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#include <iostream>
#include <coroutine>
#include <span>
#include <optional>
#include <fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <cassert>
#include <vector>
void load_flag()
{
char flag[400];
FILE* fp = fopen("flag", "rt");
fscanf(fp, "%s", flag);
fclose(fp);
}
struct io_context
{
struct entry
{
int fd;
std::coroutine_handle<> coroutine;
};
std::vector<entry> reads_;
std::vector<entry> writes_;
void run_until_done()
{
while (!reads_.empty() || !writes_.empty())
{
load_flag();
fd_set readfds;
FD_ZERO(&readfds);
fd_set writefds;
FD_ZERO(&writefds);
fd_set exceptfds;
FD_ZERO(&exceptfds);
int maxfd = 0;
for (auto& read : reads_)
{
maxfd = std::max(maxfd, read.fd);
FD_SET(read.fd, &readfds);
FD_SET(read.fd, &exceptfds);
}
for (auto& write : writes_)
{
maxfd = std::max(maxfd, write.fd);
FD_SET(write.fd, &writefds);
FD_SET(write.fd, &exceptfds);
}
int donefds = ::select(maxfd + 1, &readfds, &writefds, &exceptfds, /*timeout*/nullptr);
if (donefds == -1)
{
std::cerr << "Error performing select() errno: " << errno << '\n';
return;
}
// Take a copy as this may change
auto reads = reads_;
auto writes = writes_;
for (auto & read : reads)
{
if (FD_ISSET(read.fd, &readfds) || FD_ISSET(read.fd, &exceptfds))
{
auto coroutine = std::move(read.coroutine);
reads_.erase(std::remove_if(reads_.begin(), reads_.end(), [fd = read.fd](auto& item) { return item.fd == fd; }));
coroutine.resume();
continue;
}
}
for (auto& write : writes)
{
if (FD_ISSET(write.fd, &writefds) || FD_ISSET(write.fd, &exceptfds))
{
auto coroutine = std::move(write.coroutine);
writes_.erase(std::remove_if(writes_.begin(), writes_.end(), [fd = write.fd](auto& item) { return item.fd == fd; }));
coroutine.resume();
continue;
}
}
}
}
void add_read(int fd, std::coroutine_handle<> coroutine)
{
#ifdef _DEBUG
for (auto& read : reads_)
{
assert(read.fd != fd);
}
#endif
reads_.push_back({ fd, std::move(coroutine) });
}
void add_write(int fd, std::coroutine_handle<> coroutine)
{
#ifdef _DEBUG
for (auto& write: writes_)
{
assert(write.fd != fd);
}
#endif
writes_.push_back({ fd, std::move(coroutine) });
}
void cancel(int fd)
{
auto rit = reads_.begin();
while (rit != reads_.end())
{
if (rit->fd == fd)
{
reads_.erase(rit);
break;
}
}
auto wit = writes_.begin();
while (wit != writes_.end())
{
if (wit->fd == fd)
{
writes_.erase(wit);
break;
}
}
}
};
template<typename Result>
class Task {
public:
struct promise_type {
std::optional<Result> result_;
Task get_return_object() {
return Task{ this };
}
void unhandled_exception() noexcept {}
void return_value(Result result) noexcept { result_ = std::move(result); }
std::suspend_never initial_suspend() { return {}; }
struct FinalAwaiter {
constexpr bool await_ready() noexcept { return false; }
std::coroutine_handle<>
await_suspend(std::coroutine_handle<promise_type> coroutine) noexcept {
auto& promise = coroutine.promise();
return promise.continuation_ != nullptr ? promise.continuation_ : std::noop_coroutine();
}
// nothing to do, the coroutine will no longer be executed
void await_resume() noexcept { }
};
FinalAwaiter final_suspend() noexcept { return {}; }
void set_continuation(std::coroutine_handle<> continuation) {
continuation_ = continuation;
}
std::coroutine_handle<> continuation_;
};
explicit Task(promise_type* promise)
: handle_{ HandleT::from_promise(*promise) } {}
Task(Task&& other) : handle_{ std::exchange(other.handle_, nullptr) } { }
~Task() {
if (handle_) {
handle_.destroy();
}
}
Task & operator=(const Task&) = delete;
auto operator co_await() {
struct Awaiter {
std::coroutine_handle<promise_type> this_handle;
constexpr bool await_ready() {
assert(this_handle);
return this_handle.done();
}
void await_suspend(std::coroutine_handle<> awaiting_coroutine) {
this_handle.promise().set_continuation(awaiting_coroutine);
}
Result await_resume() {
return *this_handle.promise().result_;
}
};
return Awaiter{ handle_ };
}
using HandleT = std::coroutine_handle<promise_type>;
HandleT handle_;
};
struct NonCopyable
{
NonCopyable() = default;
NonCopyable(const NonCopyable&) = delete;
NonCopyable& operator=(const NonCopyable&) = delete;
};
int MakeNonBlocking(int fd)
{
int flags = fcntl(fd, F_GETFL, 0);
