replace library load with native code

app/src/main/cpp/CMakeLists.txt

@@ -22,4 +22,6 @@ if(NOT dobby_POPULATED)
     add_subdirectory("${dobby_SOURCE_DIR}" ${dobby_BINARY_DIR} EXCLUDE_FROM_ALL)
     target_include_directories(launcherfix PRIVATE ${dobby_SOURCE_DIR}/include)
     target_link_libraries(launcherfix dobby)
-endif()
+endif()
+
+target_link_libraries(launcherfix log)

app/src/main/cpp/launcher-fix.cpp

@@ -1,6 +1,9 @@
+#include <android/dlext.h>
+#include <android/log.h>
 #include <dlfcn.h>
-#include <string>
 #include <jni.h>
+#include <string>
+#include <unistd.h>
 
 #ifndef DISABLE_LAUNCHER_FIX
 #include <dobby.h>
@@ -30,6 +33,8 @@ JNIEXPORT void JNICALL Java_com_geode_launcher_LauncherFix_setDataPath(
     auto data_path_str = env->GetStringUTFChars(data_path, &is_copy);
 
     DataPaths::get_instance().data_path = std::string(data_path_str);
+
+    env->ReleaseStringUTFChars(data_path, data_path_str);
 }
 
 extern "C"
@@ -42,6 +47,38 @@ JNIEXPORT void JNICALL Java_com_geode_launcher_LauncherFix_setOriginalDataPath(
     auto data_path_str = env->GetStringUTFChars(data_path, &is_copy);
 
     DataPaths::get_instance().original_data_path = std::string(data_path_str);
+
+    env->ReleaseStringUTFChars(data_path, data_path_str);
+}
+
+extern "C"
+JNIEXPORT jboolean JNICALL Java_com_geode_launcher_LauncherFix_loadLibraryFromOffset(JNIEnv *env, jobject, jstring library_name, jint fd, jlong offset) {
+    // loads a given library at an offset and file descriptor
+    // assumes we have ownership of the file passed in fd
+
+    auto is_copy = jboolean();
+    auto library_cname = env->GetStringUTFChars(library_name, &is_copy);
+
+    android_dlextinfo ext_info{};
+    ext_info.flags = ANDROID_DLEXT_USE_LIBRARY_FD | ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET;
+    ext_info.library_fd = fd;
+    ext_info.library_fd_offset = offset;
+
+    auto handle = android_dlopen_ext(library_cname, RTLD_NOW | RTLD_GLOBAL, &ext_info);
+    env->ReleaseStringUTFChars(library_name, library_cname);
+    close(fd);
+
+    if (handle == nullptr) {
+        auto error = dlerror();
+        __android_log_print(ANDROID_LOG_WARN, "GeodeLauncher-Fix", "dlopen_ext failed. given: %s\n", error);
+
+        return false;
+    }
+
+    // we don't need the library anymore
+    dlclose(handle);
+
+    return true;
 }
 
 FILE* (*fopen_original)(const char *pathname, const char *mode);

app/src/main/java/com/geode/launcher/GeometryDashActivity.kt

@@ -123,19 +123,9 @@ class GeometryDashActivity : AppCompatActivity(), Cocos2dxHelper.Cocos2dxHelperL
         }
     }
 
-    @SuppressLint("UnsafeDynamicallyLoadedCode")
     private fun loadLibraryFromAssets(libraryName: String) {
-        // loads a library loaded in assets
-        // this currently requires copying the library to a non-compressed directory
-        // ideally a better solution would be found, but i'm out of ideas
-
-        val libraryCopy = File(cacheDir, "lib$libraryName.so")
-        if (libraryCopy.exists()) {
-            // don't force a copy on each load
-            // (you will have to clear cache if the library updates, so maybe remove this check)
-            System.load(libraryCopy.path)
-            return
-        }
+        // loads a library loaded in assets (which points to the apk + an offset)
+        // these libraries are available to the application after merging
 
         // find the first instance of the library in preferred abi order
         val libraryFd = Build.SUPPORTED_ABIS.asSequence()
@@ -148,14 +138,17 @@ class GeometryDashActivity : AppCompatActivity(), Cocos2dxHelper.Cocos2dxHelperL
             }
             .firstOrNull() ?: throw UnsatisfiedLinkError("Could not find library lib$libraryName.so")
 
-        // copy the library to a path we can access
-        // there doesn't seem to be a way to load a library from a file descriptor
-        val libraryOutput = libraryCopy.outputStream()
-        copyFile(libraryFd.createInputStream(), libraryOutput)
+        val fdOffset = libraryFd.startOffset
+        val fdDescriptor = libraryFd.parcelFileDescriptor.detachFd()
 
-        System.load(libraryCopy.path)
+        if (!LauncherFix.loadLibraryFromOffset("lib$libraryName.so", fdDescriptor, fdOffset)) {
+            throw UnsatisfiedLinkError("Failed to load asset lib$libraryName.so")
+        }
 
-        return
+        // after the library is opened in native code, it should be available for loading
+        // you can read more about the behavior:
+        // https://android.googlesource.com/platform/libcore/+/7f3eb2e0ac87bdea471bc577380cf50025aebde5/ojluni/src/main/java/java/lang/Runtime.java#1060
+        System.loadLibrary(libraryName)
     }
 
     @SuppressLint("UnsafeDynamicallyLoadedCode")

app/src/main/java/com/geode/launcher/LauncherFix.kt

@@ -10,4 +10,6 @@ object LauncherFix {
     external fun setDataPath(dataPath: String)
 
     external fun setOriginalDataPath(dataPath: String)
+
+    external fun loadLibraryFromOffset(libraryName: String, fd: Int, offset: Long): Boolean
 }