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

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#pragma once
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <DB/Common/ProfileEvents.h>
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#include <DB/IO/WriteBufferFromFileDescriptor.h>
namespace DB
{
/** Принимает имя файла. Самостоятельно открывает и закрывает файл.
*/
class WriteBufferFromFile : public WriteBufferFromFileDescriptor
{
private:
std::string file_name;
public:
WriteBufferFromFile(const std::string & file_name_, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE, int flags = -1, mode_t mode = 0666,
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char * existing_memory = nullptr, size_t alignment = 0)
: WriteBufferFromFileDescriptor(-1, buf_size, existing_memory, alignment), file_name(file_name_)
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{
ProfileEvents::increment(ProfileEvents::FileOpen);
fd = open(file_name.c_str(), flags == -1 ? O_WRONLY | O_TRUNC | O_CREAT : flags, mode);
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if (-1 == fd)
throwFromErrno("Cannot open file " + file_name, errno == ENOENT ? ErrorCodes::FILE_DOESNT_EXIST : ErrorCodes::CANNOT_OPEN_FILE);
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}
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~WriteBufferFromFile()
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{
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try
{
next();
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}
catch (...)
{
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tryLogCurrentException(__PRETTY_FUNCTION__);
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}
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close(fd);
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}
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/** fsync() transfers ("flushes") all modified in-core data of (i.e., modified buffer cache pages for) the file
* referred to by the file descriptor fd to the disk device (or other permanent storage device)
* so that all changed information can be retrieved even after the system crashed or was rebooted.
* This includes writing through or flushing a disk cache if present. The call blocks until the device
* reports that the transfer has completed. It also flushes metadata information associated with the file (see stat(2)).
* - man fsync */
void sync()
{
fsync(fd);
}
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virtual std::string getFileName()
{
return file_name;
}
};
}