ladybird/Kernel/DoubleBuffer.cpp

43 lines
1.2 KiB
C++

#include "DoubleBuffer.h"
inline void DoubleBuffer::compute_emptiness()
{
m_empty = m_read_buffer_index >= m_read_buffer->size() && m_write_buffer->is_empty();
}
void DoubleBuffer::flip()
{
ASSERT(m_read_buffer_index == m_read_buffer->size());
swap(m_read_buffer, m_write_buffer);
if (m_write_buffer->capacity() < 32)
m_write_buffer->clear_with_capacity();
else
m_write_buffer->clear();
m_read_buffer_index = 0;
compute_emptiness();
}
ssize_t DoubleBuffer::write(const byte* data, size_t size)
{
ASSERT_INTERRUPTS_ENABLED();
LOCKER(m_lock);
m_write_buffer->append(data, size);
compute_emptiness();
return size;
}
ssize_t DoubleBuffer::read(byte* data, size_t size)
{
ASSERT_INTERRUPTS_ENABLED();
LOCKER(m_lock);
if (m_read_buffer_index >= m_read_buffer->size() && !m_write_buffer->is_empty())
flip();
if (m_read_buffer_index >= m_read_buffer->size())
return 0;
ssize_t nread = min(m_read_buffer->size() - m_read_buffer_index, size);
memcpy(data, m_read_buffer->data() + m_read_buffer_index, nread);
m_read_buffer_index += nread;
compute_emptiness();
return nread;
}