1 /* Isaac Turner 29 April 2014 Public Domain */
2 #ifndef SORT_R_H_
3 #define SORT_R_H_
4
5 #include <stdlib.h>
6 #include <string.h>
7
8 /*
9
10 sort_r function to be exported.
11
12 Parameters:
13 base is the array to be sorted
14 nel is the number of elements in the array
15 width is the size in bytes of each element of the array
16 compar is the comparison function
17 arg is a pointer to be passed to the comparison function
18
19 void sort_r(void *base, size_t nel, size_t width,
20 int (*compar)(const void *_a, const void *_b, void *_arg),
21 void *arg);
22
23 */
24
25 #define _SORT_R_INLINE inline
26
27 #if (defined __gnu_hurd__ || defined __GNU__ || \
28 defined __linux__ || defined __MINGW32__ || defined __GLIBC__)
29 # define _SORT_R_LINUX
30 #elif (defined __APPLE__ || defined __MACH__ || defined __DARWIN__ || \
31 defined __FreeBSD__ || defined __DragonFly__)
32 # define _SORT_R_BSD
33 #elif (defined _WIN32 || defined _WIN64 || defined __WINDOWS__)
34 # define _SORT_R_WINDOWS
35 # undef _SORT_R_INLINE
36 # define _SORT_R_INLINE __inline
37 #else
38 /* Using our own recursive quicksort sort_r_simple() */
39 #endif
40
41 #if (defined NESTED_QSORT && NESTED_QSORT == 0)
42 # undef NESTED_QSORT
43 #endif
44
45 #define SORT_R_SWAP(a,b,tmp) ((tmp) = (a), (a) = (b), (b) = (tmp))
46
47 /* swap a and b */
48 /* a and b must not be equal! */
sort_r_swap(char * __restrict a,char * __restrict b,size_t w)49 static _SORT_R_INLINE void sort_r_swap(char *__restrict a, char *__restrict b,
50 size_t w)
51 {
52 char tmp, *end = a+w;
53 for(; a < end; a++, b++) { SORT_R_SWAP(*a, *b, tmp); }
54 }
55
56 /* swap a, b iff a>b */
57 /* a and b must not be equal! */
58 /* __restrict is same as restrict but better support on old machines */
sort_r_cmpswap(char * __restrict a,char * __restrict b,size_t w,int (* compar)(const void * _a,const void * _b,void * _arg),void * arg)59 static _SORT_R_INLINE int sort_r_cmpswap(char *__restrict a,
60 char *__restrict b, size_t w,
61 int (*compar)(const void *_a,
62 const void *_b,
63 void *_arg),
64 void *arg)
65 {
66 if(compar(a, b, arg) > 0) {
67 sort_r_swap(a, b, w);
68 return 1;
69 }
70 return 0;
71 }
72
73 /*
74 Swap consecutive blocks of bytes of size na and nb starting at memory addr ptr,
75 with the smallest swap so that the blocks are in the opposite order. Blocks may
76 be internally re-ordered e.g.
77
78 12345ab -> ab34512
79 123abc -> abc123
80 12abcde -> deabc12
81 */
sort_r_swap_blocks(char * ptr,size_t na,size_t nb)82 static _SORT_R_INLINE void sort_r_swap_blocks(char *ptr, size_t na, size_t nb)
83 {
84 if(na > 0 && nb > 0) {
85 if(na > nb) { sort_r_swap(ptr, ptr+na, nb); }
86 else { sort_r_swap(ptr, ptr+nb, na); }
87 }
88 }
89
90 /* Implement recursive quicksort ourselves */
91 /* Note: quicksort is not stable, equivalent values may be swapped */
sort_r_simple(void * base,size_t nel,size_t w,int (* compar)(const void * _a,const void * _b,void * _arg),void * arg)92 static _SORT_R_INLINE void sort_r_simple(void *base, size_t nel, size_t w,
93 int (*compar)(const void *_a,
94 const void *_b,
95 void *_arg),
96 void *arg)
97 {
98 char *b = (char *)base, *end = b + nel*w;
99
100 /* for(size_t i=0; i<nel; i++) {printf("%4i", *(int*)(b + i*sizeof(int)));}
101 printf("\n"); */
102
103 if(nel < 10) {
104 /* Insertion sort for arbitrarily small inputs */
105 char *pi, *pj;
106 for(pi = b+w; pi < end; pi += w) {
107 for(pj = pi; pj > b && sort_r_cmpswap(pj-w,pj,w,compar,arg); pj -= w) {}
108 }
109 }
110 else
111 {
112 /* nel > 6; Quicksort */
113
114 int cmp;
115 char *pl, *ple, *pr, *pre, *pivot;
116 char *last = b+w*(nel-1), *tmp;
