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new cyclic writer

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This commit is contained in:
awe
2026-04-09 18:27:59 +03:00
parent 9b521641c9
commit af462ab46a
3 changed files with 402 additions and 219 deletions
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418
tty_protocol_writer.cpp
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@ -1,48 +1,68 @@
#include "tty_protocol_writer.h"
#include <algorithm>
#include <array>
#include <chrono>
#include <cstring>
#include <exception>
#include <stdexcept>
#include <thread>
#include <utility>
#include <vector>
#ifdef _WIN32
TtyProtocolWriter::TtyProtocolWriter(std::string path) : path_(std::move(path)) {
struct TtyProtocolWriter::Impl {};
TtyProtocolWriter::TtyProtocolWriter(std::string path, std::size_t ring_capacity_bytes)
: path_(std::move(path)) {
(void) ring_capacity_bytes;
throw std::runtime_error("tty output is supported only on Linux/POSIX");
}
TtyProtocolWriter::~TtyProtocolWriter() = default;
TtyProtocolWriter::TtyProtocolWriter(TtyProtocolWriter&& other) noexcept = default;
void TtyProtocolWriter::emit_packet_start() {}
TtyProtocolWriter& TtyProtocolWriter::operator=(TtyProtocolWriter&& other) noexcept = default;
void TtyProtocolWriter::emit_packet_start() const {}
void TtyProtocolWriter::emit_step(uint16_t index, int16_t ch1_avg, int16_t ch2_avg) const {
void TtyProtocolWriter::emit_step(uint16_t index, int16_t ch1_avg, int16_t ch2_avg) {
(void) index;
(void) ch1_avg;
(void) ch2_avg;
}
void TtyProtocolWriter::enqueue_encoded_frames(const uint16_t* words, std::size_t frame_count) {
(void) words;
(void) frame_count;
}
TtyProtocolWriter::StatsSnapshot TtyProtocolWriter::stats() const {
return {};
}
const std::string& TtyProtocolWriter::path() const {
return path_;
}
void TtyProtocolWriter::write_frame(uint16_t word0, uint16_t word1, uint16_t word2, uint16_t word3) const {
void TtyProtocolWriter::throw_if_failed() const {}
void TtyProtocolWriter::shutdown() {}
void TtyProtocolWriter::enqueue_frame(uint16_t word0, uint16_t word1, uint16_t word2, uint16_t word3) {
(void) word0;
(void) word1;
(void) word2;
(void) word3;
}
void TtyProtocolWriter::close_fd() noexcept {}
void TtyProtocolWriter::worker_loop() {}
#else
#include <array>
#include <cerrno>
#include <cstring>
#include <condition_variable>
#include <fcntl.h>
#include <limits.h>
#include <mutex>
#include <optional>
#include <pty.h>
#include <sstream>
@ -53,12 +73,24 @@ void TtyProtocolWriter::close_fd() noexcept {}
namespace {
constexpr std::size_t kFrameWordCount = 4U;
constexpr std::size_t kFrameByteCount = kFrameWordCount * sizeof(uint16_t);
using EncodedFrame = std::array<std::uint8_t, kFrameByteCount>;
std::string io_error(const std::string& action, const std::string& path) {
std::ostringstream out;
out << action << " '" << path << "': " << std::strerror(errno);
return out.str();
}
void close_fd_if_open(int& fd) noexcept {
if (fd >= 0) {
::close(fd);
fd = -1;
}
}
void set_fd_raw(int fd) {
struct termios tio {};
if (::tcgetattr(fd, &tio) != 0) {
@ -94,146 +126,286 @@ std::optional<std::string> read_link_target(const std::string& path) {
return std::string(buf.data());
}
EncodedFrame encode_frame(uint16_t word0, uint16_t word1, uint16_t word2, uint16_t word3) {
