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Add new radixsort and sradixsort functions
Taken from FreeBSD.
This commit is contained in:
Guillem Jover
327
src/radixsort.c
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327
src/radixsort.c
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/*-
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Peter McIlroy and by Dan Bernstein at New York University,
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)radixsort.c 8.2 (Berkeley) 4/28/95";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/*
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* Radixsort routines.
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*
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* Program r_sort_a() is unstable but uses O(logN) extra memory for a stack.
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* Use radixsort(a, n, trace, endchar) for this case.
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*
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* For stable sorting (using N extra pointers) use sradixsort(), which calls
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* r_sort_b().
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*
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* For a description of this code, see D. McIlroy, P. McIlroy, K. Bostic,
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* "Engineering Radix Sort".
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*/
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#include <sys/types.h>
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#include <stdlib.h>
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#include <stddef.h>
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#include <errno.h>
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typedef struct {
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const u_char **sa;
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int sn, si;
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} stack;
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static inline void simplesort
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(const u_char **, int, int, const u_char *, u_int);
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static void r_sort_a(const u_char **, int, int, const u_char *, u_int);
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static void r_sort_b(const u_char **, const u_char **, int, int,
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const u_char *, u_int);
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#define THRESHOLD 20 /* Divert to simplesort(). */
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#define SIZE 512 /* Default stack size. */
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#define SETUP { \
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if (tab == NULL) { \
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tr = tr0; \
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for (c = 0; c < endch; c++) \
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tr0[c] = c + 1; \
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tr0[c] = 0; \
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for (c++; c < 256; c++) \
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tr0[c] = c; \
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endch = 0; \
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} else { \
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endch = tab[endch]; \
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tr = tab; \
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if (endch != 0 && endch != 255) { \
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errno = EINVAL; \
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return (-1); \
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} \
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} \
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}
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int
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radixsort(a, n, tab, endch)
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const u_char **a, *tab;
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int n;
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u_int endch;
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{
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const u_char *tr;
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int c;
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u_char tr0[256];
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SETUP;
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r_sort_a(a, n, 0, tr, endch);
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return (0);
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}
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int
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sradixsort(a, n, tab, endch)
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const u_char **a, *tab;
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int n;
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u_int endch;
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{
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const u_char *tr, **ta;
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int c;
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u_char tr0[256];
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SETUP;
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if (n < THRESHOLD)
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simplesort(a, n, 0, tr, endch);
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else {
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if ((ta = malloc(n * sizeof(a))) == NULL)
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return (-1);
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r_sort_b(a, ta, n, 0, tr, endch);
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free(ta);
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}
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return (0);
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}
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#define empty(s) (s >= sp)
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#define pop(a, n, i) a = (--sp)->sa, n = sp->sn, i = sp->si
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#define push(a, n, i) sp->sa = a, sp->sn = n, (sp++)->si = i
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#define swap(a, b, t) t = a, a = b, b = t
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/* Unstable, in-place sort. */
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static void
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r_sort_a(a, n, i, tr, endch)
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const u_char **a;
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int n, i;
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const u_char *tr;
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u_int endch;
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{
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static int count[256], nc, bmin;
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int c;
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const u_char **ak, *r;
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stack s[SIZE], *sp, *sp0, *sp1, temp;
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int *cp, bigc;
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const u_char **an, *t, **aj, **top[256];
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/* Set up stack. */
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sp = s;
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push(a, n, i);
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while (!empty(s)) {
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pop(a, n, i);
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if (n < THRESHOLD) {
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simplesort(a, n, i, tr, endch);
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continue;
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}
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an = a + n;
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/* Make character histogram. */
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if (nc == 0) {
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bmin = 255; /* First occupied bin, excluding eos. */
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for (ak = a; ak < an;) {
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c = tr[(*ak++)[i]];
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if (++count[c] == 1 && c != endch) {
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if (c < bmin)
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bmin = c;
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nc++;
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}
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}
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if (sp + nc > s + SIZE) { /* Get more stack. */
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r_sort_a(a, n, i, tr, endch);
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continue;
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}
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}
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/*
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* Special case: if all strings have the same
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* character at position i, move on to the next
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* character.
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*/
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if (nc == 1 && count[bmin] == n) {
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push(a, n, i+1);
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nc = count[bmin] = 0;
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continue;
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}
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/*
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* Set top[]; push incompletely sorted bins onto stack.