117
118 /*
119 Use median of second, middle and second-last items as pivot.
120 First and last may have been swapped with pivot and therefore be extreme
121 */
122 char *l[3];
123 l[0] = b + w;
124 l[1] = b+w*(nel/2);
125 l[2] = last - w;
126
127 /* printf("pivots: %i, %i, %i\n", *(int*)l[0], *(int*)l[1], *(int*)l[2]); */
128
129 if(compar(l[0],l[1],arg) > 0) { SORT_R_SWAP(l[0], l[1], tmp); }
130 if(compar(l[1],l[2],arg) > 0) {
131 SORT_R_SWAP(l[1], l[2], tmp);
132 if(compar(l[0],l[1],arg) > 0) { SORT_R_SWAP(l[0], l[1], tmp); }
133 }
134
135 /* swap mid value (l[1]), and last element to put pivot as last element */
136 if(l[1] != last) { sort_r_swap(l[1], last, w); }
137
138 /*
139 pl is the next item on the left to be compared to the pivot
140 pr is the last item on the right that was compared to the pivot
141 ple is the left position to put the next item that equals the pivot
142 ple is the last right position where we put an item that equals the pivot
143
144 v- end (beyond the array)
145 EEEEEELLLLLLLLuuuuuuuuGGGGGGGEEEEEEEE.
146 ^- b ^- ple ^- pl ^- pr ^- pre ^- last (where the pivot is)
147
148 Pivot comparison key:
149 E = equal, L = less than, u = unknown, G = greater than, E = equal
150 */
151 pivot = last;
152 ple = pl = b;
153 pre = pr = last;
154
155 /*
156 Strategy:
157 Loop into the list from the left and right at the same time to find:
158 - an item on the left that is greater than the pivot
159 - an item on the right that is less than the pivot
160 Once found, they are swapped and the loop continues.
161 Meanwhile items that are equal to the pivot are moved to the edges of the
162 array.
163 */
164 while(pl < pr) {
165 /* Move left hand items which are equal to the pivot to the far left.
166 break when we find an item that is greater than the pivot */
167 for(; pl < pr; pl += w) {
168 cmp = compar(pl, pivot, arg);
169 if(cmp > 0) { break; }
170 else if(cmp == 0) {
171 if(ple < pl) { sort_r_swap(ple, pl, w); }
172 ple += w;
173 }
174 }
175 /* break if last batch of left hand items were equal to pivot */
176 if(pl >= pr) { break; }
177 /* Move right hand items which are equal to the pivot to the far right.
