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      1 /*	$NetBSD: position.c,v 1.5 2003/10/13 14:34:25 agc Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1988 Mark Nudelman
      5  * Copyright (c) 1988, 1993
      6  *	The Regents of the University of California.  All rights reserved.
      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. Neither the name of the University nor the names of its contributors
     17  *    may be used to endorse or promote products derived from this software
     18  *    without specific prior written permission.
     19  *
     20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     30  * SUCH DAMAGE.
     31  */
     32 
     33 #include <sys/cdefs.h>
     34 #ifndef lint
     35 #if 0
     36 static char sccsid[] = "@(#)position.c	8.1 (Berkeley) 6/6/93";
     37 #else
     38 __RCSID("$NetBSD: position.c,v 1.5 2003/10/13 14:34:25 agc Exp $");
     39 #endif
     40 #endif /* not lint */
     41 
     42 /*
     43  * Routines dealing with the "position" table.
     44  * This is a table which tells the position (in the input file) of the
     45  * first char on each currently displayed line.
     46  *
     47  * {{ The position table is scrolled by moving all the entries.
     48  *    Would be better to have a circular table
     49  *    and just change a couple of pointers. }}
     50  */
     51 
     52 #include <sys/types.h>
     53 #include <stdlib.h>
     54 
     55 #include "less.h"
     56 #include "extern.h"
     57 
     58 static off_t *table;		/* The position table */
     59 static int tablesize;
     60 
     61 /*
     62  * Return the starting file position of a line displayed on the screen.
     63  * The line may be specified as a line number relative to the top
     64  * of the screen, but is usually one of these special cases:
     65  *	the top (first) line on the screen
     66  *	the second line on the screen
     67  *	the bottom line on the screen
     68  *	the line after the bottom line on the screen
     69  */
     70 off_t
     71 position(where)
     72 	int where;
     73 {
     74 	switch (where)
     75 	{
     76 	case BOTTOM:
     77 		where = sc_height - 2;
     78 		break;
     79 	case BOTTOM_PLUS_ONE:
     80 		where = sc_height - 1;
     81 		break;
     82 	case MIDDLE:
     83 		where = sc_height / 2;
     84 	}
     85 	return (table[where]);
     86 }
     87 
     88 /*
     89  * Add a new file position to the bottom of the position table.
     90  */
     91 void
     92 add_forw_pos(pos)
     93 	off_t pos;
     94 {
     95 	int i;
     96 
     97 	/*
     98 	 * Scroll the position table up.
     99 	 */
    100 	for (i = 1;  i < sc_height;  i++)
    101 		table[i-1] = table[i];
    102 	table[sc_height - 1] = pos;
    103 }
    104 
    105 /*
    106  * Add a new file position to the top of the position table.
    107  */
    108 void
    109 add_back_pos(pos)
    110 	off_t pos;
    111 {
    112 	int i;
    113 
    114 	/*
    115 	 * Scroll the position table down.
    116 	 */
    117 	for (i = sc_height - 1;  i > 0;  i--)
    118 		table[i] = table[i-1];
    119 	table[0] = pos;
    120 }
    121 
    122 void
    123 copytable()
    124 {
    125 	int a, b;
    126 
    127 	for (a = 0; a < sc_height && table[a] == NULL_POSITION; a++);
    128 	for (b = 0; a < sc_height; a++, b++) {
    129 		table[b] = table[a];
    130 		table[a] = NULL_POSITION;
    131 	}
    132 }
    133 
    134 /*
    135  * Initialize the position table, done whenever we clear the screen.
    136  */
    137 void
    138 pos_clear()
    139 {
    140 	int i;
    141 
    142 	if (table == 0) {
    143 		tablesize = sc_height > 25 ? sc_height : 25;
    144 		table = (off_t *)malloc(tablesize * sizeof *table);
    145 	} else if (sc_height >= tablesize) {
    146 		tablesize = sc_height;
    147 		table = (off_t *)realloc(table, tablesize * sizeof *table);
    148 	}
    149 
    150 	for (i = 0;  i < sc_height;  i++)
    151 		table[i] = NULL_POSITION;
    152 }
    153 
    154 /*
    155  * See if the byte at a specified position is currently on the screen.
    156  * Check the position table to see if the position falls within its range.
    157  * Return the position table entry if found, -1 if not.
    158  */
    159 int
    160 onscreen(pos)
    161 	off_t pos;
    162 {
    163 	int i;
    164 
    165 	if (pos < table[0])
    166 		return (-1);
    167 	for (i = 1;  i < sc_height;  i++)
    168 		if (pos < table[i])
    169 			return (i-1);
    170 	return (-1);
    171 }
    172