1 /*- 2 * Copyright (c) 1991 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * David Hitz of Auspex Systems, Inc. 7 * 8 * %sccs.include.redist.c% 9 */ 10 11 #ifndef lint 12 char copyright[] = 13 "@(#) Copyright (c) 1991 The Regents of the University of California.\n\ 14 All rights reserved.\n"; 15 #endif /* not lint */ 16 17 #ifndef lint 18 static char sccsid[] = "@(#)look.c 5.1 (Berkeley) 07/21/91"; 19 #endif /* not lint */ 20 21 /* 22 * look -- find lines in a sorted list. 23 * 24 * The man page said that TABs and SPACEs participate in -d comparisons. 25 * In fact, they were ignored. This implements historic practice, not 26 * the manual page. 27 */ 28 29 #include <sys/types.h> 30 #include <sys/mman.h> 31 #include <sys/stat.h> 32 #include <errno.h> 33 #include <fcntl.h> 34 #include <stdio.h> 35 #include <stdlib.h> 36 #include <string.h> 37 #include <ctype.h> 38 #include "pathnames.h" 39 40 /* 41 * FOLD and DICT convert characters to a normal form for comparison, 42 * according to the user specified flags. 43 * 44 * DICT expects integers because it uses a non-character value to 45 * indicate a character which should not participate in comparisons. 46 */ 47 #define EQUAL 0 48 #define GREATER 1 49 #define LESS (-1) 50 #define NO_COMPARE (-2) 51 52 #define FOLD(c) (isascii(c) && isupper(c) ? tolower(c) : (c)) 53 #define DICT(c) (isascii(c) && isalnum(c) ? (c) : NO_COMPARE) 54 55 int dflag, fflag; 56 57 char *binary_search __P((char *, char *, char *)); 58 int compare __P((char *, char *, char *)); 59 void err __P((const char *fmt, ...)); 60 char *linear_search __P((char *, char *, char *)); 61 int look __P((char *, char *, char *)); 62 void print_from __P((char *, char *, char *)); 63 void usage __P((void)); 64 65 main(argc, argv) 66 int argc; 67 char *argv[]; 68 { 69 struct stat sb; 70 int ch, fd; 71 char *back, *file, *front, *string; 72 73 file = _PATH_WORDS; 74 while ((ch = getopt(argc, argv, "df")) != EOF) 75 switch(ch) { 76 case 'd': 77 dflag = 1; 78 break; 79 case 'f': 80 fflag = 1; 81 break; 82 case '?': 83 default: 84 usage(); 85 } 86 argc -= optind; 87 argv += optind; 88 89 switch (argc) { 90 case 2: /* Don't set -df for user. */ 91 string = *argv++; 92 file = *argv; 93 break; 94 case 1: /* But set -df by default. */ 95 dflag = fflag = 1; 96 string = *argv; 97 break; 98 default: 99 usage(); 100 } 101 102 if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb) || 103 (front = mmap(NULL, sb.st_size, PROT_READ, MAP_FILE, fd, 104 (off_t)0)) == NULL) 105 err("%s: %s", file, strerror(errno)); 106 back = front + sb.st_size; 107 exit(look(string, front, back)); 108 } 109 110 look(string, front, back) 111 char *string, *front, *back; 112 { 113 register int ch; 114 register char *readp, *writep; 115 116 /* Reformat string string to avoid doing it multiple times later. */ 117 for (readp = writep = string; ch = *readp++;) { 118 if (fflag) 119 ch = FOLD(ch); 120 if (dflag) 121 ch = DICT(ch); 122 if (ch != NO_COMPARE) 123 *(writep++) = ch; 124 } 125 *writep = '\0'; 126 127 front = binary_search(string, front, back); 128 front = linear_search(string, front, back); 129 130 if (front) 131 print_from(string, front, back); 132 return (front ? 0 : 1); 133 } 134 135 136 /* 137 * Binary search for "string" in memory between "front" and "back". 138 * 139 * This routine is expected to return a pointer to the start of a line at 140 * *or before* the first word matching "string". Relaxing the constraint 141 * this way simplifies the algorithm. 142 * 143 * Invariants: 144 * front points to the beginning of a line at or before the first 145 * matching string. 146 * 147 * back points to the beginning of a line at or after the first 148 * matching line. 149 * 150 * Base of the Invariants. 