callback_buffer.hpp

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#ifndef OSMIUM_MEMORY_CALLBACK_BUFFER_HPP
#define OSMIUM_MEMORY_CALLBACK_BUFFER_HPP
 
/*
 
This file is part of Osmium (https://osmcode.org/libosmium).
 
Copyright 2013-2026 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/memory/buffer.hpp>
 
#include <cstddef>
#include <functional>
#include <utility>
 
namespace osmium {
 
    namespace memory {

        class CallbackBuffer {
 
        public:

            using callback_func_type = std::function<void(osmium::memory::Buffer&&)>;
 
        private:
 
            enum {
                default_initial_buffer_size = 1024UL * 1024UL
            };
 
            enum {
                default_max_buffer_size = 800UL * 1024UL
            };
 
            osmium::memory::Buffer m_buffer;
            std::size_t m_initial_buffer_size;
            std::size_t m_max_buffer_size;
            callback_func_type m_callback;
 
        public:

            explicit CallbackBuffer(std::size_t initial_buffer_size = default_initial_buffer_size, std::size_t max_buffer_size = default_max_buffer_size) :
                m_buffer(initial_buffer_size, osmium::memory::Buffer::auto_grow::yes),
                m_initial_buffer_size(initial_buffer_size),
                m_max_buffer_size(max_buffer_size),
                m_callback(nullptr) {
            }

            explicit CallbackBuffer(callback_func_type callback, std::size_t initial_buffer_size = default_initial_buffer_size, std::size_t max_buffer_size = default_max_buffer_size) :
                m_buffer(initial_buffer_size, osmium::memory::Buffer::auto_grow::yes),
                m_initial_buffer_size(initial_buffer_size),
                m_max_buffer_size(max_buffer_size),
                m_callback(std::move(callback)) {
            }

            osmium::memory::Buffer& buffer() noexcept {
                return m_buffer;
            }

            void set_callback(const callback_func_type& callback = nullptr) noexcept {
                m_callback = callback;
            }

            void flush() {
                if (m_callback && m_buffer.committed() > 0) {
                    m_callback(read());
                }
            }

            void possibly_flush() {
                if (m_buffer.committed() > m_max_buffer_size) {
                    flush();
                }
            }

            osmium::memory::Buffer read() {
                osmium::memory::Buffer new_buffer{m_initial_buffer_size, osmium::memory::Buffer::auto_grow::yes};
                using std::swap;
                swap(new_buffer, m_buffer);
                return new_buffer;
            }
 
        }; // class CallbackBuffer
 
    } // namespace memory
 
} // namespace osmium
 
#endif // OSMIUM_MEMORY_CALLBACK_BUFFER_HPP