mirror of
https://github.com/valitydev/osquery-1.git
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112 lines
3.2 KiB
C++
112 lines
3.2 KiB
C++
/**
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* Copyright (c) 2014-present, The osquery authors
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*
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* This source code is licensed as defined by the LICENSE file found in the
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* root directory of this source tree.
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*
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* SPDX-License-Identifier: (Apache-2.0 OR GPL-2.0-only)
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*/
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#pragma once
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#include <map>
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#include <unordered_map>
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#include <osquery/utils/expected/expected.h>
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namespace osquery {
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/**
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* Helper functions to look up in key-value tables.
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*
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* There are several reasons for using this code:
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* 1. To reduce amount of code and increase the readability of it.
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* Instead of verbose piece of code such as:
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* @code{.cpp}
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* auto takenValue = ValueType{};
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* auto const it = table.find("key");
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* if (it != table.end()) {
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* takenValue = it->second;
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* }
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* @endcode
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* Have more short and simple:
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* @code{.cpp}
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* auto const takenValue = tryTakeCopy(table, "key").takeOr(ValueType{});
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* @endcode
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*
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* 2. To avoid nonoptimal code with two exactly the same lookups, e.g.:
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* @code{.cpp}
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* auto takenValue = table.count(key) ? table.at(key) : ValueType{};
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* @endcode
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*
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* 3. To reduce the possibility of dangerous misstypes such as:
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* @code{.cpp}
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* auto takenValue = table.count("key") ? table.at("KeY") : ValueType{};
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* @endcode
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*/
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enum class MapTakeError {
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NoSuchKey = 1,
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};
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namespace impl {
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template <typename T>
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struct IsMap : std::false_type {};
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template <typename... TemplateArgs>
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struct IsMap<std::map<TemplateArgs...>> : std::true_type {};
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template <typename... TemplateArgs>
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struct IsMap<std::unordered_map<TemplateArgs...>> : std::true_type {};
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} // namespace impl
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/**
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* @brief Take out object from the table by key
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*
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* @param table to look up (std::map or std::unordered_map)
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* @param key to look up by in the table
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*
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* @return Expected object with value if such key exists in the table,
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* otherwise Error of type MapTakeError
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*/
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template <typename MapType,
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typename KeyType = typename MapType::key_type,
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typename ValueType = typename MapType::mapped_type>
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inline typename std::enable_if<impl::IsMap<MapType>::value,
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Expected<ValueType, MapTakeError>>::type
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tryTake(MapType& table, const KeyType& key) {
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auto it = table.find(key);
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if (it == table.end()) {
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return createError(MapTakeError::NoSuchKey) << "no such key in the table";
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}
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auto item = std::move(it->second);
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table.erase(it);
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return item;
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}
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/**
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* @brief Take object copy from the table by key
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*
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* @param table to look up (std::map or std::unordered_map)
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* @param key to look up by in the table
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*
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* @return Expected object with value if such key exists in the table,
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* otherwise Error of type MapTakeError
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*/
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template <typename MapType,
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typename KeyType = typename MapType::key_type,
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typename ValueType = typename MapType::mapped_type>
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inline typename std::enable_if<impl::IsMap<MapType>::value,
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Expected<ValueType, MapTakeError>>::type
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tryTakeCopy(MapType const& from, KeyType const& key) {
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auto const it = from.find(key);
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if (it == from.end()) {
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return createError(MapTakeError::NoSuchKey) << "no such key in the table";
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}
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return it->second;
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}
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} // namespace osquery
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