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EnigmA Amiga Run 1996 February
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EnigmA AMIGA RUN 04 (1996)(G.R. Edizioni)(IT)[!][issue 1996-02][Skylink CD III].iso
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random.c
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1992-09-02
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RCS_ID_C="$Id: random.c,v 1.1 1994/01/20 08:26:10 ppessi Exp $";
/*
* random.c --- random numbers
*
* Author: ppessi <Pekka.Pessi@hut.fi>
*
* This file is part of the AmiTCP/IP User Library.
*
* Copyright © 1993 AmiTCP/IP Group, <AmiTCP-Group@hut.fi>
* Helsinki University of Technology, Finland.
*
* Created : Wed Sep 15 01:25:26 1993 ppessi
* Last modified: Wed Jan 19 10:21:44 1994 ppessi
*/
#include <exec/types.h>
#include <exec/io.h>
#include <devices/timer.h>
#include <proto/timer.h>
extern struct Library *TimerBase;
/****i* random.module/LRandom ******************************************
*
* NAME
* LRandom -- Random number generator
*
* SYNOPSIS
* value = LRandom()
*
* LONG InitLRandom(void)
*
* FUNCTION
* Generates a random long integer. The random number generator
* must have been initialized before calling LRandom() or strange
* things will happen.
*
* LRandom() generates fairly good random numbers, all bits in the
* long word seem to be useful.
*
* BUGS
* None known.
*
* SEE ALSO
* InitLRandom, timer.device/GetSysTime()
*
******************************************************************************
*/
static union random_seed {
struct timeval time;
ULONG longs[2];
UWORD words[4];
} seed;
static const UWORD random_offset[4] = { 0x7823, 0xab34, 0x93b4, 0x7673 };
static const UWORD random_eor[4] = { 0xc97d, 0x6988, 0x32e9, 0x8487 };
ULONG LRandom(void)
{
ULONG carry = 0;
int i;
for (i = 3; i >= 0; i--) {
carry += seed.words[i]*34639L + random_offset[i];
seed.words[i] = carry ^ random_eor[i];
carry >>= 16;
}
return (ULONG)(seed.words[3] << 24) + (seed.words[2]<<16) +
(seed.words[1] << 8) + seed.words[0];
}
/****i* random.module/LRandomInit ******************************************
*
* NAME
* LRandomInit -- initialize LRandom generator
*
* SYNOPSIS
* error = LRandomInit();
*
* int LRandomInit(void);
*
* FUNCTION
* Initializes the random number generator with the current time.
*
* NOTES
* This function uses GetSysTime() to get the initial seed for the
* random number generator. Thus it needs the V36 timer.device.
*
* RETURN VALUE
* Nonzero after initialization error.
*
* BUGS
* None known.
*
* SEE ALSO
* LRandom, timer.device/GetSysTime()
*
******************************************************************************
*/
int LRandomInit(void)
{
if (TimerBase) {
GetSysTime(&seed.time);
LRandom(); LRandom(); LRandom(); LRandom();
LRandom(); LRandom(); LRandom(); LRandom();
return 0;
}
return -1;
}