Add a downloader tools to download files.

The downloader is using libaria2.

For now, only one download can be run a the time.
A download will start only if (and as soon as) no download is running.

include/downloader.h

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2018 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.
+ */
+
+#ifndef KIWIX_DOWNLOADER_H
+#define KIWIX_DOWNLOADER_H
+
+#include <string>
+#include <aria2/aria2.h>
+#include <pthread.h>
+
+namespace kiwix
+{
+
+
+struct DownloadedFile {
+  DownloadedFile()
+   : success(false) {}
+  bool success;
+  std::string path;
+};
+
+/**
+ * A tool to download things.
+ *
+ */
+class Downloader
+{
+ public:
+  Downloader();
+  ~Downloader();
+
+  /**
+   * Download a content.
+   *
+   * @param url the url to download
+   * @return the content downloaded.
+   */
+  DownloadedFile download(const std::string& url);
+
+ private:
+  static pthread_mutex_t globalLock;
+
+  aria2::Session* session;
+  DownloadedFile* fileHandle;
+  std::string tmpDir;
+
+  static int downloadEventCallback(aria2::Session* session,
+                                   aria2::DownloadEvent event,
+                                   aria2::A2Gid gid,
+                                   void* userData);
+};
+}
+
+#endif

include/meson.build

@@ -2,6 +2,7 @@ headers = [
   'library.h',
   'manager.h',
   'opds_dumper.h',
+  'downloader.h',
   'reader.h',
   'searcher.h'
 ]

meson.build

@@ -12,6 +12,7 @@ thread_dep = dependency('threads')
 libicu_dep = dependency('icu-i18n', static:static_deps)
 libzim_dep = dependency('libzim', version : '>=3.2.0', static:static_deps)
 pugixml_dep = dependency('pugixml', static:static_deps)
+libaria2_dep = dependency('libaria2', static:static_deps)
 
 ctpp2_include_path = ''
 has_ctpp2_dep = false
@@ -72,7 +73,7 @@ endif
 
 xapian_dep = dependency('xapian-core', required:false, static:static_deps)
 
-all_deps = [thread_dep, libicu_dep, libzim_dep, xapian_dep, pugixml_dep]
+all_deps = [thread_dep, libicu_dep, libzim_dep, xapian_dep, pugixml_dep, libaria2_dep]
 if has_ctpp2_dep
   all_deps += [ctpp2_dep]
 endif
@@ -88,7 +89,7 @@ subdir('scripts')
 subdir('static')
 subdir('src')
 
-pkg_requires = ['libzim', 'icu-i18n', 'pugixml']
+pkg_requires = ['libzim', 'icu-i18n', 'pugixml', 'libaria2']
 if xapian_dep.found()
     pkg_requires += ['xapian-core']
 endif

src/downloader.cpp

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2018 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.
+ */
+
+#include "downloader.h"
+#include "common/pathTools.h"
+
+#include <unistd.h>
+#include <iostream>
+
+namespace kiwix
+{
+
+pthread_mutex_t Downloader::globalLock = PTHREAD_MUTEX_INITIALIZER;
+
+
+/* Constructor */
+Downloader::Downloader()
+{
+  aria2::SessionConfig config;
+  config.downloadEventCallback = Downloader::downloadEventCallback;
+  config.userData = this;
+  tmpDir = makeTmpDirectory();
+  aria2::KeyVals options;
+  options.push_back(std::pair<std::string, std::string>("dir", tmpDir));
+  session = aria2::sessionNew(options, config);
+}
+
+
+/* Destructor */
+Downloader::~Downloader()
+{
+  aria2::sessionFinal(session);
+  rmdir(tmpDir.c_str());
+}
+
+
+int Downloader::downloadEventCallback(aria2::Session* session,
+                                      aria2::DownloadEvent event,
+                                      aria2::A2Gid gid,
+                                      void* userData)
+{
+  Downloader* downloader = static_cast<Downloader*>(userData);
+
+  auto fileHandle = downloader->fileHandle;
+  auto dh = aria2::getDownloadHandle(session, gid);
+
+  if (!dh) {
+    return 0;
+  }
+
+  switch (event) {
+    case aria2::EVENT_ON_DOWNLOAD_COMPLETE:
+      {
+        if (dh->getNumFiles() > 0) {
+          auto f = dh->getFile(1);
+          fileHandle->path = f.path;
+          fileHandle->success = true;
+        }
+      }
+      break;
+    case aria2::EVENT_ON_DOWNLOAD_ERROR:
+      {
+        fileHandle->success = false;
+      }
+      break;
+    default:
+      break;
+  }
+  aria2::deleteDownloadHandle(dh);
+  return 0;
+}
+
+DownloadedFile Downloader::download(const std::string& url) {
+  pthread_mutex_lock(&globalLock);
+  DownloadedFile fileHandle;
+  try {
+    std::vector<std::string> uris = {url};
+    aria2::KeyVals options;
+    aria2::A2Gid gid;
+    int ret;
+    DownloadedFile fileHandle;
+    
+    ret = aria2::addUri(session, &gid, uris, options);
+    if (ret < 0) {
+      std::cerr << "Failed to download" << std::endl;
+    } else {
+      this->fileHandle = &fileHandle;
+      aria2::run(session, aria2::RUN_DEFAULT);
+    }
+  } catch (...) {};
+  this->fileHandle = nullptr;
+  pthread_mutex_unlock(&globalLock);
+  return fileHandle;
+}
+
+}

src/meson.build

@@ -2,6 +2,7 @@ kiwix_sources = [
   'library.cpp',
   'manager.cpp',
   'opds_dumper.cpp',
+  'downloader.cpp',
   'reader.cpp',
   'searcher.cpp',
   'common/base64.cpp',