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