freebsd-dev/usr.bin/more/position.c

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1994-05-27 12:33:43 +00:00
/*
* Copyright (c) 1988 Mark Nudleman
* Copyright (c) 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef lint
static char sccsid[] = "@(#)position.c 8.1 (Berkeley) 6/6/93";
#endif /* not lint */
/*
* Routines dealing with the "position" table.
* This is a table which tells the position (in the input file) of the
* first char on each currently displayed line.
*
* {{ The position table is scrolled by moving all the entries.
1995-05-30 06:41:30 +00:00
* Would be better to have a circular table
1994-05-27 12:33:43 +00:00
* and just change a couple of pointers. }}
*/
#include <sys/types.h>
#include <less.h>
static off_t *table; /* The position table */
static int tablesize;
extern int sc_height;
/*
* Return the starting file position of a line displayed on the screen.
* The line may be specified as a line number relative to the top
* of the screen, but is usually one of these special cases:
* the top (first) line on the screen
* the second line on the screen
* the bottom line on the screen
* the line after the bottom line on the screen
*/
off_t
position(where)
int where;
{
switch (where)
{
case BOTTOM:
where = sc_height - 2;
break;
case BOTTOM_PLUS_ONE:
where = sc_height - 1;
break;
case MIDDLE:
where = sc_height / 2;
}
return (table[where]);
}
/*
* Add a new file position to the bottom of the position table.
*/
add_forw_pos(pos)
off_t pos;
{
register int i;
/*
* Scroll the position table up.
*/
for (i = 1; i < sc_height; i++)
table[i-1] = table[i];
table[sc_height - 1] = pos;
}
/*
* Add a new file position to the top of the position table.
*/
add_back_pos(pos)
off_t pos;
{
register int i;
/*
* Scroll the position table down.
*/
for (i = sc_height - 1; i > 0; i--)
table[i] = table[i-1];
table[0] = pos;
}
copytable()
{
register int a, b;
for (a = 0; a < sc_height && table[a] == NULL_POSITION; a++);
for (b = 0; a < sc_height; a++, b++) {
table[b] = table[a];
table[a] = NULL_POSITION;
}
}
/*
* Initialize the position table, done whenever we clear the screen.
*/
pos_clear()
{
register int i;
extern char *malloc(), *realloc();
if (table == 0) {
tablesize = sc_height > 25 ? sc_height : 25;
table = (off_t *)malloc(tablesize * sizeof *table);
} else if (sc_height >= tablesize) {
tablesize = sc_height;
table = (off_t *)realloc(table, tablesize * sizeof *table);
}
for (i = 0; i < sc_height; i++)
table[i] = NULL_POSITION;
}
/*
* See if the byte at a specified position is currently on the screen.
* Check the position table to see if the position falls within its range.
* Return the position table entry if found, -1 if not.
*/
onscreen(pos)
off_t pos;
{
register int i;
if (pos < table[0])
return (-1);
for (i = 1; i < sc_height; i++)
if (pos < table[i])
return (i-1);
return (-1);
}