Cache result of ls command.

src/navigate/listdircontent.cpp

@@ -0,0 +1,92 @@
+/* Copyright 2015, 2016, Michele Santullo
+ * This file is part of "dindexer".
+ *
+ * "dindexer" 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
+ * (at your option) any later version.
+ *
+ * "dindexer" 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 "dindexer".  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "listdircontent.hpp"
+#include "genericpath.hpp"
+#include "dbsource.hpp"
+#include "helpers/infix_iterator.hpp"
+#include <cassert>
+#include <utility>
+#include <boost/range/algorithm/copy.hpp>
+#include <sstream>
+#include <ciso646>
+#include <boost/lexical_cast.hpp>
+#include <algorithm>
+
+namespace din {
+	namespace {
+		template <typename V> std::vector<std::string> db_result_to_vec ( const V& parResult );
+		const std::size_t g_max_cached_lists = 4;
+
+		template <typename V>
+		std::vector<std::string> db_result_to_vec (const V& parResult) {
+			std::vector<std::string> result;
+			result.reserve(parResult.size());
+
+			for (const auto& row : parResult) {
+				std::ostringstream oss;
+				boost::copy(row, infix_ostream_iterator<std::string>(oss, "\t"));
+				result.push_back(oss.str());
+			}
+			return std::move(result);
+		}
+	} //unnamed namespace
+
+	ListDirContent::ListDirContent (DBSource* parDB) :
+		m_cache(g_max_cached_lists),
+		m_db(parDB)
+	{
+		assert(m_db);
+	}
+
+	auto ListDirContent::ls (const GenericPath& parDir) const -> const ListType& {
+		const auto curr_path = parDir.to_string();
+
+		//Check if requested item is already cached
+		auto it_found = std::find_if(m_cache.begin(), m_cache.end(), [&curr_path](const CachedItemType& itm) { return itm.first == curr_path; });
+		if (it_found != m_cache.end()) {
+			CachedItemType tmp;
+			std::swap(tmp, *it_found);
+			assert(it_found->first.empty());
+			assert(it_found->second.empty());
+			assert(tmp.first == curr_path);
+			m_cache.erase(it_found);
+			assert(m_cache.size() < g_max_cached_lists);
+			m_cache.push_back(std::move(tmp));
+			assert(not m_cache.empty());
+			assert(m_cache.back().first == curr_path);
+			return m_cache.back().second;
+		}
+
+		//Requested item is not cached, so we need to query the db now
+		if ("/" == curr_path) {
+			auto sets_ids = m_db->sets();
+			auto sets_info = m_db->set_details<SetDetail_ID, SetDetail_Desc, SetDetail_CreeationDate>(sets_ids);
+			m_cache.push_back(std::make_pair(curr_path, db_result_to_vec(sets_info)));
+		}
+		else {
+			const auto start_from = curr_path.find('/', 1);
+			auto path_prefix = boost::string_ref(curr_path).substr(start_from == curr_path.npos ? curr_path.size() : start_from + 1);
+			const auto set_id = boost::lexical_cast<uint32_t>(parDir[0]);
+			auto files_info = m_db->file_details<FileDetail_Path>(set_id, parDir.level(), path_prefix);
+			m_cache.push_back(std::make_pair(curr_path, db_result_to_vec(files_info)));
+		}
+		assert(not m_cache.empty());
+		assert(m_cache.back().first == curr_path);
+		return m_cache.back().second;
+	}
+} //namespace din