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| Current File : //usr/src/lib/libc/stdlib/radixsort.c |
/*-
* 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.
* 4. 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: release/9.1.0/lib/libc/stdlib/radixsort.c 165903 2007-01-09 00:28:16Z imp $");
/*
* 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(a, n, tab, endch)
const u_char **a, *tab;
int n;
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(a, n, tab, endch)
const u_char **a, *tab;
int n;
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(a, n, i, tr, endch)
const u_char **a;
int n, 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(a, ta, n, i, tr, endch)
const u_char **a, **ta;
int n, 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;
}
}
static inline void
simplesort(a, n, b, tr, endch) /* insertion sort */
const u_char **a;
int n, 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);
}
}