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#include "BoundedReadBuffer.h"
#include <IO/SwapHelper.h>
namespace DB
{
BoundedReadBuffer::BoundedReadBuffer(std::unique_ptr<SeekableReadBuffer> impl_)
: ReadBufferFromFileDecorator(std::move(impl_))
{
}
void BoundedReadBuffer::setReadUntilPosition(size_t position)
{
read_until_position = position;
}
void BoundedReadBuffer::setReadUntilEnd()
{
read_until_position.reset();
}
off_t BoundedReadBuffer::getPosition()
{
return file_offset_of_buffer_end - (working_buffer.end() - pos);
}
bool BoundedReadBuffer::nextImpl()
{
if (read_until_position && file_offset_of_buffer_end == *read_until_position)
return false;
bool result;
{
SwapHelper swap(*this, *impl);
result = impl->next();
}
chassert(file_offset_of_buffer_end + available() == impl->getFileOffsetOfBufferEnd());
if (result && read_until_position)
{
size_t remaining_size_to_read = *read_until_position - file_offset_of_buffer_end;
if (working_buffer.size() > remaining_size_to_read)
{
/// file: [______________________________]
/// working buffer: [_______________]
/// ^
/// read_until_position
/// ^
/// file_offset_of_buffer_end
working_buffer.resize(remaining_size_to_read);
}
}
file_offset_of_buffer_end += available();
return result;
}
off_t BoundedReadBuffer::seek(off_t off, int whence)
{
swap(*impl);
auto result = impl->seek(off, whence);
swap(*impl);
file_offset_of_buffer_end = impl->getFileOffsetOfBufferEnd();
return result;
}
}
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