ClickHouse/dbms/src/IO/WriteBufferFromVector.h

#pragma once

#include <vector>

#include <IO/WriteBuffer.h>


#define WRITE_BUFFER_FROM_VECTOR_INITIAL_SIZE_IF_EMPTY 32


namespace DB
{

/** Initialized by vector. Writes data to it. When the vector is finished, it doubles its size.
  * CharType - char or unsigned char.
  */
template <typename VectorType = std::vector<char>>
class WriteBufferFromVector : public WriteBuffer
{
private:
    VectorType & vector;

    void nextImpl() override
    {
        size_t old_size = vector.size();
        vector.resize(old_size * 2);
        internal_buffer = Buffer(reinterpret_cast<Position>(&vector[old_size]), reinterpret_cast<Position>(vector.data() + vector.size()));
        working_buffer = internal_buffer;
    }

public:
    WriteBufferFromVector(VectorType & vector_)
        : WriteBuffer(reinterpret_cast<Position>(vector_.data()), vector_.size()), vector(vector_)
    {
        if (vector.empty())
        {
            vector.resize(WRITE_BUFFER_FROM_VECTOR_INITIAL_SIZE_IF_EMPTY);
            set(reinterpret_cast<Position>(&vector[0]), vector.size());
        }
    }
};

}