diff options
Diffstat (limited to 'Kernel/Library/DoubleBuffer.h')
-rw-r--r-- | Kernel/Library/DoubleBuffer.h | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/Kernel/Library/DoubleBuffer.h b/Kernel/Library/DoubleBuffer.h new file mode 100644 index 0000000000..56e71deeab --- /dev/null +++ b/Kernel/Library/DoubleBuffer.h @@ -0,0 +1,78 @@ +/* + * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org> + * + * SPDX-License-Identifier: BSD-2-Clause + */ + +#pragma once + +#include <AK/Types.h> +#include <Kernel/Library/KBuffer.h> +#include <Kernel/Library/UserOrKernelBuffer.h> +#include <Kernel/Locking/Mutex.h> +#include <Kernel/Tasks/Thread.h> + +namespace Kernel { + +class DoubleBuffer { +public: + static ErrorOr<NonnullOwnPtr<DoubleBuffer>> try_create(StringView name, size_t capacity = 65536); + ErrorOr<size_t> write(UserOrKernelBuffer const&, size_t); + ErrorOr<size_t> write(u8 const* 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 { 0 }; + }; + + 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"sv }; +}; + +} |