JNIKiwixReader can open an embedded ZIM archive

include/reader.h

@@ -57,6 +57,7 @@ class Reader
    */
   explicit Reader(const string zimFilePath);
   explicit Reader(int fd);
+  Reader(int fd, zim::offset_type offset, zim::size_type size);
   ~Reader() = default;
 
   /**

src/reader.cpp

@@ -90,7 +90,14 @@ Reader::Reader(int fd)
   :  zimArchive(new zim::Archive(fd)),
      zimFilePath("")
 {
+  /* initialize random seed: */
+  srand(time(nullptr));
+}
 
+Reader::Reader(int fd, zim::offset_type offset, zim::size_type size)
+  :  zimArchive(new zim::Archive(fd, offset, size)),
+     zimFilePath("")
+{
   /* initialize random seed: */
   srand(time(nullptr));
 }

src/wrapper/java/kiwixreader.cpp

@@ -74,6 +74,23 @@ JNIEXPORT jlong JNICALL Java_org_kiwix_kiwixlib_JNIKiwixReader_getNativeReaderBy
   }
 }
 
+JNIEXPORT jlong JNICALL Java_org_kiwix_kiwixlib_JNIKiwixReader_getNativeReaderEmbedded(
+    JNIEnv* env, jobject obj, jobject fdObj, jlong offset, jlong size)
+{
+  int fd = jni2fd(fdObj, env);
+
+  LOG("Attempting to create reader with fd: %d", fd);
+  Lock l;
+  try {
+    kiwix::Reader* reader = new kiwix::Reader(fd, offset, size);
+    return reinterpret_cast<jlong>(new Handle<kiwix::Reader>(reader));
+  } catch (std::exception& e) {
+    LOG("Error opening ZIM file");
+    LOG(e.what());
+    return 0;
+  }
+}
+
 JNIEXPORT void JNICALL
 Java_org_kiwix_kiwixlib_JNIKiwixReader_dispose(JNIEnv* env, jobject obj)
 {

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

@@ -161,6 +161,15 @@ public class JNIKiwixReader
     }
   }
 
+  public JNIKiwixReader(FileDescriptor fd, long offset, long size)
+      throws JNIKiwixException
+  {
+    nativeHandle = getNativeReaderEmbedded(fd, offset, size);
+    if (nativeHandle == 0) {
+        throw new JNIKiwixException(String.format("Cannot open embedded zimfile (fd=%s, offset=%d, size=%d)", fd, offset, size));
+    }
+  }
+
   public JNIKiwixReader() {
 
   }
@@ -168,5 +177,6 @@ public class JNIKiwixReader
 
   private native long getNativeReader(String filename);
   private native long getNativeReaderByFD(FileDescriptor fd);
+  private native long getNativeReaderEmbedded(FileDescriptor fd, long offset, long size);
   private long nativeHandle;
 }

src/wrapper/java/org/kiwix/testing/test.java

@@ -59,6 +59,25 @@ throws JNIKiwixException, IOException
 
 }
 
+@Test
+public void testReaderWithAnEmbeddedArchive()
+throws JNIKiwixException, IOException
+{
+  File plainArchive = new File("small.zim");
+  FileInputStream fis = new FileInputStream("small.zim.embedded");
+  JNIKiwixReader reader = new JNIKiwixReader(fis.getFD(), 8, plainArchive.length());
+  assertEquals("Test ZIM file", reader.getTitle());
+  assertEquals(45, reader.getFileSize()); // The file size is in KiB
+  assertEquals("A/main.html", reader.getMainPage());
+  String s = getFileContent("small_zimfile_data/main.html");
+  byte[] c = reader.getContent(new JNIKiwixString("A/main.html"),
+                                new JNIKiwixString(),
+                                new JNIKiwixString(),
+                                new JNIKiwixInt());
+  assertEquals(s, new String(c));
+
+}
+
 @Test
 public void testLibrary()
 throws IOException