1 /*- 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Peter McIlroy. 7 * 8 * %sccs.include.redist.c% 9 */ 10 11 #if defined(LIBC_SCCS) && !defined(lint) 12 static char sccsid[] = "@(#)merge.c 8.2 (Berkeley) 02/14/94"; 13 #endif /* LIBC_SCCS and not lint */ 14 15 /* 16 * Hybrid exponential search/linear search merge sort with hybrid 17 * natural/pairwise first pass. Requires about .3% more comparisons 18 * for random data than LSMS with pairwise first pass alone. 19 * It works for objects as small as two bytes. 20 */ 21 22 #define NATURAL 23 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */ 24 25 /* #define NATURAL to get hybrid natural merge. 26 * (The default is pairwise merging.) 27 */ 28 29 #include <sys/types.h> 30 31 #include <errno.h> 32 #include <stdlib.h> 33 #include <string.h> 34 35 static void setup __P((u_char *, u_char *, size_t, size_t, int (*)())); 36 static void insertionsort __P((u_char *, size_t, size_t, int (*)())); 37 38 #define ISIZE sizeof(int) 39 #define PSIZE sizeof(u_char *) 40 #define ICOPY_LIST(src, dst, last) \ 41 do \ 42 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \ 43 while(src < last) 44 #define ICOPY_ELT(src, dst, i) \ 45 do \ 46 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \ 47 while (i -= ISIZE) 48 49 #define CCOPY_LIST(src, dst, last) \ 50 do \ 51 *dst++ = *src++; \ 52 while (src < last) 53 #define CCOPY_ELT(src, dst, i) \ 54 do \ 55 *dst++ = *src++; \ 56 while (i -= 1) 57 58 /* 59 * Find the next possible pointer head. (Trickery for forcing an array 60 * to do double duty as a linked list when objects do not align with word 61 * boundaries. 62 */ 63 /* Assumption: PSIZE is a power of 2. */ 64 #define EVAL(p) (u_char **) \ 65 ((u_char *)0 + \ 66 (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1))) 67 68 /* 69 * Arguments are as for qsort. 70 */ 71 int 72 mergesort(base, nmemb, size, cmp) 73 void *base; 74 size_t nmemb; 75 register size_t size; 76 int (*cmp) __P((const void *, const void *)); 77 { 78 register int i, sense; 79 int big, iflag; 80 register u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2; 81 u_char *list2, *list1, *p2, *p, *last, **p1; 82 83 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */ 84 errno = EINVAL; 85 return (-1); 86 } 87 88 /* 89 * XXX 90 * Stupid subtraction for the Cray. 91 */ 92 iflag = 0; 93 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) 94 iflag = 1; 95 96 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL) 97 return (-1); 98 99 list1 = base; 100 setup(list1, list2, nmemb, size, cmp); 101 last = list2 + nmemb * size; 102 i = big = 0; 103 while (*EVAL(list2) != last) { 104 l2 = list1; 105 p1 = EVAL(list1); 106 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) { 107 p2 = *EVAL(p2); 108 f1 = l2; 109 f2 = l1 = list1 + (p2 - list2); 110 if (p2 != last) 111 p2 = *EVAL(p2); 112 l2 = list1 + (p2 - list2); 113 while (f1 < l1 && f2 < l2) { 114 if ((*cmp)(f1, f2) <= 0) { 115 q = f2; 116 b = f1, t = l1; 117 sense = -1; 118 } else { 119 q = f1; 120 b = f2, t = l2; 121 sense = 0; 122 } 123 if (!big) { /* here i = 0 */ 124 LINEAR: while ((b += size) < t && cmp(q, b) >sense) 125 if (++i == 6) { 126 big = 1; 127 goto EXPONENTIAL; 128 } 129 } else { 130 EXPONENTIAL: for (i = size; ; i <<= 1) 131 if ((p = (b + i)) >= t) { 132 if ((p = t - size) > b && 133 (*cmp)(q, p) <= sense) 134 t = p; 135 else 136 b = p; 137 break; 138 } else if ((*cmp)(q, p) <= sense) { 139 t = p; 140 if (i == size) 141 big = 0; 142 goto FASTCASE; 143 } else 144 b = p; 145 SLOWCASE: while (t > b+size) { 146 i = (((t - b) / size) >> 1) * size; 147 if ((*cmp)(q, p = b + i) <= sense) 148 t = p; 149 else 150 b = p; 151 } 152 goto COPY; 153 FASTCASE: while (i > size) 154 if ((*cmp)(q, 155 p = b + (i >>= 1)) <= sense) 156 t = p; 157 