1 /* $NetBSD: look.c,v 1.14 2009/04/26 15:55:50 christos 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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 #ifndef lint 37 __COPYRIGHT("@(#) Copyright (c) 1991, 1993\ 38 The Regents of the University of California. All rights reserved."); 39 #endif /* not lint */ 40 41 #ifndef lint 42 #if 0 43 static char sccsid[] = "@(#)look.c 8.2 (Berkeley) 5/4/95"; 44 #endif 45 __RCSID("$NetBSD: look.c,v 1.14 2009/04/26 15:55:50 christos Exp $"); 46 #endif /* not lint */ 47 48 /* 49 * look -- find lines in a sorted list. 50 * 51 * The man page said that TABs and SPACEs participate in -d comparisons. 52 * In fact, they were ignored. This implements historic practice, not 53 * the manual page. 54 */ 55 56 #include <sys/types.h> 57 #include <sys/mman.h> 58 #include <sys/stat.h> 59 60 #include <ctype.h> 61 #include <errno.h> 62 #include <fcntl.h> 63 #include <limits.h> 64 #include <stdio.h> 65 #include <stdlib.h> 66 #include <string.h> 67 #include <unistd.h> 68 #include <err.h> 69 70 #include "pathnames.h" 71 72 /* 73 * FOLD and DICT convert characters to a normal form for comparison, 74 * according to the user specified flags. 75 * 76 * DICT expects integers because it uses a non-character value to 77 * indicate a character which should not participate in comparisons. 78 */ 79 #define EQUAL 0 80 #define GREATER 1 81 #define LESS (-1) 82 #define NO_COMPARE (-2) 83 84 #define FOLD(c) (isascii(c) && isupper(c) ? tolower(c) : (c)) 85 #define DICT(c) (isascii(c) && isalnum(c) ? (c) : NO_COMPARE) 86 87 int dflag, fflag; 88 89 char *binary_search __P((char *, char *, char *)); 90 int compare __P((char *, char *, char *)); 91 char *linear_search __P((char *, char *, char *)); 92 int look __P((char *, char *, char *)); 93 int main __P((int, char **)); 94 void print_from __P((char *, char *, char *)); 95 void usage __P((void)); 96 97 int 98 main(argc, argv) 99 int argc; 100 char *argv[]; 101 { 102 struct stat sb; 103 int ch, fd, termchar; 104 char *back, *front, *string, *p; 105 const char *file; 106 size_t len; 107 108 string = NULL; 109 file = _PATH_WORDS; 110 termchar = '\0'; 111 while ((ch = getopt(argc, argv, "dft:")) != -1) 112 switch(ch) { 113 case 'd': 114 dflag = 1; 115 break; 116 case 'f': 117 fflag = 1; 118 break; 119 case 't': 120 termchar = *optarg; 121 break; 122 case '?': 123 default: 124 usage(); 125 } 126 argc -= optind; 127 argv += optind; 128 129 switch (argc) { 130 case 2: /* Don't set -df for user. */ 131 string = *argv++; 132 file = *argv; 133 break; 134 case 1: /* But set -df by default. */ 135 dflag = fflag = 1; 136 string = *argv; 137 break; 138 default: 139 usage(); 140 } 141 142 if (termchar != '\0' && (p = strchr(string, termchar)) != NULL) 143 *++p = '\0'; 144 145 if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb)) 146 err(2, "%s", file); 147 len = (size_t)sb.st_size; 148 if ((off_t)len != sb.st_size) { 149 errno = EFBIG; 150 err(2, "%s", file); 151 } 152 if ((front = mmap(NULL, len, 153 PROT_READ, MAP_FILE|MAP_SHARED, fd, (off_t)0)) == NULL) 154 err(2, "%s", file); 155 back = front + len; 156 exit(look(string, front, back)); 157 } 158 159 int 160 look(string, front, back) 161 char *string, *front, *back; 162 { 163 int ch; 164 char *readp, *writep; 165 166 /* Reformat string string to avoid doing it multiple times later. */ 167 for (readp = writep = string; (ch = *readp++) != 0; ) { 168 if (fflag) 169 ch = FOLD(ch); 170 if (dflag) 171 ch = DICT(ch); 172 if (ch != NO_COMPARE) 173 *(writep++) = ch; 174 } 175 *writep = '\0'; 176 177 front = binary_search(string, front, back); 178 front = linear_search(string, front, back); 179 180 if (front) 181 print_from(string, front, back); 182 return (front ? 0 : 1); 183 } 184 185 186 /* 187 * Binary search for "string" in memory between "front" and "back". 