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102 lines
2.8 KiB
C++
102 lines
2.8 KiB
C++
// This file is a part of toml++ and is subject to the the terms of the MIT license.
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// Copyright (c) Mark Gillard <mark.gillard@outlook.com.au>
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// See https://github.com/marzer/tomlplusplus/blob/master/LICENSE for the full license text.
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// SPDX-License-Identifier: MIT
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// This example demonstrates a method of merging one TOML data tree into another.
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#include "examples.h"
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#include <toml++/toml.h>
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using namespace std::string_view_literals;
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namespace
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{
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// recursively merge 'rhs' into 'lhs'.
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//
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// note that this implementation always prioritizes 'rhs' over 'lhs' in the event of a conflict;
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// extending it to handle conflicts in some other manner is left as an exercise to the reader :)
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static void merge_left(toml::table& lhs, toml::table&& rhs);
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static void merge_left(toml::array& lhs, toml::array&& rhs)
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{
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rhs.for_each(
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[&](std::size_t index, auto&& rhs_val)
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{
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// rhs index not found in lhs - direct move
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if (lhs.size() <= index)
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{
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lhs.push_back(std::move(rhs_val));
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return;
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}
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// both elements were the same container type - recurse into them
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if constexpr (toml::is_container<decltype(rhs_val)>)
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{
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using rhs_type = std::remove_cv_t<std::remove_reference_t<decltype(rhs_val)>>;
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if (auto lhs_child = lhs[index].as<rhs_type>())
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{
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merge_left(*lhs_child, std::move(rhs_val));
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return;
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}
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}
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// replace lhs element with rhs
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lhs.replace(lhs.cbegin() + static_cast<std::ptrdiff_t>(index), std::move(rhs_val));
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});
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}
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static void merge_left(toml::table& lhs, toml::table&& rhs)
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{
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rhs.for_each(
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[&](const toml::key& rhs_key, auto&& rhs_val)
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{
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auto lhs_it = lhs.lower_bound(rhs_key);
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// rhs key not found in lhs - direct move
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if (lhs_it == lhs.cend() || lhs_it->first != rhs_key)
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{
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using rhs_type = std::remove_cv_t<std::remove_reference_t<decltype(rhs_val)>>;
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lhs.emplace_hint<rhs_type>(lhs_it, rhs_key, std::move(rhs_val));
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return;
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}
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// both children were the same container type - recurse into them
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if constexpr (toml::is_container<decltype(rhs_val)>)
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{
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using rhs_type = std::remove_cv_t<std::remove_reference_t<decltype(rhs_val)>>;
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if (auto lhs_child = lhs_it->second.as<rhs_type>())
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{
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merge_left(*lhs_child, std::move(rhs_val));
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return;
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}
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}
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// replace lhs value with rhs
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lhs.insert_or_assign(rhs_key, std::move(rhs_val));
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});
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}
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}
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int main(int argc, char** argv)
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{
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const auto base_path = argc > 1 ? std::string_view{ argv[1] } : "merge_base.toml"sv;
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const auto overrides_path = argc > 2 ? std::string_view{ argv[2] } : "merge_overrides.toml"sv;
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toml::table tbl;
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try
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{
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tbl = toml::parse_file(base_path);
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merge_left(tbl, toml::parse_file(overrides_path));
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}
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catch (const toml::parse_error& err)
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{
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std::cerr << err << "\n";
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return 1;
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}
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std::cout << tbl << "\n";
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return 0;
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}
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