user-gcc/src/env_fake.cpp

/* Copyright 2020, Michele Santullo
 * This file is part of user-gcc.
 *
 * User-gcc is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * User-gcc is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with user-gcc.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "env_fake.hpp"
#include "to_var_map.hpp"
#include "safe_print.hpp"
#include "string_view_cat.hpp"
#include <unistd.h>
#include <utility>
#include <optional>
#include <type_traits>
#include <cassert>
#include <algorithm>

namespace duck {
namespace {
	template <
		typename M,
		typename I,
		typename F,
		typename R=decltype(std::declval<F>()(std::declval<decltype(std::declval<M>().find(std::declval<I>()))&>())),
		//not supposed to be altered by the caller
		bool FIsNoex=noexcept(std::declval<F>()(std::declval<decltype(std::declval<M>().find(std::declval<I>()))&>())) and noexcept(R())
	>
	R run_if_found (M& map, const I& item, F func) noexcept(FIsNoex) {
		typedef decltype(map.find(item)) iterator_type;

		iterator_type it_found;
		if constexpr (FIsNoex) {
			try {
				it_found = map.find(item);
			}
			catch (...) {
				safe_print_error("Unexpected exception in run_if_found() will be ignored");
			}
		}
		else {
			it_found = map.find(item);
		}

		if constexpr (std::is_same<R, void>::value) {
			if (map.end() != it_found) {
				func(it_found);
			}
		}
		else {
			if (map.end() != it_found) {
				return func(it_found);
			}
			else {
				return R{};
			}
		}
	}
} //unnamed namespace

EnvFake::EnvFake (bool starts_empty) :
	m_map_strong_cpy(),
	m_map(starts_empty ? map_type() : to_var_map_ignore_ownership(environ))
{
}

std::optional<std::string_view> EnvFake::get (std::string_view name) const noexcept {
	return run_if_found(m_map, name, [](auto& it)noexcept{return std::make_optional(it->second);});
}

std::string_view EnvFake::get (std::string_view name, std::string_view def) const noexcept {
	bool ret_def{true};
	std::string_view maybe_ret(run_if_found(m_map, name, [&ret_def](auto& it)noexcept{ret_def=false; return it->second;}));
	if (ret_def)
		return def;
	else
		return maybe_ret;
}

void EnvFake::set (std::string_view name, std::string_view value) {
	assert(not name.empty());
	if (name.empty())
		return;

	const std::size_t size = name.size() + value.size();
	std::unique_ptr<char[]> buff = std::make_unique<char[]>(size);
	std::copy(name.begin(), name.end(), buff.get());
	std::copy(value.begin(), value.end(), buff.get() + name.size());

	const std::string_view new_name(buff.get(), name.size());
	assert(new_name == name);
	const std::string_view new_value(buff.get() + name.size(), value.size());
	assert(new_value == value);

	m_map_strong_cpy.insert_or_assign(std::string_view(new_name), std::move(buff));
	m_map.insert_or_assign(std::string_view(new_name), std::string_view(new_value));
	assert(m_map.at(name) == value);
	assert(m_map.find(name)->first.data() == new_name.data());
}

void EnvFake::unset (std::string_view name) noexcept {
	run_if_found(m_map, name, [&](auto& it)noexcept{m_map.erase(it);});
	run_if_found(m_map_strong_cpy, name, [&](auto& it)noexcept{m_map_strong_cpy.erase(it);});
}

bool EnvFake::is_set (std::string_view name) const noexcept {
	return run_if_found(m_map, name, [](auto&)noexcept{return true;});
}

auto EnvFake::size() const noexcept -> size_type {
	return m_map.size();
}

void EnvFake::clear() noexcept {
	m_map.clear();
	m_map_strong_cpy.clear();
}

} //namespace duck