/*
 * zrand - subtractive 100 shuffle generator
 *
 * Copyright (C) 1999-2007,2014,2026  Landon Curt Noll
 *
 * Calc is open software; you can redistribute it and/or modify it under
 * the terms of the version 2.1 of the GNU Lesser General Public License
 * as published by the Free Software Foundation.
 *
 * Calc 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 Lesser General
 * Public License for more details.
 *
 * A copy of version 2.1 of the GNU Lesser General Public License is
 * distributed with calc under the filename COPYING-LGPL.  You should have
 * received a copy with calc; if not, write to Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Under source code control:   1995/01/07 09:45:26
 * File existed as early as:    1994
 *
 * chongo <was here> /\oo/\     http://www.isthe.com/chongo/
 * Share and enjoy!  :-)        http://www.isthe.com/chongo/tech/comp/calc/
 */

/*
 * random number generator - see zrand.c for details
 */

#if !defined(INCLUDE_ZRAND_H)
#  define INCLUDE_ZRAND_H

/*
 * s100 generator defines
 *
 * NOTE: SBITS must be a power of two to make the (&= (SBITS-1))
 *       in slotcp() to work.
 */
#  define SBITS (64)                     /* size of subtractive or shuffle entry in bits */
#  define SBYTES (SBITS / 8)             /* size of subtractive or shuffle entry in bytes */
#  define SHALFS (SBYTES / sizeof(HALF)) /* size in HALFs */

/*
 * seed defines
 */
#  define SEEDXORBITS 64 /* low bits of s100 seed devoted to xor */

/*
 * shuffle table defines
 */
#  define SHUFPOW 8                /* power of 2 size of the shuffle table */
#  define SHUFCNT (1 << SHUFPOW)   /* size of shuffle table */
#  define SHUFLEN (SLEN * SHUFCNT) /* length of shuffle table in FULLs */
#  define SHUFMASK (SHUFLEN - 1)   /* mask for shuffle table entry selection */

/*
 * subtractive 100 constants
 */
#  define S100 100  /* slots in an subtractive 100 table */
#  define INIT_J 36 /* initial first walking table index */
#  define INIT_K 99 /* initial second walking table index */

/*
 * subtractive 100 table defines
 *
 * SLEN         - length in FULLs of an subtractive 100 slot
 *
 * SLOAD(s,i,z) - load table slot i from subtractive 100 state s with zvalue z
 *                s: type RAND
 *                i: type int, s.slot[i] slot index
 *                z: type ZVALUE, what to load into s.slot[i]
 *
 * SSUB(s,k,j)  - slot[k] -= slot[j]
 *                s: type RAND
 *                k: type int, s.slot[k] slot index, what to gets changed
 *                j: type int, s.slot[j] slot index, what to add to s.slot[k]
 *                (may use local variable tmp)
 *
 * SINDX(s,k)   - select the shuffle table entry from slot[k] (uses top bits)
 *                s: type RAND
 *                k: type int, s.slot[k] slot index, selects shuffle entry
 *                result type int, refers to s.shuf[SINDX(s,k)]
 *
 * SBUFFER(s,t) - load s100 buffer with t
 *                s: type RAND
 *                t: type int, s.shuf[t] entry index, replace buffer with it
 *
 * SSHUF(s,t,k) - save slot[k] into shuffle entry t
 *                s: type RAND
 *                t: type int, s.shuf[t] entry index, what gets changed
 *                k: type int, s.slot[k] slot index, load into  s.shuf[t]
 *
 * SSWAP(s,j,k) - swap slot[j] with slot[k]
 *                s: type RAND
 *                j: type int, s.slot[j] slot index, goes into s.slot[k]
 *                k: type int, s.slot[k] slot index, goes into s.slot[j]
 *                (uses local variable tmp)
 *
 * SMOD64(t,z)  - t = seed z mod 2^64
 *                t: type FULL*, array of FULLs that get z mod 2^64
 *                z: type ZVALUE, what gets (mod 2^64) placed into t
 *
 * SOXR(s,i,v)  - xor slot[i] with lower 64 bits of slot value v
 *                s: type RAND
 *                i: type int, s.slot[i] slot index, what gets xored
 *                v: type FULL*, 64 bit value to xor into s.slot[i]
 *
 * SCNT         - length of an subtractive 100 table in FULLs
 */
#  if FULL_BITS == SBITS