const uint16_t words[kFrameWordCount] = {word0, word1, word2, word3};
EncodedFrame frame {};
std::memcpy(frame.data(), words, sizeof(words));
return frame;
}
} // namespace
TtyProtocolWriter::TtyProtocolWriter(std::string path) : path_(std::move(path)) {
struct TtyProtocolWriter::Impl {
explicit Impl(std::size_t ring_capacity_bytes)
: capacity_frames(std::max<std::size_t>(1U, ring_capacity_bytes / kFrameByteCount)),
ring(capacity_frames) {}
int fd = -1;
int slave_fd = -1;
std::string slave_path;
bool owns_link = false;
const std::size_t capacity_frames;
std::vector<EncodedFrame> ring;
std::size_t head = 0;
std::size_t size = 0;
mutable std::mutex mutex;
std::condition_variable data_ready_cv;
std::thread worker;
bool stop_requested = false;
std::exception_ptr failure;
StatsSnapshot stats;
};
TtyProtocolWriter::TtyProtocolWriter(std::string path, std::size_t ring_capacity_bytes)
: path_(std::move(path)),
impl_(std::make_unique<Impl>(ring_capacity_bytes)) {
if (is_character_device_path(path_)) {
fd_ = ::open(path_.c_str(), O_WRONLY | O_NOCTTY);
if (fd_ < 0) {
impl_->fd = ::open(path_.c_str(), O_WRONLY | O_NOCTTY);
if (impl_->fd < 0) {
throw std::runtime_error(io_error("Cannot open tty output", path_));
}
return;
}
std::array<char, PATH_MAX> slave_name {};
if (::openpty(&fd_, &slave_fd_, slave_name.data(), nullptr, nullptr) != 0) {
throw std::runtime_error(io_error("Cannot create PTY bridge for", path_));
}
try {
slave_path_ = slave_name.data();
set_fd_raw(slave_fd_);
struct stat st {};
if (::lstat(path_.c_str(), &st) == 0) {
if (!S_ISLNK(st.st_mode) && !S_ISREG(st.st_mode)) {
throw std::runtime_error("Refusing to replace non-link path '" + path_ + "'");
}
if (::unlink(path_.c_str()) != 0) {
throw std::runtime_error(io_error("Cannot remove existing tty link", path_));
}
} else if (errno != ENOENT) {
throw std::runtime_error(io_error("Cannot inspect tty link path", path_));
} else {
std::array<char, PATH_MAX> slave_name {};
if (::openpty(&impl_->fd, &impl_->slave_fd, slave_name.data(), nullptr, nullptr) != 0) {
throw std::runtime_error(io_error("Cannot create PTY bridge for", path_));
}
if (::symlink(slave_path_.c_str(), path_.c_str()) != 0) {
throw std::runtime_error(io_error("Cannot create tty symlink", path_));
try {
impl_->slave_path = slave_name.data();
set_fd_raw(impl_->slave_fd);
struct stat st {};
if (::lstat(path_.c_str(), &st) == 0) {
if (!S_ISLNK(st.st_mode) && !S_ISREG(st.st_mode)) {
throw std::runtime_error("Refusing to replace non-link path '" + path_ + "'");
}
if (::unlink(path_.c_str()) != 0) {
throw std::runtime_error(io_error("Cannot remove existing tty link", path_));
}
} else if (errno != ENOENT) {
throw std::runtime_error(io_error("Cannot inspect tty link path", path_));
}
if (::symlink(impl_->slave_path.c_str(), path_.c_str()) != 0) {
throw std::runtime_error(io_error("Cannot create tty symlink", path_));
}
impl_->owns_link = true;
} catch (...) {
close_fd_if_open(impl_->slave_fd);
close_fd_if_open(impl_->fd);
throw;
}
} catch (...) {
close_slave_fd();
close_fd();
throw;
}
owns_link_ = true;
impl_->worker = std::thread([this]() { worker_loop(); });
}
TtyProtocolWriter::~TtyProtocolWriter() {
remove_owned_link();
close_slave_fd();
close_fd();
}
TtyProtocolWriter::TtyProtocolWriter(TtyProtocolWriter&& other) noexcept
