rspamd/src/libutil/cxx/util.hxx

/*
 * Copyright 2023 Vsevolod Stakhov
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#ifndef RSPAMD_UTIL_HXX
#define RSPAMD_UTIL_HXX

#pragma once

#include <memory>
#include <array>
#include <string_view>
#include <optional>
#include <tuple>
#include <algorithm>

/*
 * Common C++ utilities
 */

namespace rspamd {
/*
 * Creates std::array from a standard C style array with automatic size calculation
 */
template<typename... Ts>
constexpr auto array_of(Ts &&...t) -> std::array<typename std::decay_t<typename std::common_type_t<Ts...>>, sizeof...(Ts)>
{
	using T = typename std::decay_t<typename std::common_type_t<Ts...>>;
	return {{std::forward<T>(t)...}};
}

/**
 * Find a value in a map
 * @tparam C Map type
 * @tparam K Key type
 * @tparam V Value type
 * @param c Map to search
 * @param k Key to search
 * @return Value if found or std::nullopt otherwise
 */
template<class C, class K, class V = typename C::mapped_type, typename std::enable_if_t<std::is_constructible_v<typename C::key_type, K> && std::is_constructible_v<typename C::mapped_type, V>, bool> = false>
constexpr auto find_map(const C &c, const K &k) -> std::optional<std::reference_wrapper<const V>>
{
	auto f = c.find(k);

	if (f != c.end()) {
		return std::cref<V>(f->second);
	}

	return std::nullopt;
}


template<typename It>
inline constexpr auto make_string_view_from_it(It begin, It end)
{
	using result_type = std::string_view;

	return result_type{((begin != end) ? &*begin : nullptr),
					   (typename result_type::size_type) std::max(std::distance(begin, end),
																  (typename result_type::difference_type) 0)};
}

/**
 * Iterate over lines in a string, newline characters are dropped
 * @tparam S
 * @tparam F
 * @param input
 * @param functor
 * @return
 */
template<class S, class F, typename std::enable_if_t<std::is_invocable_v<F, std::string_view> && std::is_constructible_v<std::string_view, S>, bool> = true>
inline auto string_foreach_line(const S &input, const F &functor)
{
	auto it = input.begin();
	auto end = input.end();

	while (it != end) {
		auto next = std::find(it, end, '\n');
		while (next >= it && (*next == '\n' || *next == '\r')) {
			--next;
		}
		functor(make_string_view_from_it(it, next));
		it = next;

		if (it != end) {
			++it;
		}
	}
}

/**
 * Iterate over elements in a string
 * @tparam S string type
 * @tparam D delimiter type
 * @tparam F functor type
 * @param input string to iterate
 * @param delim delimiter to use
 * @param functor functor to call
 * @param ignore_empty ignore empty elements
 * @return nothing
 */
template<class S, class D, class F,
		 typename std::enable_if_t<std::is_invocable_v<F, std::string_view> && std::is_constructible_v<std::string_view, S> && std::is_constructible_v<std::string_view, D>, bool> = true>
inline auto string_foreach_delim(const S &input, const D &delim, const F &functor, const bool ignore_empty = true) -> void
{
	size_t first = 0;
	auto sv_input = std::string_view{input};
	auto sv_delim = std::string_view{delim};

	while (first < sv_input.size()) {
		const auto second = sv_input.find_first_of(sv_delim, first);

		if (first != second || !ignore_empty) {
			functor(sv_input.substr(first, second - first));
		}

		if (second == std::string_view::npos) {
			break;
		}

		first = second + 1;
	}
}

/**
 * Split string on a character
 * @tparam S string type
 * @param input string to split
 * @param chr character to split on
 * @return pair of strings
 */
template<class S, typename std::enable_if_t<std::is_constructible_v<std::string_view, S>, bool> = true>
inline auto string_split_on(const S &input, std::string_view::value_type chr) -> std::pair<std::string_view, std::string_view>
{
	auto pos = std::find(std::begin(input), std::end(input), chr);

	if (pos != input.end()) {
		auto first = std::string_view{std::begin(input), static_cast<std::size_t>(std::distance(std::begin(input), pos))};
		while (*pos == chr && pos != input.end()) {
			++pos;
		}
		auto last = std::string_view{pos, static_cast<std::size_t>(std::distance(pos, std::end(input)))};

		return {first, last};
	}

	return {std::string_view{input}, std::string_view{}};
}

/**
 * Enumerate for range loop
 * @tparam T iterable type
 * @tparam TIter iterator type
 * @param iterable iterable object
 * @return iterator object
 */
template<typename T,
		 typename TIter = decltype(std::begin(std::declval<T>())),
		 typename = decltype(std::end(std::declval<T>()))>
constexpr auto enumerate(T &&iterable)
{
	struct iterator {
		size_t i;
		TIter iter;
		bool operator!=(const iterator &other) const
		{
			return iter != other.iter;
		}
		void operator++()
		{
			++i;
			++iter;
		}
		auto operator*() const
		{
			return std::tie(i, *iter);
		}
	};
	struct iterable_wrapper {
		T iterable;
		auto begin()
		{
			return iterator{0, std::begin(iterable)};
		}
		auto end()
		{
			return iterator{0, std::end(iterable)};
		}
	};
	return iterable_wrapper{std::forward<T>(iterable)};
}

/**
 * Allocator that cleans up memory in a secure way on destruction
 * @tparam T
 */
template<class T>
class secure_mem_allocator : public std::allocator<T> {
public:
	using value_type = typename std::allocator<T>::value_type;
	using size_type = typename std::allocator<T>::size_type;
	template<class U>
	struct rebind {
		typedef secure_mem_allocator<U> other;
	};
	secure_mem_allocator() noexcept = default;
	secure_mem_allocator(const secure_mem_allocator &_) noexcept
		: std::allocator<T>(_)
	{
	}
	template<class U>
	explicit secure_mem_allocator(const secure_mem_allocator<U> &) noexcept
	{
	}

	void deallocate(value_type *p, size_type num) noexcept
	{
		rspamd_explicit_memzero((void *) p, num);
		std::allocator<T>::deallocate(p, num);
	}
};


}// namespace rspamd

#endif//RSPAMD_UTIL_HXX