167 lines
5.5 KiB
C
167 lines
5.5 KiB
C
/*
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* Copyright (c) 1989 The Regents of the University of California.
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* 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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* James A. Woods.
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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. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. 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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#ifndef lint
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char copyright[] =
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"@(#) Copyright (c) 1989 The Regents of the University of California.\n\
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All rights reserved.\n";
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#endif /* not lint */
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#ifndef lint
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/*static char sccsid[] = "from: @(#)locate.code.c 4.8 (Berkeley) 6/1/90";*/
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static char rcsid[] = "$Id: locate.code.c,v 1.2 1993/08/01 18:13:52 mycroft Exp $";
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#endif /* not lint */
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/*
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* PURPOSE: sorted list compressor (works with a modified 'find'
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* to encode/decode a filename database)
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*
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* USAGE: bigram < list > bigrams
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* process bigrams (see updatedb) > common_bigrams
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* code common_bigrams < list > squozen_list
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*
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* METHOD: Uses 'front compression' (see ";login:", Volume 8, Number 1
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* February/March 1983, p. 8 ). Output format is, per line, an
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* offset differential count byte followed by a partially bigram-
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* encoded ascii residue. A bigram is a two-character sequence,
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* the first 128 most common of which are encoded in one byte.
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*
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* EXAMPLE: For simple front compression with no bigram encoding,
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* if the input is... then the output is...
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*
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* /usr/src 0 /usr/src
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* /usr/src/cmd/aardvark.c 8 /cmd/aardvark.c
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* /usr/src/cmd/armadillo.c 14 armadillo.c
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* /usr/tmp/zoo 5 tmp/zoo
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*
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* The codes are:
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*
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* 0-28 likeliest differential counts + offset to make nonnegative
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* 30 switch code for out-of-range count to follow in next word
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* 128-255 bigram codes (128 most common, as determined by 'updatedb')
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* 32-127 single character (printable) ascii residue (ie, literal)
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*
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* SEE ALSO: updatedb.csh, bigram.c, find.c
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*
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* AUTHOR: James A. Woods, Informatics General Corp.,
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* NASA Ames Research Center, 10/82
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*/
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#include <sys/param.h>
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#include <stdio.h>
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#include "locate.h"
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#define BGBUFSIZE (NBG * 2) /* size of bigram buffer */
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char buf1[MAXPATHLEN] = " ";
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char buf2[MAXPATHLEN];
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char bigrams[BGBUFSIZE + 1] = { 0 };
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main ( argc, argv )
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int argc; char *argv[];
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{
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register char *cp, *oldpath = buf1, *path = buf2;
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int code, count, diffcount, oldcount = 0;
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FILE *fp;
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if ((fp = fopen(argv[1], "r")) == NULL) {
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printf("Usage: code common_bigrams < list > squozen_list\n");
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exit(1);
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}
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/* first copy bigram array to stdout */
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fgets ( bigrams, BGBUFSIZE + 1, fp );
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fwrite ( bigrams, 1, BGBUFSIZE, stdout );
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fclose( fp );
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while ( fgets ( path, sizeof(buf2), stdin ) != NULL ) {
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/* truncate newline */
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cp = path + strlen(path) - 1;
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if (cp > path && *cp == '\n')
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*cp = '\0';
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/* squelch characters that would botch the decoding */
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for ( cp = path; *cp != NULL; cp++ ) {
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if ( (unsigned char)*cp >= PARITY )
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*cp &= PARITY-1;
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else if ( *cp <= SWITCH )
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*cp = '?';
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}
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/* skip longest common prefix */
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for ( cp = path; *cp == *oldpath; cp++, oldpath++ )
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if ( *oldpath == NULL )
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break;
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count = cp - path;
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diffcount = count - oldcount + OFFSET;
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oldcount = count;
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if ( diffcount < 0 || diffcount > 2*OFFSET ) {
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putc ( SWITCH, stdout );
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putw ( diffcount, stdout );
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}
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else
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putc ( diffcount, stdout );
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while ( *cp != NULL ) {
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if ( *(cp + 1) == NULL ) {
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putchar ( *cp );
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break;
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}
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if ( (code = bgindex ( cp )) < 0 ) {
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putchar ( *cp++ );
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putchar ( *cp++ );
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}
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else { /* found, so mark byte with parity bit */
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putchar ( (code / 2) | PARITY );
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cp += 2;
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}
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}
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if ( path == buf1 ) /* swap pointers */
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path = buf2, oldpath = buf1;
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else
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path = buf1, oldpath = buf2;
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}
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}
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bgindex ( bg ) /* return location of bg in bigrams or -1 */
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char *bg;
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{
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register char *p;
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register char bg0 = bg[0], bg1 = bg[1];
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for ( p = bigrams; *p != NULL; p++ )
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if ( *p++ == bg0 && *p == bg1 )
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break;
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return ( *p == NULL ? -1 : --p - bigrams );
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}
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