1 /* $NetBSD */ 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; 112 113 if (sc_height <= table_size) 114 return; 115 /* 116 * If we already have a table, remember the first line in it 117 * before we free it, so we can copy that line to the new table. 118 */ 119 if (table != NULL) 120 { 121 get_scrpos(&scrpos); 122 free((char*)table); 123 } else 124 scrpos.pos = NULL_POSITION; 125 table = (POSITION *) ecalloc(sc_height, sizeof(POSITION)); 126 table_size = sc_height; 127 pos_clear(); 128 if (scrpos.pos != NULL_POSITION) 129 table[scrpos.ln-1] = scrpos.pos; 130 } 131 132 /* 133 * See if the byte at a specified position is currently on the screen. 134 * Check the position table to see if the position falls within its range. 135 * Return the position table entry if found, -1 if not. 136 */ 137 public int 138 onscreen(pos) 139 POSITION pos; 140 { 141 register int i; 142 143 if (pos < table[0]) 144 return (-1); 145 for (i = 1; i < sc_height; i++) 146 if (pos < table[i]) 147 return (i-1); 148 return (-1); 149 } 150 151 /* 152 * See if the entire screen is empty. 153 */ 154 public int 155 empty_screen() 156 { 157 return (empty_lines(0, sc_height-1)); 158 } 159 160 public int 161 empty_lines(s, e) 162 int s; 163 int e; 164 { 165 register int i; 166 167 for (i = s; i <= e; i++) 168 if (table[i] != NULL_POSITION) 169 return (0); 170 return (1); 171 } 172 173 /* 174 * Get the current screen position. 175 * The screen position consists of both a file position and 176 * a screen line number where the file position is placed on the screen. 177 * Normally the screen line number is 0, but if we are positioned 178 * such that the top few lines are empty, we may have to set 179 * the screen line to a number > 0. 180 */ 181 public void 182 get_scrpos(scrpos) 183 struct scrpos *scrpos; 184 { 185 register int i; 186 187 /* 188 * Find the first line on the screen which has something on it, 189 * and return the screen line number and the file position. 190 */ 191 for (i = 0; i < sc_height; i++) 192 if (table[i] != NULL_POSITION) 193 { 194 scrpos->ln = i+1; 195 scrpos->pos = table[i]; 196 return; 197 } 198 /* 199 * The screen is empty. 200 */ 201 scrpos->pos = NULL_POSITION; 202 } 203 204 /* 205 * Adjust a screen line number to be a simple positive integer 206 * in the range { 0 .. sc_height-2 }. 207 * (The bottom line, sc_height-1, is reserved for prompts, etc.) 208 * The given "sline" may be in the range { 1 .. sc_height-1 } 209 * to refer to lines relative to the top of the screen (starting from 1), 210 * or it may be in { -1 .. -(sc_height-1) } to refer to lines 211 * relative to the bottom of the screen. 212 */ 213 public int 214 adjsline(sline) 215 int sline; 216 { 217 /* 218 * Negative screen line number means 219 * relative to the bottom of the screen. 220 */ 221 if (sline < 0) 222 sline += sc_height; 223 /* 224 * Can't be less than 1 or greater than sc_height-1. 225 */ 226 if (sline <= 0) 227 sline = 1; 228 if (sline >= sc_height) 229 sline = sc_height - 1; 230 /* 231 * Return zero-based line number, not one-based. 232 */ 233 return (sline-1); 234 } 235