Ton

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/*
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    This file is part of TON Blockchain Library.
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    TON Blockchain Library is free software: you can redistribute it and/or modify
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    it under the terms of the GNU Lesser General Public License as published by
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    the Free Software Foundation, either version 2 of the License, or
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    (at your option) any later version.
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    TON Blockchain Library is distributed in the hope that it will be useful,
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    but WITHOUT ANY WARRANTY; without even the implied warranty of
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    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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    GNU Lesser General Public License for more details.
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    You should have received a copy of the GNU Lesser General Public License
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    along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
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    Copyright 2017-2020 Telegram Systems LLP
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*/
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#include "CyclicBuffer.h"
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#include "td/utils/misc.h"
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#include "td/utils/Slice.h"
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#include <atomic>
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#include <limits>
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#include <memory>
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namespace td {
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namespace detail {
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class CyclicBuffer : public StreamWriterInterface, public StreamReaderInterface {
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 public:
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  using Options = ::td::CyclicBuffer::Options;
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  CyclicBuffer(Options options) {
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    CHECK(options.chunk_size != 0);
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    CHECK(options.count != 0);
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    CHECK(options.alignment != 0);
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    CHECK(options.chunk_size < (std::numeric_limits<size_t>::max() - options.alignment) / options.count);
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    shared_.options_ = options;
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    shared_.raw_data_ = std::make_unique<char[]>(options.size() + options.alignment - 1);
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    auto pos = reinterpret_cast<uint64>(shared_.raw_data_.get());
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    auto offset = (options.alignment - static_cast<size_t>(pos % options.alignment)) % options.alignment;
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    CHECK(offset < options.alignment);
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    shared_.data_ = MutableSlice(shared_.raw_data_.get() + offset, options.size());
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  }
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  // StreamReaderInterface
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  size_t reader_size() override {
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    auto offset = reader_.pos_.load(std::memory_order_relaxed);
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    auto size = writer_.pos_.load(std::memory_order_acquire) - offset;
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    return narrow_cast<size_t>(size);
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  }
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  Slice prepare_read() override {
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    auto offset = reader_.pos_.load(std::memory_order_relaxed);
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    auto size = narrow_cast<size_t>(writer_.pos_.load(std::memory_order_acquire) - offset);
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    if (size == 0) {
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      return {};
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    }
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    offset %= (shared_.options_.chunk_size * shared_.options_.count);
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    return shared_.data_.substr(narrow_cast<size_t>(offset)).truncate(size).truncate(shared_.options_.chunk_size);
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  }
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  Span<IoSlice> prepare_readv() override {
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    reader_.io_slice_ = as_io_slice(prepare_read());
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    return span_one(reader_.io_slice_);
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  }
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  void confirm_read(size_t size) override {
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    reader_.pos_.store(reader_.pos_.load(std::memory_order_relaxed) + size);
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  }
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  void close_reader(Status error) override {
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    CHECK(!reader_.is_closed_);
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    reader_.status_ = std::move(error);
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    reader_.is_closed_.store(true, std::memory_order_release);
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  }
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  bool is_writer_closed() const override {
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    return writer_.is_closed_.load(std::memory_order_acquire);
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  }
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  Status &writer_status() override {
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    CHECK(is_writer_closed());
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    return writer_.status_;
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  }
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  // StreamWriterInterface
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  size_t writer_size() override {
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    auto offset = reader_.pos_.load(std::memory_order_acquire);
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    auto size = writer_.pos_.load(std::memory_order_relaxed) - offset;
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    return narrow_cast<size_t>(size);
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  }
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  MutableSlice prepare_write() override {
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    auto max_offset =
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        reader_.pos_.load(std::memory_order_acquire) + shared_.options_.chunk_size * (shared_.options_.count - 1);
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    auto offset = writer_.pos_.load(std::memory_order_relaxed);
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    if (offset > max_offset) {
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      return {};
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    }
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    offset %= (shared_.options_.chunk_size * shared_.options_.count);
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    return shared_.data_.substr(narrow_cast<size_t>(offset), shared_.options_.chunk_size);
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  }
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  MutableSlice prepare_write_at_least(size_t size) override {
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    UNREACHABLE();
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  }
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  void confirm_write(size_t size) override {
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    writer_.pos_.store(writer_.pos_.load(std::memory_order_relaxed) + size);
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  }
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  void append(Slice data) override {
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    UNREACHABLE();
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  }
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  void append(BufferSlice data) override {
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    UNREACHABLE();
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  }
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  void append(std::string data) override {
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    UNREACHABLE();
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  }
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  void close_writer(Status error) override {
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    CHECK(!writer_.is_closed_);
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    writer_.status_ = std::move(error);
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    writer_.is_closed_.store(true, std::memory_order_release);
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  }
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  bool is_reader_closed() const override {
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    return reader_.is_closed_.load(std::memory_order_acquire);
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  }
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  Status &reader_status() override {
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    CHECK(is_reader_closed());
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    return reader_.status_;
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  }
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 private:
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  struct SharedData {
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    std::unique_ptr<char[]> raw_data_;
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    MutableSlice data_;
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    Options options_;
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  } shared_;
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  struct ReaderData {
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    std::atomic<uint64> pos_{0};
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    std::atomic<bool> is_closed_{false};
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    Status status_;
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    IoSlice io_slice_;
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  } reader_;
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  char pad[128];
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  struct WriterData {
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    std::atomic<uint64> pos_{0};
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    std::atomic<bool> is_closed_{false};
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    Status status_;
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  } writer_;
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};
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}  // namespace detail
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std::pair<CyclicBuffer::Reader, CyclicBuffer::Writer> CyclicBuffer::create(Options options) {
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  auto impl = std::make_shared<detail::CyclicBuffer>(options);
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  return {Reader(impl), Writer(impl)};
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}
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}  // namespace td
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