ClickHouse/dbms/src/IO/WriteBufferFromTemporaryFile.cpp

#include <IO/WriteBufferFromTemporaryFile.h>
#include <IO/ReadBufferFromFile.h>

#include <fcntl.h>


namespace DB
{

namespace ErrorCodes
{
    extern const int CANNOT_OPEN_FILE;
    extern const int CANNOT_SEEK_THROUGH_FILE;
}


WriteBufferFromTemporaryFile::WriteBufferFromTemporaryFile(std::unique_ptr<TemporaryFile> && tmp_file_)
    : WriteBufferFromFile(tmp_file_->path(), DBMS_DEFAULT_BUFFER_SIZE, O_RDWR | O_TRUNC | O_CREAT, 0600), tmp_file(std::move(tmp_file_))
{}


WriteBufferFromTemporaryFile::Ptr WriteBufferFromTemporaryFile::create(const std::string & tmp_dir)
{
    return Ptr{new WriteBufferFromTemporaryFile(createTemporaryFile(tmp_dir))};
}


class ReadBufferFromTemporaryWriteBuffer : public ReadBufferFromFile
{
public:
    static ReadBufferPtr createFrom(WriteBufferFromTemporaryFile * origin)
    {
        int fd = origin->getFD();
        std::string file_name = origin->getFileName();

        off_t res = lseek(fd, 0, SEEK_SET);
        if (-1 == res)
            throwFromErrnoWithPath("Cannot reread temporary file " + file_name, file_name,
                                   ErrorCodes::CANNOT_SEEK_THROUGH_FILE);

        return std::make_shared<ReadBufferFromTemporaryWriteBuffer>(fd, file_name, std::move(origin->tmp_file));
    }

    ReadBufferFromTemporaryWriteBuffer(int fd_, const std::string & file_name_, std::unique_ptr<TemporaryFile> && tmp_file_)
        : ReadBufferFromFile(fd_, file_name_), tmp_file(std::move(tmp_file_))
    {}

    std::unique_ptr<TemporaryFile> tmp_file;
};


ReadBufferPtr WriteBufferFromTemporaryFile::getReadBufferImpl()
{
    /// ignore buffer, write all data to file and reread it
    next();

    auto res = ReadBufferFromTemporaryWriteBuffer::createFrom(this);

    /// invalidate FD to avoid close(fd) in destructor
    setFD(-1);
    file_name = {};

    return res;
}


WriteBufferFromTemporaryFile::~WriteBufferFromTemporaryFile() = default;


}