Re: Why is network reading slow?

Hector Santos <>
Thu, 14 Jan 2010 22:42:06 -0500
Our application server product (DOS version) was introduced in 1984,
the 32 bit version introduced in 1996. I don't recall if these
extended 64 bit file I/O functions were available for the original
design engineers to use. Obviously 32 bit was the NEW THING and
equivalent to the same or near 32 bit to 64 bit design pressures as it
was for the 16 bit to 32 bit design pressues. I suspect 64 bit was the
LAST THING on anyone's mind nor a consideration.

Yes, we need to do more serious testing with the ss64lib code. Its not
in production. What I posted was first "drafts" with limited proof of
concept testing. I do appreciate your input on proper c/c++ syntaxing
or casting.

Overall, we were still stuck in a badly quoted proverbial:

      "To do full 64 bit or not do full 64 bit (only partial)"

design dilemma :)

Going full 64 bit would be a major, I mean major RPC client/server
framework redesign with a 250 function client API that is still based
on 32 bit I/O and structures. Changing it is not an option without
breaking thousands of 3rd party client applications and customer
embedded server side code applications and we need to still deal with
the "Shim" idea for backward compatibility 32 bit clients connecting
to a new 64 bit server over RPC!


Joseph M. Newcomer wrote:

It wouldn't have occurred to me that seeking was a problem, because if I were doing any
serious file system, I would not be using anything with a 32-bit limitation. Haven't
really worried about this problem since about 1997, when I did my first database that was
expected to hit terabytes. We just ignored the primitive and outdated C library, since it
did nothing useful for us. I notice you are still using the obsolete SetFilePointer,
instead of the more modern SetFilePointerEx, which has been around for a decade.

Also, returning the .QuadPart component should fail in any environment in which TINT is
declared as a DWORD, since the compiler should complain about truncation of a value (you
should always build at /W4). You should use the same cast as for the file size, (TINT).

On Thu, 14 Jan 2010 21:51:24 -0500, Hector Santos <> wrote:

Joseph M. Newcomer wrote:

Yes, but the file size was given as 50MB.
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>


# define TINT INT64
# define TWORD QWORD
# define TFILESIZE INT64
# define MAXQWORD _UI64_MAX
# define MAXINT64 _I64_MAX
# define TINT DWORD
# define TWORD DWORD

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);

#endif // __SS64LIB_H

// File Name : ss64lib.cpp

#include "ss64lib.h"

TINT ssFileSeek(HANDLE hf, TINT dist, WORD method)
   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);

   li.LowPart = GetFileSize(hf,(DWORD *)&li.HighPart);
   return (TINT)li.QuadPart;

Joseph M. Newcomer [MVP]
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