1 /* $OpenBSD: look.c,v 1.13 2009/10/27 23:59:40 deraadt Exp $ */ 2 /* $NetBSD: look.c,v 1.7 1995/08/31 22:41:02 jtc Exp $ */ 3 4 /*- 5 * Copyright (c) 1991, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * David Hitz of Auspex Systems, Inc. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 /* 37 * look -- find lines in a sorted list. 38 * 39 * The man page said that TABs and SPACEs participate in -d comparisons. 40 * In fact, they were ignored. This implements historic practice, not 41 * the manual page. 42 */ 43 44 #include <sys/types.h> 45 #include <sys/mman.h> 46 #include <sys/stat.h> 47 48 #include <ctype.h> 49 #include <errno.h> 50 #include <fcntl.h> 51 #include <limits.h> 52 #include <stdio.h> 53 #include <stdlib.h> 54 #include <string.h> 55 #include <unistd.h> 56 #include <err.h> 57 58 #include "pathnames.h" 59 60 /* 61 * FOLD and DICT convert characters to a normal form for comparison, 62 * according to the user specified flags. 63 * 64 * DICT expects integers because it uses a non-character value to 65 * indicate a character which should not participate in comparisons. 66 */ 67 #define EQUAL 0 68 #define GREATER 1 69 #define LESS (-1) 70 #define NO_COMPARE (-2) 71 72 #define FOLD(c) (isascii(c) && isupper(c) ? tolower(c) : (c)) 73 #define DICT(c) (isascii(c) && isalnum(c) ? (c) : NO_COMPARE) 74 75 int dflag, fflag; 76 77 char *binary_search(char *, char *, char *); 78 int compare(char *, char *, char *); 79 char *linear_search(char *, char *, char *); 80 int look(char *, char *, char *); 81 void print_from(char *, char *, char *); 82 void usage(void); 83 84 int 85 main(int argc, char *argv[]) 86 { 87 struct stat sb; 88 int ch, fd, termchar; 89 char *back, *file, *front, *string, *p; 90 91 file = _PATH_WORDS; 92 termchar = '\0'; 93 while ((ch = getopt(argc, argv, "dft:")) != -1) 94 switch(ch) { 95 case 'd': 96 dflag = 1; 97 break; 98 case 'f': 99 fflag = 1; 100 break; 101 case 't': 102 termchar = *optarg; 103 break; 104 case '?': 105 default: 106 usage(); 107 } 108 argc -= optind; 109 argv += optind; 110 111 switch (argc) { 112 case 2: /* Don't set -df for user. */ 113 string = *argv++; 114 file = *argv; 115 break; 116 case 1: /* But set -df by default. */ 117 dflag = fflag = 1; 118 string = *argv; 119 break; 120 default: 121 usage(); 122 } 123 124 if (termchar != '\0' && (p = strchr(string, termchar)) != NULL) 125 *++p = '\0'; 126 127 if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb)) 128 err(2, "%s", file); 129 if (sb.st_size > SIZE_T_MAX) 130 errx(2, "%s: %s", file, strerror(EFBIG)); 131 if ((front = mmap(NULL, 132 (size_t)sb.st_size, PROT_READ, MAP_PRIVATE, fd, (off_t)0)) == MAP_FAILED) 133 err(2, "%s", file); 134 back = front + sb.st_size; 135 exit(look(string, front, back)); 136 } 137 138 int 139 look(char *string, char *front, char *back) 140 { 141 int ch; 142 char *readp, *writep; 143 144 /* Reformat string to avoid doing it multiple times later. */ 145 for (readp = writep = string; ch = *readp++;) { 146 if (fflag) 147 ch = FOLD(ch); 148 if (dflag) 149 ch = DICT(ch); 150 if (ch != NO_COMPARE) 151 *(writep++) = ch; 152 } 153 *writep = '\0'; 154 155 front = binary_search(string, front, back); 156 front = linear_search(string, front, back); 157 158 if (front) 159 print_from(string, front, back); 160 return (front ? 0 : 1); 161 } 162 163 164 /* 165 * Binary search for "string" in memory between "front" and "back". 166 * 167 * This routine is expected to return a pointer to the start of a line at 168 * *or before* the first word matching "string". Relaxing the constraint 169 * this way simplifies the algorithm. 170 * 171 * Invariants: 172 * front points to the beginning of a line at or before the first 173 * matching string. 