151 * front = NULL; 152 * back = EOF; 153 * 154 * Advancing the Invariants: 155 * 156 * p = first newline after halfway point from front to back. 157 * 158 * If the string at "p" is not greater than the string to match, 159 * p is the new front. Otherwise it is the new back. 160 * 161 * Termination: 162 * 163 * The definition of the routine allows it return at any point, 164 * since front is always at or before the line to print. 165 * 166 * In fact, it returns when the chosen "p" equals "back". This 167 * implies that there exists a string is least half as long as 168 * (back - front), which in turn implies that a linear search will 169 * be no more expensive than the cost of simply printing a string or two. 170 * 171 * Trying to continue with binary search at this point would be 172 * more trouble than it's worth. 173 */ 174 #define SKIP_PAST_NEWLINE(p, back) \ 175 while (p < back && *p++ != '\n'); 176 177 char * 178 binary_search(string, front, back) 179 register char *string, *front, *back; 180 { 181 register char *p; 182 183 p = front + (back - front) / 2; 184 SKIP_PAST_NEWLINE(p, back); 185 186 while (p != back) { 187 if (compare(string, p, back) == GREATER) 188 front = p; 189 else 190 back = p; 191 p = front + (back - front) / 2; 192 SKIP_PAST_NEWLINE(p, back); 193 } 194 return (front); 195 } 196 197 /* 198 * Find the first line that starts with string, linearly searching from front 199 * to back. 200 * 201 * Return NULL for no such line. 202 * 203 * This routine assumes: 204 * 205 * o front points at the first character in a line. 206 * o front is before or at the first line to be printed. 207 */ 208 char * 209 linear_search(string, front, back) 210 char *string, *front, *back; 211 { 212 while (front < back) { 213 switch (compare(string, front, back)) { 214 case EQUAL: /* Found it. */ 215 return (front); 216 break; 217 case LESS: /* No such string. */ 218 return (NULL); 219 break; 220 case GREATER: /* Keep going. */ 221 break; 222 } 223 SKIP_PAST_NEWLINE(front, back); 224 } 225 return (NULL); 226 } 227 228 /* 229 * Print as many lines as match string, starting at front. 230 */ 231 void 232 print_from(string, front, back) 233 register char *string, *front, *back; 234 { 235 for (; front < back && compare(string, front, back) == EQUAL; ++front) { 236 for (; front < back && *front != '\n'; ++front) 237 if (putchar(*front) == EOF) 238 err("stdout: %s", strerror(errno)); 239 if (putchar('\n') == EOF) 240 err("stdout: %s", strerror(errno)); 241 } 242 } 243 244 /* 245 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with 246 * string2 (s1 ??? s2). 247 * 248 * o Matches up to len(s1) are EQUAL. 249 * o Matches up to len(s2) are GREATER. 250 * 251 * Compare understands about the -f and -d flags, and treats comparisons 252 * appropriately. 253 * 254 * The string "s1" is null terminated. The string s2 is '\n' terminated (or 255 * "back" terminated). 256 */ 257 int 258 compare(s1, s2, back) 259 register char *s1, *s2, *back; 260 { 261 register int ch; 262 263 for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) { 264 ch = *s2; 265 if (fflag) 266 ch = FOLD(ch); 267 if (dflag) 268 ch = DICT(ch); 269 270 if (ch == NO_COMPARE) { 271 ++s2; /* Ignore character in comparison. */ 272 continue; 273 } 274 if (*s1 != ch) 275 return (*s1 < ch ? LESS : GREATER); 276 } 277 return (*s1 ? GREATER : EQUAL); 278 } 279 280 static void 281 usage() 282 { 283 (void)fprintf(stderr, "usage: look [-df] string [file]\n"); 284 exit(2); 285 } 286 287 #if __STDC__ 288 #include <stdarg.h> 289 #else 290 #include <varargs.h> 291 #endif 292 293 void 294 #if __STDC__ 295 err(const char *fmt, ...) 296 #else 297 err(fmt, va_alist) 298 char *fmt; 299 va_dcl 300 #endif 301 { 302 va_list ap; 303 #if __STDC__ 304 va_start(ap, fmt); 305 #else 306 va_start(ap); 307 #endif 308 (void)fprintf(stderr, "look: "); 309 (void)vfprintf(stderr, fmt, ap); 310 va_end(ap); 311 (void)fprintf(stderr, "\n"); 312 exit(2); 313 /* NOTREACHED */ 314 } 315