Add NRO icon loading

app/src/main/java/gq/cyuubi/lightswitch/NroMeta.java

@@ -1,8 +1,13 @@
 package gq.cyuubi.lightswitch;
 
+import android.content.Context;
+import android.content.ContextWrapper;
+import android.os.Environment;
 import android.util.Log;
 
+import java.io.FileOutputStream;
 import java.io.IOException;
+import java.io.OutputStreamWriter;
 import java.io.RandomAccessFile;
 
 final class TitleEntry {
@@ -54,4 +59,34 @@ public class NroMeta {
             return null;
         }
     }
+
+    public static String LoadImage(String file, MainActivity context) {
+        try {
+            RandomAccessFile f = new RandomAccessFile(file, "r");
+            f.seek(0x18); // Skip to NroHeader.size
+            int asetOffset = Integer.reverseBytes(f.readInt());
+            f.seek(asetOffset); // Skip to the offset specified by NroHeader.size
+            byte[] buffer = new byte[4];
+            f.read(buffer);
+            if(!(new String(buffer).equals("ASET")))
+                return null;
+
+            f.skipBytes(0x4);
+            long iconOffset = Long.reverseBytes(f.readLong());
+            long iconSize = Long.reverseBytes(f.readLong());
+            if(iconOffset == 0 || iconSize == 0)
+                return null;
+            f.seek(asetOffset + iconOffset);
+
+            byte[] iconData = new byte[(int)iconSize];
+            f.read(iconData);
+
+            new FileOutputStream(context.getFilesDir() + "/tmp.jpg").write(iconData);
+            return context.getFilesDir() + "/tmp.jpg";
+        }
+        catch(IOException e) {
+            Log.e("app_process64", "Error while loading ASET: " + e.getMessage());
+            return null;
+        }
+    }
 }