To resolve unhandled exception

'JNI DETECTED ERROR IN APPLICATION: input is not valid Modified UTF-8: illegal continuation byte 0'
that can be produced by invalid filename (broken sdcard, etc)
or 'JNI WARNING: input is not valid Modified UTF-8: illegal start byte 0xf0'
that can be generated if 4-byte UTF-8 sequence found in the filename on Android older than 6.0 (API 23),
we implement own directory listing method instead of File.listFiles().

Author: virxkane

android/jni/cr3engine.cpp

@@ -709,6 +709,45 @@ JNIEXPORT jboolean JNICALL Java_org_coolreader_crengine_Engine_checkFontLanguage
 	return res;
 }
 
+/*
+ * Class:     org_coolreader_crengine_Engine
+ * Method:    listFilesInternal
+ * Signature: (Ljava/io/File;)[Ljava/io/File;
+ */
+JNIEXPORT jobjectArray JNICALL Java_org_coolreader_crengine_Engine_listFilesInternal
+		(JNIEnv *env, jclass, jobject jdir)
+{
+	jclass fileClass = env->FindClass("java/io/File");
+	if (NULL == fileClass)
+		return NULL;
+	jmethodID mFileGetAbsolutePath = env->GetMethodID(fileClass, "getAbsolutePath", "()Ljava/lang/String;");
+	if (NULL == mFileGetAbsolutePath)
+		return NULL;
+	jmethodID fileCtor = env->GetMethodID(fileClass, "<init>", "(Ljava/lang/String;)V");
+	if (NULL == fileCtor)
+		return NULL;
+	jstring jpathname = (jstring)env->CallObjectMethod(jdir, mFileGetAbsolutePath);
+	jboolean iscopy;
+	const char * s = env->GetStringUTFChars(jpathname, &iscopy);
+	lString16 path = (CRJNIEnv::sdk_int >= ANDROID_SDK_M) ? Utf8ToUnicode(s) : Wtf8ToUnicode(s);
+	LVContainerRef dir = LVOpenDirectory(path);
+	jobjectArray jarray = NULL;
+	if ( !dir.isNull() ) {
+		jstring emptyString = env->NewStringUTF("");
+		jobject emptyFile = env->NewObject(fileClass, fileCtor, emptyString);
+		jarray = env->NewObjectArray(dir->GetObjectCount(), fileClass, emptyFile);
+		for (int i = 0; i < dir->GetObjectCount(); i++) {
+			const LVContainerItemInfo *item = dir->GetObjectInfo(i);
+			lString16 fileName = path + "/" + item->GetName();
+			jstring jfilename = env->NewStringUTF((CRJNIEnv::sdk_int >= ANDROID_SDK_M) ? UnicodeToUtf8(fileName).c_str() : UnicodeToWtf8(fileName).c_str());
+			jobject jfile = env->NewObject(fileClass, fileCtor, jfilename);
+			env->SetObjectArrayElement(jarray, i, jfile);
+		}
+	}
+	env->ReleaseStringUTFChars(jpathname, s);
+	return jarray;
+}
+
 /*
  * Class:     org_coolreader_crengine_Engine
  * Method:    isLink
@@ -789,6 +828,9 @@ static JNINativeMethod sEngineMethods[] = {
   {"setKeyBacklightInternal", "(I)Z", (void*)Java_org_coolreader_crengine_Engine_setKeyBacklightInternal},
   {"scanBookCoverInternal", "(Ljava/lang/String;)[B", (void*)Java_org_coolreader_crengine_Engine_scanBookCoverInternal},
   {"drawBookCoverInternal", "(Landroid/graphics/Bitmap;[BLjava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;II)V", (void*)Java_org_coolreader_crengine_Engine_drawBookCoverInternal},
+  {"haveFcLangCodeInternal", "(Ljava/lang/String;)Z", (void*)Java_org_coolreader_crengine_Engine_haveFcLangCodeInternal},
+  {"checkFontLanguageCompatibilityInternal", "(Ljava/lang/String;Ljava/lang/String;)Z", (void*)Java_org_coolreader_crengine_Engine_checkFontLanguageCompatibilityInternal},
+  {"listFilesInternal", "(Ljava/io/File;)[Ljava/io/File;", (void*)Java_org_coolreader_crengine_Engine_listFilesInternal}
 };
 
 

android/jni/cr3java.cpp

@@ -3,9 +3,6 @@
 
 #include <dlfcn.h>
 
-// M is for Marshmallow!
-#define ANDROID_SDK_M	23
-
 uint8_t CRJNIEnv::sdk_int = 0;
 
 lString16 CRJNIEnv::fromJavaString( jstring str )

android/jni/cr3java.h

@@ -20,6 +20,9 @@
 #include "../../crengine/include/props.h"
 #include "../../crengine/include/lvtinydom.h"
 
+// M is for Marshmallow!
+#define ANDROID_SDK_M	23
+
 //====================================================================
 // libjnigraphics replacement for pre-2.2 SDKs 
 enum AndroidBitmapFormat {

android/jni/org_coolreader_crengine_Engine.h

@@ -640,6 +640,8 @@ public void initAgain() {
 	 */
 	private native static boolean checkFontLanguageCompatibilityInternal(String fontFace, String langCode);
 
+	private native static File[] listFilesInternal(File dir);
+
 	public static void suspendLongOperation() {
 		suspendLongOperationInternal();
 	}
@@ -648,6 +650,10 @@ public synchronized static boolean checkFontLanguageCompatibility(String fontFac
 		return checkFontLanguageCompatibilityInternal(fontFace, langCode);
 	}
 
+	public static synchronized File[] listFiles(File dir) {
+		return listFilesInternal(dir);
+	}
+
 	/**
 	 * Finds the corresponding language code in embedded FontConfig language orthography catalog.
 	 *

android/src/org/coolreader/crengine/Engine.java

@@ -111,7 +111,15 @@ public boolean listDirectory(FileInfo baseDir)
 		}
 		try {
 			File dir = new File(baseDir.pathname);
-			File[] items = dir.listFiles();
+			//File[] items = dir.listFiles();
+			// To resolve unhandled exception
+			// 'JNI DETECTED ERROR IN APPLICATION: input is not valid Modified UTF-8: illegal continuation byte 0'
+			// that can be produced by invalid filename (broken sdcard, etc)
+			// or 'JNI WARNING: input is not valid Modified UTF-8: illegal start byte 0xf0'
+			// that can be generated if 4-byte UTF-8 sequence found in the filename,
+			// we implement own directory listing method instead of File.listFiles().
+			// TODO: replace other occurrences of the method File.listFiles().
+			File[] items = Engine.listFiles(dir);
 			// process normal files
 			if ( items!=null ) {
 				for ( File f : items ) {