ClickHouse/dbms/include/DB/IO/WriteBufferFromFileDescriptor.h

141 lines
3.0 KiB
C++

#pragma once
#include <unistd.h>
#include <errno.h>
#include <DB/Common/Exception.h>
#include <DB/Common/ProfileEvents.h>
#include <DB/Common/CurrentMetrics.h>
#include <DB/IO/WriteBufferFromFileBase.h>
#include <DB/IO/WriteBuffer.h>
#include <DB/IO/WriteHelpers.h>
#include <DB/IO/BufferWithOwnMemory.h>
namespace ProfileEvents
{
extern const Event WriteBufferFromFileDescriptorWrite;
extern const Event WriteBufferFromFileDescriptorWriteBytes;
}
namespace CurrentMetrics
{
extern const Metric Write;
}
namespace DB
{
namespace ErrorCodes
{
extern const int CANNOT_WRITE_TO_FILE_DESCRIPTOR;
extern const int CANNOT_FSYNC;
extern const int CANNOT_SEEK_THROUGH_FILE;
extern const int CANNOT_TRUNCATE_FILE;
}
/** Use ready file descriptor. Does not open or close a file.
*/
class WriteBufferFromFileDescriptor : public WriteBufferFromFileBase
{
protected:
int fd;
void nextImpl() override
{
if (!offset())
return;
size_t bytes_written = 0;
while (bytes_written != offset())
{
ProfileEvents::increment(ProfileEvents::WriteBufferFromFileDescriptorWrite);
ssize_t res = 0;
{
CurrentMetrics::Increment metric_increment{CurrentMetrics::Write};
res = ::write(fd, working_buffer.begin() + bytes_written, offset() - bytes_written);
}
if ((-1 == res || 0 == res) && errno != EINTR)
throwFromErrno("Cannot write to file " + getFileName(), ErrorCodes::CANNOT_WRITE_TO_FILE_DESCRIPTOR);
if (res > 0)
bytes_written += res;
}
ProfileEvents::increment(ProfileEvents::WriteBufferFromFileDescriptorWriteBytes, bytes_written);
}
/// Name or some description of file.
virtual std::string getFileName() const override
{
return "(fd = " + toString(fd) + ")";
}
public:
WriteBufferFromFileDescriptor(int fd_ = -1, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE, char * existing_memory = nullptr, size_t alignment = 0)
: WriteBufferFromFileBase(buf_size, existing_memory, alignment), fd(fd_) {}
/** Could be used before initialization if needed 'fd' was not passed to constructor.
* It's not possible to change 'fd' during work.
*/
void setFD(int fd_)
{
fd = fd_;
}
~WriteBufferFromFileDescriptor()
{
try
{
if (fd >= 0)
next();
}
catch (...)
{
tryLogCurrentException(__PRETTY_FUNCTION__);
}
}
int getFD() const override
{
return fd;
}
off_t getPositionInFile() override
{
return seek(0, SEEK_CUR);
}
void sync() override
{
/// If buffer has pending data - write it.
next();
/// Request OS to sync data with storage medium.
int res = fsync(fd);
if (-1 == res)
throwFromErrno("Cannot fsync " + getFileName(), ErrorCodes::CANNOT_FSYNC);
}
private:
off_t doSeek(off_t offset, int whence) override
{
off_t res = lseek(fd, offset, whence);
if (-1 == res)
throwFromErrno("Cannot seek through file " + getFileName(), ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
return res;
}
void doTruncate(off_t length) override
{
int res = ftruncate(fd, length);
if (-1 == res)
throwFromErrno("Cannot truncate file " + getFileName(), ErrorCodes::CANNOT_TRUNCATE_FILE);
}
};
}