mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-18 13:42:02 +00:00
114 lines
3.1 KiB
C++
114 lines
3.1 KiB
C++
#pragma once
|
||
|
||
#include <unistd.h>
|
||
#include <errno.h>
|
||
|
||
#include <DB/Common/ProfileEvents.h>
|
||
|
||
#include <DB/Core/Exception.h>
|
||
#include <DB/Core/ErrorCodes.h>
|
||
|
||
#include <DB/IO/ReadBufferFromFileBase.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 ReadBufferFromFileBase
|
||
{
|
||
protected:
|
||
int fd;
|
||
off_t pos_in_file; /// Какому сдвигу в файле соответствует working_buffer.end().
|
||
|
||
bool nextImpl()
|
||
{
|
||
size_t bytes_read = 0;
|
||
while (!bytes_read)
|
||
{
|
||
ProfileEvents::increment(ProfileEvents::ReadBufferFromFileDescriptorRead);
|
||
|
||
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;
|
||
}
|
||
|
||
pos_in_file += bytes_read;
|
||
|
||
if (bytes_read)
|
||
{
|
||
ProfileEvents::increment(ProfileEvents::ReadBufferFromFileDescriptorReadBytes, bytes_read);
|
||
working_buffer.resize(bytes_read);
|
||
}
|
||
else
|
||
return false;
|
||
|
||
return true;
|
||
}
|
||
|
||
/// Имя или описание файла
|
||
virtual std::string getFileName() const override
|
||
{
|
||
return "(fd = " + toString(fd) + ")";
|
||
}
|
||
|
||
public:
|
||
ReadBufferFromFileDescriptor(int fd_, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE, char * existing_memory = nullptr, size_t alignment = 0)
|
||
: ReadBufferFromFileBase(buf_size, existing_memory, alignment), fd(fd_), pos_in_file(0) {}
|
||
|
||
int getFD() const override
|
||
{
|
||
return fd;
|
||
}
|
||
|
||
off_t getPositionInFile() override
|
||
{
|
||
return pos_in_file - (working_buffer.end() - pos);
|
||
}
|
||
|
||
private:
|
||
/// Если offset такой маленький, что мы не выйдем за пределы буфера, настоящий seek по файлу не делается.
|
||
off_t doSeek(off_t offset, int whence) override
|
||
{
|
||
off_t new_pos = offset;
|
||
if (whence == SEEK_CUR)
|
||
new_pos = pos_in_file - (working_buffer.end() - pos) + offset;
|
||
else if (whence != SEEK_SET)
|
||
throw Exception("ReadBufferFromFileDescriptor::seek expects SEEK_SET or SEEK_CUR as whence", ErrorCodes::ARGUMENT_OUT_OF_BOUND);
|
||
|
||
/// Никуда не сдвинулись.
|
||
if (new_pos + (working_buffer.end() - pos) == pos_in_file)
|
||
return new_pos;
|
||
|
||
if (hasPendingData() && new_pos <= pos_in_file && new_pos >= pos_in_file - static_cast<off_t>(working_buffer.size()))
|
||
{
|
||
/// Остались в пределах буфера.
|
||
pos = working_buffer.begin() + (new_pos - (pos_in_file - working_buffer.size()));
|
||
return new_pos;
|
||
}
|
||
else
|
||
{
|
||
ProfileEvents::increment(ProfileEvents::Seek);
|
||
|
||
pos = working_buffer.end();
|
||
off_t res = lseek(fd, new_pos, SEEK_SET);
|
||
if (-1 == res)
|
||
throwFromErrno("Cannot seek through file " + getFileName(), ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
|
||
pos_in_file = new_pos;
|
||
return res;
|
||
}
|
||
}
|
||
};
|
||
|
||
}
|