1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Peter McIlroy and by Dan Bernstein at New York University,
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35/*
36 * Radixsort routines.
37 *
38 * Program r_sort_a() is unstable but uses O(logN) extra memory for a stack.
39 * Use radixsort(a, n, trace, endchar) for this case.
40 *
41 * For stable sorting (using N extra pointers) use sradixsort(), which calls
42 * r_sort_b().
43 *
44 * For a description of this code, see D. McIlroy, P. McIlroy, K. Bostic,
45 * "Engineering Radix Sort".
46 */
47
48#include <sys/types.h>
49#include <stdlib.h>
50#include <stddef.h>
51#include <errno.h>
52
53typedef struct {
54	const u_char **sa;
55	int sn, si;
56} stack;
57
58static inline void simplesort
59(const u_char **, int, int, const u_char *, u_int);
60static void r_sort_a(const u_char **, int, int, const u_char *, u_int);
61static void r_sort_b(const u_char **, const u_char **, int, int,
62    const u_char *, u_int);
63
64#define	THRESHOLD	20		/* Divert to simplesort(). */
65#define	SIZE		512		/* Default stack size. */
66
67#define SETUP {								\
68	if (tab == NULL) {						\
69		tr = tr0;						\
70		for (c = 0; c < endch; c++)				\
71			tr0[c] = c + 1;					\
72		tr0[c] = 0;						\
73		for (c++; c < 256; c++)					\
74			tr0[c] = c;					\
75		endch = 0;						\
76	} else {							\
77		endch = tab[endch];					\
78		tr = tab;						\
79		if (endch != 0 && endch != 255) {			\
80			errno = EINVAL;					\
81			return (-1);					\
82		}							\
83	}								\
84}
85
86int
87radixsort(const u_char **a, int n, const u_char *tab, u_int endch)
88{
89	const u_char *tr;
90	int c;
91	u_char tr0[256];
92
93	SETUP;
94	r_sort_a(a, n, 0, tr, endch);
95	return (0);
96}
97
98int
99sradixsort(const u_char **a, int n, const u_char *tab, u_int endch)
100{
101	const u_char *tr, **ta;
102	int c;
103	u_char tr0[256];
104
105	SETUP;
106	if (n < THRESHOLD)
107		simplesort(a, n, 0, tr, endch);
108	else {
109		if ((ta = malloc(n * sizeof(a))) == NULL)
110			return (-1);
111		r_sort_b(a, ta, n, 0, tr, endch);
112		free(ta);
113	}
114	return (0);
115}
116
117#define empty(s)	(s >= sp)
118#define pop(a, n, i)	a = (--sp)->sa, n = sp->sn, i = sp->si
119#define push(a, n, i)	sp->sa = a, sp->sn = n, (sp++)->si = i
120#define swap(a, b, t)	t = a, a = b, b = t
121
122/* Unstable, in-place sort. */
123static void
124r_sort_a(const u_char **a, int n, int i, const u_char *tr, u_int endch)
125{
126	static int count[256], nc, bmin;
127	int c;
128	const u_char **ak, *r;
129	stack s[SIZE], *sp, *sp0, *sp1, temp;
130	int *cp, bigc;
131	const u_char **an, *t, **aj, **top[256];
132
133	/* Set up stack. */
134	sp = s;
135	push(a, n, i);
136	while (!empty(s)) {
137		pop(a, n, i);
138		if (n < THRESHOLD) {
139			simplesort(a, n, i, tr, endch);
140			continue;
141		}
142		an = a + n;
143
144		/* Make character histogram. */
145		if (nc == 0) {
146			bmin = 255;	/* First occupied bin, excluding eos. */
147			for (ak = a; ak < an;) {
148				c = tr[(*ak++)[i]];
149				if (++count[c] == 1 && c != endch) {
150					if (c < bmin)
151						bmin = c;
152					nc++;
153				}
154			}
155			if (sp + nc > s + SIZE) {	/* Get more stack. */
156				r_sort_a(a, n, i, tr, endch);
157				continue;
158			}
159		}
160
161		/*
162		 * Special case: if all strings have the same
163		 * character at position i, move on to the next
164		 * character.
165		 */
166		if (nc == 1 && count[bmin] == n) {
167			push(a, n, i+1);
168			nc = count[bmin] = 0;
169			continue;
170		}
171
172		/*
173		 * Set top[]; push incompletely sorted bins onto stack.
174		 * top[] = pointers to last out-of-place element in bins.