flags |= O_NONBLOCK;
return fcntl(fd, F_SETFL, flags);
}
class RecvAsync : NonCopyable {
public:
RecvAsync(io_context& ctx, int fd, std::span<std::byte> buffer) : NonCopyable(),
ctx_{ ctx },
fd_{ fd },
buffer_{ buffer }
{
}
auto operator co_await() {
struct Awaiter {
io_context& ctx_;
int fd_;
std::optional<int> result_;
std::span<std::byte> buffer_;
Awaiter(io_context& ctx, int fd, std::span<std::byte> buffer) :
ctx_{ ctx }, fd_{ fd }, buffer_{ buffer } {
}
bool await_ready() {
int result = ::recv(fd_, buffer_.data(), buffer_.size(), 0);
if (result == -1 && (errno == EAGAIN || errno == EWOULDBLOCK) )
{
return false;
}
result_ = result;
return true;
}
void await_suspend(std::coroutine_handle<> handle) noexcept {
ctx_.add_read(fd_, std::move(handle));
}
int await_resume() {
if (result_.has_value())
{
return result_.value();
}
int result = ::recv(fd_, buffer_.data(), buffer_.size(), 0);
if (result == -1)
{
assert(errno != EAGAIN && errno != EWOULDBLOCK);
}
return result;
}
};
return Awaiter{ ctx_, fd_, buffer_ };
}
private:
io_context& ctx_;
int fd_;
std::span<std::byte> buffer_;
};
class SendAsync : NonCopyable {
public:
SendAsync(io_context& ctx, int fd, std::span<std::byte> buffer) : NonCopyable(),
ctx_{ ctx },
fd_{ fd },
buffer_{ buffer }
{
}
auto operator co_await() {
struct Awaiter {
io_context& ctx_;
int fd_;
std::optional<int> result_;
std::span<std::byte> buffer_;
Awaiter(io_context& ctx, int fd, std::span<std::byte> buffer) :
ctx_{ ctx }, fd_{ fd }, buffer_{ buffer } {
}
bool await_ready() {
int result = ::send(fd_, buffer_.data(), buffer_.size(), 0);
if (result == -1 && (errno == EAGAIN || errno == EWOULDBLOCK))
{
return false;
}
result_ = result;
return true;
}
void await_suspend(std::coroutine_handle<> handle) noexcept {
ctx_.add_write(fd_, std::move(handle));
}
int await_resume() {
if (result_.has_value())
{
return result_.value();
}
int result = ::send(fd_, buffer_.data(), buffer_.size(), 0);
if (result == -1)
{
assert(errno != EAGAIN && errno != EWOULDBLOCK);
}
return result;
}
};
return Awaiter{ ctx_, fd_, buffer_ };
}
private:
io_context& ctx_;
int fd_;
std::span<std::byte> buffer_;
};
Task<bool> SendAllAsync(io_context& ctx, int socket, std::span<std::byte> buffer)
{
int offset = 0;
while (offset < buffer.size())
{
int result = co_await SendAsync(ctx, socket, std::span(buffer.data() + offset, buffer.size() - offset));
if (result == -1)
{
co_return false;
}
offset += result;
}
co_return true;
}
Task<bool> SendAllAsyncNewline(io_context& ctx, int socket, std::span<std::byte> buffer)
{
std::byte buffer2[513];
std::copy(buffer.begin(), buffer.end(), buffer2);
buffer2[buffer.size()] = (std::byte)'\n';
return SendAllAsync(ctx, socket, std::span(buffer2, buffer.size()+1));
}
Task<bool> client_loop(io_context& ctx, int socket)
{
while (true)
{
std::byte buffer[512];
int recved = co_await RecvAsync(ctx, socket, buffer);
if (recved == 0)
{
std::cout << "Disconnected\n";
co_return true;
}
if (recved == -1)
{
std::cout << "Could not receive\n";
co_return false;
}
bool send_result = co_await SendAllAsyncNewline(ctx, socket, std::span(buffer, recved));
if (!send_result)
{
std::cout << "Could not send: " << errno << "\n";
co_return false;
}
}
}
Task<bool> server(io_context & ctx)
{
int sock = socket(AF_INET, SOCK_STREAM, 0);
assert(sock != -1);
int listen_result = listen(sock, 1);
assert(listen_result != -1);
struct sockaddr_in sin;
socklen_t len = sizeof(sin);
int getsockname_result = ::getsockname(sock, (sockaddr*)&sin, &len);
assert(getsockname_result != -1);
std::cout << "port number " << ntohs(sin.sin_port) << "\n";
int client_size;
struct sockaddr_in client_addr;
socklen_t client_addr_size = sizeof(client_addr);
int accept_result = accept(sock, (sockaddr*)&client_addr, &client_addr_size);
assert(accept_result != -1);
MakeNonBlocking(accept_result);
int sendbuff = 128;
setsockopt(accept_result, SOL_SOCKET, SO_SNDBUF, &sendbuff, sizeof(sendbuff)); // sendbuf 128
co_await client_loop(ctx, accept_result);
co_return true;
}
int main(int argc, char* argv[])
{
setbuf(stdout, nullptr);
io_context ctx;
auto s = server(ctx);
ctx.run_until_done();
return EXIT_SUCCESS;
}
|
roderick
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