else 158 b = p; 159 COPY: b = t; 160 } 161 i = size; 162 if (q == f1) { 163 if (iflag) { 164 ICOPY_LIST(f2, tp2, b); 165 ICOPY_ELT(f1, tp2, i); 166 } else { 167 CCOPY_LIST(f2, tp2, b); 168 CCOPY_ELT(f1, tp2, i); 169 } 170 } else { 171 if (iflag) { 172 ICOPY_LIST(f1, tp2, b); 173 ICOPY_ELT(f2, tp2, i); 174 } else { 175 CCOPY_LIST(f1, tp2, b); 176 CCOPY_ELT(f2, tp2, i); 177 } 178 } 179 } 180 if (f2 < l2) { 181 if (iflag) 182 ICOPY_LIST(f2, tp2, l2); 183 else 184 CCOPY_LIST(f2, tp2, l2); 185 } else if (f1 < l1) { 186 if (iflag) 187 ICOPY_LIST(f1, tp2, l1); 188 else 189 CCOPY_LIST(f1, tp2, l1); 190 } 191 *p1 = l2; 192 } 193 tp2 = list1; /* swap list1, list2 */ 194 list1 = list2; 195 list2 = tp2; 196 last = list2 + nmemb*size; 197 } 198 if (base == list2) { 199 memmove(list2, list1, nmemb*size); 200 list2 = list1; 201 } 202 free(list2); 203 return (0); 204 } 205 206 #define swap(a, b) { \ 207 s = b; \ 208 i = size; \ 209 do { \ 210 tmp = *a; *a++ = *s; *s++ = tmp; \ 211 } while (--i); \ 212 a -= size; \ 213 } 214 #define reverse(bot, top) { \ 215 s = top; \ 216 do { \ 217 i = size; \ 218 do { \ 219 tmp = *bot; *bot++ = *s; *s++ = tmp; \ 220 } while (--i); \ 221 s -= size2; \ 222 } while(bot < s); \ 223 } 224 225 /* 226 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of 227 * increasing order, list2 in a corresponding linked list. Checks for runs 228 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL 229 * is defined. Otherwise simple pairwise merging is used.) 230 */ 231 void 232 setup(list1, list2, n, size, cmp) 233 size_t n, size; 234 int (*cmp) __P((const void *, const void *)); 235 u_char *list1, *list2; 236 { 237 int i, length, size2, tmp, sense; 238 u_char *f1, *f2, *s, *l2, *last, *p2; 239 240 size2 = size*2; 241 if (n <= 5) { 242 insertionsort(list1, n, size, cmp); 243 *EVAL(list2) = (u_char*) list2 + n*size; 244 return; 245 } 246 /* 247 * Avoid running pointers out of bounds; limit n to evens 248 * for simplicity. 249 */ 250 i = 4 + (n & 1); 251 insertionsort(list1 + (n - i) * size, i, size, cmp); 252 last = list1 + size * (n - i); 253 *EVAL(list2 + (last - list1)) = list2 + n * size; 254 255 #ifdef NATURAL 256 p2 = list2; 257 f1 = list1; 258 sense = (cmp(f1, f1 + size) > 0); 259 for (; f1 < last; sense = !sense) { 260 length = 2; 261 /* Find pairs with same sense. */ 262 for (f2 = f1 + size2; f2 < last; f2 += size2) { 263 if ((cmp(f2, f2+ size) > 0) != sense) 264 break; 265 length += 2; 266 } 267 if (length < THRESHOLD) { /* Pairwise merge */ 268 do { 269 p2 = *EVAL(p2) = f1 + size2 - list1 + list2; 270 if (sense > 0) 271 swap (f1, f1 + size); 272 } while ((f1 += size2) < f2); 273 } else { /* Natural merge */ 274 l2 = f2; 275 for (f2 = f1 + size2; f2 < l2; f2 += size2) { 276 if ((cmp(f2-size, f2) > 0) != sense) { 277 p2 = *EVAL(p2) = f2 - list1 + list2; 278 if (sense > 0) 279 reverse(f1, f2-size); 280 f1 = f2; 281 } 282 } 283 if (sense > 0) 284 reverse (f1, f2-size); 285 f1 = f2; 286 if (f2 < last || cmp(f2 - size, f2) > 0) 287 p2 = *EVAL(p2) = f2 - list1 + list2; 288 else 289 p2 = *EVAL(p2) = list2 + n*size; 290 } 291 } 292 #else /* pairwise merge only. */ 293 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { 294 p2 = *EVAL(p2) = p2 + size2; 295 if (cmp (f1, f1 + size) > 0) 296 swap(f1, f1 + size); 297 } 298 #endif /* NATURAL */ 299 } 300 301 /* 302 * This is to avoid out-of-bounds addresses in sorting the 303 * last 4 elements. 304 */ 305 static void 306 insertionsort(a, n, size, cmp) 307 u_char *a; 308 size_t n, size; 309 int (*cmp) __P((const void *, const void *)); 310 { 311 u_char *ai, *s, *t, *u, tmp; 312 int i; 313 314 for (ai = a+size; --n >= 1; ai += size) 315 for (t = ai; t > a; t -= size) { 316 u = t - size; 317 if (cmp(u, t) <= 0) 318 break; 319 swap(u, t); 320 } 321 } 322