mariadb-columnstore-engine/utils/idbdatafile/IDBDataFile.h

/* Copyright (C) 2014 InfiniDB, Inc.

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; version 2 of
   the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
   MA 02110-1301, USA. */

#ifndef IDBDATAFILE_H_
#define IDBDATAFILE_H_
#define _FILE_OFFSET_BITS 64
#include <stdlib.h>
#include <string>
#include "largefile64.h"
#include<sys/types.h>
#include "stdint.h"
#include <unistd.h>
#ifdef _MSC_VER
#undef tell
#else
#define INVALID_HANDLE_VALUE 0      // Defined already in MSC
#endif

namespace idbdatafile
{

/**
 * IDBDataFile is a combination abstract base class and factory.  The purpose
 * is to encapsulate different underlying storage types from the InfiniDB
 * engine.  The interface is designed so that behavior is consistent across
 * storage types, knowing that options like HDFS are somewhat limited as
 * compared to normal POSIX file systems.
 *
 * to-do think about const-correctness
 */
class IDBDataFile
{
public:
    /**
     * The TYPE enum defines the supported underlying storage types
     */
    enum Types
    {
        UNKNOWN    = 0x0000,
        BUFFERED   = 0x0001,
        UNBUFFERED = 0x0002,
        HDFS	   = 0x0003,
    };

    /**
     * The Options enum defines elements of a bitmask that can be passed into
     * the open method for controlling specific options relating to the
     * particular file type in question.  If an option is unsupported by the
     * particular type the open() method will fail.
     *   USE_ODIRECT - requests the O_DIRECT flag to be set, only for
     *                 unbuffered files
     *   USE_VBUF    - requests that a non-default buffer is use for a
     *                 buffered file.  For now, the size of the buffer is
     *                 hard-coded to match DEFAULT_BUFSIZ in writeengine
     *                 (1*1024*1024)
     *   USE_NOVBUF  - requests that buffering is disabled when using a
     *                 buffered type file
     *   USE_TMPFILE - requests to output the membuffer to a temp file i/o
     *                 overwrite the original file
     */
    enum Options
    {
        USE_ODIRECT = 0x0001,
        USE_VBUF    = 0x0002,
        USE_NOVBUF  = 0x0004,
        USE_TMPFILE = 0x0008
    };

    /**
     * DEFSIZE is used as the starting size for the memory buffer of read/write
     * HDFS files.  Thes files are entirely buffered in memory and modified
     * there since HDFS does not support any file updates.  This value was
     * engineered to accomodate the standard default extent for a 4-byte column
     * <Deprecated>
     */
    static const int DEFSIZE = 33562624;
    /**
     * EXTENTSIZE is used with the passed in col width the starting size for the
     * memory buffer of read/write HDFS files.  Thes files are entirely buffered
     * in memory and modified there since HDFS does not support any file updates.
     */
    static const int EXTENTSIZE = 8390656;

    /**
     * This is an alternate factory method that accepts a typical mode
     * string (ala fopen).  Note that in general IDBDataFile only recognizes
     * a subset of the possible mode string that fopen supports however
     * at present time, the mode string will be passed through directly to
     * the BufferedFile constructor and through to fopen.  The eventual goal
     * is not complete support but rather only that necessary for Infinidb so
     * this will be reconsidered.
     */
    static IDBDataFile* open(Types type, const char* fname, const char* mode, unsigned opts, unsigned colWidth = 4);

    /**
     * Library users should assume that the destructor closes the file.
     * This actually occurs in the derived clasess - hence the protected
     * member close() here
     */
    virtual ~IDBDataFile();

    /**
     * This returns the name of the file.
     */
    const std::string& name() const;

    /**
     * This is a positional read method similar to kernel style pread
     * or fseek followed by read for C-library FILE*.  Return value
     * is the number of bytes read.
     */
    virtual ssize_t pread(void* ptr, off64_t offset, size_t count) = 0;

    /**
     * This is a read method similar to kernel style read or C library
     * fread().  Return value is the number of bytes read.
     */
    virtual ssize_t read(void* ptr, size_t count) = 0;

    /**
     * The write() call semantics match the standard library.  There is
     * no positional write and further there is no lseek or equivalent so
     * all writing must therefore occur sequentially - either from the
     * beginning of a file (open via WRITE) or the end of a file (open via
     * APPEND).  Return value is the number of bytes written.
     */
    virtual ssize_t write(const void* ptr, size_t count) = 0;

    /**
     * The seek() method is equivalent to the lseek() and fseek() functions.
     * The whence parameter accepts SEEK_SET, SEEK_CUR, SEEK_END just as
     * those functions do.  Note that not all file systems support this
     * operation - ex. HDFS will not support it for files opened for writing
     * Returns 0 on success, -1 on error
     */
    virtual int seek(off64_t offset, int whence) = 0;

    /**
     * The truncate() method is equivalent to the ftruncate method.  Note
     * that not all file types support this operation - ex.  HDFS files opened
     * or write or append do not, but HDFS files opened for modification do.
     * Returns 0 on success, -1 on error.
     */
    virtual int truncate(off64_t length) = 0;

    /**
     * The size() method returns the size of the file in a manner consistent
     * with the underlying filesystem.  Note that this method will always
     * return the correct size from the perspective of the open file handle,
     * thus depending on the semantics of the underlying file system an
     * external view of size may differ (ex. if writing buffered i/o before
     * a flush/sync or if writing an open HDFS file).  Returns -1 on error.
     */
    virtual off64_t size() = 0;

    /**
     * The tell() call returns the current offset in the file.  This is
     * similar to lseek with 0 offset in the standard library and ftell
     * for buffered FILE *s.
     */
    virtual off64_t tell() = 0;

    /**
     * The flush() method instructs the file to write any buffered contents
     * to disk.  Where relevant this method will include a call to fsync
     */
    virtual int flush() = 0;

    /**
     * The mtime() method returns the modification time of the file in
     * seconds.  Returns -1 on error.
     */
    virtual time_t mtime() = 0;

    int colWidth()
    {
        return m_fColWidth;
    }

protected:
    /**
     * Constructor - takes the filename to be stored in a member variable
     * for logging purposes
     */
    IDBDataFile( const char* fname );

    /**
     * The close() method closes the file.  It is defined as protected
     * because the preference is for close() to happen automatically during
     * deletion of the object
     */
    virtual int close() = 0;

    /**
     * file name
     */
    std::string m_fname;

    /**
     * Column width. If not applicable, defaults to 4.
     * We use this to determine the initial size of hdfs ram buffers.
     */
    int m_fColWidth;

};

inline
IDBDataFile::IDBDataFile( const char* fname ) :
    m_fname( fname ),
    m_fColWidth( 4 )
{
}

inline
IDBDataFile::~IDBDataFile()
{
}

inline
const std::string& IDBDataFile::name() const
{
    return m_fname;
}

}
#endif /* IDBDATAFILE_H_ */