: path_(std::move(other.path_)),
fd_(other.fd_),
slave_fd_(other.slave_fd_),
slave_path_(std::move(other.slave_path_)),
owns_link_(other.owns_link_) {
other.fd_ = -1;
other.slave_fd_ = -1;
other.owns_link_ = false;
}
TtyProtocolWriter& TtyProtocolWriter::operator=(TtyProtocolWriter&& other) noexcept {
if (this != &other) {
remove_owned_link();
close_slave_fd();
close_fd();
path_ = std::move(other.path_);
fd_ = other.fd_;
slave_fd_ = other.slave_fd_;
slave_path_ = std::move(other.slave_path_);
owns_link_ = other.owns_link_;
other.fd_ = -1;
other.slave_fd_ = -1;
other.owns_link_ = false;
try {
shutdown();
} catch (...) {
}
return *this;
if (!impl_) {
return;
}
if (impl_->owns_link && !path_.empty()) {
try {
const auto target = read_link_target(path_);
if (target && (*target == impl_->slave_path)) {
::unlink(path_.c_str());
}
} catch (...) {
}
impl_->owns_link = false;
}
close_fd_if_open(impl_->slave_fd);
close_fd_if_open(impl_->fd);
}
void TtyProtocolWriter::emit_packet_start() const {
write_frame(0x000A, 0xFFFF, 0xFFFF, 0xFFFF);
void TtyProtocolWriter::emit_packet_start() {
enqueue_frame(0x000A, 0xFFFF, 0xFFFF, 0xFFFF);
}
void TtyProtocolWriter::emit_step(uint16_t index, int16_t ch1_avg, int16_t ch2_avg) const {
write_frame(0x000A,
index,
static_cast<uint16_t>(ch1_avg),
static_cast<uint16_t>(ch2_avg));
void TtyProtocolWriter::emit_step(uint16_t index, int16_t ch1_avg, int16_t ch2_avg) {
enqueue_frame(0x000A,
index,
static_cast<uint16_t>(ch1_avg),
static_cast<uint16_t>(ch2_avg));
}
void TtyProtocolWriter::enqueue_encoded_frames(const uint16_t* words, std::size_t frame_count) {
if ((frame_count == 0U) || (words == nullptr)) {
return;
}
throw_if_failed();
std::lock_guard<std::mutex> lock(impl_->mutex);
if (impl_->failure) {
std::rethrow_exception(impl_->failure);
}
if (impl_->stop_requested) {
throw std::runtime_error("tty writer is already shut down");
}
std::size_t start_frame = 0;
std::size_t frames_to_copy = frame_count;
std::size_t dropped_frames = 0;
if (frame_count >= impl_->capacity_frames) {
start_frame = frame_count - impl_->capacity_frames;
frames_to_copy = impl_->capacity_frames;
dropped_frames = impl_->size + start_frame;
impl_->head = 0;
impl_->size = 0;
} else {
const std::size_t available_frames = impl_->capacity_frames - impl_->size;
if (frame_count > available_frames) {
dropped_frames = frame_count - available_frames;
impl_->head = (impl_->head + dropped_frames) % impl_->capacity_frames;
impl_->size -= dropped_frames;
}
}
if (dropped_frames != 0U) {
impl_->stats.frames_dropped += static_cast<std::uint64_t>(dropped_frames);
++impl_->stats.ring_overflows;
}
for (std::size_t i = 0; i < frames_to_copy; ++i) {
const std::size_t src_index = (start_frame + i) * kFrameWordCount;
const std::size_t dst_index = (impl_->head + impl_->size) % impl_->capacity_frames;
impl_->ring[dst_index] = encode_frame(words[src_index + 0U],
words[src_index + 1U],
words[src_index + 2U],
words[src_index + 3U]);
++impl_->size;
}
impl_->data_ready_cv.notify_one();
}
TtyProtocolWriter::StatsSnapshot TtyProtocolWriter::stats() const {
if (!impl_) {
return {};
}
std::lock_guard<std::mutex> lock(impl_->mutex);
return impl_->stats;
}
const std::string& TtyProtocolWriter::path() const {
return path_;
}
void TtyProtocolWriter::write_frame(uint16_t word0, uint16_t word1, uint16_t word2, uint16_t word3) const {
