Add a JNI method to check if an url exists and is a redirection.

src/android/kiwixreader.cpp

@@ -224,6 +224,21 @@ JNIEXPORT jstring JNICALL Java_org_kiwix_kiwixlib_JNIKiwixReader_getMimeType(
   return mimeType;
 }
 
+JNIEXPORT jstring JNICALL Java_org_kiwix_kiwixlib_JNIKiwixReader_checkUrl(
+     JNIEnv* env, jobject obj, jstring url)
+{
+  jstring finalUrl;
+  std::string cUrl = jni2c(url, env);
+  try {
+    auto entry = READER->getEntryFromEncodedPath(cUrl);
+    entry = entry.getFinalEntry();
+    finalUrl = c2jni(entry.getPath(), env);
+  } catch (std::exception& e) {
+    finalUrl = c2jni("", env);
+  }
+  return finalUrl;
+}
+
 JNIEXPORT jbyteArray JNICALL Java_org_kiwix_kiwixlib_JNIKiwixReader_getContent(
     JNIEnv* env, jobject obj, jobject url, jobject titleObj, jobject mimeTypeObj, jobject sizeObj)
 {

src/android/org/kiwix/kiwixlib/JNIKiwixReader.java

@@ -38,6 +38,16 @@ public class JNIKiwixReader
 
   public native String getMimeType(String url);
 
+  /**
+   * Check if a url exists and is a redirect or not.
+   *
+   * Return an empty string if the url doesn't exist in the reader.
+   * Return the url of the "final" entry.
+   * - equal to the input url if the entry is not a redirection.
+   * - different if the url is a redirection (and the webview should redirect to it).
+   */
+  public native String checkUrl(String url);
+
   /**
    * Get the content of a article.
    *