look.c revision 1.4
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 1.4 1993/10/13 18:34:30 jtc 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 <unistd.h> 66 #include "pathnames.h" 67 68 /* 69 * FOLD and DICT convert characters to a normal form for comparison, 70 * according to the user specified flags. 71 * 72 * DICT expects integers because it uses a non-character value to 73 * indicate a character which should not participate in comparisons. 74 */ 75 #define EQUAL 0 76 #define GREATER 1 77 #define LESS (-1) 78 #define NO_COMPARE (-2) 79 80 #define FOLD(c) (isascii(c) && isupper(c) ? tolower(c) : (c)) 81 #define DICT(c) (isascii(c) && isalnum(c) ? (c) : NO_COMPARE) 82 83 int dflag, fflag; 84 85 char *binary_search __P((char *, char *, char *)); 86 int compare __P((char *, char *, char *)); 87 void err __P((const char *fmt, ...)); 88 char *linear_search __P((char *, char *, char *)); 89 int look __P((char *, char *, char *)); 90 void print_from __P((char *, char *, char *)); 91 static void usage __P((void)); 92 93 main(argc, argv) 94 int argc; 95 char *argv[]; 96 { 97 struct stat sb; 98 int ch, fd; 99 char *back, *file, *front, *string; 100 101 file = _PATH_WORDS; 102 while ((ch = getopt(argc, argv, "df")) != EOF) 103 switch(ch) { 104 case 'd': 105 dflag = 1; 106 break; 107 case 'f': 108 fflag = 1; 109 break; 110 case '?': 111 default: 112 usage(); 113 } 114 argc -= optind; 115 argv += optind; 116 117 switch (argc) { 118 case 2: /* Don't set -df for user. */ 119 string = *argv++; 120 file = *argv; 121 break; 122 case 1: /* But set -df by default. */ 123 dflag = fflag = 1; 124 string = *argv; 125 break; 126 default: 127 usage(); 128 } 129 130 if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb) || 131 (front = mmap(NULL, sb.st_size, PROT_READ, MAP_FILE, fd, 132 (off_t)0)) == NULL) 133 err("%s: %s", file, strerror(errno)); 134 back = front + sb.st_size; 135 exit(look(string, front, back)); 136 } 137 138 look(string, front, back) 139 char *string, *front, *back; 140 { 141 register int ch; 142 register char *readp, *writep; 143 144 /* Reformat string 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(string, front, back) 207 register char *string, *front, *back; 208 { 209 register char *p; 210 211 p = front + (back - front) / 2; 212 SKIP_PAST_NEWLINE(p, back); 213 214 while (p != back) { 215 if (compare(string, p, back) == GREATER) 216 front = p; 217 else 218 back = p; 219 p = front + (back - front) / 2; 220 SKIP_PAST_NEWLINE(p, back); 221 } 222 return (front); 223 } 224 225 /* 226 * Find the first line that starts with string, linearly searching from front 227 * to back. 228 * 229 * Return NULL for no such line. 230 * 231 * This routine assumes: 232 * 233 * o front points at the first character in a line. 234 * o front is before or at the first line to be printed. 235 */ 236 char * 237 linear_search(string, front, back) 238 char *string, *front, *back; 239 { 240 while (front < back) { 241 switch (compare(string, front, back)) { 242 case EQUAL: /* Found it. */ 243 return (front); 244 break; 245 case LESS: /* No such string. */ 246 return (NULL); 247 break; 248 case GREATER: /* Keep going. */ 249 break; 250 } 251 SKIP_PAST_NEWLINE(front, back); 252 } 253 return (NULL); 254 } 255 256 /* 257 * Print as many lines as match string, starting at front. 258 */ 259 void 260 print_from(string, front, back) 261 register char *string, *front, *back; 262 { 263 for (; front < back && compare(string, front, back) == EQUAL; ++front) { 264 for (; front < back && *front != '\n'; ++front) 265 if (putchar(*front) == EOF) 266 err("stdout: %s", strerror(errno)); 267 if (putchar('\n') == EOF) 268 err("stdout: %s", strerror(errno)); 269 } 270 } 271 272 /* 273 * Return LESS, GREATER, or EQUAL depending on how the string1 compares with 274 * string2 (s1 ??? s2). 275 * 276 * o Matches up to len(s1) are EQUAL. 277 * o Matches up to len(s2) are GREATER. 278 * 279 * Compare understands about the -f and -d flags, and treats comparisons 280 * appropriately. 281 * 282 * The string "s1" is null terminated. The string s2 is '\n' terminated (or 283 * "back" terminated). 284 */ 285 int 286 compare(s1, s2, back) 287 register char *s1, *s2, *back; 288 { 289 register 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 static void 309 usage() 310 { 311 (void)fprintf(stderr, "usage: look [-df] string [file]\n"); 312 exit(2); 313 } 314 315 #if __STDC__ 316 #include <stdarg.h> 317 #else 318 #include <varargs.h> 319 #endif 320 321 void 322 #if __STDC__ 323 err(const char *fmt, ...) 324 #else 325 err(fmt, va_alist) 326 char *fmt; 327 va_dcl 328 #endif 329 { 330 va_list ap; 331 #if __STDC__ 332 va_start(ap, fmt); 333 #else 334 va_start(ap); 335 #endif 336 (void)fprintf(stderr, "look: "); 337 (void)vfprintf(stderr, fmt, ap); 338 va_end(ap); 339 (void)fprintf(stderr, "\n"); 340 exit(2); 341 /* NOTREACHED */ 342 } 343
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