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diff --git a/src/common/settings.h b/src/common/settings.h
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+++ b/src/common/settings.h
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+// Copyright (c) 2019-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_COMMON_SETTINGS_H
+#define BITCOIN_COMMON_SETTINGS_H
+
+#include <util/fs.h>
+
+#include <cstddef>
+#include <map>
+#include <string>
+#include <vector>
+
+class UniValue;
+
+namespace common {
+
+//! Settings value type (string/integer/boolean/null variant).
+//!
+//! @note UniValue is used here for convenience and because it can be easily
+//!       serialized in a readable format. But any other variant type that can
+//!       be assigned strings, int64_t, and bool values and has get_str(),
+//!       getInt<int64_t>(), get_bool(), isNum(), isBool(), isFalse(), isTrue() and
+//!       isNull() methods can be substituted if there's a need to move away
+//!       from UniValue. (An implementation with boost::variant was posted at
+//!       https://github.com/bitcoin/bitcoin/pull/15934/files#r337691812)
+using SettingsValue = UniValue;
+
+//! Stored settings. This struct combines settings from the command line, a
+//! read-only configuration file, and a read-write runtime settings file.
+struct Settings {
+    //! Map of setting name to forced setting value.
+    std::map<std::string, SettingsValue> forced_settings;
+    //! Map of setting name to list of command line values.
+    std::map<std::string, std::vector<SettingsValue>> command_line_options;
+    //! Map of setting name to read-write file setting value.
+    std::map<std::string, SettingsValue> rw_settings;
+    //! Map of config section name and setting name to list of config file values.
+    std::map<std::string, std::map<std::string, std::vector<SettingsValue>>> ro_config;
+};
+
+//! Read settings file.
+bool ReadSettings(const fs::path& path,
+    std::map<std::string, SettingsValue>& values,
+    std::vector<std::string>& errors);
+
+//! Write settings file.
+bool WriteSettings(const fs::path& path,
+    const std::map<std::string, SettingsValue>& values,
+    std::vector<std::string>& errors);
+
+//! Get settings value from combined sources: forced settings, command line
+//! arguments, runtime read-write settings, and the read-only config file.
+//!
+//! @param ignore_default_section_config - ignore values in the default section
+//!                                        of the config file (part before any
+//!                                        [section] keywords)
+//! @param ignore_nonpersistent - ignore non-persistent settings values (forced
+//!                               settings values and values specified on the
+//!                               command line). Only return settings in the
+//!                               read-only config and read-write settings
+//!                               files.
+//! @param get_chain_type - enable special backwards compatible behavior
+//!                         for GetChainType
+SettingsValue GetSetting(const Settings& settings,
+    const std::string& section,
+    const std::string& name,
+    bool ignore_default_section_config,
+    bool ignore_nonpersistent,
+    bool get_chain_type);
+
+//! Get combined setting value similar to GetSetting(), except if setting was
+//! specified multiple times, return a list of all the values specified.
+std::vector<SettingsValue> GetSettingsList(const Settings& settings,
+    const std::string& section,
+    const std::string& name,
+    bool ignore_default_section_config);
+
+//! Return true if a setting is set in the default config file section, and not
+//! overridden by a higher priority command-line or network section value.
+//!
+//! This is used to provide user warnings about values that might be getting
+//! ignored unintentionally.
+bool OnlyHasDefaultSectionSetting(const Settings& settings, const std::string& section, const std::string& name);
+
+//! Accessor for list of settings that skips negated values when iterated over.
+//! The last boolean `false` value in the list and all earlier values are
+//! considered negated.
+struct SettingsSpan {
+    explicit SettingsSpan() = default;
+    explicit SettingsSpan(const SettingsValue& value) noexcept : SettingsSpan(&value, 1) {}
+    explicit SettingsSpan(const SettingsValue* data, size_t size) noexcept : data(data), size(size) {}
+    explicit SettingsSpan(const std::vector<SettingsValue>& vec) noexcept;
+    const SettingsValue* begin() const; //!< Pointer to first non-negated value.
+    const SettingsValue* end() const;   //!< Pointer to end of values.
+    bool empty() const;                 //!< True if there are any non-negated values.
+    bool last_negated() const;          //!< True if the last value is negated.
+    size_t negated() const;             //!< Number of negated values.
+
+    const SettingsValue* data = nullptr;
+    size_t size = 0;
+};
+
+//! Map lookup helper.
+template <typename Map, typename Key>
+auto FindKey(Map&& map, Key&& key) -> decltype(&map.at(key))
+{
+    auto it = map.find(key);
+    return it == map.end() ? nullptr : &it->second;
+}
+
+} // namespace common
+
+#endif // BITCOIN_COMMON_SETTINGS_H