91 lines
1.8 KiB
C++
91 lines
1.8 KiB
C++
//
|
|
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2022
|
|
//
|
|
// Distributed under the Boost Software License, Version 1.0. (See accompanying
|
|
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
|
|
//
|
|
#pragma once
|
|
|
|
#include "td/utils/common.h"
|
|
#include "td/utils/port/sleep.h"
|
|
#include "td/utils/port/thread.h"
|
|
#include "td/utils/type_traits.h"
|
|
|
|
#include <atomic>
|
|
#include <cstring>
|
|
#include <memory>
|
|
|
|
namespace td {
|
|
|
|
template <class T>
|
|
class AtomicRead {
|
|
public:
|
|
void read(T &dest) const {
|
|
int it = 0;
|
|
const int wait_each_it = 4;
|
|
auto wait = [&]() {
|
|
it++;
|
|
if (it % wait_each_it == 0) {
|
|
usleep_for(1);
|
|
}
|
|
};
|
|
|
|
while (true) {
|
|
static_assert(TD_IS_TRIVIALLY_COPYABLE(T), "T must be trivially copyable");
|
|
auto version_before = version.load();
|
|
if (version_before % 2 == 0) {
|
|
std::memcpy(&dest, &value, sizeof(dest));
|
|
auto version_after = version.load();
|
|
if (version_before == version_after) {
|
|
break;
|
|
}
|
|
}
|
|
wait();
|
|
}
|
|
}
|
|
|
|
struct Write {
|
|
explicit Write(AtomicRead *read) {
|
|
read->do_lock();
|
|
ptr.reset(read);
|
|
}
|
|
struct Destructor {
|
|
void operator()(AtomicRead *read) const {
|
|
read->do_unlock();
|
|
}
|
|
};
|
|
T &operator*() {
|
|
return value();
|
|
}
|
|
T *operator->() {
|
|
return &value();
|
|
}
|
|
T &value() {
|
|
CHECK(ptr);
|
|
return ptr->value;
|
|
}
|
|
|
|
private:
|
|
std::unique_ptr<AtomicRead, Destructor> ptr;
|
|
};
|
|
|
|
Write lock() {
|
|
return Write(this);
|
|
}
|
|
|
|
private:
|
|
std::atomic<uint64> version{0};
|
|
T value;
|
|
|
|
void do_lock() {
|
|
bool is_locked = ++version % 2 == 1;
|
|
CHECK(is_locked);
|
|
}
|
|
void do_unlock() {
|
|
bool is_unlocked = ++version % 2 == 0;
|
|
CHECK(is_unlocked);
|
|
}
|
|
};
|
|
|
|
} // namespace td
|