writer.hpp

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#ifndef OSMIUM_IO_WRITER_HPP
#define OSMIUM_IO_WRITER_HPP

/*

This file is part of Osmium (https://osmcode.org/libosmium).

Copyright 2013-2021 Jochen Topf <jochen@topf.org> and others (see README).

Boost Software License - Version 1.0 - August 17th, 2003

Permission is hereby granted, free of charge, to any person or organization
obtaining a copy of the software and accompanying documentation covered by
this license (the "Software") to use, reproduce, display, distribute,
execute, and transmit the Software, and to prepare derivative works of the
Software, and to permit third-parties to whom the Software is furnished to
do so, all subject to the following:

The copyright notices in the Software and this entire statement, including
the above license grant, this restriction and the following disclaimer,
must be included in all copies of the Software, in whole or in part, and
all derivative works of the Software, unless such copies or derivative
works are solely in the form of machine-executable object code generated by
a source language processor.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

*/

#include <osmium/io/compression.hpp>
#include <osmium/io/detail/output_format.hpp>
#include <osmium/io/detail/queue_util.hpp>
#include <osmium/io/detail/read_write.hpp>
#include <osmium/io/detail/write_thread.hpp>
#include <osmium/io/error.hpp>
#include <osmium/io/file.hpp>
#include <osmium/io/header.hpp>
#include <osmium/io/writer_options.hpp>
#include <osmium/memory/buffer.hpp>
#include <osmium/thread/pool.hpp>
#include <osmium/thread/util.hpp>
#include <osmium/util/config.hpp>
#include <osmium/version.hpp>

#include <cassert>
#include <cstddef>
#include <exception>
#include <functional>
#include <future>
#include <initializer_list>
#include <memory>
#include <string>
#include <utility>

namespace osmium {

    namespace memory {
        class Item;
    } //namespace memory

    namespace io {

        namespace detail {

            inline std::size_t get_output_queue_size() noexcept {
                return osmium::config::get_max_queue_size("OUTPUT", 20);
            }

        } // namespace detail

        class Writer {

            enum {
                default_buffer_size = 10UL * 1024UL * 1024UL
            };

            osmium::io::File m_file;

            detail::future_string_queue_type m_output_queue{detail::get_output_queue_size(), "raw_output"};

            std::unique_ptr<osmium::io::detail::OutputFormat> m_output{nullptr};

            osmium::memory::Buffer m_buffer{};

            size_t m_buffer_size = default_buffer_size;

            std::future<std::size_t> m_write_future{};

            osmium::thread::thread_handler m_thread{};

            enum class status {
                okay   = 0, // normal writing
                error  = 1, // some error occurred while writing
                closed = 2  // close() called successfully
            } m_status = status::okay;

            // This function will run in a separate thread.
            static void write_thread(detail::future_string_queue_type& output_queue,
                                     std::unique_ptr<osmium::io::Compressor>&& compressor,
                                     std::promise<std::size_t>&& write_promise) {
                detail::WriteThread write_thread{output_queue,
                                                 std::move(compressor),
                                                 std::move(write_promise)};
                write_thread();
            }

            void do_write(osmium::memory::Buffer&& buffer) {
                if (buffer && buffer.committed() > 0) {
                    m_output->write_buffer(std::move(buffer));
                }
            }

            void do_flush() {
                osmium::thread::check_for_exception(m_write_future);
                if (m_buffer && m_buffer.committed() > 0) {
                    osmium::memory::Buffer buffer{m_buffer_size,
                                                  osmium::memory::Buffer::auto_grow::no};
                    using std::swap;
                    swap(m_buffer, buffer);

                    m_output->write_buffer(std::move(buffer));
                }
            }

            template <typename TFunction, typename... TArgs>
            void ensure_cleanup(TFunction func, TArgs&&... args) {
                if (m_status != status::okay) {
                    throw io_error("Can not write to writer when in status 'closed' or 'error'");
                }

                try {
                    func(std::forward<TArgs>(args)...);
                } catch (...) {
                    m_status = status::error;
                    detail::add_to_queue(m_output_queue, std::current_exception());
                    detail::add_end_of_data_to_queue(m_output_queue);
                    throw;
                }
            }

