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Kernel: Share code between DoubleBuffer's read() and peek()

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The only difference between these is whether the buffer index is
advanced after the read.
This commit is contained in:
Andreas Kling 2021-11-21 10:50:59 +01:00
parent 9387271049
commit b820ae2828
2 changed files with 13 additions and 17 deletions
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28
Kernel/DoubleBuffer.cpp
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@ -60,40 +60,34 @@ ErrorOr<size_t> DoubleBuffer::write(const UserOrKernelBuffer& data, size_t size)
return bytes_to_write; return bytes_to_write;
} }
ErrorOr<size_t> DoubleBuffer::read(UserOrKernelBuffer& data, size_t size) ErrorOr<size_t> DoubleBuffer::read_impl(UserOrKernelBuffer& data, size_t size, MutexLocker&, bool advance_buffer_index)
{ {
if (!size) if (size == 0)
return 0; return 0;
MutexLocker locker(m_lock);
if (m_read_buffer_index >= m_read_buffer->size && m_write_buffer->size != 0) if (m_read_buffer_index >= m_read_buffer->size && m_write_buffer->size != 0)
flip(); flip();
if (m_read_buffer_index >= m_read_buffer->size) if (m_read_buffer_index >= m_read_buffer->size)
return 0; return 0;
size_t nread = min(m_read_buffer->size - m_read_buffer_index, size); size_t nread = min(m_read_buffer->size - m_read_buffer_index, size);
TRY(data.write(m_read_buffer->data + m_read_buffer_index, nread)); TRY(data.write(m_read_buffer->data + m_read_buffer_index, nread));
m_read_buffer_index += nread; if (advance_buffer_index)
m_read_buffer_index += nread;
compute_lockfree_metadata(); compute_lockfree_metadata();
if (m_unblock_callback && m_space_for_writing > 0) if (m_unblock_callback && m_space_for_writing > 0)
m_unblock_callback(); m_unblock_callback();
return nread; return nread;
} }
ErrorOr<size_t> DoubleBuffer::read(UserOrKernelBuffer& data, size_t size)
{
MutexLocker locker(m_lock);
return read_impl(data, size, locker, true);
}
ErrorOr<size_t> DoubleBuffer::peek(UserOrKernelBuffer& data, size_t size) ErrorOr<size_t> DoubleBuffer::peek(UserOrKernelBuffer& data, size_t size)
{ {
if (!size)
return 0;
MutexLocker locker(m_lock); MutexLocker locker(m_lock);
if (m_read_buffer_index >= m_read_buffer->size && m_write_buffer->size != 0) { return read_impl(data, size, locker, false);
flip();
}
if (m_read_buffer_index >= m_read_buffer->size)
return 0;
size_t nread = min(m_read_buffer->size - m_read_buffer_index, size);
TRY(data.write(m_read_buffer->data + m_read_buffer_index, nread));
compute_lockfree_metadata();
if (m_unblock_callback && m_space_for_writing > 0)
m_unblock_callback();
return nread;
} }
} }

2
Kernel/DoubleBuffer.h
View file

@ -54,6 +54,8 @@ private:
void flip(); void flip();
void compute_lockfree_metadata(); void compute_lockfree_metadata();
ErrorOr<size_t> read_impl(UserOrKernelBuffer&, size_t, MutexLocker&, bool advance_buffer_index);
struct InnerBuffer { struct InnerBuffer {
u8* data { nullptr }; u8* data { nullptr };
size_t size; size_t size;