/***************************************************************************
 *
 * random.h - Header for the Standard Library random generator
 *
 * $Id: random.h,v 1.6 1996/08/28 01:30:28 smithey Exp $
 *
 ***************************************************************************
 *    
 *  Copyright 2000 Compaq Computer Corporation
 *
 *  COMPAQ Registered in U.S. Patent and Trademark Office.
 *
 *  Confidential computer software. Valid license from Compaq required for
 *  possession, use or copying. Consistent with FAR 12.211 and 12.212,
 *  Commercial Computer Software, Computer Software Documentation, and
 *  Technical Data for Commercial Items are licensed to the U.S. Government
 *  under vendor's standard commercial license.
 *
 ****************************************************************************
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 ***************************************************************************
 *
 * (c) Copyright 1994, 1998 Rogue Wave Software, Inc.
 * ALL RIGHTS RESERVED
 *
 * The software and information contained herein are proprietary to, and
 * comprise valuable trade secrets of, Rogue Wave Software, Inc., which
 * intends to preserve as trade secrets such software and information.
 * This software is furnished pursuant to a written license agreement and
 * may be used, copied, transmitted, and stored only in accordance with
 * the terms of such license and with the inclusion of the above copyright
 * notice.  This software and information or any other copies thereof may
 * not be provided or otherwise made available to any other person.
 *
 * Notwithstanding any other lease or license that may pertain to, or
 * accompany the delivery of, this computer software and information, the
 * rights of the Government regarding its use, reproduction and disclosure
 * are as set forth in Section 52.227-19 of the FARS Computer
 * Software-Restricted Rights clause.
 * 
 * Use, duplication, or disclosure by the Government is subject to
 * restrictions as set forth in subparagraph (c)(1)(ii) of the Rights in
 * Technical Data and Computer Software clause at DFARS 252.227-7013.
 * Contractor/Manufacturer is Rogue Wave Software, Inc.,
 * P.O. Box 2328, Corvallis, Oregon 97339.
 *
 * This computer software and information is distributed with "restricted
 * rights."  Use, duplication or disclosure is subject to restrictions as
 * set forth in NASA FAR SUP 18-52.227-79 (April 1985) "Commercial
 * Computer Software-Restricted Rights (April 1985)."  If the Clause at
 * 18-52.227-74 "Rights in Data General" is specified in the contract,
 * then the "Alternate III" clause applies.
 *
 **************************************************************************/

#if !defined(__DECFIXCXXL1187)
#ifndef __STD_RANDOM
#define __STD_RANDOM
#endif

#include <stdcomp>
#include <stddefs>   
#ifdef _RWSTD_MULTI_THREAD
#include <stdmutex>
#endif

#if defined(__VMS) && defined(__DECCXX) && !defined(__DECFIXCXXL1158)
#pragma __extern_prefix __save
#pragma __extern_prefix "CXXL$" 
#endif

#if defined(__DECCXX)
#   ifdef __PRAGMA_ENVIRONMENT
#      pragma __environment __save
#      pragma __environment __header_defaults
#   endif
#endif


#ifndef _RWSTD_NO_NAMESPACE
namespace _RWrwstd {
#endif

class _RWSTDExport  _RWrandom_generator
{
  protected:

    enum { LENGTH = 55 };

    unsigned long table[LENGTH];
    size_t        index1;
    size_t        index2;
#ifdef _RWSTD_MULTI_THREAD
    _RWSTDMutex    mutex;
#endif

    void seed (unsigned long j);

  public:

    unsigned long operator() (unsigned long limit)
    {
#ifdef _RWSTD_MULTI_THREAD
        _RWSTDGuard guard(mutex);
#endif
        index1 = (index1 + 1) % LENGTH;
        index2 = (index2 + 1) % LENGTH;
        table[index1] = table[index1] - table[index2];
        return table[index1] % limit;
    }

    _RWrandom_generator (unsigned long j) { this->seed(j); }
   
};

#ifndef _RWSTD_NO_NAMESPACE
}
#endif

#if defined(__VMS) && defined(__DECCXX) && !defined(__DECFIXCXXL1158)
#   pragma __extern_prefix __restore
#endif

#if defined(__DECCXX)
#   ifdef __PRAGMA_ENVIRONMENT
#      pragma __environment __restore
#   endif
#endif

#if !defined(__DECFIXCXXL1187)
#endif // __STD_RANDOM
#endif
