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Diffstat (limited to 'tomlplusplus/examples/toml_merger.cpp')
| -rw-r--r-- | tomlplusplus/examples/toml_merger.cpp | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/tomlplusplus/examples/toml_merger.cpp b/tomlplusplus/examples/toml_merger.cpp new file mode 100644 index 0000000000..5835b81693 --- /dev/null +++ b/tomlplusplus/examples/toml_merger.cpp @@ -0,0 +1,101 @@ +// 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.hpp" +#include <toml++/toml.hpp> + +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; +} |