178 break when we find an item that is less than the pivot */
179 for(; pl < pr; ) {
180 pr -= w; /* Move right pointer onto an unprocessed item */
181 cmp = compar(pr, pivot, arg);
182 if(cmp == 0) {
183 pre -= w;
184 if(pr < pre) { sort_r_swap(pr, pre, w); }
185 }
186 else if(cmp < 0) {
187 if(pl < pr) { sort_r_swap(pl, pr, w); }
188 pl += w;
189 break;
190 }
191 }
192 }
193
194 pl = pr; /* pr may have gone below pl */
195
196 /*
197 Now we need to go from: EEELLLGGGGEEEE
198 to: LLLEEEEEEEGGGG
199
200 Pivot comparison key:
201 E = equal, L = less than, u = unknown, G = greater than, E = equal
202 */
203 sort_r_swap_blocks(b, ple-b, pl-ple);
204 sort_r_swap_blocks(pr, pre-pr, end-pre);
205
206 /*for(size_t i=0; i<nel; i++) {printf("%4i", *(int*)(b + i*sizeof(int)));}
207 printf("\n");*/
208
209 sort_r_simple(b, (pl-ple)/w, w, compar, arg);
210 sort_r_simple(end-(pre-pr), (pre-pr)/w, w, compar, arg);
211 }
212 }
213
214
215 #if defined NESTED_QSORT
216
sort_r(void * base,size_t nel,size_t width,int (* compar)(const void * _a,const void * _b,void * aarg),void * arg)217 static _SORT_R_INLINE void sort_r(void *base, size_t nel, size_t width,
218 int (*compar)(const void *_a,
219 const void *_b,
220 void *aarg),
221 void *arg)
222 {
223 int nested_cmp(const void *a, const void *b)
224 {
225 return compar(a, b, arg);
226 }
227
228 qsort(base, nel, width, nested_cmp);
229 }
230
231 #else /* !NESTED_QSORT */
232
233 /* Declare structs and functions */
234
235 #if defined _SORT_R_BSD
236
237 /* Ensure qsort_r is defined */
238 extern void qsort_r(void *base, size_t nel, size_t width, void *thunk,
239 int (*compar)(void *_thunk,
240 const void *_a, const void *_b));
241
242 #endif
243
244 #if defined _SORT_R_BSD || defined _SORT_R_WINDOWS
245
246 /* BSD (qsort_r), Windows (qsort_s) require argument swap */
247
248 struct sort_r_data
249 {
250 void *arg;
251 int (*compar)(const void *_a, const void *_b, void *_arg);
252 };
253
sort_r_arg_swap(void * s,const void * a,const void * b)254 static _SORT_R_INLINE int sort_r_arg_swap(void *s,
255 const void *a, const void *b)
256 {
257 struct sort_r_data *ss = (struct sort_r_data*)s;
258 return (ss->compar)(a, b, ss->arg);
259 }
260
261 #endif
262
263 #if defined _SORT_R_LINUX
264
265 typedef int(* __compar_d_fn_t)(const void *, const void *, void *);
266 extern void qsort_r(void *base, size_t nel, size_t width,
267 __compar_d_fn_t __compar, void *arg)
268 __attribute__((nonnull (1, 4)));
269
270 #endif
271
272 /* implementation */
273
sort_r(void * base,size_t nel,size_t width,int (* compar)(const void * _a,const void * _b,void * _arg),void * arg)274 static _SORT_R_INLINE void sort_r(void *base, size_t nel, size_t width,
275 int (*compar)(const void *_a,
276 const void *_b, void *_arg),
277 void *arg)
278 {
279 #if defined _SORT_R_LINUX
280
281 #if defined __GLIBC__ && ((__GLIBC__ < 2) || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 8))
282
283 /* no qsort_r in glibc before 2.8, need to use nested qsort */
284 sort_r_simple(base, nel, width, compar, arg);
285
286 #else
287
288 qsort_r(base, nel, width, compar, arg);
289
290 #endif
291
292 #elif defined _SORT_R_BSD
293
294 struct sort_r_data tmp;
295 tmp.arg = arg;
296 tmp.compar = compar;
297 qsort_r(base, nel, width, &tmp, sort_r_arg_swap);
298
299 #elif defined _SORT_R_WINDOWS
300
301 struct sort_r_data tmp;
302 tmp.arg = arg;
303 tmp.compar = compar;
304 qsort_s(base, nel, width, sort_r_arg_swap, &tmp);
305
306 #else
307
308 /* Fall back to our own quicksort implementation */
309 sort_r_simple(base, nel, width, compar, arg);
310
311 #endif
312 }
313
314 #endif /* !NESTED_QSORT */
315
316 #undef _SORT_R_INLINE
317 #undef _SORT_R_WINDOWS
318 #undef _SORT_R_LINUX
319 #undef _SORT_R_BSD
320
321 #endif /* SORT_R_H_ */
322