162 lines
3.6 KiB
C
162 lines
3.6 KiB
C
/*
|
|
* Copyright (C) 2004, 2005 Internet Systems Consortium, Inc. ("ISC")
|
|
* Copyright (C) 1999-2002 Internet Software Consortium.
|
|
*
|
|
* Permission to use, copy, modify, and distribute this software for any
|
|
* purpose with or without fee is hereby granted, provided that the above
|
|
* copyright notice and this permission notice appear in all copies.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
|
|
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
|
|
* AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
|
|
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
|
|
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
|
|
* OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
|
|
* PERFORMANCE OF THIS SOFTWARE.
|
|
*/
|
|
|
|
/* $Id: lfsr.c,v 1.14.18.4 2005/10/14 01:28:29 marka Exp $ */
|
|
|
|
/*! \file */
|
|
|
|
#include <config.h>
|
|
|
|
#include <stddef.h>
|
|
#include <stdlib.h>
|
|
|
|
#include <isc/assertions.h>
|
|
#include <isc/lfsr.h>
|
|
#include <isc/util.h>
|
|
|
|
#define VALID_LFSR(x) (x != NULL)
|
|
|
|
void
|
|
isc_lfsr_init(isc_lfsr_t *lfsr, isc_uint32_t state, unsigned int bits,
|
|
isc_uint32_t tap, unsigned int count,
|
|
isc_lfsrreseed_t reseed, void *arg)
|
|
{
|
|
REQUIRE(VALID_LFSR(lfsr));
|
|
REQUIRE(8 <= bits && bits <= 32);
|
|
REQUIRE(tap != 0);
|
|
|
|
lfsr->state = state;
|
|
lfsr->bits = bits;
|
|
lfsr->tap = tap;
|
|
lfsr->count = count;
|
|
lfsr->reseed = reseed;
|
|
lfsr->arg = arg;
|
|
|
|
if (count == 0 && reseed != NULL)
|
|
reseed(lfsr, arg);
|
|
if (lfsr->state == 0)
|
|
lfsr->state = 0xffffffffU >> (32 - lfsr->bits);
|
|
}
|
|
|
|
/*!
|
|
* Return the next state of the lfsr.
|
|
*/
|
|
static inline isc_uint32_t
|
|
lfsr_generate(isc_lfsr_t *lfsr)
|
|
{
|
|
|
|
/*
|
|
* If the previous state is zero, we must fill it with something
|
|
* here, or we will begin to generate an extremely predictable output.
|
|
*
|
|
* First, give the reseed function a crack at it. If the state is
|
|
* still 0, set it to all ones.
|
|
*/
|
|
if (lfsr->state == 0) {
|
|
if (lfsr->reseed != NULL)
|
|
lfsr->reseed(lfsr, lfsr->arg);
|
|
if (lfsr->state == 0)
|
|
lfsr->state = 0xffffffffU >> (32 - lfsr->bits);
|
|
}
|
|
|
|
if (lfsr->state & 0x01) {
|
|
lfsr->state = (lfsr->state >> 1) ^ lfsr->tap;
|
|
return (1);
|
|
} else {
|
|
lfsr->state >>= 1;
|
|
return (0);
|
|
}
|
|
}
|
|
|
|
void
|
|
isc_lfsr_generate(isc_lfsr_t *lfsr, void *data, unsigned int count)
|
|
{
|
|
unsigned char *p;
|
|
unsigned int bit;
|
|
unsigned int byte;
|
|
|
|
REQUIRE(VALID_LFSR(lfsr));
|
|
REQUIRE(data != NULL);
|
|
REQUIRE(count > 0);
|
|
|
|
p = data;
|
|
byte = count;
|
|
|
|
while (byte--) {
|
|
*p = 0;
|
|
for (bit = 0; bit < 7; bit++) {
|
|
*p |= lfsr_generate(lfsr);
|
|
*p <<= 1;
|
|
}
|
|
*p |= lfsr_generate(lfsr);
|
|
p++;
|
|
}
|
|
|
|
if (lfsr->count != 0 && lfsr->reseed != NULL) {
|
|
if (lfsr->count <= count * 8)
|
|
lfsr->reseed(lfsr, lfsr->arg);
|
|
else
|
|
lfsr->count -= (count * 8);
|
|
}
|
|
}
|
|
|
|
static inline isc_uint32_t
|
|
lfsr_skipgenerate(isc_lfsr_t *lfsr, unsigned int skip)
|
|
{
|
|
while (skip--)
|
|
(void)lfsr_generate(lfsr);
|
|
|
|
(void)lfsr_generate(lfsr);
|
|
|
|
return (lfsr->state);
|
|
}
|
|
|
|
/*
|
|
* Skip "skip" states in "lfsr".
|
|
*/
|
|
void
|
|
isc_lfsr_skip(isc_lfsr_t *lfsr, unsigned int skip)
|
|
{
|
|
REQUIRE(VALID_LFSR(lfsr));
|
|
|
|
while (skip--)
|
|
(void)lfsr_generate(lfsr);
|
|
}
|
|
|
|
/*
|
|
* Skip states in lfsr1 and lfsr2 using the other's current state.
|
|
* Return the final state of lfsr1 ^ lfsr2.
|
|
*/
|
|
isc_uint32_t
|
|
isc_lfsr_generate32(isc_lfsr_t *lfsr1, isc_lfsr_t *lfsr2)
|
|
{
|
|
isc_uint32_t state1, state2;
|
|
isc_uint32_t skip1, skip2;
|
|
|
|
REQUIRE(VALID_LFSR(lfsr1));
|
|
REQUIRE(VALID_LFSR(lfsr2));
|
|
|
|
skip1 = lfsr1->state & 0x01;
|
|
skip2 = lfsr2->state & 0x01;
|
|
|
|
/* cross-skip. */
|
|
state1 = lfsr_skipgenerate(lfsr1, skip2);
|
|
state2 = lfsr_skipgenerate(lfsr2, skip1);
|
|
|
|
return (state1 ^ state2);
|
|
}
|