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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:
- [[nodiscard]] static OwnPtr<DoubleBuffer> try_create(size_t capacity = 65536);
- [[nodiscard]] KResultOr<size_t> write(const UserOrKernelBuffer&, size_t);
- [[nodiscard]] KResultOr<size_t> write(const u8* data, size_t size)
- {
- return write(UserOrKernelBuffer::for_kernel_buffer(const_cast<u8*>(data)), size);
- }
- [[nodiscard]] KResultOr<size_t> read(UserOrKernelBuffer&, size_t);
- [[nodiscard]] KResultOr<size_t> read(u8* data, size_t size)
- {
- auto buffer = UserOrKernelBuffer::for_kernel_buffer(data);
- return read(buffer, size);
- }
- [[nodiscard]] KResultOr<size_t> peek(UserOrKernelBuffer&, size_t);
- [[nodiscard]] KResultOr<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();
- 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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