188 * 189 * This routine is expected to return a pointer to the start of a line at 190 * *or before* the first word matching "string". Relaxing the constraint 191 * this way simplifies the algorithm. 192 * 193 * Invariants: 194 * front points to the beginning of a line at or before the first 195 * matching string. 196 * 197 * back points to the beginning of a line at or after the first 198 * matching line. 199 * 200 * Base of the Invariants. 201 * front = NULL; 202 * back = EOF; 203 * 204 * Advancing the Invariants: 205 * 206 * p = first newline after halfway point from front to back. 207 * 208 * If the string at "p" is not greater than the string to match, 209 * p is the new front. Otherwise it is the new back. 210 * 211 * Termination: 212 * 213 * The definition of the routine allows it return at any point, 214 * since front is always at or before the line to print. 215 * 216 * In fact, it returns when the chosen "p" equals "back". This 217 * implies that there exists a string is least half as long as 218 * (back - front), which in turn implies that a linear search will 219 * be no more expensive than the cost of simply printing a string or two. 220 * 221 * Trying to continue with binary search at this point would be 222 * more trouble than it's worth. 223 */ 224 #define SKIP_PAST_NEWLINE(p, back) \ 225 while (p < back && *p++ != '\n'); 226 227 char * 228 binary_search(string, front, back) 229 char *string, *front, *back; 230 { 231 char *p; 232 233 p = front + (back - front) / 2; 234 SKIP_PAST_NEWLINE(p, back); 235 236 /* 237 * If the file changes underneath us, make sure we don't 238 * infinitely loop. 239 */ 240 while (p < back && back > front) { 241 if (compare(string, p, back) == GREATER) 242 front = p; 243 else 244 back = p; 245 p = front + (back - front) / 2; 246 SKIP_PAST_NEWLINE(p, back); 247 } 248 return (front); 249 } 250 251 /* 252 * Find the first line that starts with string, linearly searching from front 253 * to back. 254 * 255 * Return NULL for no such line. 256 * 257 * This routine assumes: 258 * 259 * o front points at the first character in a line. 260 * o front is before or at the first line to be printed. 261 */ 262 char * 263 linear_search(string, front, back) 264 char *string, *front, *back; 265 { 266 while (front < back) { 267 switch (compare(string, front, back)) { 268 case EQUAL: /* Found it. */ 269 return (front); 270 break; 271 case LESS: /* No such string. */ 272 return (NULL); 273 break; 274 case GREATER: /* Keep going. */ 275 break; 276 } 277 SKIP_PAST_NEWLINE(front, back); 278 } 279 return (NULL); 280 } 281 282 /* 283 * Print as many lines as match string, starting at front. 284 */ 285 void 286 print_from(string, front, back) 287 char *string, *front, *back; 288 { 289 for (; front < back && compare(string, front, back) == EQUAL; ++front) { 290 for (; front < back && *front != '\n'; ++front) 291 if (putchar(*front) == EOF) 292 err(2, "stdout"); 293 if (putchar('\n') == EOF) 294 err(2, "stdout"); 295 } 296 } 297 298 /* 299 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with 300 * string2 (s1 ??? s2). 301 * 302 * o Matches up to len(s1) are EQUAL. 303 * o Matches up to len(s2) are GREATER. 304 * 305 * Compare understands about the -f and -d flags, and treats comparisons 306 * appropriately. 307 * 308 * The string "s1" is null terminated. The string s2 is '\n' terminated (or 309 * "back" terminated). 310 */ 311 int 312 compare(s1, s2, back) 313 char *s1, *s2, *back; 314 { 315 int ch; 316 317 for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) { 318 ch = *s2; 319 if (fflag) 320 ch = FOLD(ch); 321 if (dflag) 322 ch = DICT(ch); 323 324 if (ch == NO_COMPARE) { 325 ++s2; /* Ignore character in comparison. */ 326 continue; 327 } 328 if (*s1 != ch) 329 return (*s1 < ch ? LESS : GREATER); 330 } 331 return (*s1 ? GREATER : EQUAL); 332 } 333 334 void 335 usage() 336 { 337 (void)fprintf(stderr, "usage: look [-df] [-t char] string [file]\n"); 338 exit(2); 339 } 340