[JAVA] Add a method to get the size of an article.

Fix #327

src/wrapper/java/kiwixreader.cpp

@@ -21,6 +21,7 @@
 
 #include <jni.h>
 #include <zim/file.h>
+#include <exception>
 #include "org_kiwix_kiwixlib_JNIKiwixReader.h"
 
 #include "tools/base64.h"
@@ -305,6 +306,22 @@ JNIEXPORT jbyteArray JNICALL Java_org_kiwix_kiwixlib_JNIKiwixReader_getContentPa
   return data;
 }
 
+JNIEXPORT jlong JNICALL
+Java_org_kiwix_kiwixlib_JNIKiwixReader_getArticleSize(
+    JNIEnv* env, jobject obj, jstring url)
+{
+  std::string cUrl = jni2c(url, env);
+  try {
+    auto entry = READER->getEntryFromEncodedPath(cUrl);
+    entry = entry.getFinalEntry();
+    return c2jni(entry.getSize(), env);
+  } catch(std::exception& e) {
+    LOG("Unable to get size for url : %s", cUrl.c_str());
+    LOG(e.what());
+  }
+  return c2jni(0, env);
+}
+
 JNIEXPORT jobject JNICALL
 Java_org_kiwix_kiwixlib_JNIKiwixReader_getDirectAccessInformation(
     JNIEnv* env, jobject obj, jstring url)

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

@@ -82,6 +82,16 @@ public class JNIKiwixReader
                                       int len,
                                       JNIKiwixInt size);
 
+  /**
+   *
+   * Get the size of an article.
+   *
+   * @param   url The url of the article.
+   * @return  The size of the final (redirections are resolved) article (in byte).
+   *          Return 0 if the article is not found.
+   */
+  public native long getArticleSize(String url);
+
   /**
    * getDirectAccessInformation.
    *