1 /* 2 * Copyright (C) 1984-2012 Mark Nudelman 3 * Modified for use with illumos by Garrett D'Amore. 4 * Copyright 2014 Garrett D'Amore <garrett@damore.org> 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, see the README file. 10 */ 11 12 /* 13 * Routines dealing with the "position" table. 14 * This is a table which tells the position (in the input file) of the 15 * first char on each currently displayed line. 16 * 17 * {{ The position table is scrolled by moving all the entries. 18 * Would be better to have a circular table 19 * and just change a couple of pointers. }} 20 */ 21 22 #include "less.h" 23 #include "position.h" 24 25 static off_t *table = NULL; /* The position table */ 26 static int table_size; 27 28 extern int sc_width, sc_height; 29 30 /* 31 * Return the starting file position of a line displayed on the screen. 32 * The line may be specified as a line number relative to the top 33 * of the screen, but is usually one of these special cases: 34 * the top (first) line on the screen 35 * the second line on the screen 36 * the bottom line on the screen 37 * the line after the bottom line on the screen 38 */ 39 off_t 40 position(int where) 41 { 42 switch (where) { 43 case BOTTOM: 44 where = sc_height - 2; 45 break; 46 case BOTTOM_PLUS_ONE: 47 where = sc_height - 1; 48 break; 49 case MIDDLE: 50 where = (sc_height - 1) / 2; 51 } 52 return (table[where]); 53 } 54 55 /* 56 * Add a new file position to the bottom of the position table. 57 */ 58 void 59 add_forw_pos(off_t pos) 60 { 61 int i; 62 63 /* 64 * Scroll the position table up. 65 */ 66 for (i = 1; i < sc_height; i++) 67 table[i-1] = table[i]; 68 table[sc_height - 1] = pos; 69 } 70 71 /* 72 * Add a new file position to the top of the position table. 73 */ 74 void 75 add_back_pos(off_t pos) 76 { 77 int i; 78 79 /* 80 * Scroll the position table down. 81 */ 82 for (i = sc_height - 1; i > 0; i--) 83 table[i] = table[i-1]; 84 table[0] = pos; 85 } 86 87 /* 88 * Initialize the position table, done whenever we clear the screen. 89 */ 90 void 91 pos_clear(void) 92 { 93 int i; 94 95 for (i = 0; i < sc_height; i++) 96 table[i] = -1; 97 } 98 99 /* 100 * Allocate or reallocate the position table. 101 */ 102 void 103 pos_init(void) 104 { 105 struct scrpos scrpos; 106 107 if (sc_height <= table_size) 108 return; 109 /* 110 * If we already have a table, remember the first line in it 111 * before we free it, so we can copy that line to the new table. 112 */ 113 if (table != NULL) { 114 get_scrpos(&scrpos); 115 free(table); 116 } else { 117 scrpos.pos = -1; 118 } 119 table = ecalloc(sc_height, sizeof (off_t)); 120 table_size = sc_height; 121 pos_clear(); 122 if (scrpos.pos != -1) 123 table[scrpos.ln-1] = scrpos.pos; 124 } 125 126 /* 127 * See if the byte at a specified position is currently on the screen. 128 * Check the position table to see if the position falls within its range. 129 * Return the position table entry if found, -1 if not. 130 */ 131 int 132 onscreen(off_t pos) 133 { 134 int i; 135 136 if (pos < table[0]) 137 return (-1); 138 for (i = 1; i < sc_height; i++) 139 if (pos < table[i]) 140 return (i-1); 141 return (-1); 142 } 143 144 /* 145 * See if the entire screen is empty. 146 */ 147 int 148 empty_screen(void) 149 { 150 return (empty_lines(0, sc_height-1)); 151 } 152 153 int 154 empty_lines(int s, int e) 155 { 156 int i; 157 158 for (i = s; i <= e; i++) 159 if (table[i] != -1 && table[i] != 0) 160 return (0); 161 return (1); 162 } 163 164 /* 165 * Get the current screen position. 166 * The screen position consists of both a file position and 167 * a screen line number where the file position is placed on the screen. 168 * Normally the screen line number is 0, but if we are positioned 169 * such that the top few lines are empty, we may have to set 170 * the screen line to a number > 0. 171 */ 172 void 173 get_scrpos(struct scrpos *scrpos) 174 { 175 int i; 176 177 /* 178 * Find the first line on the screen which has something on it, 179 * and return the screen line number and the file position. 180 */ 181 for (i = 0; i < sc_height; i++) 182 if (table[i] != -1) { 183 scrpos->ln = i+1; 184 scrpos->pos = table[i]; 185 return; 186 } 187 /* 188 * The screen is empty. 189 */ 190 scrpos->pos = -1; 191 } 192 193 /* 194 * Adjust a screen line number to be a simple positive integer 195 * in the range { 0 .. sc_height-2 }. 196 * (The bottom line, sc_height-1, is reserved for prompts, etc.) 197 * The given "sline" may be in the range { 1 .. sc_height-1 } 198 * to refer to lines relative to the top of the screen (starting from 1), 199 * or it may be in { -1 .. -(sc_height-1) } to refer to lines 200 * relative to the bottom of the screen. 201 */ 202 int 203 adjsline(int sline) 204 { 205 /* 206 * Negative screen line number means 207 * relative to the bottom of the screen. 208 */ 209 if (sline < 0) 210 sline += sc_height; 211 /* 212 * Can't be less than 1 or greater than sc_height-1. 213 */ 214 if (sline <= 0) 215 sline = 1; 216 if (sline >= sc_height) 217 sline = sc_height - 1; 218 /* 219 * Return zero-based line number, not one-based. 220 */ 221 return (sline-1); 222 } 223