freebsd-dev/lib/libc/stdlib/radixsort.c
Pedro F. Giffuni 8a16b7a18f General further adoption of SPDX licensing ID tags.
Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
2017-11-20 19:49:47 +00:00

314 lines
7.9 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* 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.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)radixsort.c 8.2 (Berkeley) 4/28/95";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* Radixsort routines.
*
* Program r_sort_a() is unstable but uses O(logN) extra memory for a stack.
* Use radixsort(a, n, trace, endchar) for this case.
*
* For stable sorting (using N extra pointers) use sradixsort(), which calls
* r_sort_b().
*
* For a description of this code, see D. McIlroy, P. McIlroy, K. Bostic,
* "Engineering Radix Sort".
*/
#include <sys/types.h>
#include <stdlib.h>
#include <stddef.h>
#include <errno.h>
typedef struct {
const u_char **sa;
int sn, si;
} stack;
static inline void simplesort
(const u_char **, int, int, const u_char *, u_int);
static void r_sort_a(const u_char **, int, int, const u_char *, u_int);
static void r_sort_b(const u_char **, const u_char **, int, int,
const u_char *, u_int);
#define THRESHOLD 20 /* Divert to simplesort(). */
#define SIZE 512 /* Default stack size. */
#define SETUP { \
if (tab == NULL) { \
tr = tr0; \
for (c = 0; c < endch; c++) \
tr0[c] = c + 1; \
tr0[c] = 0; \
for (c++; c < 256; c++) \
tr0[c] = c; \
endch = 0; \
} else { \
endch = tab[endch]; \
tr = tab; \
if (endch != 0 && endch != 255) { \
errno = EINVAL; \
return (-1); \
} \
} \
}
int
radixsort(const u_char **a, int n, const u_char *tab, u_int endch)
{
const u_char *tr;
int c;
u_char tr0[256];
SETUP;
r_sort_a(a, n, 0, tr, endch);
return (0);
}
int
sradixsort(const u_char **a, int n, const u_char *tab, u_int endch)
{
const u_char *tr, **ta;
int c;
u_char tr0[256];
SETUP;
if (n < THRESHOLD)
simplesort(a, n, 0, tr, endch);
else {
if ((ta = malloc(n * sizeof(a))) == NULL)
return (-1);
r_sort_b(a, ta, n, 0, tr, endch);
free(ta);
}
return (0);
}
#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
/* Unstable, in-place sort. */
static void
r_sort_a(const u_char **a, int n, int i, const u_char *tr, u_int endch)
{
static int count[256], nc, bmin;
int c;
const u_char **ak, *r;
stack s[SIZE], *sp, *sp0, *sp1, temp;
int *cp, bigc;
const u_char **an, *t, **aj, **top[256];
/* Set up stack. */
sp = s;
push(a, n, i);
while (!empty(s)) {
pop(a, n, i);
if (n < THRESHOLD) {
simplesort(a, n, i, tr, endch);
continue;
}
an = a + n;
/* Make character histogram. */
if (nc == 0) {
bmin = 255; /* First occupied bin, excluding eos. */
for (ak = a; ak < an;) {
c = tr[(*ak++)[i]];
if (++count[c] == 1 && c != endch) {
if (c < bmin)
bmin = c;
nc++;
}
}
if (sp + nc > s + SIZE) { /* Get more stack. */
r_sort_a(a, n, i, tr, endch);
continue;
}
}
/*
* Special case: if all strings have the same
* character at position i, move on to the next
* character.
*/
if (nc == 1 && count[bmin] == n) {
push(a, n, i+1);
nc = count[bmin] = 0;
continue;
}
/*
* Set top[]; push incompletely sorted bins onto stack.
* top[] = pointers to last out-of-place element in bins.
* count[] = counts of elements in bins.
* Before permuting: top[c-1] + count[c] = top[c];
* during deal: top[c] counts down to top[c-1].
*/
sp0 = sp1 = sp; /* Stack position of biggest bin. */
bigc = 2; /* Size of biggest bin. */
if (endch == 0) /* Special case: set top[eos]. */
top[0] = ak = a + count[0];
else {
ak = a;
top[255] = an;
}
for (cp = count + bmin; nc > 0; cp++) {
while (*cp == 0) /* Find next non-empty pile. */
cp++;
if (*cp > 1) {
if (*cp > bigc) {
bigc = *cp;
sp1 = sp;
}
push(ak, *cp, i+1);
}
top[cp-count] = ak += *cp;
nc--;
}
swap(*sp0, *sp1, temp); /* Play it safe -- biggest bin last. */
/*
* Permute misplacements home. Already home: everything
* before aj, and in bin[c], items from top[c] on.
* Inner loop:
* r = next element to put in place;
* ak = top[r[i]] = location to put the next element.
* aj = bottom of 1st disordered bin.
* Outer loop:
* Once the 1st disordered bin is done, ie. aj >= ak,
* aj<-aj + count[c] connects the bins in a linked list;
* reset count[c].
*/
for (aj = a; aj < an; *aj = r, aj += count[c], count[c] = 0)
for (r = *aj; aj < (ak = --top[c = tr[r[i]]]);)
swap(*ak, r, t);
}
}
/* Stable sort, requiring additional memory. */
static void
r_sort_b(const u_char **a, const u_char **ta, int n, int i, const u_char *tr,
u_int endch)
{
static int count[256], nc, bmin;
int c;
const u_char **ak, **ai;
stack s[512], *sp, *sp0, *sp1, temp;
const u_char **top[256];
int *cp, bigc;
sp = s;
push(a, n, i);
while (!empty(s)) {
pop(a, n, i);
if (n < THRESHOLD) {
simplesort(a, n, i, tr, endch);
continue;
}
if (nc == 0) {
bmin = 255;
for (ak = a + n; --ak >= a;) {
c = tr[(*ak)[i]];
if (++count[c] == 1 && c != endch) {
if (c < bmin)
bmin = c;
nc++;
}
}
if (sp + nc > s + SIZE) {
r_sort_b(a, ta, n, i, tr, endch);
continue;
}
}
sp0 = sp1 = sp;
bigc = 2;
if (endch == 0) {
top[0] = ak = a + count[0];
count[0] = 0;
} else {
ak = a;
top[255] = a + n;
count[255] = 0;
}
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, i+1);
}
top[cp-count] = ak += c;
*cp = 0; /* Reset count[]. */
nc--;
}
swap(*sp0, *sp1, temp);
for (ak = ta + n, ai = a+n; ak > ta;) /* Copy to temp. */
*--ak = *--ai;
for (ak = ta+n; --ak >= ta;) /* Deal to piles. */
*--top[tr[(*ak)[i]]] = *ak;
}
}
/* insertion sort */
static inline void
simplesort(const u_char **a, int n, int b, const u_char *tr, u_int endch)
{
u_char ch;
const u_char **ak, **ai, *s, *t;
for (ak = a+1; --n >= 1; ak++)
for (ai = ak; ai > a; ai--) {
for (s = ai[0] + b, t = ai[-1] + b;
(ch = tr[*s]) != endch; s++, t++)
if (ch != tr[*t])
break;
if (ch >= tr[*t])
break;
swap(ai[0], ai[-1], s);
}
}