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#pragma once
#include <IO/ReadBufferFromFileDescriptor.h>
#include <IO/OpenedFileCache.h>
#include <Common/CurrentMetrics.h>
namespace CurrentMetrics
{
extern const Metric OpenFileForRead;
}
namespace DB
{
/** Accepts path to file and opens it, or pre-opened file descriptor.
* Closes file by himself (thus "owns" a file descriptor).
*/
class ReadBufferFromFile : public ReadBufferFromFileDescriptor
{
protected:
std::string file_name;
CurrentMetrics::Increment metric_increment{CurrentMetrics::OpenFileForRead};
public:
explicit ReadBufferFromFile(
const std::string & file_name_,
size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
int flags = -1,
char * existing_memory = nullptr,
size_t alignment = 0,
std::optional<size_t> file_size_ = std::nullopt,
ThrottlerPtr throttler = {});
/// Use pre-opened file descriptor.
explicit ReadBufferFromFile(
int & fd, /// Will be set to -1 if constructor didn't throw and ownership of file descriptor is passed to the object.
const std::string & original_file_name = {},
size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
char * existing_memory = nullptr,
size_t alignment = 0,
std::optional<size_t> file_size_ = std::nullopt,
ThrottlerPtr throttler = {});
~ReadBufferFromFile() override;
/// Close file before destruction of object.
void close();
std::string getFileName() const override
{
return file_name;
}
size_t getFileOffsetOfBufferEnd() const override { return file_offset_of_buffer_end; }
};
/** Similar to ReadBufferFromFile but it is using 'pread' instead of 'read'.
*/
class ReadBufferFromFilePRead : public ReadBufferFromFile
{
public:
explicit ReadBufferFromFilePRead(
const std::string & file_name_,
size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
int flags = -1,
char * existing_memory = nullptr,
size_t alignment = 0,
std::optional<size_t> file_size_ = std::nullopt)
: ReadBufferFromFile(file_name_, buf_size, flags, existing_memory, alignment, file_size_)
{
use_pread = true;
}
};
/** Similar to ReadBufferFromFilePRead but also transparently shares open file descriptors.
*/
class ReadBufferFromFilePReadWithDescriptorsCache : public ReadBufferFromFileDescriptorPRead
{
private:
std::string file_name;
OpenedFileCache::OpenedFilePtr file;
public:
explicit ReadBufferFromFilePReadWithDescriptorsCache(
const std::string & file_name_,
size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
int flags = -1,
char * existing_memory = nullptr,
size_t alignment = 0,
std::optional<size_t> file_size_ = std::nullopt,
ThrottlerPtr throttler_ = {})
: ReadBufferFromFileDescriptorPRead(-1, buf_size, existing_memory, alignment, file_size_, throttler_)
, file_name(file_name_)
{
file = OpenedFileCache::instance().get(file_name, flags);
fd = file->getFD();
}
std::string getFileName() const override
{
return file_name;
}
};
}
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