171 lines
4.7 KiB
C
171 lines
4.7 KiB
C
/*
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* Copyright (c) 1988 Mark Nudleman
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* Copyright (c) 1988, 1993
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* The Regents of the University of California. All rights reserved.
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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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static char sccsid[] = "@(#)position.c 8.1 (Berkeley) 6/6/93";
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#endif /* not lint */
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/*
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* Routines dealing with the "position" table.
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* This is a table which tells the position (in the input file) of the
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* first char on each currently displayed line.
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*
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* {{ The position table is scrolled by moving all the entries.
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* Would be better to have a circular table
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* and just change a couple of pointers. }}
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*/
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#include <sys/types.h>
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#include <less.h>
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static off_t *table; /* The position table */
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static int tablesize;
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extern int sc_height;
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/*
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* Return the starting file position of a line displayed on the screen.
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* The line may be specified as a line number relative to the top
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* of the screen, but is usually one of these special cases:
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* the top (first) line on the screen
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* the second line on the screen
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* the bottom line on the screen
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* the line after the bottom line on the screen
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*/
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off_t
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position(where)
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int where;
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{
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switch (where)
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{
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case BOTTOM:
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where = sc_height - 2;
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break;
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case BOTTOM_PLUS_ONE:
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where = sc_height - 1;
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break;
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case MIDDLE:
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where = sc_height / 2;
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}
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return (table[where]);
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}
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/*
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* Add a new file position to the bottom of the position table.
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*/
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add_forw_pos(pos)
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off_t pos;
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{
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register int i;
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/*
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* Scroll the position table up.
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*/
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for (i = 1; i < sc_height; i++)
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table[i-1] = table[i];
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table[sc_height - 1] = pos;
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}
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/*
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* Add a new file position to the top of the position table.
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*/
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add_back_pos(pos)
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off_t pos;
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{
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register int i;
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/*
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* Scroll the position table down.
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*/
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for (i = sc_height - 1; i > 0; i--)
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table[i] = table[i-1];
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table[0] = pos;
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}
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/*
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* Remove any NULL_POSITION markers from the top of the table, moving
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* the bottom part up, if necessary.
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*/
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copytable()
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{
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register int a, b;
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for (a = 0; a < sc_height && table[a] == NULL_POSITION; a++);
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for (b = 0; a < sc_height; a++, b++) {
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table[b] = table[a];
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table[a] = NULL_POSITION;
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}
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}
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/*
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* Initialize the position table, done whenever we clear the screen.
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*/
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pos_clear()
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{
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register int i;
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extern char *malloc(), *realloc();
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if (table == 0) {
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tablesize = sc_height > 25 ? sc_height : 25;
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table = (off_t *)malloc(tablesize * sizeof *table);
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} else if (sc_height >= tablesize) {
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tablesize = sc_height;
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table = (off_t *)realloc(table, tablesize * sizeof *table);
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}
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for (i = 0; i < sc_height; i++)
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table[i] = NULL_POSITION;
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}
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/*
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* See if the byte at a specified position is currently on the screen.
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* Check the position table to see if the position falls within its range.
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* Return the position table entry if found, -1 if not.
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*
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* This function doesn't really work when horizontal scrolling is enabled.
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* I suspect it may not work in a few other cases, too.
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*/
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onscreen(pos)
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off_t pos;
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{
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register int i;
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if (pos < table[0])
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return (-1);
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for (i = 1; i < sc_height; i++)
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if (pos < table[i])
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return (i-1);
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return (-1);
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}
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