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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <AK/Types.h>
#include <Kernel/KBuffer.h>
#include <Kernel/Lock.h>
#include <Kernel/UserOrKernelBuffer.h>
namespace Kernel {
class DoubleBuffer {
public:
explicit DoubleBuffer(size_t capacity = 65536);
[[nodiscard]] ssize_t write(const UserOrKernelBuffer&, size_t);
[[nodiscard]] ssize_t write(const u8* data, size_t size)
{
return write(UserOrKernelBuffer::for_kernel_buffer(const_cast<u8*>(data)), size);
}
[[nodiscard]] ssize_t read(UserOrKernelBuffer&, size_t);
[[nodiscard]] ssize_t read(u8* data, size_t size)
{
auto buffer = UserOrKernelBuffer::for_kernel_buffer(data);
return read(buffer, size);
}
bool is_empty() const { return m_empty; }
size_t space_for_writing() const { return m_space_for_writing; }
private:
void flip();
void compute_lockfree_metadata();
struct InnerBuffer {
u8* data { nullptr };
size_t size;
};
InnerBuffer* m_write_buffer { nullptr };
InnerBuffer* m_read_buffer { nullptr };
InnerBuffer m_buffer1;
InnerBuffer m_buffer2;
KBuffer m_storage;
size_t m_capacity { 0 };
size_t m_read_buffer_index { 0 };
size_t m_space_for_writing { 0 };
bool m_empty { true };
mutable Lock m_lock { "DoubleBuffer" };
};
}
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