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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2026
//
// 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/buffer.h"
#include "td/utils/common.h"
#include "td/utils/format.h"
#include "td/utils/logging.h"
#include "td/utils/port/detail/PollableFd.h"
#include "td/utils/port/IoSlice.h"
#include "td/utils/Slice.h"
#include "td/utils/Span.h"
#include "td/utils/Status.h"
#include <limits>
namespace td {
// just reads from given reader and writes to given writer
template <class FdT>
class BufferedFdBase : public FdT {
public:
BufferedFdBase() = default;
explicit BufferedFdBase(FdT &&fd);
// TODO: make move constructor and move assignment safer
Result<size_t> flush_read(size_t max_read = std::numeric_limits<size_t>::max()) TD_WARN_UNUSED_RESULT;
Result<size_t> flush_write() TD_WARN_UNUSED_RESULT;
bool need_flush_write(size_t at_least = 0) {
return ready_for_flush_write() > at_least;
}
size_t ready_for_flush_write() {
CHECK(write_);
write_->sync_with_writer();
return write_->size();
}
void sync_with_poll() {
::td::sync_with_poll(*this);
}
void set_input_writer(ChainBufferWriter *read) {
read_ = read;
}
void set_output_reader(ChainBufferReader *write) {
write_ = write;
}
private:
ChainBufferWriter *read_ = nullptr;
ChainBufferReader *write_ = nullptr;
};
template <class FdT>
class BufferedFd final : public BufferedFdBase<FdT> {
using Parent = BufferedFdBase<FdT>;
ChainBufferWriter input_writer_;
ChainBufferReader input_reader_;
ChainBufferWriter output_writer_;
ChainBufferReader output_reader_;
void init();
void init_ptr();
public:
BufferedFd();
explicit BufferedFd(FdT &&fd);
BufferedFd(BufferedFd &&) noexcept;
BufferedFd &operator=(BufferedFd &&) noexcept;
BufferedFd(const BufferedFd &) = delete;
BufferedFd &operator=(const BufferedFd &) = delete;
~BufferedFd();
void close();
size_t left_unread() const {
return input_reader_.size();
}
size_t left_unwritten() const {
return output_reader_.size();
}
Result<size_t> flush_read(size_t max_read = std::numeric_limits<size_t>::max()) TD_WARN_UNUSED_RESULT;
Result<size_t> flush_write() TD_WARN_UNUSED_RESULT;
// Yep, direct access to buffers. It is IO interface too.
ChainBufferReader &input_buffer();
ChainBufferWriter &output_buffer();
};
// IMPLEMENTATION
/*** BufferedFd ***/
template <class FdT>
BufferedFdBase<FdT>::BufferedFdBase(FdT &&fd) : FdT(std::move(fd)) {
}
template <class FdT>
Result<size_t> BufferedFdBase<FdT>::flush_read(size_t max_read) {
CHECK(read_);
size_t result = 0;
while (::td::can_read_local(*this) && max_read) {
MutableSlice slice = read_->prepare_append();
slice.truncate(max_read);
TRY_RESULT(x, FdT::read(slice));
slice.truncate(x);
read_->confirm_append(x);
result += x;
max_read -= x;
}
return result;
}
template <class FdT>
Result<size_t> BufferedFdBase<FdT>::flush_write() {
// TODO: sync on demand
write_->sync_with_writer();
size_t result = 0;
while (!write_->empty() && ::td::can_write_local(*this)) {
constexpr size_t BUF_SIZE = 20;
IoSlice buf[BUF_SIZE];
auto it = write_->clone();
size_t buf_i;
for (buf_i = 0; buf_i < BUF_SIZE; buf_i++) {
Slice slice = it.prepare_read();
if (slice.empty()) {
break;
}
buf[buf_i] = as_io_slice(slice);
it.confirm_read(slice.size());
}
TRY_RESULT(x, FdT::writev(Span<IoSlice>(buf, buf_i)));
write_->advance(x);
result += x;
}
if (result == 0) {
if (write_->empty()) {
LOG(DEBUG) << "Nothing to write to " << FdT::get_poll_info().native_fd();
} else {
LOG(DEBUG) << "Can't flush write to " << FdT::get_poll_info().native_fd()
<< " with flags = " << FdT::get_poll_info().get_flags_local();
}
}
return result;
}
/*** BufferedFd ***/
template <class FdT>
void BufferedFd<FdT>::init() {
input_reader_ = input_writer_.extract_reader();
output_reader_ = output_writer_.extract_reader();
init_ptr();
}
template <class FdT>
void BufferedFd<FdT>::init_ptr() {
this->set_input_writer(&input_writer_);
this->set_output_reader(&output_reader_);
}
template <class FdT>
BufferedFd<FdT>::BufferedFd() {
init();
}
template <class FdT>
BufferedFd<FdT>::BufferedFd(FdT &&fd) : Parent(std::move(fd)) {
init();
}
template <class FdT>
BufferedFd<FdT>::BufferedFd(BufferedFd &&from) noexcept {
*this = std::move(from);
}
template <class FdT>
BufferedFd<FdT> &BufferedFd<FdT>::operator=(BufferedFd &&from) noexcept {
FdT::operator=(std::move(static_cast<FdT &>(from)));
input_reader_ = std::move(from.input_reader_);
input_writer_ = std::move(from.input_writer_);
output_reader_ = std::move(from.output_reader_);
output_writer_ = std::move(from.output_writer_);
init_ptr();
return *this;
}
template <class FdT>
BufferedFd<FdT>::~BufferedFd() {
close();
}
template <class FdT>
void BufferedFd<FdT>::close() {
FdT::close();
// TODO: clear buffers
}
template <class FdT>
Result<size_t> BufferedFd<FdT>::flush_read(size_t max_read) {
TRY_RESULT(result, Parent::flush_read(max_read));
if (result) {
// TODO: faster sync is possible if you owns writer.
input_reader_.sync_with_writer();
LOG(DEBUG) << "Flush read: +" << format::as_size(result) << tag("total", format::as_size(input_reader_.size()));
}
return result;
}
template <class FdT>
Result<size_t> BufferedFd<FdT>::flush_write() {
TRY_RESULT(result, Parent::flush_write());
if (result) {
LOG(DEBUG) << "Flush write: +" << format::as_size(result) << tag("left", format::as_size(output_reader_.size()));
}
return result;
}
// Yep, direct access to buffers. It is IO interface too.
template <class FdT>
ChainBufferReader &BufferedFd<FdT>::input_buffer() {
return input_reader_;
}
template <class FdT>
ChainBufferWriter &BufferedFd<FdT>::output_buffer() {
return output_writer_;
}
} // namespace td
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