340 lines
8.5 KiB
C
340 lines
8.5 KiB
C
/* $NetBSD: look.c,v 1.14 2009/04/26 15:55:50 christos Exp $ */
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/*-
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* David Hitz of Auspex Systems, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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#ifndef lint
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__COPYRIGHT("@(#) Copyright (c) 1991, 1993\
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The Regents of the University of California. All rights reserved.");
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#endif /* not lint */
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#ifndef lint
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#if 0
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static char sccsid[] = "@(#)look.c 8.2 (Berkeley) 5/4/95";
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#endif
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__RCSID("$NetBSD: look.c,v 1.14 2009/04/26 15:55:50 christos Exp $");
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#endif /* not lint */
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/*
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* look -- find lines in a sorted list.
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*
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* The man page said that TABs and SPACEs participate in -d comparisons.
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* In fact, they were ignored. This implements historic practice, not
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* the manual page.
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*/
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <ctype.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <err.h>
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#include "pathnames.h"
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/*
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* FOLD and DICT convert characters to a normal form for comparison,
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* according to the user specified flags.
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*
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* DICT expects integers because it uses a non-character value to
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* indicate a character which should not participate in comparisons.
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*/
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#define EQUAL 0
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#define GREATER 1
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#define LESS (-1)
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#define NO_COMPARE (-2)
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#define FOLD(c) (isascii(c) && isupper(c) ? tolower(c) : (c))
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#define DICT(c) (isascii(c) && isalnum(c) ? (c) : NO_COMPARE)
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int dflag, fflag;
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char *binary_search __P((char *, char *, char *));
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int compare __P((char *, char *, char *));
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char *linear_search __P((char *, char *, char *));
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int look __P((char *, char *, char *));
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int main __P((int, char **));
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void print_from __P((char *, char *, char *));
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void usage __P((void));
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int
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main(argc, argv)
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int argc;
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char *argv[];
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{
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struct stat sb;
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int ch, fd, termchar;
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char *back, *front, *string, *p;
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const char *file;
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size_t len;
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string = NULL;
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file = _PATH_WORDS;
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termchar = '\0';
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while ((ch = getopt(argc, argv, "dft:")) != -1)
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switch(ch) {
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case 'd':
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dflag = 1;
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break;
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case 'f':
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fflag = 1;
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break;
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case 't':
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termchar = *optarg;
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break;
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case '?':
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default:
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usage();
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}
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argc -= optind;
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argv += optind;
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switch (argc) {
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case 2: /* Don't set -df for user. */
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string = *argv++;
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file = *argv;
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break;
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case 1: /* But set -df by default. */
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dflag = fflag = 1;
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string = *argv;
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break;
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default:
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usage();
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}
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if (termchar != '\0' && (p = strchr(string, termchar)) != NULL)
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*++p = '\0';
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if ((fd = open(file, O_RDONLY, 0)) < 0 || fstat(fd, &sb))
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err(2, "%s", file);
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len = (size_t)sb.st_size;
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if ((off_t)len != sb.st_size) {
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errno = EFBIG;
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err(2, "%s", file);
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}
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if ((front = mmap(NULL, len,
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PROT_READ, MAP_FILE|MAP_SHARED, fd, (off_t)0)) == NULL)
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err(2, "%s", file);
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back = front + len;
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exit(look(string, front, back));
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}
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int
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look(string, front, back)
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char *string, *front, *back;
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{
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int ch;
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char *readp, *writep;
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/* Reformat string string to avoid doing it multiple times later. */
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for (readp = writep = string; (ch = *readp++) != 0; ) {
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if (fflag)
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ch = FOLD(ch);
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if (dflag)
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ch = DICT(ch);
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if (ch != NO_COMPARE)
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*(writep++) = ch;
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}
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*writep = '\0';
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front = binary_search(string, front, back);
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front = linear_search(string, front, back);
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if (front)
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print_from(string, front, back);
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return (front ? 0 : 1);
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}
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/*
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* Binary search for "string" in memory between "front" and "back".