const uint16_t frame[4] = {word0, word1, word2, word3};
const std::uint8_t* bytes = reinterpret_cast<const std::uint8_t*>(frame);
std::size_t remaining = sizeof(frame);
while (remaining != 0U) {
const ssize_t written = ::write(fd_, bytes, remaining);
if (written < 0) {
if (errno == EINTR) {
continue;
}
throw std::runtime_error(io_error("Cannot write tty frame to", path_));
}
if (written == 0) {
throw std::runtime_error("tty write returned 0 bytes for '" + path_ + "'");
}
bytes += static_cast<std::size_t>(written);
remaining -= static_cast<std::size_t>(written);
}
}
void TtyProtocolWriter::close_fd() noexcept {
if (fd_ >= 0) {
::close(fd_);
fd_ = -1;
}
}
void TtyProtocolWriter::close_slave_fd() noexcept {
if (slave_fd_ >= 0) {
::close(slave_fd_);
slave_fd_ = -1;
}
}
void TtyProtocolWriter::remove_owned_link() noexcept {
if (!owns_link_ || path_.empty()) {
void TtyProtocolWriter::throw_if_failed() const {
if (!impl_) {
return;
}
try {
const auto target = read_link_target(path_);
if (target && (*target == slave_path_)) {
::unlink(path_.c_str());
}
} catch (...) {
std::exception_ptr failure;
{
std::lock_guard<std::mutex> lock(impl_->mutex);
failure = impl_->failure;
}
owns_link_ = false;
if (failure) {
std::rethrow_exception(failure);
}
}
void TtyProtocolWriter::shutdown() {
if (!impl_) {
return;
}
{
std::lock_guard<std::mutex> lock(impl_->mutex);
impl_->stop_requested = true;
}
close_fd_if_open(impl_->fd);
impl_->data_ready_cv.notify_all();
if (impl_->worker.joinable()) {
impl_->worker.join();
}
}
void TtyProtocolWriter::enqueue_frame(uint16_t word0, uint16_t word1, uint16_t word2, uint16_t word3) {
const uint16_t words[kFrameWordCount] = {word0, word1, word2, word3};
enqueue_encoded_frames(words, 1U);
}
void TtyProtocolWriter::worker_loop() {
for (;;) {
EncodedFrame frame {};
{
std::unique_lock<std::mutex> lock(impl_->mutex);
impl_->data_ready_cv.wait(lock, [this]() {
return impl_->stop_requested || impl_->failure || (impl_->size != 0U);
});
if (impl_->failure || impl_->stop_requested) {
return;
}
frame = impl_->ring[impl_->head];
impl_->head = (impl_->head + 1U) % impl_->capacity_frames;
--impl_->size;
}
const std::uint8_t* bytes = frame.data();
std::size_t remaining = frame.size();
while (remaining != 0U) {
const ssize_t written = ::write(impl_->fd, bytes, remaining);
if (written < 0) {
if (errno == EINTR) {
continue;
}
if ((errno == EAGAIN) || (errno == EWOULDBLOCK) || (errno == EIO)) {
{
std::lock_guard<std::mutex> lock(impl_->mutex);
if (impl_->stop_requested) {
return;
}
}
std::this_thread::sleep_for(std::chrono::milliseconds(5));
continue;
}
std::lock_guard<std::mutex> lock(impl_->mutex);
if (!impl_->stop_requested) {
impl_->failure = std::make_exception_ptr(
std::runtime_error(io_error("Cannot write tty frame to", path_)));
}
impl_->data_ready_cv.notify_all();
return;
}
if (written == 0) {
std::lock_guard<std::mutex> lock(impl_->mutex);
if (!impl_->stop_requested) {
impl_->failure = std::make_exception_ptr(
std::runtime_error("tty write returned 0 bytes for '" + path_ + "'"));
}
impl_->data_ready_cv.notify_all();
return;
}
bytes += static_cast<std::size_t>(written);
remaining -= static_cast<std::size_t>(written);
}
{
std::lock_guard<std::mutex> lock(impl_->mutex);
++impl_->stats.frames_written;
}
}
}
#endif