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* top[] = pointers to last out-of-place element in bins.
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* count[] = counts of elements in bins.
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* Before permuting: top[c-1] + count[c] = top[c];
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* during deal: top[c] counts down to top[c-1].
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*/
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sp0 = sp1 = sp; /* Stack position of biggest bin. */
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bigc = 2; /* Size of biggest bin. */
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if (endch == 0) /* Special case: set top[eos]. */
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top[0] = ak = a + count[0];
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else {
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ak = a;
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top[255] = an;
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}
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for (cp = count + bmin; nc > 0; cp++) {
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while (*cp == 0) /* Find next non-empty pile. */
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cp++;
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if (*cp > 1) {
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if (*cp > bigc) {
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bigc = *cp;
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sp1 = sp;
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}
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push(ak, *cp, i+1);
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}
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top[cp-count] = ak += *cp;
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nc--;
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}
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swap(*sp0, *sp1, temp); /* Play it safe -- biggest bin last. */
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/*
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* Permute misplacements home. Already home: everything
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* before aj, and in bin[c], items from top[c] on.
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* Inner loop:
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* r = next element to put in place;
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* ak = top[r[i]] = location to put the next element.
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* aj = bottom of 1st disordered bin.
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* Outer loop:
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* Once the 1st disordered bin is done, ie. aj >= ak,
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* aj<-aj + count[c] connects the bins in a linked list;
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* reset count[c].
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*/
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for (aj = a; aj < an; *aj = r, aj += count[c], count[c] = 0)
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for (r = *aj; aj < (ak = --top[c = tr[r[i]]]);)
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swap(*ak, r, t);
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}
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}
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/* Stable sort, requiring additional memory. */
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static void
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r_sort_b(a, ta, n, i, tr, endch)
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const u_char **a, **ta;
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int n, i;
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const u_char *tr;
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u_int endch;
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{
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static int count[256], nc, bmin;
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int c;
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const u_char **ak, **ai;
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stack s[512], *sp, *sp0, *sp1, temp;
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const u_char **top[256];
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int *cp, bigc;
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sp = s;
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push(a, n, i);
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while (!empty(s)) {
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pop(a, n, i);
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if (n < THRESHOLD) {
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simplesort(a, n, i, tr, endch);
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continue;
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}
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if (nc == 0) {
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bmin = 255;
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for (ak = a + n; --ak >= a;) {
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c = tr[(*ak)[i]];
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if (++count[c] == 1 && c != endch) {
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if (c < bmin)
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bmin = c;
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nc++;
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}
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}
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if (sp + nc > s + SIZE) {
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r_sort_b(a, ta, n, i, tr, endch);
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continue;
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}
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}
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sp0 = sp1 = sp;
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bigc = 2;
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if (endch == 0) {
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top[0] = ak = a + count[0];
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count[0] = 0;
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} else {
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ak = a;
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top[255] = a + n;
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count[255] = 0;
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}
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for (cp = count + bmin; nc > 0; cp++) {
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while (*cp == 0)
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cp++;
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if ((c = *cp) > 1) {
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if (c > bigc) {
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bigc = c;
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sp1 = sp;
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}
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push(ak, c, i+1);
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}
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top[cp-count] = ak += c;
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*cp = 0; /* Reset count[]. */
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nc--;
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}
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swap(*sp0, *sp1, temp);
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for (ak = ta + n, ai = a+n; ak > ta;) /* Copy to temp. */
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*--ak = *--ai;
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for (ak = ta+n; --ak >= ta;) /* Deal to piles. */
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*--top[tr[(*ak)[i]]] = *ak;
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}
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}
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static inline void
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simplesort(a, n, b, tr, endch) /* insertion sort */
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const u_char **a;
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int n, b;
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const u_char *tr;
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u_int endch;
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{
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u_char ch;
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const u_char **ak, **ai, *s, *t;
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for (ak = a+1; --n >= 1; ak++)
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for (ai = ak; ai > a; ai--) {
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for (s = ai[0] + b, t = ai[-1] + b;
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(ch = tr[*s]) != endch; s++, t++)
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if (ch != tr[*t])
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break;
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if (ch >= tr[*t])
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break;
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swap(ai[0], ai[-1], s);
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}
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}
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