mirror of
https://github.com/SerenityOS/serenity
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69 lines
2.2 KiB
C++
69 lines
2.2 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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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 are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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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 ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Types.h>
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#include <Kernel/KBuffer.h>
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#include <Kernel/Lock.h>
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namespace Kernel {
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class DoubleBuffer {
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public:
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explicit DoubleBuffer(size_t capacity = 65536);
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ssize_t write(const u8*, ssize_t);
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ssize_t read(u8*, ssize_t);
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bool is_empty() const { return m_empty; }
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size_t space_for_writing() const { return m_space_for_writing; }
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private:
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void flip();
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void compute_lockfree_metadata();
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struct InnerBuffer {
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u8* data { nullptr };
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size_t size;
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};
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InnerBuffer* m_write_buffer { nullptr };
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InnerBuffer* m_read_buffer { nullptr };
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InnerBuffer m_buffer1;
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InnerBuffer m_buffer2;
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KBuffer m_storage;
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size_t m_capacity { 0 };
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size_t m_read_buffer_index { 0 };
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size_t m_space_for_writing { 0 };
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bool m_empty { true };
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mutable Lock m_lock { "DoubleBuffer" };
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};
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}
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