look.c revision 1.2
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 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #ifndef lint 38 char copyright[] = 39 "@(#) Copyright (c) 1991 The Regents of the University of California.\n\ 40 All rights reserved.\n"; 41 #endif /* not lint */ 42 43 #ifndef lint 44 static char sccsid[] = "@(#)look.c 5.1 (Berkeley) 7/21/91"; 45 #endif /* not lint */ 46 47 /* 48 * look -- find lines in a sorted list. 49 * 50 * The man page said that TABs and SPACEs participate in -d comparisons. 51 * In fact, they were ignored. This implements historic practice, not 52 * the manual page. 53 */ 54 55 #include <sys/types.h> 56 #include <sys/mman.h> 57 #include <sys/stat.h> 58 #include <errno.h> 59 #include <fcntl.h> 60 #include <stdio.h> 61 #include <stdlib.h> 62 #include <string.h> 63 #include <ctype.h> 64 #include "pathnames.h" 65 66 /* 67 * FOLD and DICT convert characters to a normal form for comparison, 68 * according to the user specified flags. 69 * 70 * DICT expects integers because it uses a non-character value to 71 * indicate a character which should not participate in comparisons. 72 */ 73 #define EQUAL 0 74 #define GREATER 1 75 #define LESS (-1) 76 #define NO_COMPARE (-2) 77 78 #define FOLD(c) (isascii(c) && isupper(c) ? tolower(c) : (c)) 79 #define DICT(c) (isascii(c) && isalnum(c) ? (c) : NO_COMPARE) 80 81 int dflag, fflag; 82 83 char *binary_search __P((char *, char *, char *)); 84 int compare __P((char *, char *, char *)); 85 void err __P((const char *fmt, ...)); 86 char *linear_search __P((char *, char *, char *)); 87 int look __P((char *, char *, char *)); 88 void print_from __P((char *, char *, char *)); 89 static void usage __P((void)); 90 91 main(argc, argv) 92 int argc; 93 char *argv[]; 94 { 95 struct stat sb; 96 int ch, fd; 97 char *back, *file, *front, *string; 98 99 file = _PATH_WORDS; 100 while ((ch = getopt(argc, argv, "df")) != EOF) 101 switch(ch) { 102 case 'd': 103 dflag = 1; 104 break; 105 case 'f': 106 fflag = 1; 107 break; 108 case '?': 109 default: 110 usage(); 111 } 112 argc -= optind; 113 argv += optind; 114 115 switch (argc) { 116 case 2: /* Don't set -df for user. */ 117 string = *argv++; 118 file = *argv; 119 break; 120 case 1: /* But set -df by default. */ 121 dflag = fflag = 1; 122 string = *argv; 123 break; 124 default: 125 usage(); 126 } 127 128 if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb) || 129 (front = mmap(NULL, sb.st_size, PROT_READ, MAP_FILE, fd, 130 (off_t)0)) == NULL) 131 err("%s: %s", file, strerror(errno)); 132 back = front + sb.st_size; 133 exit(look(string, front, back)); 134 } 135 136 look(string, front, back) 137 char *string, *front, *back; 138 { 139 register int ch; 140 register char *readp, *writep; 141 142 /* Reformat string string to avoid doing it multiple times later. */ 143 for (readp = writep = string; ch = *readp++;) { 144 if (fflag) 145 ch = FOLD(ch); 146 if (dflag) 147 ch = DICT(ch); 148 if (ch != NO_COMPARE) 149 *(writep++) = ch; 150 } 151 *writep = '\0'; 152 153 front = binary_search(string, front, back); 154 front = linear_search(string, front, back); 155 156 if (front) 157 print_from(string, front, back); 158 return (front ? 0 : 1); 159 } 160 161 162 /* 163 * Binary search for "string" in memory between "front" and "back". 164 * 165 * This routine is expected to return a pointer to the start of a line at 166 * *or before* the first word matching "string". Relaxing the constraint 167 * this way simplifies the algorithm. 168 * 169 * Invariants: 170 * front points to the beginning of a line at or before the first 171 * matching string. 172 * 173 * back points to the beginning of a line at or after the first 174 * matching line. 175 * 176 * Base of the Invariants. 