ClickHouse/src/Core/examples/coro.cpp

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#include <iostream>
#include <cassert>
#include <iostream>
#include <string>
#include <optional>
#include <Common/Exception.h>
#include <base/logger_useful.h>
#include <Poco/ConsoleChannel.h>
#include <Poco/Logger.h>
#include <Poco/AutoPtr.h>
#if defined(__clang__)
#include <experimental/coroutine>
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namespace std
{
using namespace experimental::coroutines_v1;
}
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#else
#include <coroutine>
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#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
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#endif
template <typename T>
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struct suspend_value // NOLINT(readability-identifier-naming)
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{
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constexpr bool await_ready() const noexcept { return true; } // NOLINT(readability-identifier-naming)
constexpr void await_suspend(std::coroutine_handle<>) const noexcept {} // NOLINT(readability-identifier-naming)
constexpr T await_resume() const noexcept // NOLINT(readability-identifier-naming)
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{
std::cout << " ret " << val << std::endl;
return val;
}
T val;
};
template <typename T>
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struct Task
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{
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struct promise_type // NOLINT(readability-identifier-naming)
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{
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using coro_handle = std::coroutine_handle<promise_type>;
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auto get_return_object() { return coro_handle::from_promise(*this); } // NOLINT(readability-identifier-naming)
auto initial_suspend() { return std::suspend_never(); } // NOLINT(readability-identifier-naming)
auto final_suspend() noexcept { return suspend_value<T>{*r->value}; } // NOLINT(readability-identifier-naming)
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//void return_void() {}
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void return_value(T value_) { r->value = value_; } // NOLINT(readability-identifier-naming)
void unhandled_exception() // NOLINT(readability-identifier-naming)
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{
DB::tryLogCurrentException("Logger");
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r->exception = std::current_exception(); // NOLINT(bugprone-throw-keyword-missing)
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}
explicit promise_type(std::string tag_) : tag(tag_) {}
~promise_type() { std::cout << "~promise_type " << tag << std::endl; }
std::string tag;
coro_handle next;
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Task * r = nullptr;
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};
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using coro_handle = std::coroutine_handle<promise_type>;
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bool await_ready() const noexcept { return false; } // NOLINT(readability-identifier-naming)
void await_suspend(coro_handle g) noexcept // NOLINT(readability-identifier-naming)
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{
std::cout << " await_suspend " << my.promise().tag << std::endl;
std::cout << " g tag " << g.promise().tag << std::endl;
g.promise().next = my;
}
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T await_resume() noexcept // NOLINT(readability-identifier-naming)
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{
std::cout << " await_res " << my.promise().tag << std::endl;
return *value;
}
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explicit Task(coro_handle handle) : my(handle), tag(handle.promise().tag)
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{
assert(handle);
my.promise().r = this;
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std::cout << " Task " << tag << std::endl;
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}
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Task(Task &) = delete;
Task(Task &&rhs) : my(rhs.my), tag(rhs.tag)
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{
rhs.my = {};
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std::cout << " Task&& " << tag << std::endl;
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}
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static bool resumeImpl(Task *r)
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{
if (r->value)
return false;
auto & next = r->my.promise().next;
if (next)
{
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if (resumeImpl(next.promise().r))
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return true;
next = {};
}
if (!r->value)
{
r->my.resume();
if (r->exception)
std::rethrow_exception(r->exception);
}
return !r->value;
}
bool resume()
{
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return resumeImpl(this);
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}
T res()
{
return *value;
}
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~Task()
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{
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std::cout << " ~Task " << tag << std::endl;
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}
private:
coro_handle my;
std::string tag;
std::optional<T> value;
std::exception_ptr exception;
};
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Task<int> boo([[maybe_unused]] std::string tag)
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{
std::cout << "x" << std::endl;
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co_await std::suspend_always();
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std::cout << StackTrace().toString();
std::cout << "y" << std::endl;
co_return 1;
}
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Task<int> bar([[maybe_unused]] std::string tag)
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{
std::cout << "a" << std::endl;
int res1 = co_await boo("boo1");
std::cout << "b " << res1 << std::endl;
int res2 = co_await boo("boo2");
if (res2 == 1)
throw DB::Exception(1, "hello");
std::cout << "c " << res2 << std::endl;
co_return res1 + res2; // 1 + 1 = 2
}
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Task<int> foo([[maybe_unused]] std::string tag) {
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std::cout << "Hello" << std::endl;
auto res1 = co_await bar("bar1");
std::cout << "Coro " << res1 << std::endl;
auto res2 = co_await bar("bar2");
std::cout << "World " << res2 << std::endl;
co_return res1 * res2; // 2 * 2 = 4
}
int main()
{
Poco::AutoPtr<Poco::ConsoleChannel> app_channel(new Poco::ConsoleChannel(std::cerr));
Poco::Logger::root().setChannel(app_channel);
Poco::Logger::root().setLevel("trace");
LOG_INFO(&Poco::Logger::get(""), "Starting");
try
{
auto t = foo("foo");
std::cout << ".. started" << std::endl;
while (t.resume())
std::cout << ".. yielded" << std::endl;
std::cout << ".. done: " << t.res() << std::endl;
}
catch (DB::Exception & e)
{
std::cout << "Got exception " << e.what() << std::endl;
std::cout << e.getStackTraceString() << std::endl;
}
}