qsort.c raw
1 /* Copyright (C) 2011 by Valentin Ochs
2 *
3 * Permission is hereby granted, free of charge, to any person obtaining a copy
4 * of this software and associated documentation files (the "Software"), to
5 * deal in the Software without restriction, including without limitation the
6 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
7 * sell copies of the Software, and to permit persons to whom the Software is
8 * furnished to do so, subject to the following conditions:
9 *
10 * The above copyright notice and this permission notice shall be included in
11 * all copies or substantial portions of the Software.
12 *
13 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
14 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
16 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
17 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
18 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
19 * IN THE SOFTWARE.
20 */
21
22 /* Minor changes by Rich Felker for integration in musl, 2011-04-27. */
23
24 /* Smoothsort, an adaptive variant of Heapsort. Memory usage: O(1).
25 Run time: Worst case O(n log n), close to O(n) in the mostly-sorted case. */
26
27 #define _BSD_SOURCE
28 #include <stdint.h>
29 #include <stdlib.h>
30 #include <string.h>
31
32 #include "atomic.h"
33 #define ntz(x) a_ctz_l((x))
34
35 typedef int (*cmpfun)(const void *, const void *, void *);
36
37 static inline int pntz(size_t p[2]) {
38 int r = ntz(p[0] - 1);
39 if(r != 0 || (r = 8*sizeof(size_t) + ntz(p[1])) != 8*sizeof(size_t)) {
40 return r;
41 }
42 return 0;
43 }
44
45 static void cycle(size_t width, unsigned char* ar[], int n)
46 {
47 unsigned char tmp[256];
48 size_t l;
49 int i;
50
51 if(n < 2) {
52 return;
53 }
54
55 ar[n] = tmp;
56 while(width) {
57 l = sizeof(tmp) < width ? sizeof(tmp) : width;
58 memcpy(ar[n], ar[0], l);
59 for(i = 0; i < n; i++) {
60 memcpy(ar[i], ar[i + 1], l);
61 ar[i] += l;
62 }
63 width -= l;
64 }
65 }
66
67 /* shl() and shr() need n > 0 */
68 static inline void shl(size_t p[2], int n)
69 {
70 if(n >= 8 * sizeof(size_t)) {
71 n -= 8 * sizeof(size_t);
72 p[1] = p[0];
73 p[0] = 0;
74 }
75 p[1] <<= n;
76 p[1] |= p[0] >> (sizeof(size_t) * 8 - n);
77 p[0] <<= n;
78 }
79
80 static inline void shr(size_t p[2], int n)
81 {
82 if(n >= 8 * sizeof(size_t)) {
83 n -= 8 * sizeof(size_t);
84 p[0] = p[1];
85 p[1] = 0;
86 }
87 p[0] >>= n;
88 p[0] |= p[1] << (sizeof(size_t) * 8 - n);
89 p[1] >>= n;
90 }
91
92 static void sift(unsigned char *head, size_t width, cmpfun cmp, void *arg, int pshift, size_t lp[])
93 {
94 unsigned char *rt, *lf;
95 unsigned char *ar[14 * sizeof(size_t) + 1];
96 int i = 1;
97
98 ar[0] = head;
99 while(pshift > 1) {
100 rt = head - width;
101 lf = head - width - lp[pshift - 2];
102
103 if(cmp(ar[0], lf, arg) >= 0 && cmp(ar[0], rt, arg) >= 0) {
104 break;
105 }
106 if(cmp(lf, rt, arg) >= 0) {
107 ar[i++] = lf;
108 head = lf;
109 pshift -= 1;
110 } else {
111 ar[i++] = rt;
112 head = rt;
113 pshift -= 2;
114 }
115 }
116 cycle(width, ar, i);
117 }
118
119 static void trinkle(unsigned char *head, size_t width, cmpfun cmp, void *arg, size_t pp[2], int pshift, int trusty, size_t lp[])
120 {
121 unsigned char *stepson,
122 *rt, *lf;
123 size_t p[2];
124 unsigned char *ar[14 * sizeof(size_t) + 1];
125 int i = 1;
126 int trail;
127
128 p[0] = pp[0];
129 p[1] = pp[1];
130
131 ar[0] = head;
132 while(p[0] != 1 || p[1] != 0) {
133 stepson = head - lp[pshift];
134 if(cmp(stepson, ar[0], arg) <= 0) {
135 break;
136 }
137 if(!trusty && pshift > 1) {
138 rt = head - width;
139 lf = head - width - lp[pshift - 2];
140 if(cmp(rt, stepson, arg) >= 0 || cmp(lf, stepson, arg) >= 0) {
141 break;
142 }
143 }
144
145 ar[i++] = stepson;
146 head = stepson;
147 trail = pntz(p);
148 shr(p, trail);
149 pshift += trail;
150 trusty = 0;
151 }
152 if(!trusty) {
153 cycle(width, ar, i);
154 sift(head, width, cmp, arg, pshift, lp);
155 }
156 }
157
158 void __qsort_r(void *base, size_t nel, size_t width, cmpfun cmp, void *arg)
159 {
160 size_t lp[12*sizeof(size_t)];
161 size_t i, size = width * nel;
162 unsigned char *head, *high;
163 size_t p[2] = {1, 0};
164 int pshift = 1;
165 int trail;
166
167 if (!size) return;
168
169 head = base;
170 high = head + size - width;
171
172 /* Precompute Leonardo numbers, scaled by element width */
173 for(lp[0]=lp[1]=width, i=2; (lp[i]=lp[i-2]+lp[i-1]+width) < size; i++);
174
175 while(head < high) {
176 if((p[0] & 3) == 3) {
177 sift(head, width, cmp, arg, pshift, lp);
178 shr(p, 2);
179 pshift += 2;
180 } else {
181 if(lp[pshift - 1] >= high - head) {
182 trinkle(head, width, cmp, arg, p, pshift, 0, lp);
183 } else {
184 sift(head, width, cmp, arg, pshift, lp);
185 }
186
187 if(pshift == 1) {
188 shl(p, 1);
189 pshift = 0;
190 } else {
191 shl(p, pshift - 1);
192 pshift = 1;
193 }
194 }
195
196 p[0] |= 1;
197 head += width;
198 }
199
200 trinkle(head, width, cmp, arg, p, pshift, 0, lp);
201
202 while(pshift != 1 || p[0] != 1 || p[1] != 0) {
203 if(pshift <= 1) {
204 trail = pntz(p);
205 shr(p, trail);
206 pshift += trail;
207 } else {
208 shl(p, 2);
209 pshift -= 2;
210 p[0] ^= 7;
211 shr(p, 1);
212 trinkle(head - lp[pshift] - width, width, cmp, arg, p, pshift + 1, 1, lp);
213 shl(p, 1);
214 p[0] |= 1;
215 trinkle(head - width, width, cmp, arg, p, pshift, 1, lp);
216 }
217 head -= width;
218 }
219 }
220
221 weak_alias(__qsort_r, qsort_r);
222