1 /* $NetBSD: look.c,v 1.10 1998/02/20 09:26:00 mycroft Exp $ */ 2 3 /*- 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * David Hitz of Auspex Systems, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #ifndef lint 41 __COPYRIGHT("@(#) Copyright (c) 1991, 1993\n\ 42 The Regents of the University of California. All rights reserved.\n"); 43 #endif /* not lint */ 44 45 #ifndef lint 46 #if 0 47 static char sccsid[] = "@(#)look.c 8.2 (Berkeley) 5/4/95"; 48 #endif 49 __RCSID("$NetBSD: look.c,v 1.10 1998/02/20 09:26:00 mycroft Exp $"); 50 #endif /* not lint */ 51 52 /* 53 * look -- find lines in a sorted list. 54 * 55 * The man page said that TABs and SPACEs participate in -d comparisons. 56 * In fact, they were ignored. This implements historic practice, not 57 * the manual page. 58 */ 59 60 #include <sys/types.h> 61 #include <sys/mman.h> 62 #include <sys/stat.h> 63 64 #include <ctype.h> 65 #include <errno.h> 66 #include <fcntl.h> 67 #include <limits.h> 68 #include <stdio.h> 69 #include <stdlib.h> 70 #include <string.h> 71 #include <unistd.h> 72 #include <err.h> 73 74 #include "pathnames.h" 75 76 /* 77 * FOLD and DICT convert characters to a normal form for comparison, 78 * according to the user specified flags. 79 * 80 * DICT expects integers because it uses a non-character value to 81 * indicate a character which should not participate in comparisons. 82 */ 83 #define EQUAL 0 84 #define GREATER 1 85 #define LESS (-1) 86 #define NO_COMPARE (-2) 87 88 #define FOLD(c) (isascii(c) && isupper(c) ? tolower(c) : (c)) 89 #define DICT(c) (isascii(c) && isalnum(c) ? (c) : NO_COMPARE) 90 91 int dflag, fflag; 92 93 char *binary_search __P((char *, char *, char *)); 94 int compare __P((char *, char *, char *)); 95 char *linear_search __P((char *, char *, char *)); 96 int look __P((char *, char *, char *)); 97 int main __P((int, char **)); 98 void print_from __P((char *, char *, char *)); 99 void usage __P((void)); 100 101 int 102 main(argc, argv) 103 int argc; 104 char *argv[]; 105 { 106 struct stat sb; 107 int ch, fd, termchar; 108 char *back, *file, *front, *string, *p; 109 110 string = NULL; 111 file = _PATH_WORDS; 112 termchar = '\0'; 113 while ((ch = getopt(argc, argv, "dft:")) != -1) 114 switch(ch) { 115 case 'd': 116 dflag = 1; 117 break; 118 case 'f': 119 fflag = 1; 120 break; 121 case 't': 122 termchar = *optarg; 123 break; 124 case '?': 125 default: 126 usage(); 127 } 128 argc -= optind; 129 argv += optind; 130 131 switch (argc) { 132 case 2: /* Don't set -df for user. */ 133 string = *argv++; 134 file = *argv; 135 break; 136 case 1: /* But set -df by default. */ 137 dflag = fflag = 1; 138 string = *argv; 139 break; 140 default: 141 usage(); 142 } 143 144 if (termchar != '\0' && (p = strchr(string, termchar)) != NULL) 145 *++p = '\0'; 146 147 if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb)) 148 err(2, "%s", file); 149 if (sb.st_size > SIZE_T_MAX) 150 err(2, "%s: %s", file, strerror(EFBIG)); 151 if ((front = mmap(NULL, (size_t)sb.st_size, 152 PROT_READ, MAP_FILE|MAP_SHARED, fd, (off_t)0)) == NULL) 153 err(2, "%s", file); 154 back = front + sb.st_size; 155 exit(look(string, front, back)); 156 } 157 158 int 159 look(string, front, back) 160 char *string, *front, *back; 161 { 162 int ch; 163 char *readp, *writep; 164 165 /* Reformat string string to avoid doing it multiple times later. */ 166 for (readp = writep = string; (ch = *readp++) != 0; ) { 167 if (fflag) 168 ch = FOLD(ch); 169 if (dflag) 170 ch = DICT(ch); 171 if (ch != NO_COMPARE) 172 *(writep++) = ch; 173 } 174 *writep = '\0'; 175 176 front = binary_search(string, front, back); 177 front = linear_search(string, front, back); 178 179 if (front) 180 print_from(string, front, back); 181 return (front ? 0 : 1); 182 } 183 184 185 /* 186 * Binary search for "string" in memory between "front" and "back". 