Write new files from a Stream at first to a .tmp file. This avoids fragmentation.

src/de/mas/wiiu/jnus/utils/CheckedFunction.java

@@ -0,0 +1,8 @@
+package de.mas.wiiu.jnus.utils;
+
+import java.io.IOException;
+
+@FunctionalInterface
+public interface CheckedFunction<T> {
+    void apply(T t) throws IOException;
+}

src/de/mas/wiiu/jnus/utils/FileUtils.java

@@ -20,6 +20,8 @@ import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.RandomAccessFile;
 
 import lombok.NonNull;
 
@@ -55,16 +57,41 @@ public final class FileUtils {
         return true;
     }
 
+    public static void saveInputStreamToFile(@NonNull File outputFile, InputStream inputStream, long filesize) throws IOException {
+        FileAsOutputStreamWrapper(outputFile, filesize, outputStream -> StreamUtils.saveInputStreamToOutputStream(inputStream, outputStream, filesize));
+    }
+
     /**
-     * Saves a byte array to a file (and overwrite it if its already exists) DOES NOT IF THE PATH/FILE EXIST OR IS IT EVEN A FILE
+     * Allows to write into a target file as OutputStream with some extras. The provided OutputStream already has the needed memory allocated. This results in a
+     * non-fragmented file.
      * 
-     * @param output
-     * @param inputStream
+     * @param outputFile
+     * @param filesize
+     * @param action
      * @throws IOException
      */
-    public static void saveInputStreamToFile(@NonNull File output, InputStream inputStream, long filesize) throws IOException {
-        FileOutputStream out = new FileOutputStream(output);
-        StreamUtils.saveInputStreamToOutputStream(inputStream, out, filesize);
+    public static void FileAsOutputStreamWrapper(@NonNull File outputFile, long filesize, CheckedFunction<OutputStream> action) throws IOException {
+        // Create a new temp file which already has the target filesize allocated.
+        String tempFilePath = outputFile.getAbsolutePath() + "." + outputFile.getAbsolutePath().hashCode() + ".part";
+        File tempFile = new File(tempFilePath);
+        if (tempFile.exists()) {
+            tempFile.delete();
+        }
+
+        tempFile.createNewFile();
+        RandomAccessFile outStream = new RandomAccessFile(tempFilePath, "rw");
+        outStream.setLength(filesize);
+        outStream.seek(0L);
+
+        action.apply(new RandomFileOutputStream(outStream));
+
+        outStream.close();
+
+        // Rename temp file.
+        if (outputFile.exists()) {
+            outputFile.delete();
+        }
+        tempFile.renameTo(outputFile);
     }
 
 }

src/de/mas/wiiu/jnus/utils/RandomFileOutputStream.java

@@ -0,0 +1,111 @@
+package de.mas.wiiu.jnus.utils;
+
+import java.io.File;
+import java.io.FileDescriptor;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.RandomAccessFile;
+
+public class RandomFileOutputStream extends OutputStream {
+
+    // *****************************************************************************
+    // INSTANCE PROPERTIES
+    // *****************************************************************************
+
+    protected RandomAccessFile randomFile; // the random file to write to
+    protected boolean sync; // whether to synchronize every write
+
+    // *****************************************************************************
+    // INSTANCE CONSTRUCTION/INITIALIZATON/FINALIZATION, OPEN/CLOSE
+    // *****************************************************************************
+
+    public RandomFileOutputStream(String fnm) throws IOException {
+        this(fnm, false);
+    }
+
+    public RandomFileOutputStream(String fnm, boolean syn) throws IOException {
+        this(new File(fnm), syn);
+    }
+
+    public RandomFileOutputStream(File fil) throws IOException {
+        this(fil, false);
+    }
+
+    public RandomFileOutputStream(RandomAccessFile ran) throws IOException {
+        randomFile = ran;
+        sync = false;
+    }
+
+    public RandomFileOutputStream(File fil, boolean syn) throws IOException {
+        super();
+
+        File par; // parent file
+
+        fil = fil.getAbsoluteFile();
+        if ((par = fil.getParentFile()) != null) {
+            Utils.createDir(par.getAbsolutePath());
+        }
+        randomFile = new RandomAccessFile(fil, "rw");
+        sync = syn;
+    }
+
+    // *****************************************************************************
+    // INSTANCE METHODS - OUTPUT STREAM IMPLEMENTATION
+    // *****************************************************************************
+
+    public void write(int val) throws IOException {
+        randomFile.write(val);
+        if (sync) {
+            randomFile.getFD().sync();
+        }
+    }
+
+    public void write(byte[] val) throws IOException {
+        randomFile.write(val);
+        if (sync) {
+            randomFile.getFD().sync();
+        }
+    }
+
+    public void write(byte[] val, int off, int len) throws IOException {
+        randomFile.write(val, off, len);
+        if (sync) {
+            randomFile.getFD().sync();
+        }
+    }
+
+    public void flush() throws IOException {
+        if (sync) {
+            randomFile.getFD().sync();
+        }
+    }
+
+    public void close() throws IOException {
+        randomFile.close();
+    }
+
+    // *****************************************************************************
+    // INSTANCE METHODS - RANDOM ACCESS EXTENSIONS
+    // *****************************************************************************
+
+    public long getFilePointer() throws IOException {
+        return randomFile.getFilePointer();
+    }
+
+    public void setFilePointer(long pos) throws IOException {
+        randomFile.seek(pos);
+    }
+
+    public long getFileSize() throws IOException {
+        return randomFile.length();
+    }
+
+    public void setFileSize(long len) throws IOException {
+        randomFile.setLength(len);
+    }
+
+    public FileDescriptor getFD() throws IOException {
+        return randomFile.getFD();
+    }
+
+} // END PUBLIC CLASS