look.c revision 1.3
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[] = "from: @(#)look.c 5.1 (Berkeley) 7/21/91";*/ 45 static char rcsid[] = "$Id: look.c,v 1.3 1993/08/01 18:13:24 mycroft 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 #include <errno.h> 60 #include <fcntl.h> 61 #include <stdio.h> 62 #include <stdlib.h> 63 #include <string.h> 64 #include <ctype.h> 65 #include "pathnames.h" 66 67 /* 68 * FOLD and DICT convert characters to a normal form for comparison, 69 * according to the user specified flags. 70 * 71 * DICT expects integers because it uses a non-character value to 72 * indicate a character which should not participate in comparisons. 73 */ 74 #define EQUAL 0 75 #define GREATER 1 76 #define LESS (-1) 77 #define NO_COMPARE (-2) 78 79 #define FOLD(c) (isascii(c) && isupper(c) ? tolower(c) : (c)) 80 #define DICT(c) (isascii(c) && isalnum(c) ? (c) : NO_COMPARE) 81 82 int dflag, fflag; 83 84 char *binary_search __P((char *, char *, char *)); 85 int compare __P((char *, char *, char *)); 86 void err __P((const char *fmt, ...)); 87 char *linear_search __P((char *, char *, char *)); 88 int look __P((char *, char *, char *)); 89 void print_from __P((char *, char *, char *)); 90 static void usage __P((void)); 91 92 main(argc, argv) 93 int argc; 94 char *argv[]; 95 { 96 struct stat sb; 97 int ch, fd; 98 char *back, *file, *front, *string; 99 100 file = _PATH_WORDS; 101 while ((ch = getopt(argc, argv, "df")) != EOF) 102 switch(ch) { 103 case 'd': 104 dflag = 1; 105 break; 106 case 'f': 107 fflag = 1; 108 break; 109 case '?': 110 default: 111 usage(); 112 } 113 argc -= optind; 114 argv += optind; 115 116 switch (argc) { 117 case 2: /* Don't set -df for user. */ 118 string = *argv++; 119 file = *argv; 120 break; 121 case 1: /* But set -df by default. */ 122 dflag = fflag = 1; 123 string = *argv; 124 break; 125 default: 126 usage(); 127 } 128 129 if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb) || 130 (front = mmap(NULL, sb.st_size, PROT_READ, MAP_FILE, fd, 131 (off_t)0)) == NULL) 132 err("%s: %s", file, strerror(errno)); 133 back = front + sb.st_size; 134 exit(look(string, front, back)); 135 } 136 137 look(string, front, back) 138 char *string, *front, *back; 139 { 140 register int ch; 141 register char *readp, *writep; 142 143 /* Reformat string string to avoid doing it multiple times later. */ 144 for (readp = writep = string; ch = *readp++;) { 145 if (fflag) 146 ch = FOLD(ch); 147 if (dflag) 148 ch = DICT(ch); 149 if (ch != NO_COMPARE) 150 *(writep++) = ch; 151 } 152 *writep = '\0'; 153 154 front = binary_search(string, front, back); 155 front = linear_search(string, front, back); 156 157 if (front) 158 print_from(string, front, back); 159 return (front ? 0 : 1); 160 } 161 162 163 /* 164 * Binary search for "string" in memory between "front" and "back". 165 * 166 * This routine is expected to return a pointer to the start of a line at 167 * *or before* the first word matching "string". Relaxing the constraint 168 * this way simplifies the algorithm. 169 * 170 * Invariants: 171 * front points to the beginning of a line at or before the first 172 * matching string. 173 * 174 * back points to the beginning of a line at or after the first 175 * matching line. 176 * 177 * Base of the Invariants. 178 * front = NULL; 179 * back = EOF; 180 * 181 * Advancing the Invariants: 182 * 183 * p = first newline after halfway point from front to back. 184 * 185 * If the string at "p" is not greater than the string to match, 186 * p is the new front. Otherwise it is the new back. 187 * 188 * Termination: 189 * 190 * The definition of the routine allows it return at any point, 191 * since front is always at or before the line to print. 