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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Types.h>
#include <Kernel/KBuffer.h>
#include <Kernel/Locking/Mutex.h>
#include <Kernel/Thread.h>
#include <Kernel/UserOrKernelBuffer.h>
namespace Kernel {
class DoubleBuffer {
public:
static ErrorOr<NonnullOwnPtr<DoubleBuffer>> try_create(size_t capacity = 65536);
ErrorOr<size_t> write(const UserOrKernelBuffer&, size_t);
ErrorOr<size_t> write(const u8* data, size_t size)
{
return write(UserOrKernelBuffer::for_kernel_buffer(const_cast<u8*>(data)), size);
}
ErrorOr<size_t> read(UserOrKernelBuffer&, size_t);
ErrorOr<size_t> read(u8* data, size_t size)
{
auto buffer = UserOrKernelBuffer::for_kernel_buffer(data);
return read(buffer, size);
}
ErrorOr<size_t> peek(UserOrKernelBuffer&, size_t);
ErrorOr<size_t> peek(u8* data, size_t size)
{
auto buffer = UserOrKernelBuffer::for_kernel_buffer(data);
return peek(buffer, size);
}
bool is_empty() const { return m_empty; }
size_t space_for_writing() const { return m_space_for_writing; }
size_t immediately_readable() const
{
return (m_read_buffer->size - m_read_buffer_index) + m_write_buffer->size;
}
void set_unblock_callback(Function<void()> callback)
{
VERIFY(!m_unblock_callback);
m_unblock_callback = move(callback);
}
private:
explicit DoubleBuffer(size_t capacity, NonnullOwnPtr<KBuffer> storage);
void flip();
void compute_lockfree_metadata();
ErrorOr<size_t> read_impl(UserOrKernelBuffer&, size_t, MutexLocker&, bool advance_buffer_index);
struct InnerBuffer {
u8* data { nullptr };
size_t size;
};
InnerBuffer* m_write_buffer { nullptr };
InnerBuffer* m_read_buffer { nullptr };
InnerBuffer m_buffer1;
InnerBuffer m_buffer2;
NonnullOwnPtr<KBuffer> m_storage;
Function<void()> m_unblock_callback;
size_t m_capacity { 0 };
size_t m_read_buffer_index { 0 };
size_t m_space_for_writing { 0 };
bool m_empty { true };
mutable Mutex m_lock { "DoubleBuffer" };
};
}
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