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https://github.com/ClickHouse/ClickHouse.git
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111 lines
2.6 KiB
C++
111 lines
2.6 KiB
C++
#pragma once
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#include <unistd.h>
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#include <errno.h>
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#include <DB/Core/Exception.h>
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#include <DB/Core/ErrorCodes.h>
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#include <DB/IO/WriteBufferFromFileBase.h>
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#include <DB/IO/WriteBuffer.h>
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#include <DB/IO/WriteHelpers.h>
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#include <DB/IO/BufferWithOwnMemory.h>
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namespace DB
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{
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/** Работает с готовым файловым дескриптором. Не открывает и не закрывает файл.
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*/
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class WriteBufferFromFileDescriptor : public WriteBufferFromFileBase
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{
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protected:
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int fd;
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void nextImpl()
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{
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if (!offset())
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return;
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size_t bytes_written = 0;
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while (bytes_written != offset())
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{
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ssize_t res = ::write(fd, working_buffer.begin() + bytes_written, offset() - bytes_written);
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if ((-1 == res || 0 == res) && errno != EINTR)
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throwFromErrno("Cannot write to file " + getFileName(), ErrorCodes::CANNOT_WRITE_TO_FILE_DESCRIPTOR);
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if (res > 0)
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bytes_written += res;
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}
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}
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/// Имя или описание файла
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virtual std::string getFileName() const noexcept override
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{
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return "(fd = " + toString(fd) + ")";
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}
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public:
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WriteBufferFromFileDescriptor(int fd_ = -1, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE, char * existing_memory = nullptr, size_t alignment = 0)
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: WriteBufferFromFileBase(buf_size, existing_memory, alignment), fd(fd_) {}
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/** Можно вызывать для инициализации, если нужный fd не был передан в конструктор.
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* Менять fd во время работы нельзя.
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*/
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void setFD(int fd_)
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{
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fd = fd_;
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}
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~WriteBufferFromFileDescriptor()
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{
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try
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{
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next();
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}
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catch (...)
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{
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tryLogCurrentException(__PRETTY_FUNCTION__);
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}
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}
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int getFD() const noexcept override
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{
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return fd;
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}
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off_t seek(off_t offset, int whence = SEEK_SET) override
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{
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off_t res = lseek(fd, offset, whence);
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if (-1 == res)
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throwFromErrno("Cannot seek through file " + getFileName(), ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
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return res;
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}
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off_t getPositionInFile() override
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{
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return seek(0, SEEK_CUR);
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}
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void truncate(off_t length = 0) override
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{
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int res = ftruncate(fd, length);
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if (-1 == res)
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throwFromErrno("Cannot truncate file " + getFileName(), ErrorCodes::CANNOT_TRUNCATE_FILE);
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}
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void sync() override
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{
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/// Если в буфере ещё остались данные - запишем их.
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next();
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/// Попросим ОС сбросить данные на диск.
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int res = fsync(fd);
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if (-1 == res)
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throwFromErrno("Cannot fsync " + getFileName(), ErrorCodes::CANNOT_FSYNC);
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}
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};
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}
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