            struct options_type {
                osmium::io::Header header;
                overwrite allow_overwrite = overwrite::no;
                fsync sync = fsync::no;
                osmium::thread::Pool* pool = nullptr;
            };

            static void set_option(options_type& options, osmium::thread::Pool& pool) {
                options.pool = &pool;
            }

            static void set_option(options_type& options, const osmium::io::Header& header) {
                options.header = header;
            }

            static void set_option(options_type& options, overwrite value) {
                options.allow_overwrite = value;
            }

            static void set_option(options_type& options, fsync value) {
                options.sync = value;
            }

            void do_close() {
                if (m_status == status::okay) {
                    ensure_cleanup([&](){
                        do_write(std::move(m_buffer));
                        m_output->write_end();
                        m_status = status::closed;
                        detail::add_end_of_data_to_queue(m_output_queue);
                    });
                }
            }

        public:

            template <typename... TArgs>
            explicit Writer(const osmium::io::File& file, TArgs&&... args) :
                m_file(file.check()) {
                assert(!m_file.buffer()); // XXX can't handle pseudo-files

                options_type options;
                (void)std::initializer_list<int>{
                    (set_option(options, args), 0)...
                };

                if (!options.pool) {
                    options.pool = &thread::Pool::default_instance();
                }

                m_output = osmium::io::detail::OutputFormatFactory::instance().create_output(*options.pool, m_file, m_output_queue);

                if (options.header.get("generator").empty()) {
                    options.header.set("generator", "libosmium/" LIBOSMIUM_VERSION_STRING);
                }

                std::unique_ptr<osmium::io::Compressor> compressor =
                    CompressionFactory::instance().create_compressor(file.compression(),
                                                                     osmium::io::detail::open_for_writing(m_file.filename(), options.allow_overwrite),
                                                                     options.sync);

                std::promise<std::size_t> write_promise;
                m_write_future = write_promise.get_future();
                m_thread = osmium::thread::thread_handler{write_thread, std::ref(m_output_queue), std::move(compressor), std::move(write_promise)};

                ensure_cleanup([&](){
                    m_output->write_header(options.header);
                });
            }

            template <typename... TArgs>
            explicit Writer(const std::string& filename, TArgs&&... args) :
                Writer(osmium::io::File{filename}, std::forward<TArgs>(args)...) {
            }

            template <typename... TArgs>
            explicit Writer(const char* filename, TArgs&&... args) :
                Writer(osmium::io::File{filename}, std::forward<TArgs>(args)...) {
            }

            Writer(const Writer&) = delete;
            Writer& operator=(const Writer&) = delete;

            Writer(Writer&&) = delete;
            Writer& operator=(Writer&&) = delete;

            ~Writer() noexcept {
                try {
                    do_close();
                } catch (...) {
                    // Ignore any exceptions because destructor must not throw.
                }
            }

            size_t buffer_size() const noexcept {
                return m_buffer_size;
            }

            void set_buffer_size(size_t size) noexcept {
                m_buffer_size = size;
            }

            void flush() {
                ensure_cleanup([&](){
                    do_flush();
                });
            }

            void operator()(osmium::memory::Buffer&& buffer) {
                ensure_cleanup([&](){
                    do_flush();
                    do_write(std::move(buffer));
                });
            }

            void operator()(const osmium::memory::Item& item) {
                ensure_cleanup([&](){
                    if (!m_buffer) {
                        m_buffer = osmium::memory::Buffer{m_buffer_size,
                                                          osmium::memory::Buffer::auto_grow::no};
                    }
                    try {
                        m_buffer.push_back(item);
                    } catch (const osmium::buffer_is_full&) {
                        do_flush();
                        m_buffer.push_back(item);
                    }
                });
            }

            std::size_t close() {
                do_close();

                if (m_write_future.valid()) {
                    return m_write_future.get();
                }

                return 0;
            }

        }; // class Writer

    } // namespace io

} // namespace osmium

#endif // OSMIUM_IO_WRITER_HPP