'#1861: use workaround just if needed, convert relative path to absolute

iped-utils/src/main/java/iped/utils/FileInputStreamFactory.java

@@ -2,22 +2,36 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.InvalidPathException;
 import java.nio.file.Path;
+import java.nio.file.Paths;
 
 import iped.io.SeekableInputStream;
 
 public class FileInputStreamFactory extends SeekableInputStreamFactory {
 
+    private static final boolean IS_WINDOWS = System.getProperty("os.name").toLowerCase().startsWith("windows");
+
     public FileInputStreamFactory(Path dataSource) {
         super(dataSource.toUri());
     }
 
     public File getFile(String subPath) {
-        if (System.getProperty("os.name").toLowerCase().startsWith("windows")) {
-            //this is a workaround to support cases where there are folders with trailing spaces on the name
-            return new File("\\\\?\\" + new File(subPath).getAbsolutePath());
-        } else {
-            return new File(subPath);
+        Path source = Paths.get(this.dataSource);
+        try {
+            return source.resolve(subPath).toFile();
+
+        } catch (InvalidPathException e) {
+            File file = new File(subPath);
+            if (!file.isAbsolute()) {
+                file = new File(source.toFile(), subPath);
+            }
+            if (IS_WINDOWS) {
+                //this is a workaround to support cases where there are folders with trailing spaces on the name
+                return new File("\\\\?\\" + file.getAbsolutePath());
+            } else {
+                return file;
+            }
         }
     }