/*      $NetBSD: radix_sort.c,v 1.4 2009/09/19 16:18:00 dsl Exp $       */

/*-
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Peter McIlroy and by Dan Bernstein at New York University, 
 *
 * 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.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)radixsort.c 8.2 (Berkeley) 4/28/95";
#else
__RCSID("$NetBSD: radix_sort.c,v 1.4 2009/09/19 16:18:00 dsl Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

/*
 * 'stable' radix sort initially from libc/stdlib/radixsort.c
 */

#include <sys/types.h>

#include <assert.h>
#include <errno.h>
#include <util.h>
#include "sort.h"

typedef struct {
        RECHEADER **sa;         /* Base of saved area */
        int sn;                 /* Number of entries */
        int si;                 /* index into data for compare */
} stack;

static void simplesort(RECHEADER **, int, int);

#define THRESHOLD       20              /* Divert to simplesort(). */

#define empty(s)        (s >= sp)
#define pop(a, n, i)    a = (--sp)->sa, n = sp->sn, i = sp->si
#define push(a, n, i)   sp->sa = a, sp->sn = n, (sp++)->si = i
#define swap(a, b, t)   t = a, a = b, b = t

void
radix_sort(RECHEADER **a, RECHEADER **ta, int n)
{
        u_int count[256], nc, bmin;
        u_int c;
        RECHEADER **ak, **tai, **lim;
        RECHEADER *hdr;
        int stack_size = 512;
        stack *s, *sp, *sp0, *sp1, temp;
        RECHEADER **top[256];
        u_int *cp, bigc;
        int data_index = 0;

        if (n < THRESHOLD && !DEBUG('r')) {
                simplesort(a, n, 0);
                return;
        }

        s = emalloc(stack_size * sizeof *s);
        memset(&count, 0, sizeof count);
        /* Technically 'top' doesn't need zeroing */
        memset(&top, 0, sizeof top);

        sp = s;
        push(a, n, data_index);
        while (!empty(s)) {
                pop(a, n, data_index);
                if (n < THRESHOLD && !DEBUG('r')) {
                        simplesort(a, n, data_index);
                        continue;
                }

                /* Count number of times each 'next byte' occurs */
                nc = 0;
                bmin = 255;
                lim = a + n;
                for (ak = a, tai = ta; ak < lim; ak++) {
                        hdr = *ak;
                        if (data_index >= hdr->keylen) {
                                /* Short key, copy to start of output */
                                if (UNIQUE && a != sp->sa)
                                        /* Stop duplicate being written out */
                                        hdr->keylen = -1;
                                *a++ = hdr;
                                n--;
                                continue;
                        }
                        /* Save in temp buffer for distribute */
                        *tai++ = hdr;
                        c = hdr->data[data_index];
                        if (++count[c] == 1) {
                                if (c < bmin)
                                        bmin = c;
                                nc++;
                        }
                }
                /*
                 * We need save the bounds for each 'next byte' that
                 * occurs more so we can sort each block.
                 */
                if (sp + nc > s + stack_size) {
                        stack_size *= 2;
                        sp1 = erealloc(s, stack_size * sizeof *s);
                        sp = sp1 + (sp - s);
                        s = sp1;
                }

                /* Minor optimisation to do the largest set last */
                sp0 = sp1 = sp;
                bigc = 2;
                /* Convert 'counts' positions, saving bounds for later sorts */
                ak = a;
                for (cp = count + bmin; nc > 0; cp++) {
                        while (*cp == 0)
                                cp++;
                        if ((c = *cp) > 1) {
                                if (c > bigc) {
                                        bigc = c;
                                        sp1 = sp;
                                }
                                push(ak, c, data_index+1);
                        }
                        ak += c;
                        top[cp-count] = ak;
                        *cp = 0;                        /* Reset count[]. */
                        nc--;
                }
                swap(*sp0, *sp1, temp);

                for (ak = ta+n; --ak >= ta;)            /* Deal to piles. */
                        *--top[(*ak)->data[data_index]] = *ak;
        }

        free(s);
}

/* insertion sort, short records are sorted before long ones */
static void
simplesort(RECHEADER **a, int n, int data_index)
{
        RECHEADER **ak, **ai;
        RECHEADER *akh;
        RECHEADER **lim = a + n;
        const u_char *s, *t;
        int s_len, t_len;
        int i;
        int r;

        if (n <= 1)
                return;

        for (ak = a+1; ak < lim; ak++) {
                akh = *ak;
                s = akh->data;
                s_len = akh->keylen;
                for (ai = ak; ;) {
                        ai--;
                        t_len = (*ai)->keylen;
                        if (t_len != -1) {
                                t = (*ai)->data;
                                for (i = data_index; ; i++) {
                                        if (i >= s_len || i >= t_len) {
                                                r = s_len - t_len;
                                                break;
                                        }
                                        r =  s[i]  - t[i];
                                        if (r != 0)
                                                break;
                                }
                                if (r >= 0) {
                                        if (r == 0 && UNIQUE) {
                                                /* Put record below existing */
                                                ai[1] = ai[0];
                                                /* Mark as duplicate - ignore */
                                                akh->keylen = -1;
                                        } else {
                                                ai++;
                                        }
                                        break;
                                }
                        }
                        ai[1] = ai[0];
                        if (ai == a)
                                break;
                }
                ai[0] = akh;
        }
}