#    define SLEN 1 /* a 64 bit slot can be held in a FULL */
#    define SLOAD(s, i, z) ((s).slot[i] = ztofull(z))
#    define SSUB(s, k, j) ((s).slot[k] -= (s).slot[j])
#    define SINDX(s, k) ((int)((s).slot[k] >> (FULL_BITS - SHUFPOW)))
#    define SBUFFER(s, t)                           \
        {                                           \
            (s).buffer[0] = ((s).shuf[t] & BASE1);  \
            (s).buffer[1] = ((s).shuf[t] >> BASEB); \
        }
#    define SSHUF(s, t, k) ((s).shuf[t] = (s).slot[k])
#    define SSWAP(s, j, k)             \
        {                              \
            FULL tmp = (s).slot[j];    \
            (s).slot[j] = (s).slot[k]; \
            (s).slot[k] = tmp;         \
        }
#    define SMOD64(t, z) ((t)[0] = ztofull(z))
#    define SXOR(s, i, v) ((s).slot[i] ^= (v)[0])

#  elif 2 * FULL_BITS == SBITS

#    define SLEN 2 /* a 64 bit slot needs 2 FULLs */
#    define SLOAD(s, i, z)                                                                                                 \
        {                                                                                                                  \
            (s).slot[(i) << 1] = ztofull(z);                                                                               \
            (s).slot[1 + ((i) << 1)] =                                                                                     \
                (((z).len <= 2) ? (FULL)0                                                                                  \
                                : (((z).len == 3) ? (FULL)((z).v[2]) : ((FULL)((z).v[2]) + ((FULL)((z).v[3]) << BASEB)))); \
        }
#    define SSUB(s, k, j)                                                                                                        \
        {                                                                                                                        \
            FULL tmp = (s).slot[(k) << 1];                                                                                       \
            (s).slot[(k) << 1] -= (s).slot[(j) << 1];                                                                            \
            (s).slot[1 + ((k) << 1)] -= ((tmp <= (s).slot[(k) << 1]) ? (s).slot[1 + ((j) << 1)] : (s).slot[1 + ((j) << 1)] + 1); \
        }
#    define SINDX(s, k) ((int)((s).slot[1 + ((k) << 1)] >> (FULL_BITS - SHUFPOW)))
#    define SBUFFER(s, t)                                        \
        {                                                        \
            (s).buffer[0] = ((s).shuf[(t) << 1] & BASE1);        \
            (s).buffer[1] = ((s).shuf[(t) << 1] >> BASEB);       \
            (s).buffer[2] = ((s).shuf[1 + ((t) << 1)] & BASE1);  \
            (s).buffer[3] = ((s).shuf[1 + ((t) << 1)] >> BASEB); \
        }
#    define SSHUF(s, t, k)                                       \
        {                                                        \
            (s).shuf[(t) << 1] = (s).slot[(k) << 1];             \
            (s).shuf[1 + ((t) << 1)] = (s).slot[1 + ((k) << 1)]; \
        }
#    define SSWAP(s, j, k)                                       \
        {                                                        \
            FULL tmp = (s).slot[(j) << 1];                       \
            (s).slot[(j) << 1] = (s).slot[(k) << 1];             \
            (s).slot[(k) << 1] = tmp;                            \
            tmp = (s).slot[1 + ((j) << 1)];                      \
            (s).slot[1 + ((j) << 1)] = (s).slot[1 + ((k) << 1)]; \
            (s).slot[1 + ((k) << 1)] = tmp;                      \
        }
#    define SMOD64(t, z)                                                                                                        \
        {                                                                                                                       \
            (t)[0] = ztofull(z);                                                                                                \
            (t)[1] = (((z).len <= 2) ? (FULL)0                                                                                  \
                                     : (((z).len == 3) ? (FULL)((z).v[2]) : ((FULL)((z).v[2]) + ((FULL)((z).v[3]) << BASEB)))); \
        }
#    define SXOR(s, i, v)                       \
        {                                       \
            (s).slot[(i) << 1] ^= (v)[0];       \
            (s).slot[1 + ((i) << 1)] ^= (v)[1]; \
        }

#  else

/\../\ FULL_BITS must be 32 or 64 /\../\ !!!

#  endif

#  define SCNT (SLEN * S100) /* length of subtractive 100 table in FULLs */

#  define RAND_CONSEQ_USE (100)              /* use this many before skipping */
#  define RAND_SKIP (1009 - RAND_CONSEQ_USE) /* skip this many after use */

/*
 * s100 generator state
 */
struct rand {
    int seeded;         /* 1 => state has been seeded */
    int bits;           /* buffer bit count */
    FULL buffer[SLEN];  /* unused random bits from last call */
    int j;              /* first walking table index */
    int k;              /* second walking table index */
    int need_to_skip;   /* 1 => skip the next 909 values */
    FULL slot[SCNT];    /* subtractive 100 table */
    FULL shuf[SHUFLEN]; /* shuffle table entries */
};
typedef struct rand RAND;

#endif
