Don't leak temporary file during test and inital loading of lib. (#141)

Motivation:

We did leak a file during our tests and also during the initial loading of the native lib

Modifications:

Use a tempory file / directory and so ensure the file is deleted

Result:

No leaked file

transport-classes-io_uring/src/main/java/io/netty/incubator/channel/uring/Native.java

@@ -26,8 +26,10 @@
 import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
 
+import java.io.File;
 import java.io.IOException;
 import java.nio.channels.Selector;
+import java.nio.file.Path;
 import java.util.Arrays;
 import java.util.Locale;
 
@@ -59,14 +61,17 @@ final class Native {
                 PeerCredentials.class, java.io.FileDescriptor.class
         );
 
+        File tmpDir = PlatformDependent.tmpdir();
+        Path tmpFile = tmpDir.toPath().resolve("netty_io_uring.tmp");
         try {
             // First, try calling a side-effect free JNI method to see if the library was already
             // loaded by the application.
-            Native.createFile();
+            Native.createFile(tmpFile.toString());
         } catch (UnsatisfiedLinkError ignore) {
             // The library was not previously loaded, load it now.
             loadNativeLibrary();
         } finally {
+            tmpFile.toFile().delete();
             try {
                 if (selector != null) {
                     selector.close();
@@ -256,23 +261,23 @@ private static boolean checkKernelVersion0(String kernelVersion) {
     private static native boolean ioUringProbe(int ringFd, int[] ios);
     private static native long[][] ioUringSetup(int entries);
 
-    public static native int ioUringEnter(int ringFd, int toSubmit, int minComplete, int flags);
+    static native int ioUringEnter(int ringFd, int toSubmit, int minComplete, int flags);
 
-    public static native void eventFdWrite(int fd, long value);
+    static native void eventFdWrite(int fd, long value);
 
-    public static FileDescriptor newBlockingEventFd() {
+    static FileDescriptor newBlockingEventFd() {
         return new FileDescriptor(blockingEventFd());
     }
 
-    public static native void ioUringExit(long submissionQueueArrayAddress, int submissionQueueRingEntries,
+    static native void ioUringExit(long submissionQueueArrayAddress, int submissionQueueRingEntries,
                                           long submissionQueueRingAddress, int submissionQueueRingSize,
                                           long completionQueueRingAddress, int completionQueueRingSize,
                                           int ringFd);
 
     private static native int blockingEventFd();
 
-    // for testing(it is only temporary)
-    public static native int createFile();
+    // for testing only!
+    static native int createFile(String name);
 
     private static native int registerUnix();
 

transport-native-io_uring/src/main/c/netty_io_uring_native.c

@@ -296,8 +296,12 @@ static jobjectArray netty_io_uring_setup(JNIEnv *env, jclass clazz, jint entries
     return array;
 }
 
-static jint netty_create_file(JNIEnv *env, jclass class) {
-    return open("io-uring-test.txt", O_RDWR | O_TRUNC | O_CREAT, 0644);
+static jint netty_create_file(JNIEnv *env, jclass class, jstring filename) {
+    const char *file = (*env)->GetStringUTFChars(env, filename, 0);
+
+    int fd =  open(file, O_RDWR | O_TRUNC | O_CREAT, 0644);
+    (*env)->ReleaseStringUTFChars(env, filename, file);
+    return fd;
 }
 
 
@@ -592,7 +596,7 @@ static const JNINativeMethod method_table[] = {
     {"ioUringSetup", "(I)[[J", (void *) netty_io_uring_setup},
     {"ioUringProbe", "(I[I)Z", (void *) netty_io_uring_probe},
     {"ioUringExit", "(JIJIJII)V", (void *) netty_io_uring_ring_buffer_exit},
-    {"createFile", "()I", (void *) netty_create_file},
+    {"createFile", "(Ljava/lang/String;)I", (void *) netty_create_file},
     {"ioUringEnter", "(IIII)I", (void *) netty_io_uring_enter},
     {"blockingEventFd", "()I", (void *) netty_epoll_native_blocking_event_fd},
     {"eventFdWrite", "(IJ)V", (void *) netty_io_uring_eventFdWrite },

transport-native-io_uring/src/test/java/io/netty/incubator/channel/uring/NativeTest.java

@@ -17,7 +17,9 @@
 
 import io.netty.channel.unix.FileDescriptor;
 
+import java.io.File;
 import java.nio.charset.Charset;
+import java.nio.file.Path;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -37,6 +39,7 @@
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.Timeout;
+import org.junit.jupiter.api.io.TempDir;
 
 public class NativeTest {
 
@@ -46,13 +49,14 @@ public static void loadJNI() {
     }
 
     @Test
-    public void canWriteFile() throws Exception {
+    public void canWriteFile(@TempDir Path tmpDir) throws Exception {
         ByteBufAllocator allocator = new UnpooledByteBufAllocator(true);
         final ByteBuf writeEventByteBuf = allocator.directBuffer(100);
         final String inputString = "Hello World!";
         writeEventByteBuf.writeCharSequence(inputString, Charset.forName("UTF-8"));
 
-        int fd = Native.createFile();
+        Path file = tmpDir.resolve("io_uring.tmp");
+        int fd = Native.createFile(file.toString());
 
         RingBuffer ringBuffer = Native.createRingBuffer(32);
         IOUringSubmissionQueue submissionQueue = ringBuffer.ioUringSubmissionQueue();