Merge pull request #102 from kiwix/direct_access

Direct access

src/android/kiwixreader.cpp

@@ -246,8 +246,8 @@ JNIEXPORT jbyteArray JNICALL Java_org_kiwix_kiwixlib_JNIKiwixReader_getContentPa
   /* Default values */
   /* Retrieve the content */
   std::string cUrl = jni2c(url, env);
-  int cOffset = jni2c(offset);
+  unsigned int cOffset = jni2c(offset);
-  int cLen = jni2c(len);
+  unsigned int cLen = jni2c(len);
   try {
     zim::Article article;
     READER->getArticleObjectByDecodedUrl(kiwix::urlDecode(cUrl), article);
@@ -277,6 +277,40 @@ JNIEXPORT jbyteArray JNICALL Java_org_kiwix_kiwixlib_JNIKiwixReader_getContentPa
   return data;
 }
 
+JNIEXPORT jobject JNICALL
+Java_org_kiwix_kiwixlib_JNIKiwixReadear_getDirectAccessInformation(
+    JNIEnv* env, jobject obj, jstring url)
+{
+   jclass classPair = env->FindClass("org/kiwix/kiwixlib/Pair");
+   jmethodID midPairinit = env->GetMethodID(classPair, "<init>", "(D)");
+   jobject pair = env->NewObject(classPair, midPairinit);
+   setPairObjValue("", 0, pair, env);
+
+   std::string cUrl = jni2c(url, env);
+   try {
+    zim::Article article;
+    READER->getArticleObjectByDecodedUrl(kiwix::urlDecode(cUrl), article);
+    if (! article.good()) {
+      return pair;
+    }
+    int loopCounter = 0;
+    while (article.isRedirect() && loopCounter++ < 42) {
+      article = article.getRedirectArticle();
+    }
+    if (loopCounter == 42) {
+      return pair;
+    }
+
+    auto part_info = article.getDirectAccessInformation();
+    setPairObjValue(part_info.first, part_info.second, pair, env);
+  } catch (...) {
+    std::cerr << "Unable to locate direct access information for url " << cUrl
+              << std::endl;
+
+  }
+  return pair;
+}
+
 JNIEXPORT jboolean JNICALL
 Java_org_kiwix_kiwixlib_JNIKiwixReader_searchSuggestions(JNIEnv* env,
                                                          jobject obj,

src/android/meson.build

@@ -7,7 +7,8 @@ kiwix_jni = custom_target('jni',
           'org/kiwix/kiwixlib/JNIKiwixSearcher.java',
           'org/kiwix/kiwixlib/JNIKiwixInt.java',
           'org/kiwix/kiwixlib/JNIKiwixString.java',
-          'org/kiwix/kiwixlib/JNIKiwixBool.java'],
+          'org/kiwix/kiwixlib/JNIKiwixBool.java',
+          'org/kiwix/kiwixlib/Pair.java'],
   output: ['org_kiwix_kiwixlib_JNIKiwix.h',
            'org_kiwix_kiwixlib_JNIKiwixReader.h',
            'org_kiwix_kiwixlib_JNIKiwixSearcher.h',

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

@@ -23,6 +23,7 @@ package org.kiwix.kiwixlib;
 import org.kiwix.kiwixlib.JNIKiwixString;
 import org.kiwix.kiwixlib.JNIKiwixInt;
 import org.kiwix.kiwixlib.JNIKiwixSearcher;
+import org.kiwix.kiwixlib.Pair;
 
 public class JNIKiwixReader
 {
@@ -56,6 +57,24 @@ public class JNIKiwixReader
                                       int len,
                                       JNIKiwixInt size);
 
+  /**
+   * getDirectAccessInformation.
+   *
+   * Return information giving where the content is located in the zim file.
+   *
+   * Some contents (binary content) are stored uncompressed in the zim file.
+   * Knowing this information, it could be interesting to directly open
+   * the zim file (or zim part) and directly read the content from it (and so
+   * bypassing the libzim).
+   *
+   * Return a `Pair` (filename, offset) where the content is located.
+   *
+   * If the content cannot be directly accessed (content is compressed or zim
+   * file is cut in the middle of the content), the filename is an empty string
+   * and offset is zero.
+   */
+  public native Pair getDirectAccessInformation(String url);
+
   public native boolean searchSuggestions(String prefix, int count);
 
   public native boolean getNextSuggestion(JNIKiwixString title);

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

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2017 Matthieu Gautier <mgautier@kymeria.fr>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU  General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+
+package org.kiwix.kiwixlib;
+
+public class Pair
+{
+  public String filename;
+  public int offset;
+}

src/android/utils.h

@@ -137,4 +137,14 @@ inline void setBoolObjValue(const bool value, const jobject obj, JNIEnv* env)
   env->SetIntField(obj, objFid, c2jni(value));
 }
 
+inline void setPairObjValue(const std::string& filename, const int offset,
+                            const jobject obj, JNIEnv* env)
+{
+  jclass objClass = env->GetObjectClass(obj);
+  jfieldID filenameFid = env->GetFieldID(objClass, "filename", "Ljava/lang/String;");
+  env->SetObjectField(obj, filenameFid, c2jni(filename, env));
+  jfieldID offsetFid = env->GetFieldID(objClass, "offset", "I");
+  env->SetIntField(obj, offsetFid, offset);
+}
+
 #endif // _ANDROID_JNI_UTILS_H