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#pragma once
#include <vector>
#include <IO/ReadBuffer.h>
namespace DB
{
/// Reads from the concatenation of multiple ReadBuffer's
class ConcatReadBuffer : public ReadBuffer
{
public:
using Buffers = std::vector<std::unique_ptr<ReadBuffer>>;
ConcatReadBuffer() : ReadBuffer(nullptr, 0), current(buffers.end())
{
}
explicit ConcatReadBuffer(Buffers && buffers_) : ReadBuffer(nullptr, 0), buffers(std::move(buffers_)), current(buffers.begin())
{
assert(!buffers.empty());
}
ConcatReadBuffer(std::unique_ptr<ReadBuffer> buf1, std::unique_ptr<ReadBuffer> buf2) : ConcatReadBuffer()
{
appendBuffer(std::move(buf1));
appendBuffer(std::move(buf2));
}
ConcatReadBuffer(ReadBuffer & buf1, ReadBuffer & buf2) : ConcatReadBuffer()
{
appendBuffer(wrapReadBufferReference(buf1));
appendBuffer(wrapReadBufferReference(buf2));
}
void appendBuffer(std::unique_ptr<ReadBuffer> buffer)
{
assert(!count());
buffers.push_back(std::move(buffer));
current = buffers.begin();
}
protected:
Buffers buffers;
Buffers::iterator current;
bool nextImpl() override
{
if (buffers.end() == current)
return false;
/// First reading
if (working_buffer.empty())
{
if ((*current)->hasPendingData())
{
working_buffer = Buffer((*current)->position(), (*current)->buffer().end());
return true;
}
}
else
(*current)->position() = position();
if (!(*current)->next())
{
++current;
if (buffers.end() == current)
return false;
/// We skip the filled up buffers; if the buffer is not filled in, but the cursor is at the end, then read the next piece of data.
while ((*current)->eof())
{
++current;
if (buffers.end() == current)
return false;
}
}
working_buffer = Buffer((*current)->position(), (*current)->buffer().end());
return true;
}
};
}
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