| * files placed in the resource directory <tt>META-INF/services</tt>. |
| * |
| * The main difference between this class and classic service loader is in skipping |
| * verification JARs. A verification requires reading the whole JAR (and it causes problems and ANRs on Android devices) |
| * and prevents only trivial checksum issues. See #878. |
| * |
| * If any error occurs during loading, it fallbacks to [ServiceLoader], mostly to prevent R8 issues. |
| */ |
| internal object FastServiceLoader { |
| private const val PREFIX: String = "META-INF/services/" |
| |
| internal fun <S> load(service: Class<S>, loader: ClassLoader): List<S> { |
| return try { |
| loadProviders(service, loader) |
| } catch (e: Throwable) { |
| // Fallback to default service loader |
| ServiceLoader.load(service, loader).toList() |
| } |
| } |
| |
| // Visible for tests |
| internal fun <S> loadProviders(service: Class<S>, loader: ClassLoader): List<S> { |
| val fullServiceName = PREFIX + service.name |
| // Filter out situations when both JAR and regular files are in the classpath (e.g. IDEA) |
| val urls = loader.getResources(fullServiceName) |
| val providers = urls.toList().flatMap { parse(it) }.toSet() |
| require(providers.isNotEmpty()) { "No providers were loaded with FastServiceLoader" } |
| return providers.map { getProviderInstance(it, loader, service) } |
| } |
| |
| private fun <S> getProviderInstance(name: String, loader: ClassLoader, service: Class<S>): S { |
| val clazz = Class.forName(name, false, loader) |
| require(service.isAssignableFrom(clazz)) { "Expected service of class $service, but found $clazz" } |
| return service.cast(clazz.getDeclaredConstructor().newInstance()) |
| } |
| |
| private fun parse(url: URL): List<String> { |
| val path = url.toString() |
| // Fast-path for JARs |
| if (path.startsWith("jar")) { |
| val pathToJar = path.substringAfter("jar:file:").substringBefore('!') |
| val entry = path.substringAfter("!/") |
| // mind the verify = false flag! |
| (JarFile(pathToJar, false)).use { file -> |
| BufferedReader(InputStreamReader(file.getInputStream(ZipEntry(entry)), "UTF-8")).use { r -> |
| return parseFile(r) |
| } |
| } |
| } |
| // Regular path for everything else |
| return BufferedReader(InputStreamReader(url.openStream())).use { reader -> |
| parseFile(reader) |
| } |
| } |
| |
| // JarFile does no implement Closesable on Java 1.6 |
| private inline fun <R> JarFile.use(block: (JarFile) -> R): R { |
| var cause: Throwable? = null |
| try { |
| return block(this) |
| } catch (e: Throwable) { |
| cause = e |
| throw e |
| } finally { |
| try { |
| close() |
| } catch (closeException: Throwable) { |
| if (cause === null) throw closeException |
| cause.addSuppressed(closeException) |
| throw cause |
| } |
| } |
| } |
| |
| private fun parseFile(r: BufferedReader): List<String> { |
| val names = mutableSetOf<String>() |
| while (true) { |
| val line = r.readLine() ?: break |
| val serviceName = line.substringBefore("#").trim() |
| require(serviceName.all { it == '.' || Character.isJavaIdentifierPart(it) }) { "Illegal service provider class name: $serviceName" } |
| if (serviceName.isNotEmpty()) { |
| names.add(serviceName) |
| } |
| } |
| return names.toList() |
| } |
| } |