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//
// srecord - manipulate eprom load files
// Copyright (C) 2004, 2006, 2007 Peter Miller
//
// 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; either version 3 of the License, or
// (at your option) any later version.
//
// 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, see
// <http://www.gnu.org/licenses/>.
//
#include <cstdlib>
#include <time.h>
#include <unistd.h>
#include <lib/r250.h>
static unsigned long buf[250];
static unsigned long *pos;
static inline int
rand8(void)
{
return ((rand() >> 7) & 255);
}
static inline long
rand32(void)
{
return
(
((unsigned long)rand8() << 24)
|
((unsigned long)rand8() << 16)
|
((unsigned long)rand8() << 8)
|
(unsigned long)rand8()
);
}
#define SIZEOF(a) (sizeof(a) / sizeof(a[0]))
#define ENDOF(a) ((a) + SIZEOF(a))
static bool ready;
static void
r250_init(void)
{
ready = true;
/*
* initialize crummy linear congruential
*/
time_t now;
time(&now);
srand(now + getpid());
/*
* position to start of array
*/
pos = buf;
/*
* initialise contents of array
*/
unsigned long *bp;
for (bp = buf; bp < ENDOF(buf); ++bp)
*bp = rand32();
/*
* make sure the bits are linearly independent
*/
unsigned long bit;
for (bit = 1, bp = buf + 3; bit; bp += 11, bit <<= 1)
{
if (bp >= ENDOF(buf))
bp -= SIZEOF(buf);
*bp = (*bp & ~(bit - 1)) | bit;
}
}
unsigned long
r250(void)
{
if (!ready)
r250_init();
unsigned long *other = pos + 103;
if (other >= ENDOF(buf))
other -= SIZEOF(buf);
*pos ^= *other;
unsigned long result = *pos++;
if (pos >= ENDOF(buf))
pos = buf;
return result;
}
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