distrib/utils/more/position.c

   1 /*      $NetBSD: position.c,v 1.4 2003/08/07 09:28:01 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 1.4 2003/08/07 09:28:01 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 }