1 /* $NetBSD: position.c,v 1.3 2011/07/03 20:14:13 tron Exp $ */ 2 3 /* 4 * Copyright (C) 1984-2011 Mark Nudelman 5 * 6 * You may distribute under the terms of either the GNU General Public 7 * License or the Less License, as specified in the README file. 8 * 9 * For more information about less, or for information on how to 10 * contact the author, see the README file. 11 */ 12 13 14 /* 15 * Routines dealing with the "position" table. 16 * This is a table which tells the position (in the input file) of the 17 * first char on each currently displayed line. 18 * 19 * {{ The position table is scrolled by moving all the entries. 20 * Would be better to have a circular table 21 * and just change a couple of pointers. }} 22 */ 23 24 #include "less.h" 25 #include "position.h" 26 27 static POSITION *table = NULL; /* The position table */ 28 static int table_size; 29 30 extern int sc_width, sc_height; 31 32 /* 33 * Return the starting file position of a line displayed on the screen. 34 * The line may be specified as a line number relative to the top 35 * of the screen, but is usually one of these special cases: 36 * the top (first) line on the screen 37 * the second line on the screen 38 * the bottom line on the screen 39 * the line after the bottom line on the screen 40 */ 41 public POSITION 42 position(where) 43 int where; 44 { 45 switch (where) 46 { 47 case BOTTOM: 48 where = sc_height - 2; 49 break; 50 case BOTTOM_PLUS_ONE: 51 where = sc_height - 1; 52 break; 53 case MIDDLE: 54 where = (sc_height - 1) / 2; 55 } 56 return (table[where]); 57 } 58 59 /* 60 * Add a new file position to the bottom of the position table. 61 */ 62 public void 63 add_forw_pos(pos) 64 POSITION pos; 65 { 66 register int i; 67 68 /* 69 * Scroll the position table up. 70 */ 71 for (i = 1; i < sc_height; i++) 72 table[i-1] = table[i]; 73 table[sc_height - 1] = pos; 74 } 75 76 /* 77 * Add a new file position to the top of the position table. 78 */ 79 public void 80 add_back_pos(pos) 81 POSITION pos; 82 { 83 register int i; 84 85 /* 86 * Scroll the position table down. 87 */ 88 for (i = sc_height - 1; i > 0; i--) 89 table[i] = table[i-1]; 90 table[0] = pos; 91 } 92 93 /* 94 * Initialize the position table, done whenever we clear the screen. 95 */ 96 public void 97 pos_clear() 98 { 99 register int i; 100 101 for (i = 0; i < sc_height; i++) 102 table[i] = NULL_POSITION; 103 } 104 105 /* 106 * Allocate or reallocate the position table. 107 */ 108 public void 109 pos_init() 110 { 111 struct scrpos scrpos; 112 scrpos.pos = scrpos.ln = 0; /* XXX: GCC */ 113 114 if (sc_height <= table_size) 115 return; 116 /* 117 * If we already have a table, remember the first line in it 118 * before we free it, so we can copy that line to the new table. 119 */ 120 if (table != NULL) 121 { 122 get_scrpos(&scrpos); 123 free((char*)table); 124 } else 125 scrpos.pos = NULL_POSITION; 126 table = (POSITION *) ecalloc(sc_height, sizeof(POSITION)); 127 table_size = sc_height; 128 pos_clear(); 129 if (scrpos.pos != NULL_POSITION) 130 table[scrpos.ln-1] = scrpos.pos; 131 } 132 133 /* 134 * See if the byte at a specified position is currently on the screen. 135 * Check the position table to see if the position falls within its range. 136 * Return the position table entry if found, -1 if not. 137 */ 138 public int 139 onscreen(pos) 140 POSITION pos; 141 { 142 register int i; 143 144 if (pos < table[0]) 145 return (-1); 146 for (i = 1; i < sc_height; i++) 147 if (pos < table[i]) 148 return (i-1); 149 return (-1); 150 } 151 152 /* 153 * See if the entire screen is empty. 154 */ 155 public int 156 empty_screen() 157 { 158 return (empty_lines(0, sc_height-1)); 159 } 160 161 public int 162 empty_lines(s, e) 163 int s; 164 int e; 165 { 166 register int i; 167 168 for (i = s; i <= e; i++) 169 if (table[i] != NULL_POSITION) 170 return (0); 171 return (1); 172 } 173 174 /* 175 * Get the current screen position. 176 * The screen position consists of both a file position and 177 * a screen line number where the file position is placed on the screen. 178 * Normally the screen line number is 0, but if we are positioned 179 * such that the top few lines are empty, we may have to set 180 * the screen line to a number > 0. 181 */ 182 public void 183 get_scrpos(scrpos) 184 struct scrpos *scrpos; 185 { 186 register int i; 187 188 /* 189 * Find the first line on the screen which has something on it, 190 * and return the screen line number and the file position. 191 */ 192 for (i = 0; i < sc_height; i++) 193 if (table[i] != NULL_POSITION) 194 { 195 scrpos->ln = i+1; 196 scrpos->pos = table[i]; 197 return; 198 } 199 /* 200 * The screen is empty. 201 */ 202 scrpos->pos = NULL_POSITION; 203 } 204 205 /* 206 * Adjust a screen line number to be a simple positive integer 207 * in the range { 0 .. sc_height-2 }. 208 * (The bottom line, sc_height-1, is reserved for prompts, etc.) 209 * The given "sline" may be in the range { 1 .. sc_height-1 } 210 * to refer to lines relative to the top of the screen (starting from 1), 211 * or it may be in { -1 .. -(sc_height-1) } to refer to lines 212 * relative to the bottom of the screen. 213 */ 214 public int 215 adjsline(sline) 216 int sline; 217 { 218 /* 219 * Negative screen line number means 220 * relative to the bottom of the screen. 221 */ 222 if (sline < 0) 223 sline += sc_height; 224 /* 225 * Can't be less than 1 or greater than sc_height-1. 226 */ 227 if (sline <= 0) 228 sline = 1; 229 if (sline >= sc_height) 230 sline = sc_height - 1; 231 /* 232 * Return zero-based line number, not one-based. 233 */ 234 return (sline-1); 235 } 236