175		 * count[] = counts of elements in bins.
176		 * Before permuting: top[c-1] + count[c] = top[c];
177		 * during deal: top[c] counts down to top[c-1].
178		 */
179		sp0 = sp1 = sp;		/* Stack position of biggest bin. */
180		bigc = 2;		/* Size of biggest bin. */
181		if (endch == 0)		/* Special case: set top[eos]. */
182			top[0] = ak = a + count[0];
183		else {
184			ak = a;
185			top[255] = an;
186		}
187		for (cp = count + bmin; nc > 0; cp++) {
188			while (*cp == 0)	/* Find next non-empty pile. */
189				cp++;
190			if (*cp > 1) {
191				if (*cp > bigc) {
192					bigc = *cp;
193					sp1 = sp;
194				}
195				push(ak, *cp, i+1);
196			}
197			top[cp-count] = ak += *cp;
198			nc--;
199		}
200		swap(*sp0, *sp1, temp);	/* Play it safe -- biggest bin last. */
201
202		/*
203		 * Permute misplacements home.  Already home: everything
204		 * before aj, and in bin[c], items from top[c] on.
205		 * Inner loop:
206		 *	r = next element to put in place;
207		 *	ak = top[r[i]] = location to put the next element.
208		 *	aj = bottom of 1st disordered bin.
209		 * Outer loop:
210		 *	Once the 1st disordered bin is done, ie. aj >= ak,
211		 *	aj<-aj + count[c] connects the bins in a linked list;
212		 *	reset count[c].
213		 */
214		for (aj = a; aj < an;  *aj = r, aj += count[c], count[c] = 0)
215			for (r = *aj;  aj < (ak = --top[c = tr[r[i]]]);)
216				swap(*ak, r, t);
217	}
218}
219
220/* Stable sort, requiring additional memory. */
221static void
222r_sort_b(const u_char **a, const u_char **ta, int n, int i, const u_char *tr,
223    u_int endch)
224{
225	static int count[256], nc, bmin;
226	int c;
227	const u_char **ak, **ai;
228	stack s[512], *sp, *sp0, *sp1, temp;
229	const u_char **top[256];
230	int *cp, bigc;
231
232	sp = s;
233	push(a, n, i);
234	while (!empty(s)) {
235		pop(a, n, i);
236		if (n < THRESHOLD) {
237			simplesort(a, n, i, tr, endch);
238			continue;
239		}
240
241		if (nc == 0) {
242			bmin = 255;
243			for (ak = a + n; --ak >= a;) {
244				c = tr[(*ak)[i]];
245				if (++count[c] == 1 && c != endch) {
246					if (c < bmin)
247						bmin = c;
248					nc++;
249				}
250			}
251			if (sp + nc > s + SIZE) {
252				r_sort_b(a, ta, n, i, tr, endch);
253				continue;
254			}
255		}
256
257		sp0 = sp1 = sp;
258		bigc = 2;
259		if (endch == 0) {
260			top[0] = ak = a + count[0];
261			count[0] = 0;
262		} else {
263			ak = a;
264			top[255] = a + n;
265			count[255] = 0;
266		}
267		for (cp = count + bmin; nc > 0; cp++) {
268			while (*cp == 0)
269				cp++;
270			if ((c = *cp) > 1) {
271				if (c > bigc) {
272					bigc = c;
273					sp1 = sp;
274				}
275				push(ak, c, i+1);
276			}
277			top[cp-count] = ak += c;
278			*cp = 0;			/* Reset count[]. */
279			nc--;
280		}
281		swap(*sp0, *sp1, temp);
282
283		for (ak = ta + n, ai = a+n; ak > ta;)	/* Copy to temp. */
284			*--ak = *--ai;
285		for (ak = ta+n; --ak >= ta;)		/* Deal to piles. */
286			*--top[tr[(*ak)[i]]] = *ak;
287	}
288}
289
290/* insertion sort */
291static inline void
292simplesort(const u_char **a, int n, int b, const u_char *tr, u_int endch)
293{
294	u_char ch;
295	const u_char  **ak, **ai, *s, *t;
296
297	for (ak = a+1; --n >= 1; ak++)
298		for (ai = ak; ai > a; ai--) {
299			for (s = ai[0] + b, t = ai[-1] + b;
300			    (ch = tr[*s]) != endch; s++, t++)
301				if (ch != tr[*t])
302					break;
303			if (ch >= tr[*t])
304				break;
305			swap(ai[0], ai[-1], s);
306		}
307}
308