random.c

/*
    Copyright (C) 1983 The Regents of the University of California.

    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

    1.  Redistributions of source code must retain the above copyright
	notice, this list of conditions and the following disclaimer.
    2.  Redistributions in binary form must reproduce the above copyright
	notice, this list of conditions and the following disclaimer in the
	documentation and/or other materials provided with the distribution.
    3.  Neither the name of the University nor the names of its contributors
	may be used to endorse or promote products derived from this software
	without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
    ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
    OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
    OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGE.
*/

/*
 * Last Modified: Dec 30, 1990
 */

/*
 * random and associated routines lifted from 4.2BSD
 */

#include <stdio.h>

#define     TYPE_0      0   /* linear congruential */
#define     BREAK_0     8
#define     DEG_0       0
#define     SEP_0       0

#define     TYPE_1      1   /* x**7 + x**3 + 1 */
#define     BREAK_1     32
#define     DEG_1       7
#define     SEP_1       3

#define     TYPE_2      2   /* x**15 + x + 1 */
#define     BREAK_2     64
#define     DEG_2       15
#define     SEP_2       1

#define     TYPE_3      3   /* x**31 + x**3 + 1 */
#define     BREAK_3     128
#define     DEG_3       31
#define     SEP_3       3

#define     TYPE_4      4   /* x**63 + x + 1 */
#define     BREAK_4     256
#define     DEG_4       63
#define     SEP_4       1

#define     MAX_TYPES   5   /* max number of types above */

static int  degrees[MAX_TYPES] = {DEG_0, DEG_1, DEG_2, DEG_3, DEG_4};

static int  seps[MAX_TYPES] = {SEP_0, SEP_1, SEP_2, SEP_3, SEP_4};

static long randtbl[DEG_3 + 1] = {TYPE_3,
    0x9a319039L, 0x32d9c024L, 0x9b663182L, 0x5da1f342L,
    0xde3b81e0L, 0xdf0a6fb5L, 0xf103bc02L, 0x48f340fbL,
    0x7449e56bL, 0xbeb1dbb0L, 0xab5c5918L, 0x946554fdL,
    0x8c2e680fL, 0xeb3d799fL, 0xb11ee0b7L, 0x2d436b86L,
    0xda672e2aL, 0x1588ca88L, 0xe369735dL, 0x904f35f7L,
    0xd7158fd6L, 0x6fa6f051L, 0x616e6b96L, 0xac94efdcL,
    0x36413f93L, 0xc622c298L, 0xf5a42ab8L, 0x8a88d77bL,
    0xf5ad9d0eL, 0x8999220bL, 0x27fb47b9L};

static long *fptr = &randtbl[SEP_3 + 1];
static long *rptr = &randtbl[1];

static long *state = &randtbl[-1];

static int  rand_type = TYPE_3;
static int  rand_deg = DEG_3;
static int  rand_sep = SEP_3;

static long *end_ptr = &randtbl[DEG_3 + 1];

srandom(x)
unsigned    x;
{
    long    random();
    int i, j;

    if (rand_type == TYPE_0)
        state[0] = x;
    else {
        j = 1;
        state[0] = x;
        for (i = 1; i < rand_deg; i++)
            state[i] = 1103515245L * state[i - 1] + 12345L;
        fptr = &state[rand_sep];
        rptr = &state[0];
        for (i = 0; i < 10 * rand_deg; i++)
            random();
    }
}

char    *
initstate(seed, arg_state, n)
unsigned int    seed;       /* seed for R. N. G. */
char    *arg_state;     /* pointer to state array */
int n;          /* # bytes of state info */
{
    char    *ostate = (char *) (&state[-1]);

    if (rand_type == TYPE_0)
        state[-1] = rand_type;
    else
        state[-1] = MAX_TYPES * (rptr - state) + rand_type;
    if (n < BREAK_1) {
        if (n < BREAK_0) {
            fprintf(stderr, "initstate: not enough state (%d bytes) with which to do jack; ignored.\n");
            return;
        }
        rand_type = TYPE_0;
        rand_deg = DEG_0;
        rand_sep = SEP_0;
    }
    else {
        if (n < BREAK_2) {
            rand_type = TYPE_1;
            rand_deg = DEG_1;
            rand_sep = SEP_1;
        }
        else {
            if (n < BREAK_3) {
                rand_type = TYPE_2;
                rand_deg = DEG_2;
                rand_sep = SEP_2;
            }
            else {
                if (n < BREAK_4) {
                    rand_type = TYPE_3;
                    rand_deg = DEG_3;
                    rand_sep = SEP_3;
                }
                else {
                    rand_type = TYPE_4;
                    rand_deg = DEG_4;
                    rand_sep = SEP_4;
                }
            }
        }
    }
    state = &(((long *) arg_state)[1]); /* first location */
    end_ptr = &state[rand_deg]; /* must set end_ptr before srandom */
    srandom(seed);
    if (rand_type == TYPE_0)
        state[-1] = rand_type;
    else
        state[-1] = MAX_TYPES * (rptr - state) + rand_type;
    return (ostate);
}

char    *
setstate(arg_state)
char    *arg_state;
{
    long    *new_state = (long *) arg_state;
    int type = new_state[0] % MAX_TYPES;
    int rear = new_state[0] / MAX_TYPES;
    char    *ostate = (char *) (&state[-1]);

    if (rand_type == TYPE_0)
        state[-1] = rand_type;
    else
        state[-1] = MAX_TYPES * (rptr - state) + rand_type;
    switch (type) {
        case TYPE_0:
        case TYPE_1:
        case TYPE_2:
        case TYPE_3:
        case TYPE_4:
            rand_type = type;
            rand_deg = degrees[type];
            rand_sep = seps[type];
            break;
        default:
            fprintf(stderr, "setstate: state info has been munged; not changed.\n");
    }
    state = &new_state[1];
    if (rand_type != TYPE_0) {
        rptr = &state[rear];
        fptr = &state[(rear + rand_sep) % rand_deg];
    }
    end_ptr = &state[rand_deg]; /* set end_ptr too */
    return (ostate);
}

long
random()
{
    long    i;

    if (rand_type == TYPE_0)
        i = state[0] = (state[0] * 1103515245L + 12345L) & 0x7fffffffL;
    else {
        *fptr += *rptr;
        i = (*fptr >> 1) & 0x7fffffffL; /* chucking least random bit */
        if (++fptr >= end_ptr) {
            fptr = state;
            ++rptr;
        }
        else if (++rptr >= end_ptr)
            rptr = state;
    }
    return (i);
}


get_rand(x, y)
int x, y;
{
    long    r, random();
    int s;
    two_sort(x, y);
    r = random();
    r = (r % ((y - x) + 1)) + x;
    s = (int) r;
    return (s);
}

rand_percent(percentage)
{
    return (get_rand(1, 100) <= percentage);
}