mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-14 11:33:46 +00:00
73 lines
1.5 KiB
C++
73 lines
1.5 KiB
C++
#pragma once
|
||
|
||
#include <unistd.h>
|
||
#include <errno.h>
|
||
|
||
#include <DB/Core/Exception.h>
|
||
#include <DB/Core/ErrorCodes.h>
|
||
|
||
#include <DB/IO/ReadBuffer.h>
|
||
#include <DB/IO/WriteHelpers.h>
|
||
#include <DB/IO/BufferWithOwnMemory.h>
|
||
|
||
|
||
namespace DB
|
||
{
|
||
|
||
/** Работает с готовым файловым дескриптором. Не открывает и не закрывает файл.
|
||
*/
|
||
class ReadBufferFromFileDescriptor : public BufferWithOwnMemory<ReadBuffer>
|
||
{
|
||
protected:
|
||
int fd;
|
||
|
||
bool nextImpl()
|
||
{
|
||
size_t bytes_read = 0;
|
||
while (!bytes_read)
|
||
{
|
||
ssize_t res = ::read(fd, internal_buffer.begin(), internal_buffer.size());
|
||
if (!res)
|
||
break;
|
||
|
||
if (-1 == res && errno != EINTR)
|
||
throwFromErrno("Cannot read from file " + getFileName(), ErrorCodes::CANNOT_READ_FROM_FILE_DESCRIPTOR);
|
||
|
||
if (res > 0)
|
||
bytes_read += res;
|
||
}
|
||
|
||
if (bytes_read)
|
||
working_buffer.resize(bytes_read);
|
||
else
|
||
return false;
|
||
|
||
return true;
|
||
}
|
||
|
||
/// Имя или описание файла
|
||
virtual std::string getFileName()
|
||
{
|
||
return "(fd = " + toString(fd) + ")";
|
||
}
|
||
|
||
public:
|
||
ReadBufferFromFileDescriptor(int fd_, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE, char * existing_memory = NULL)
|
||
: BufferWithOwnMemory<ReadBuffer>(buf_size, existing_memory), fd(fd_) {}
|
||
|
||
int getFD()
|
||
{
|
||
return fd;
|
||
}
|
||
|
||
off_t seek(off_t offset, int whence = SEEK_SET)
|
||
{
|
||
off_t res = lseek(fd, offset, whence);
|
||
if (-1 == res)
|
||
throwFromErrno("Cannot seek through file " + getFileName(), ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
|
||
return res;
|
||
}
|
||
};
|
||
|
||
}
|