Re: Why is network reading slow?

Joseph M. Newcomer wrote:

Its amazing how "big" is relative these days. My first computer had a
$1,500 Micropolis 10 meg drive! :)

BTW, it (the code posted) should not be an issue when just streaming
in a file of any size.

The problem begins when seeking a file.

When seeking is required, we know by using the 64 bit WIN32 file I/O
functions that it works for large +2gig files.

In one part of our server product file handing, a ISAM database with
four key index files have DWORD position indices. Issues occur as the
database grows and a index goes beyond a 32 bit value. A documented
limitation but a limitations that is not outdated.

A simple solution in the works was to use the 64 bit extended file I/O
functions which offer QUAD (double DWORD) positions. Its about to be
implemented in new major revision of our server.

For backward single source compatibility, I produced a header and
wrapper functions. Here is the *.h and *.cpp files:

//------------------------------------------------------------
// File Name : ss64lib.h
//------------------------------------------------------------

#ifndef __SS64LIB_H
#define __SS64LIB_H

#ifndef _WINDOWS_
#include <windows.h>
#endif

#define SUPPORT_FILEIO_64BIT

#ifdef SUPPORT_FILEIO_64BIT
# define TINT INT64
# define TWORD QWORD
# define TFILESIZE INT64
# define MAXQWORD _UI64_MAX
# define MAXINT64 _I64_MAX
#else
# define TINT DWORD
# define TWORD DWORD
# define TFILESIZE DWORD
#endif

TINT ssFileSeek(HANDLE hf, TINT distance,
                 WORD MoveMethod = FILE_BEGIN);
TINT ssFileEnd(HANDLE hf);
TINT ssFilePos(HANDLE hf);
BOOL ssFileRewind(HANDLE hf);
BOOL ssFileLock(HANDLE hf, TINT Offset, TINT nBytes);
BOOL ssFileUnlock(HANDLE hf, TINT Offset, TINT nBytes);
TFILESIZE ssFileSize(HANDLE hf);

#endif // __SS64LIB_H

//------------------------------------------------------------
// File Name : ss64lib.cpp
//------------------------------------------------------------

#include "ss64lib.h"

TINT ssFileSeek(HANDLE hf, TINT dist, WORD method)
{
    LARGE_INTEGER li;
    li.QuadPart = dist;
    li.LowPart = SetFilePointer (hf, li.LowPart, &li.HighPart, method);
    if (li.LowPart == 0xFFFFFFFF && GetLastError() != NO_ERROR) {
       li.QuadPart = -1;
    }
    return li.QuadPart;
}

BOOL ssFileRewind(HANDLE hf)
{
    return ssFileSeek(hf,0,FILE_BEGIN) == 0;
}

TINT ssFilePos(HANDLE hf)
{
    return ssFileSeek(hf,0,FILE_CURRENT);
}

TINT ssFileEnd(HANDLE hf)
{
    return ssFileSeek(hf,0,FILE_END);
}

BOOL ssFileLock(HANDLE hf, TINT Offset, TINT nBytes)
{
    LARGE_INTEGER fp, nb;
    fp.QuadPart = Offset;
    nb.QuadPart = nBytes;
    return LockFile (hf,fp.LowPart,fp.HighPart,nb.LowPart,nb.HighPart);
}

BOOL ssFileUnlock(HANDLE hf, TINT Offset, TINT nBytes)
{
    LARGE_INTEGER fp, nb;
    fp.QuadPart = Offset;
    nb.QuadPart = nBytes;
    return UnlockFile(hf,fp.LowPart,fp.HighPart,nb.LowPart,nb.HighPart);
}

TFILESIZE ssFileSize(HANDLE hf)
{
    LARGE_INTEGER li;
    li.LowPart = GetFileSize(hf,(DWORD *)&li.HighPart);
    return (TINT)li.QuadPart;
}

--
HLS