192 * 193 * In fact, it returns when the chosen "p" equals "back". This 194 * implies that there exists a string is least half as long as 195 * (back - front), which in turn implies that a linear search will 196 * be no more expensive than the cost of simply printing a string or two. 197 * 198 * Trying to continue with binary search at this point would be 199 * more trouble than it's worth. 200 */ 201 #define SKIP_PAST_NEWLINE(p, back) \ 202 while (p < back && *p++ != '\n'); 203 204 char * 205 binary_search(string, front, back) 206 register char *string, *front, *back; 207 { 208 register char *p; 209 210 p = front + (back - front) / 2; 211 SKIP_PAST_NEWLINE(p, back); 212 213 while (p != back) { 214 if (compare(string, p, back) == GREATER) 215 front = p; 216 else 217 back = p; 218 p = front + (back - front) / 2; 219 SKIP_PAST_NEWLINE(p, back); 220 } 221 return (front); 222 } 223 224 /* 225 * Find the first line that starts with string, linearly searching from front 226 * to back. 227 * 228 * Return NULL for no such line. 229 * 230 * This routine assumes: 231 * 232 * o front points at the first character in a line. 233 * o front is before or at the first line to be printed. 234 */ 235 char * 236 linear_search(string, front, back) 237 char *string, *front, *back; 238 { 239 while (front < back) { 240 switch (compare(string, front, back)) { 241 case EQUAL: /* Found it. */ 242 return (front); 243 break; 244 case LESS: /* No such string. */ 245 return (NULL); 246 break; 247 case GREATER: /* Keep going. */ 248 break; 249 } 250 SKIP_PAST_NEWLINE(front, back); 251 } 252 return (NULL); 253 } 254 255 /* 256 * Print as many lines as match string, starting at front. 257 */ 258 void 259 print_from(string, front, back) 260 register char *string, *front, *back; 261 { 262 for (; front < back && compare(string, front, back) == EQUAL; ++front) { 263 for (; front < back && *front != '\n'; ++front) 264 if (putchar(*front) == EOF) 265 err("stdout: %s", strerror(errno)); 266 if (putchar('\n') == EOF) 267 err("stdout: %s", strerror(errno)); 268 } 269 } 270 271 /* 272 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with 273 * string2 (s1 ??? s2). 274 * 275 * o Matches up to len(s1) are EQUAL. 276 * o Matches up to len(s2) are GREATER. 277 * 278 * Compare understands about the -f and -d flags, and treats comparisons 279 * appropriately. 280 * 281 * The string "s1" is null terminated. The string s2 is '\n' terminated (or 282 * "back" terminated). 283 */ 284 int 285 compare(s1, s2, back) 286 register char *s1, *s2, *back; 287 { 288 register int ch; 289 290 for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) { 291 ch = *s2; 292 if (fflag) 293 ch = FOLD(ch); 294 if (dflag) 295 ch = DICT(ch); 296 297 if (ch == NO_COMPARE) { 298 ++s2; /* Ignore character in comparison. */ 299 continue; 300 } 301 if (*s1 != ch) 302 return (*s1 < ch ? LESS : GREATER); 303 } 304 return (*s1 ? GREATER : EQUAL); 305 } 306 307 static void 308 usage() 309 { 310 (void)fprintf(stderr, "usage: look [-df] string [file]\n"); 311 exit(2); 312 } 313 314 #if __STDC__ 315 #include <stdarg.h> 316 #else 317 #include <varargs.h> 318 #endif 319 320 void 321 #if __STDC__ 322 err(const char *fmt, ...) 323 #else 324 err(fmt, va_alist) 325 char *fmt; 326 va_dcl 327 #endif 328 { 329 va_list ap; 330 #if __STDC__ 331 va_start(ap, fmt); 332 #else 333 va_start(ap); 334 #endif 335 (void)fprintf(stderr, "look: "); 336 (void)vfprintf(stderr, fmt, ap); 337 va_end(ap); 338 (void)fprintf(stderr, "\n"); 339 exit(2); 340 /* NOTREACHED */ 341 } 342
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