177 * front = NULL; 178 * back = EOF; 179 * 180 * Advancing the Invariants: 181 * 182 * p = first newline after halfway point from front to back. 183 * 184 * If the string at "p" is not greater than the string to match, 185 * p is the new front. Otherwise it is the new back. 186 * 187 * Termination: 188 * 189 * The definition of the routine allows it return at any point, 190 * since front is always at or before the line to print. 191 * 192 * In fact, it returns when the chosen "p" equals "back". This 193 * implies that there exists a string is least half as long as 194 * (back - front), which in turn implies that a linear search will 195 * be no more expensive than the cost of simply printing a string or two. 196 * 197 * Trying to continue with binary search at this point would be 198 * more trouble than it's worth. 199 */ 200 #define SKIP_PAST_NEWLINE(p, back) \ 201 while (p < back && *p++ != '\n'); 202 203 char * 204 binary_search(string, front, back) 205 register char *string, *front, *back; 206 { 207 register char *p; 208 209 p = front + (back - front) / 2; 210 SKIP_PAST_NEWLINE(p, back); 211 212 while (p != back) { 213 if (compare(string, p, back) == GREATER) 214 front = p; 215 else 216 back = p; 217 p = front + (back - front) / 2; 218 SKIP_PAST_NEWLINE(p, back); 219 } 220 return (front); 221 } 222 223 /* 224 * Find the first line that starts with string, linearly searching from front 225 * to back. 226 * 227 * Return NULL for no such line. 228 * 229 * This routine assumes: 230 * 231 * o front points at the first character in a line. 232 * o front is before or at the first line to be printed. 233 */ 234 char * 235 linear_search(string, front, back) 236 char *string, *front, *back; 237 { 238 while (front < back) { 239 switch (compare(string, front, back)) { 240 case EQUAL: /* Found it. */ 241 return (front); 242 break; 243 case LESS: /* No such string. */ 244 return (NULL); 245 break; 246 case GREATER: /* Keep going. */ 247 break; 248 } 249 SKIP_PAST_NEWLINE(front, back); 250 } 251 return (NULL); 252 } 253 254 /* 255 * Print as many lines as match string, starting at front. 256 */ 257 void 258 print_from(string, front, back) 259 register char *string, *front, *back; 260 { 261 for (; front < back && compare(string, front, back) == EQUAL; ++front) { 262 for (; front < back && *front != '\n'; ++front) 263 if (putchar(*front) == EOF) 264 err("stdout: %s", strerror(errno)); 265 if (putchar('\n') == EOF) 266 err("stdout: %s", strerror(errno)); 267 } 268 } 269 270 /* 271 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with 272 * string2 (s1 ??? s2). 273 * 274 * o Matches up to len(s1) are EQUAL. 275 * o Matches up to len(s2) are GREATER. 276 * 277 * Compare understands about the -f and -d flags, and treats comparisons 278 * appropriately. 279 * 280 * The string "s1" is null terminated. The string s2 is '\n' terminated (or 281 * "back" terminated). 282 */ 283 int 284 compare(s1, s2, back) 285 register char *s1, *s2, *back; 286 { 287 register int ch; 288 289 for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) { 290 ch = *s2; 291 if (fflag) 292 ch = FOLD(ch); 293 if (dflag) 294 ch = DICT(ch); 295 296 if (ch == NO_COMPARE) { 297 ++s2; /* Ignore character in comparison. */ 298 continue; 299 } 300 if (*s1 != ch) 301 return (*s1 < ch ? LESS : GREATER); 302 } 303 return (*s1 ? GREATER : EQUAL); 304 } 305 306 static void 307 usage() 308 { 309 (void)fprintf(stderr, "usage: look [-df] string [file]\n"); 310 exit(2); 311 } 312 313 #if __STDC__ 314 #include <stdarg.h> 315 #else 316 #include <varargs.h> 317 #endif 318 319 void 320 #if __STDC__ 321 err(const char *fmt, ...) 322 #else 323 err(fmt, va_alist) 324 char *fmt; 325 va_dcl 326 #endif 327 { 328 va_list ap; 329 #if __STDC__ 330 va_start(ap, fmt); 331 #else 332 va_start(ap); 333 #endif 334 (void)fprintf(stderr, "look: "); 335 (void)vfprintf(stderr, fmt, ap); 336 va_end(ap); 337 (void)fprintf(stderr, "\n"); 338 exit(2); 339 /* NOTREACHED */ 340 } 341
Indexes created Sun Sep 28 16:09:52 GMT 2025