Allow zim::Archive to be created with a set of File descriptor.

lib/build.gradle

@@ -354,7 +354,8 @@ String getLibzimFiles() {
         "${projectDir}/src/main/java/org/kiwix/libzim/SuggestionSearcher.java " +
         "${projectDir}/src/main/java/org/kiwix/libzim/SuggestionSearch.java " +
         "${projectDir}/src/main/java/org/kiwix/libzim/ZimFileFormatException.java " +
-        "${projectDir}/src/main/java/org/kiwix/libzim/EntryNotFoundException.java"
+        "${projectDir}/src/main/java/org/kiwix/libzim/EntryNotFoundException.java " +
+        "${projectDir}/src/main/java/org/kiwix/libzim/FdInput.java"
 }
 
 task buildLinuxBinding(type: Exec) {

lib/src/main/cpp/libzim/archive.cpp

@@ -62,6 +62,22 @@ int jni2fd(const jobject& fdObj, JNIEnv* env)
   return env->GetIntField(fdObj, field_fd);
 }
 
+zim::FdInput jni2fdInput(const jobject& fdInputObj, JNIEnv* env)
+{
+  jclass class_fdesc = env->FindClass("org/kiwix/FdInput");
+  jfieldID field_id = env->GetFieldID(class_fdesc, "fd", "java/io/FileDescriptor");
+  jobject fdObj = env->GetField(fdInputObj, field_id);
+  int fd = jni2fd(fdObj, env);
+
+  field_id = env->GetFieldID(class_fdesc, "offset", "J");
+  long offset = env->GetLongField(fdObj, field_id);
+
+  field_id = env->GetFieldID(class_fdesc, "size", "J");
+  long size = env->GetLongField(fdObj, field_id);
+
+  return zim::FdInput(fd, offset, size);
+}
+
 } // unnamed namespace
 
 JNIEXPORT void JNICALL Java_org_kiwix_libzim_Archive_setNativeArchiveByFD(
@@ -104,6 +120,55 @@ JNIEXPORT void JNICALL Java_org_kiwix_libzim_Archive_setNativeArchiveEmbedded(
 #endif
 } CATCH_EXCEPTION()
 
+JNIEXPORT void JNICALL Java_org_kiwix_libzim_Archive_setNativeArchiveEmbeddedFd(
+    JNIEnv* env, jobject thisObj, jobject fdObj) try
+{
+#ifndef _WIN32
+  auto fdInput = jni2fdInput(fdObj, env);
+
+  LOG("Attempting to create reader with fd: %d", fdInput);
+  try {
+    auto archive = std::make_shared<zim::Archive>(fdInput);
+    SET_PTR(archive);
+  } catch (std::exception& e) {
+    LOG("Error opening ZIM file");
+       LOG("%s", e.what());
+  }
+#else
+  jclass exception = env->FindClass("java/lang/UnsupportedOperationException");
+  env->ThrowNew(exception, "org.kiwix.libzim.Archive.setNativeArchiveEmbedded() is not supported under Windows");
+#endif
+} CATCH_EXCEPTION()
+
+
+JNIEXPORT void JNICALL Java_org_kiwix_libzim_Archive_setNativeArchiveEmbeddedFds(
+    JNIEnv* env, jobject thisObj, jobjectArray fdsObj) try
+{
+#ifndef _WIN32
+
+  jsize length = env->GetArrayLength(fdsObj);
+  std::vector<zim::FdInput> v(length);
+
+  int i;
+  for(i = 0; i<length; i++) {
+    jobject fdObj = env->GetObjectArrayElement(fdsObj, i);
+    auto fdInput = jni2fdInput(fdObj, env);
+    v.push_pack(fdInput);
+  }
+
+  try {
+    auto archive = std::make_shared<zim::Archive>(v);
+    SET_PTR(archive);
+  } catch (std::exception& e) {
+    LOG("Error opening ZIM file");
+       LOG("%s", e.what());
+  }
+#else
+  jclass exception = env->FindClass("java/lang/UnsupportedOperationException");
+  env->ThrowNew(exception, "org.kiwix.libzim.Archive.setNativeArchiveEmbedded() is not supported under Windows");
+#endif
+} CATCH_EXCEPTION()
+
 DISPOSE
 
 GETTER(jstring, getFilename)

lib/src/main/java/org/kiwix/libzim/Archive.java

@@ -23,6 +23,7 @@ import org.kiwix.libzim.ZimFileFormatException;
 import org.kiwix.libzim.Entry;
 import org.kiwix.libzim.Item;
 import org.kiwix.libzim.EntryIterator;
+import org.kiwix.libzim.FdInput;
 import java.io.FileDescriptor;
 
 public class Archive
@@ -44,6 +45,18 @@ public class Archive
     setNativeArchiveEmbedded(fd, offset, size);
   }
 
+  public Archive(FdInput fd)
+  throws ZimFileFormatException
+  {
+    setNativeArchiveEmbeddedFd(fd);
+  }
+
+  public Archive(FdInput[] fds)
+  throws ZimFileFormatException
+  {
+    setNativeArchiveEmbeddedFds(fds);
+  }
+
   public native String getFilename();
   public native long getFilesize();
   public native int getAllEntryCount();
@@ -94,6 +107,8 @@ public class Archive
   private native void setNativeArchive(String filename);
   private native void setNativeArchiveByFD(FileDescriptor fd);
   private native void setNativeArchiveEmbedded(FileDescriptor fd, long offset, long size);
+  private native void setNativeArchiveEmbeddedFd(FdInput fd);
+  private native void setNativeArchiveEmbeddedFds(FdInput[] fds);
 
   @Override
   protected void finalize() { dispose(); }

lib/src/main/java/org/kiwix/libzim/FdInput.java

@@ -0,0 +1,29 @@
+/*
+ * 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.libzim;
+
+import java.io.FileDescriptor;
+
+public class FdInput
+{
+  public FileDescriptor fd;
+  public long offset;
+  public long size;
+}