/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1988 AT&T */
/*        All Rights Reserved   */

/*
 *      drand48, etc. pseudo-random number generator
 *      This implementation assumes unsigned short integers of at least
 *      16 bits, long integers of at least 32 bits, and ignores
 *      overflows on adding or multiplying two unsigned integers.
 *      Two's-complement representation is assumed in a few places.
 *      Some extra masking is done if unsigneds are exactly 16 bits
 *      or longs are exactly 32 bits, but so what?
 *      An assembly-language implementation would run significantly faster.
 */
/*
 *      New assumptions (supercede those stated above) for 64-bit work.
 *      Longs are now 64 bits, and we are bound by standards to return
 *      type long, hovever all internal calculations where long was
 *      previously used (32 bit precision) are now using the int32_t
 *      type (32 bit precision in both ILP32 and LP64 worlds).
 */

#include "lint.h"
#include <mtlib.h>
#include <synch.h>
#include <thread.h>

static mutex_t seed_lock = DEFAULTMUTEX;

#define EXPORT0(TYPE, fn, fnu)  TYPE fn() { \
        TYPE res; \
        lmutex_lock(&seed_lock); \
        res = fnu(); \
        lmutex_unlock(&seed_lock); \
        return (res); }
#define EXPORT1(TYPE, fn, fnu)  TYPE fn(unsigned short xsubi[3]) { \
        TYPE res; \
        lmutex_lock(&seed_lock); \
        res = fnu(xsubi); \
        lmutex_unlock(&seed_lock); \
        return (res); }

#define N       16
#define MASK    ((unsigned)(1 << (N - 1)) + (1 << (N - 1)) - 1)
#define LOW(x)  ((unsigned)(x) & MASK)
#define HIGH(x) LOW((x) >> N)
#define MUL(x, y, z)    { int32_t l = (int32_t)(x) * (int32_t)(y); \
                (z)[0] = LOW(l); (z)[1] = HIGH(l); }
#define CARRY(x, y)     ((int32_t)(x) + (int32_t)(y) > MASK)
#define ADDEQU(x, y, z) (z = CARRY(x, (y)), x = LOW(x + (y)))
#define X0      0x330E
#define X1      0xABCD
#define X2      0x1234
#define A0      0xE66D
#define A1      0xDEEC
#define A2      0x5
#define C       0xB
#define SET3(x, x0, x1, x2)     ((x)[0] = (x0), (x)[1] = (x1), (x)[2] = (x2))
#define SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n)+1]), LOW((y)[(n)+2]))
#define SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C)
#define REST(v) for (i = 0; i < 3; i++) { xsubi[i] = x[i]; x[i] = temp[i]; } \
                return (v)
#define NEST(TYPE, f, F) static TYPE f(unsigned short *xsubi) { \
        int i; TYPE v; unsigned temp[3]; \
        for (i = 0; i < 3; i++) { temp[i] = x[i]; x[i] = LOW(xsubi[i]); }  \
        v = F(); REST(v); }

/* Way ugly solution to problem names, but it works */
#define x       _drand48_x
#define a       _drand48_a
#define c       _drand48_c
/* End way ugly */
static unsigned x[3] = { X0, X1, X2 }, a[3] = { A0, A1, A2 }, c = C;
static unsigned short lastx[3];
static void next(void);

static double
_drand48_u(void)
{
        static double two16m = 1.0 / ((int32_t)1 << N);

        next();
        return (two16m * (two16m * (two16m * x[0] + x[1]) + x[2]));
}

NEST(double, _erand48_u, _drand48_u)

static long
_lrand48_u(void)
{
        next();
        return ((long)((int32_t)x[2] << (N - 1)) + (x[1] >> 1));
}

static long
_mrand48_u(void)
{
        next();
        return ((long)((int32_t)x[2] << N) + x[1]);
}

static void
next(void)
{
        unsigned p[2], q[2], r[2], carry0, carry1;

        MUL(a[0], x[0], p);
        ADDEQU(p[0], c, carry0);
        ADDEQU(p[1], carry0, carry1);
        MUL(a[0], x[1], q);
        ADDEQU(p[1], q[0], carry0);
        MUL(a[1], x[0], r);
        x[2] = LOW(carry0 + carry1 + CARRY(p[1], r[0]) + q[1] + r[1] +
            a[0] * x[2] + a[1] * x[1] + a[2] * x[0]);
        x[1] = LOW(p[1] + r[0]);
        x[0] = LOW(p[0]);
}

void
srand48(long seedval)
{
        int32_t fixseed = (int32_t)seedval;     /* limit to 32 bits */

        lmutex_lock(&seed_lock);
        SEED(X0, LOW(fixseed), HIGH(fixseed));
        lmutex_unlock(&seed_lock);
}

unsigned short *
seed48(unsigned short seed16v[3])
{
        lmutex_lock(&seed_lock);
        SETLOW(lastx, x, 0);
        SEED(LOW(seed16v[0]), LOW(seed16v[1]), LOW(seed16v[2]));
        lmutex_unlock(&seed_lock);
        return (lastx);
}

void
lcong48(unsigned short param[7])
{
        lmutex_lock(&seed_lock);
        SETLOW(x, param, 0);
        SETLOW(a, param, 3);
        c = LOW(param[6]);
        lmutex_unlock(&seed_lock);
}

NEST(long, _nrand48_u, _lrand48_u)

NEST(long, _jrand48_u, _mrand48_u)

EXPORT0(double, drand48, _drand48_u)
EXPORT1(double, erand48, _erand48_u)

EXPORT0(long, lrand48, _lrand48_u)
EXPORT1(long, nrand48, _nrand48_u)

EXPORT0(long, mrand48, _mrand48_u)
EXPORT1(long, jrand48, _jrand48_u)

#ifdef DRIVER
/*
 *      This should print the sequences of integers in Tables 2
 *              and 1 of the TM:
 *      1623, 3442, 1447, 1829, 1305, ...
 *      657EB7255101, D72A0C966378, 5A743C062A23, ...
 */
#include <stdio.h>

main()
{
        int i;

        for (i = 0; i < 80; i++) {
                printf("%4d ", (int)(4096 * drand48()));
                printf("%.4X%.4X%.4X\n", x[2], x[1], x[0]);
        }
}
#endif