187 * 188 * This routine is expected to return a pointer to the start of a line at 189 * *or before* the first word matching "string". Relaxing the constraint 190 * this way simplifies the algorithm. 191 * 192 * Invariants: 193 * front points to the beginning of a line at or before the first 194 * matching string. 195 * 196 * back points to the beginning of a line at or after the first 197 * matching line. 198 * 199 * Base of the Invariants. 200 * front = NULL; 201 * back = EOF; 202 * 203 * Advancing the Invariants: 204 * 205 * p = first newline after halfway point from front to back. 206 * 207 * If the string at "p" is not greater than the string to match, 208 * p is the new front. Otherwise it is the new back. 209 * 210 * Termination: 211 * 212 * The definition of the routine allows it return at any point, 213 * since front is always at or before the line to print. 214 * 215 * In fact, it returns when the chosen "p" equals "back". This 216 * implies that there exists a string is least half as long as 217 * (back - front), which in turn implies that a linear search will 218 * be no more expensive than the cost of simply printing a string or two. 219 * 220 * Trying to continue with binary search at this point would be 221 * more trouble than it's worth. 222 */ 223 #define SKIP_PAST_NEWLINE(p, back) \ 224 while (p < back && *p++ != '\n'); 225 226 char * 227 binary_search(string, front, back) 228 char *string, *front, *back; 229 { 230 char *p; 231 232 p = front + (back - front) / 2; 233 SKIP_PAST_NEWLINE(p, back); 234 235 /* 236 * If the file changes underneath us, make sure we don't 237 * infinitely loop. 238 */ 239 while (p < back && back > front) { 240 if (compare(string, p, back) == GREATER) 241 front = p; 242 else 243 back = p; 244 p = front + (back - front) / 2; 245 SKIP_PAST_NEWLINE(p, back); 246 } 247 return (front); 248 } 249 250 /* 251 * Find the first line that starts with string, linearly searching from front 252 * to back. 253 * 254 * Return NULL for no such line. 255 * 256 * This routine assumes: 257 * 258 * o front points at the first character in a line. 259 * o front is before or at the first line to be printed. 260 */ 261 char * 262 linear_search(string, front, back) 263 char *string, *front, *back; 264 { 265 while (front < back) { 266 switch (compare(string, front, back)) { 267 case EQUAL: /* Found it. */ 268 return (front); 269 break; 270 case LESS: /* No such string. */ 271 return (NULL); 272 break; 273 case GREATER: /* Keep going. */ 274 break; 275 } 276 SKIP_PAST_NEWLINE(front, back); 277 } 278 return (NULL); 279 } 280 281 /* 282 * Print as many lines as match string, starting at front. 283 */ 284 void 285 print_from(string, front, back) 286 char *string, *front, *back; 287 { 288 for (; front < back && compare(string, front, back) == EQUAL; ++front) { 289 for (; front < back && *front != '\n'; ++front) 290 if (putchar(*front) == EOF) 291 err(2, "stdout"); 292 if (putchar('\n') == EOF) 293 err(2, "stdout"); 294 } 295 } 296 297 /* 298 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with 299 * string2 (s1 ??? s2). 300 * 301 * o Matches up to len(s1) are EQUAL. 302 * o Matches up to len(s2) are GREATER. 303 * 304 * Compare understands about the -f and -d flags, and treats comparisons 305 * appropriately. 306 * 307 * The string "s1" is null terminated. The string s2 is '\n' terminated (or 308 * "back" terminated). 309 */ 310 int 311 compare(s1, s2, back) 312 char *s1, *s2, *back; 313 { 314 int ch; 315 316 for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) { 317 ch = *s2; 318 if (fflag) 319 ch = FOLD(ch); 320 if (dflag) 321 ch = DICT(ch); 322 323 if (ch == NO_COMPARE) { 324 ++s2; /* Ignore character in comparison. */ 325 continue; 326 } 327 if (*s1 != ch) 328 return (*s1 < ch ? LESS : GREATER); 329 } 330 return (*s1 ? GREATER : EQUAL); 331 } 332 333 void 334 usage() 335 { 336 (void)fprintf(stderr, "usage: look [-df] [-t char] string [file]\n"); 337 exit(2); 338 } 339