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thread.cpp
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118 lines (97 loc) · 4.03 KB
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/*
* Copyright (c) 2024 The RefValue Project
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "thread.hpp"
#include "abi/memory.hpp"
#include <atomic>
#include <charconv>
#include <future>
#include <mutex>
#include <sstream>
#include <thread>
namespace essence {
abi::string serialize_thread_id() {
using abi_stringstream = std::basic_stringstream<char, std::char_traits<char>, abi::uniform_allocator<char>>;
abi_stringstream stream;
stream << std::this_thread::get_id();
return stream.str();
}
std::uint64_t decimalize_thread_id_or_zero() {
std::uint64_t result{};
const auto thread_id = serialize_thread_id();
static_cast<void>(std::from_chars(thread_id.data(), thread_id.data() + thread_id.size(), result));
return result;
}
void parallel_for(std::size_t start, std::size_t end, std::size_t thread_count,
const std::function<void(std::size_t index, std::size_t thread_index, bool& exit)>& handler) {
if (!handler) {
return;
}
if (thread_count <= 0) {
thread_count = std::thread::hardware_concurrency();
}
if (thread_count == 1) {
bool exit{};
for (std::size_t id = start; id < end; id++) {
if (!exit) {
handler(id, 0, exit);
}
}
} else {
std::vector<std::future<void>> workers;
std::atomic_size_t current{start};
std::mutex mutex;
std::exception_ptr last_exception;
for (std::size_t i = 0; i < thread_count; ++i) {
workers.emplace_back(std::async([&, i] {
for (bool exit{};;) {
const auto id = current.fetch_add(1, std::memory_order::acq_rel);
if (id >= end) {
break;
}
try {
if (!exit) {
handler(id, i, exit);
}
} catch (...) {
std::scoped_lock lock{mutex};
last_exception = std::current_exception();
/*
* This will work even when current is the largest value that
* size_t can fit, because fetch_add returns the previous value
* before the increment (what will result in overflow
* and produce 0 instead of current + 1).
*/
current.store(end, std::memory_order::release);
break;
}
}
}));
}
for (auto&& item : workers) {
item.get();
}
if (last_exception) {
std::rethrow_exception(last_exception);
}
}
}
} // namespace essence