124 lines
4.4 KiB
C++
124 lines
4.4 KiB
C++
/*
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Copyright (c) 2008-2018, Arvid Norberg
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the distribution.
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* Neither the name of the author nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef TORRENT_DISK_BUFFER_HOLDER_HPP_INCLUDED
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#define TORRENT_DISK_BUFFER_HOLDER_HPP_INCLUDED
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#include "libtorrent/config.hpp"
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#include "libtorrent/assert.hpp"
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#include "libtorrent/aux_/block_cache_reference.hpp"
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#include "libtorrent/span.hpp"
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namespace libtorrent {
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struct TORRENT_EXTRA_EXPORT buffer_allocator_interface
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{
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virtual void free_disk_buffer(char* b) = 0;
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virtual void reclaim_blocks(span<aux::block_cache_reference> refs) = 0;
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protected:
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~buffer_allocator_interface() = default;
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};
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// The disk buffer holder acts like a ``unique_ptr`` that frees a disk buffer
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// when it's destructed, unless it's released. ``release`` returns the disk
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// buffer and transfers ownership and responsibility to free it to the caller.
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//
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// ``data()`` returns the pointer without transferring ownership. If
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// this buffer has been released, ``data()`` will return nullptr.
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struct TORRENT_EXTRA_EXPORT disk_buffer_holder
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{
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// internal
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disk_buffer_holder(buffer_allocator_interface& alloc
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, char* buf, std::size_t sz) noexcept;
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disk_buffer_holder& operator=(disk_buffer_holder&&) noexcept;
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disk_buffer_holder(disk_buffer_holder&&) noexcept;
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disk_buffer_holder& operator=(disk_buffer_holder const&) = delete;
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disk_buffer_holder(disk_buffer_holder const&) = delete;
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// construct a buffer holder that will free the held buffer
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// using a disk buffer pool directly (there's only one
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// disk_buffer_pool per session)
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disk_buffer_holder(buffer_allocator_interface& alloc
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, aux::block_cache_reference const& ref
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, char* buf
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, std::size_t sz) noexcept;
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// frees any unreleased disk buffer held by this object
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~disk_buffer_holder();
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// return the held disk buffer and clear it from the
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// holder. The responsibility to free it is passed on
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// to the caller
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char* release() noexcept;
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// return a pointer to the held buffer
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char* data() const noexcept { return m_buf; }
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char* get() const noexcept { return m_buf; }
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// set the holder object to hold the specified buffer
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// (or nullptr by default). If it's already holding a
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// disk buffer, it will first be freed.
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void reset(char* buf = nullptr, std::size_t sz = 0);
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void reset(aux::block_cache_reference const& ref, char* buf, std::size_t sz);
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// swap pointers of two disk buffer holders.
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void swap(disk_buffer_holder& h) noexcept
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{
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TORRENT_ASSERT(h.m_allocator == m_allocator);
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std::swap(h.m_buf, m_buf);
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std::swap(h.m_size, m_size);
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std::swap(h.m_ref, m_ref);
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}
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// if this returns true, the buffer may not be modified in place
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bool is_mutable() const noexcept { return m_ref.cookie == aux::block_cache_reference::none; }
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// implicitly convertible to true if the object is currently holding a
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// buffer
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explicit operator bool() const noexcept { return m_buf != nullptr; }
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std::size_t size() const { return m_size; }
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private:
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buffer_allocator_interface* m_allocator;
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char* m_buf;
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std::size_t m_size;
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aux::block_cache_reference m_ref;
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};
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}
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#endif
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