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 __APPLE__ || defined __MACH__ || defined __DARWIN__ || \ 28 defined __FreeBSD__ || defined __DragonFly__) 29 # define _SORT_R_BSD 30 #elif (defined _GNU_SOURCE || defined __gnu_hurd__ || defined __GNU__ || \ 31 defined __linux__ || defined __MINGW32__ || defined __GLIBC__) 32 # define _SORT_R_LINUX 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! */ 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 */ 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 */ 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 */ 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 216 217 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 }; 253 254 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 */ 273 274 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_ */