/*

 * Copyright (c) 2008-2012 Zmanda, Inc.  All Rights Reserved.

 * Copyright (c) 2013-2016 Carbonite, Inc.  All Rights Reserved.

 *

 * 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 2

 * 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, write to the Free Software Foundation, Inc.,

 * 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA

 *

 * Contact information: Carbonite Inc., 756 N Pastoria Ave

 * Sunnyvale, CA 94086, USA, or: http://www.zmanda.com

 */

#include "amanda.h"

#include "simpleprng.h"

/* A *very* basic linear congruential generator; values are as cited in

 * http://en.wikipedia.org/wiki/Linear_congruential_generator for Numerical Recipes */

#define A 1664525

#define C 1013904223

void

simpleprng_seed(

    simpleprng_state_t *state,

    guint32 seed)

{

    g_assert(seed != 0);

    state->val = seed;

    state->count = 0;

}

guint32

simpleprng_get_seed(

    simpleprng_state_t *state)

{

    return state->val;

}

guint32 simpleprng_rand(

    simpleprng_state_t *state)

{

    state->count++;

    return (state->val = (A * state->val) + C);

}

void simpleprng_fill_buffer(

    simpleprng_state_t *state,

    gpointer buf,

    size_t len)

{

    guint8 *p = buf;

    while (len--) {

	*(p++) = simpleprng_rand_byte(state);

    }

}

static char *

hexstr(guint8 *p, int len)

{

    char *tmpbuf;

    char *result = NULL;

    int i;

    for (i = 0; i < len; i++) {

	if (result) {

	    tmpbuf = g_strdup_printf("%s %02x", result, (guint)(*(p++)));

	    g_free(result);

	    result = tmpbuf;

	}

	else

	    result = g_strdup_printf("[%02x", (guint)(*(p++)));

    }

    tmpbuf = g_strdup_printf("%s]", result);

    g_free(result);

    result = tmpbuf;

    return result;

}

gboolean simpleprng_verify_buffer(

    simpleprng_state_t *state,

    gpointer buf,

    size_t len)

{

    guint8 *p = buf;

    while (len--) {

	guint64 count = state->count;

	guint8 expected = simpleprng_rand_byte(state);

	guint8 got = *p;

	if (expected != got) {

	    int remaining = MIN(len, 16);

	    guint8 expbytes[16] = { expected };

	    char *gotstr = hexstr(p, remaining);

	    char *expstr;

	    int i;

	    for (i = 1; i < remaining; i++)

		expbytes[i] = simpleprng_rand_byte(state);

	    expstr = hexstr(expbytes, remaining);

	    g_fprintf(stderr,

		    "random value mismatch at offset %ju: got %s, expected %s\n",

		    (uintmax_t)count, gotstr, expstr);

	    g_free(gotstr);

	    g_free(expstr);

	    return FALSE;

	}

	p++;

    }

    return TRUE;

}