2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
6 * Peter McIlroy and by Dan Bernstein at New York University,
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9 * modification, are permitted provided that the following conditions
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12 * notice, this list of conditions and the following disclaimer.
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32 * @(#)radixsort.c 8.2 (Berkeley) 4/28/95
33 * $FreeBSD: src/lib/libc/stdlib/radixsort.c,v 1.8 2007/01/09 00:28:10 imp Exp $
34 * $DragonFly: src/lib/libc/stdlib/radixsort.c,v 1.5 2005/11/20 12:37:49 swildner Exp $
40 * Program r_sort_a() is unstable but uses O(logN) extra memory for a stack.
41 * Use radixsort(a, n, trace, endchar) for this case.
43 * For stable sorting (using N extra pointers) use sradixsort(), which calls
46 * For a description of this code, see D. McIlroy, P. McIlroy, K. Bostic,
47 * "Engineering Radix Sort".
50 #include <sys/types.h>
60 static inline void simplesort(const u_char **, int, int, const u_char *, u_int);
61 static void r_sort_a(const u_char **, int, int, const u_char *, u_int);
62 static void r_sort_b(const u_char **, const u_char **, int, int,
63 const u_char *, u_int);
65 #define THRESHOLD 20 /* Divert to simplesort(). */
66 #define SIZE 512 /* Default stack size. */
71 for (c = 0; c < endch; c++) \
74 for (c++; c < 256; c++) \
80 if (endch != 0 && endch != 255) { \
88 radixsort(const u_char **a, int n, const u_char *tab, u_int endch)
95 r_sort_a(a, n, 0, tr, endch);
100 sradixsort(const u_char **a, int n, const u_char *tab, u_int endch)
102 const u_char *tr, **ta;
108 simplesort(a, n, 0, tr, endch);
110 if ((ta = malloc(n * sizeof(a))) == NULL)
112 r_sort_b(a, ta, n, 0, tr, endch);
118 #define empty(s) (s >= sp)
119 #define pop(a, n, i) a = (--sp)->sa, n = sp->sn, i = sp->si
120 #define push(a, n, i) sp->sa = a, sp->sn = n, (sp++)->si = i
121 #define swap(a, b, t) t = a, a = b, b = t
123 /* Unstable, in-place sort. */
125 r_sort_a(const u_char **a, int n, int i, const u_char *tr, u_int endch)
127 static int count[256], nc, bmin;
129 const u_char **ak, *r;
130 stack s[SIZE], *sp, *sp0, *sp1, temp;
132 const u_char **an, *t, **aj, **top[256];
140 simplesort(a, n, i, tr, endch);
145 /* Make character histogram. */
147 bmin = 255; /* First occupied bin, excluding eos. */
148 for (ak = a; ak < an;) {
150 if (++count[c] == 1 && c != endch) {
156 if (sp + nc > s + SIZE) { /* Get more stack. */
157 r_sort_a(a, n, i, tr, endch);
163 * Special case: if all strings have the same
164 * character at position i, move on to the next
167 if (nc == 1 && count[bmin] == n) {
169 nc = count[bmin] = 0;
174 * Set top[]; push incompletely sorted bins onto stack.
175 * top[] = pointers to last out-of-place element in bins.
176 * count[] = counts of elements in bins.
177 * Before permuting: top[c-1] + count[c] = top[c];
178 * during deal: top[c] counts down to top[c-1].
180 sp0 = sp1 = sp; /* Stack position of biggest bin. */
181 bigc = 2; /* Size of biggest bin. */
182 if (endch == 0) /* Special case: set top[eos]. */
183 top[0] = ak = a + count[0];
188 for (cp = count + bmin; nc > 0; cp++) {
189 while (*cp == 0) /* Find next non-empty pile. */
198 top[cp-count] = ak += *cp;
201 swap(*sp0, *sp1, temp); /* Play it safe -- biggest bin last. */
204 * Permute misplacements home. Already home: everything
205 * before aj, and in bin[c], items from top[c] on.
207 * r = next element to put in place;
208 * ak = top[r[i]] = location to put the next element.
209 * aj = bottom of 1st disordered bin.
211 * Once the 1st disordered bin is done, ie. aj >= ak,
212 * aj<-aj + count[c] connects the bins in a linked list;
215 for (aj = a; aj < an; *aj = r, aj += count[c], count[c] = 0)
216 for (r = *aj; aj < (ak = --top[c = tr[r[i]]]);)
221 /* Stable sort, requiring additional memory. */
223 r_sort_b(const u_char **a, const u_char **ta, int n, int i, const u_char *tr,
226 static int count[256], nc, bmin;
228 const u_char **ak, **ai;
229 stack s[512], *sp, *sp0, *sp1, temp;
230 const u_char **top[256];
238 simplesort(a, n, i, tr, endch);
244 for (ak = a + n; --ak >= a;) {
246 if (++count[c] == 1 && c != endch) {
252 if (sp + nc > s + SIZE) {
253 r_sort_b(a, ta, n, i, tr, endch);
261 top[0] = ak = a + count[0];
268 for (cp = count + bmin; nc > 0; cp++) {
278 top[cp-count] = ak += c;
279 *cp = 0; /* Reset count[]. */
282 swap(*sp0, *sp1, temp);
284 for (ak = ta + n, ai = a+n; ak > ta;) /* Copy to temp. */
286 for (ak = ta+n; --ak >= ta;) /* Deal to piles. */
287 *--top[tr[(*ak)[i]]] = *ak;
293 simplesort(const u_char **a, int n, int b, const u_char *tr, u_int endch)
296 const u_char **ak, **ai, *s, *t;
298 for (ak = a+1; --n >= 1; ak++)
299 for (ai = ak; ai > a; ai--) {
300 for (s = ai[0] + b, t = ai[-1] + b;
301 (ch = tr[*s]) != endch; s++, t++)
306 swap(ai[0], ai[-1], s);