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*
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* This routine is expected to return a pointer to the start of a line at
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* *or before* the first word matching "string". Relaxing the constraint
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* this way simplifies the algorithm.
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*
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* Invariants:
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* front points to the beginning of a line at or before the first
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* matching string.
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*
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* back points to the beginning of a line at or after the first
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* matching line.
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*
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* Base of the Invariants.
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* front = NULL;
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* back = EOF;
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*
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* Advancing the Invariants:
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*
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* p = first newline after halfway point from front to back.
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*
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* If the string at "p" is not greater than the string to match,
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* p is the new front. Otherwise it is the new back.
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*
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* Termination:
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*
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* The definition of the routine allows it return at any point,
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* since front is always at or before the line to print.
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*
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* In fact, it returns when the chosen "p" equals "back". This
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* implies that there exists a string is least half as long as
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* (back - front), which in turn implies that a linear search will
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* be no more expensive than the cost of simply printing a string or two.
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*
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* Trying to continue with binary search at this point would be
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* more trouble than it's worth.
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*/
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#define SKIP_PAST_NEWLINE(p, back) \
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while (p < back && *p++ != '\n');
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char *
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binary_search(string, front, back)
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char *string, *front, *back;
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{
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char *p;
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p = front + (back - front) / 2;
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SKIP_PAST_NEWLINE(p, back);
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/*
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* If the file changes underneath us, make sure we don't
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* infinitely loop.
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*/
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while (p < back && back > front) {
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if (compare(string, p, back) == GREATER)
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front = p;
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else
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back = p;
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p = front + (back - front) / 2;
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SKIP_PAST_NEWLINE(p, back);
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}
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return (front);
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}
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/*
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* Find the first line that starts with string, linearly searching from front
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* to back.
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*
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* Return NULL for no such line.
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*
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* This routine assumes:
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*
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* o front points at the first character in a line.
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* o front is before or at the first line to be printed.
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*/
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char *
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linear_search(string, front, back)
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char *string, *front, *back;
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{
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while (front < back) {
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switch (compare(string, front, back)) {
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case EQUAL: /* Found it. */
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return (front);
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break;
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case LESS: /* No such string. */
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return (NULL);
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break;
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case GREATER: /* Keep going. */
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break;
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}
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SKIP_PAST_NEWLINE(front, back);
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}
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return (NULL);
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}
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/*
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* Print as many lines as match string, starting at front.
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*/
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void
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print_from(string, front, back)
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char *string, *front, *back;
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{
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for (; front < back && compare(string, front, back) == EQUAL; ++front) {
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for (; front < back && *front != '\n'; ++front)
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if (putchar(*front) == EOF)
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err(2, "stdout");
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if (putchar('\n') == EOF)
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err(2, "stdout");
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}
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}
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/*
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* Return LESS, GREATER, or EQUAL depending on how the string1 compares with
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* string2 (s1 ??? s2).
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*
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* o Matches up to len(s1) are EQUAL.
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* o Matches up to len(s2) are GREATER.
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*
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* Compare understands about the -f and -d flags, and treats comparisons
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* appropriately.
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*
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* The string "s1" is null terminated. The string s2 is '\n' terminated (or
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* "back" terminated).
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*/
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int
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compare(s1, s2, back)
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char *s1, *s2, *back;
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{
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int ch;
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for (; *s1 && s2 < back && *s2 != '\n'; ++s1, ++s2) {
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ch = *s2;
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if (fflag)
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ch = FOLD(ch);
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if (dflag)
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ch = DICT(ch);
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if (ch == NO_COMPARE) {
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++s2; /* Ignore character in comparison. */
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continue;
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}
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if (*s1 != ch)
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return (*s1 < ch ? LESS : GREATER);
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}
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return (*s1 ? GREATER : EQUAL);
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}
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void
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usage()
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{
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(void)fprintf(stderr, "usage: look [-df] [-t char] string [file]\n");
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exit(2);
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}
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