174 * 175 * back points to the beginning of a line at or after the first 176 * matching line. 177 * 178 * Base of the Invariants. 179 * front = NULL; 180 * back = EOF; 181 * 182 * Advancing the Invariants: 183 * 184 * p = first newline after halfway point from front to back. 185 * 186 * If the string at "p" is not greater than the string to match, 187 * p is the new front. Otherwise it is the new back. 188 * 189 * Termination: 190 * 191 * The definition of the routine allows it return at any point, 192 * since front is always at or before the line to print. 193 * 194 * In fact, it returns when the chosen "p" equals "back". This 195 * implies that there exists a string is least half as long as 196 * (back - front), which in turn implies that a linear search will 197 * be no more expensive than the cost of simply printing a string or two. 198 * 199 * Trying to continue with binary search at this point would be 200 * more trouble than it's worth. 201 */ 202 #define SKIP_PAST_NEWLINE(p, back) \ 203 while (p < back && *p++ != '\n'); 204 205 char * 206 binary_search(char *string, char *front, char *back) 207 { 208 char *p; 209 210 p = front + (back - front) / 2; 211 SKIP_PAST_NEWLINE(p, back); 212 213 /* 214 * If the file changes underneath us, make sure we don't 215 * infinitely loop. 216 */ 217 while (p < back && back > front) { 218 if (compare(string, p, back) == GREATER) 219 front = p; 220 else 221 back = p; 222 p = front + (back - front) / 2; 223 SKIP_PAST_NEWLINE(p, back); 224 } 225 return (front); 226 } 227 228 /* 229 * Find the first line that starts with string, linearly searching from front 230 * to back. 231 * 232 * Return NULL for no such line. 233 * 234 * This routine assumes: 235 * 236 * o front points at the first character in a line. 237 * o front is before or at the first line to be printed. 238 */ 239 char * 240 linear_search(char *string, char *front, char *back) 241 { 242 while (front < back) { 243 switch (compare(string, front, back)) { 244 case EQUAL: /* Found it. */ 245 return (front); 246 break; 247 case LESS: /* No such string. */ 248 return (NULL); 249 break; 250 case GREATER: /* Keep going. */ 251 break; 252 } 253 SKIP_PAST_NEWLINE(front, back); 254 } 255 return (NULL); 256 } 257 258 /* 259 * Print as many lines as match string, starting at front. 260 */ 261 void 262 print_from(char *string, char *front, char *back) 263 { 264 for (; front < back && compare(string, front, back) == EQUAL; ++front) { 265 for (; front < back && *front != '\n'; ++front) 266 if (putchar(*front) == EOF) 267 err(2, "stdout"); 268 if (putchar('\n') == EOF) 269 err(2, "stdout"); 270 } 271 } 272 273 /* 274 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with 275 * string2 (s1 ??? s2). 276 * 277 * o Matches up to len(s1) are EQUAL. 278 * o Matches up to len(s2) are GREATER. 279 * 280 * Compare understands about the -f and -d flags, and treats comparisons 281 * appropriately. 282 * 283 * The string "s1" is null terminated. The string s2 is '\n' terminated (or 284 * "back" terminated). 285 */ 286 int 287 compare(char *s1, char *s2, char *back) 288 { 289 int ch; 290 291 for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) { 292 ch = *s2; 293 if (fflag) 294 ch = FOLD(ch); 295 if (dflag) 296 ch = DICT(ch); 297 298 if (ch == NO_COMPARE) { 299 ++s2; /* Ignore character in comparison. */ 300 continue; 301 } 302 if (*s1 != ch) 303 return (*s1 < ch ? LESS : GREATER); 304 } 305 return (*s1 ? GREATER : EQUAL); 306 } 307 308 void 309 usage(void) 310 { 311 (void)fprintf(stderr, 312 "usage: look [-df] [-t termchar] string [file]\n"); 313 exit(2); 314 } 315