Annotation of src/usr.bin/less/position.c, Revision 1.3
1.3 ! niklas 1: /* $OpenBSD$ */
! 2:
1.1 etheisen 3: /*
4: * Copyright (c) 1984,1985,1989,1994,1995 Mark Nudelman
5: * All rights reserved.
6: *
7: * Redistribution and use in source and binary forms, with or without
8: * modification, are permitted provided that the following conditions
9: * are met:
10: * 1. Redistributions of source code must retain the above copyright
11: * notice, this list of conditions and the following disclaimer.
12: * 2. Redistributions in binary form must reproduce the above copyright
13: * notice in the documentation and/or other materials provided with
14: * the distribution.
15: *
16: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY
17: * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19: * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE
20: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21: * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
22: * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
23: * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24: * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
25: * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
26: * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27: */
28:
29:
30: /*
31: * Routines dealing with the "position" table.
32: * This is a table which tells the position (in the input file) of the
33: * first char on each currently displayed line.
34: *
35: * {{ The position table is scrolled by moving all the entries.
36: * Would be better to have a circular table
37: * and just change a couple of pointers. }}
38: */
39:
40: #include "less.h"
41: #include "position.h"
42:
43: static POSITION *table = NULL; /* The position table */
44: static int table_size;
45:
46: extern int sc_width, sc_height;
47:
48: /*
49: * Return the starting file position of a line displayed on the screen.
50: * The line may be specified as a line number relative to the top
51: * of the screen, but is usually one of these special cases:
52: * the top (first) line on the screen
53: * the second line on the screen
54: * the bottom line on the screen
55: * the line after the bottom line on the screen
56: */
57: public POSITION
58: position(where)
59: int where;
60: {
1.2 millert 61: if (where >= table_size)
62: where = BOTTOM;
63:
1.1 etheisen 64: switch (where)
65: {
66: case BOTTOM:
67: where = sc_height - 2;
68: break;
69: case BOTTOM_PLUS_ONE:
70: where = sc_height - 1;
71: break;
72: case MIDDLE:
73: where = (sc_height - 1) / 2;
74: }
75: return (table[where]);
76: }
77:
78: /*
79: * Add a new file position to the bottom of the position table.
80: */
81: public void
82: add_forw_pos(pos)
83: POSITION pos;
84: {
85: register int i;
86:
87: /*
88: * Scroll the position table up.
89: */
90: for (i = 1; i < sc_height; i++)
91: table[i-1] = table[i];
92: table[sc_height - 1] = pos;
93: }
94:
95: /*
96: * Add a new file position to the top of the position table.
97: */
98: public void
99: add_back_pos(pos)
100: POSITION pos;
101: {
102: register int i;
103:
104: /*
105: * Scroll the position table down.
106: */
107: for (i = sc_height - 1; i > 0; i--)
108: table[i] = table[i-1];
109: table[0] = pos;
110: }
111:
112: /*
113: * Initialize the position table, done whenever we clear the screen.
114: */
115: public void
116: pos_clear()
117: {
118: register int i;
119:
120: for (i = 0; i < sc_height; i++)
121: table[i] = NULL_POSITION;
122: }
123:
124: /*
125: * Allocate or reallocate the position table.
126: */
127: public void
128: pos_init()
129: {
130: struct scrpos scrpos;
131:
132: if (sc_height <= table_size)
133: return;
134: /*
135: * If we already have a table, remember the first line in it
136: * before we free it, so we can copy that line to the new table.
137: */
138: if (table != NULL)
139: {
140: get_scrpos(&scrpos);
141: free((char*)table);
142: } else
143: scrpos.pos = NULL_POSITION;
144: table = (POSITION *) ecalloc(sc_height, sizeof(POSITION));
145: table_size = sc_height;
146: pos_clear();
147: if (scrpos.pos != NULL_POSITION)
148: table[scrpos.ln-1] = scrpos.pos;
149: }
150:
151: /*
152: * See if the byte at a specified position is currently on the screen.
153: * Check the position table to see if the position falls within its range.
154: * Return the position table entry if found, -1 if not.
155: */
156: public int
157: onscreen(pos)
158: POSITION pos;
159: {
160: register int i;
161:
162: if (pos < table[0])
163: return (-1);
164: for (i = 1; i < sc_height; i++)
165: if (pos < table[i])
166: return (i-1);
167: return (-1);
168: }
169:
170: /*
171: * See if the entire screen is empty.
172: */
173: public int
174: empty_screen()
175: {
176: return (empty_lines(0, sc_height-1));
177: }
178:
179: public int
180: empty_lines(s, e)
181: int s;
182: int e;
183: {
184: register int i;
185:
186: for (i = s; i <= e; i++)
187: if (table[i] != NULL_POSITION)
188: return (0);
189: return (1);
190: }
191:
192: /*
193: * Get the current screen position.
194: * The screen position consists of both a file position and
195: * a screen line number where the file position is placed on the screen.
196: * Normally the screen line number is 0, but if we are positioned
197: * such that the top few lines are empty, we may have to set
198: * the screen line to a number > 0.
199: */
200: public void
201: get_scrpos(scrpos)
202: struct scrpos *scrpos;
203: {
204: register int i;
205:
206: /*
207: * Find the first line on the screen which has something on it,
208: * and return the screen line number and the file position.
209: */
210: for (i = 0; i < sc_height; i++)
211: if (table[i] != NULL_POSITION)
212: {
213: scrpos->ln = i+1;
214: scrpos->pos = table[i];
215: return;
216: }
217: /*
218: * The screen is empty.
219: */
220: scrpos->pos = NULL_POSITION;
221: }
222:
223: /*
224: * Adjust a screen line number to be a simple positive integer
225: * in the range { 0 .. sc_height-2 }.
226: * (The bottom line, sc_height-1, is reserved for prompts, etc.)
227: * The given "sline" may be in the range { 1 .. sc_height-1 }
228: * to refer to lines relative to the top of the screen (starting from 1),
229: * or it may be in { -1 .. -(sc_height-1) } to refer to lines
230: * relative to the bottom of the screen.
231: */
232: public int
233: adjsline(sline)
234: int sline;
235: {
236: /*
237: * Negative screen line number means
238: * relative to the bottom of the screen.
239: */
240: if (sline < 0)
241: sline += sc_height;
242: /*
243: * Can't be less than 1 or greater than sc_height-1.
244: */
245: if (sline <= 0)
246: sline = 1;
247: if (sline >= sc_height)
248: sline = sc_height - 1;
249: /*
250: * Return zero-based line number, not one-based.
251: */
252: return (sline-1);
253: }
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