jump.c revision 195941 
1/*
2 * Copyright (C) 1984-2009  Mark Nudelman
3 *
4 * You may distribute under the terms of either the GNU General Public
5 * License or the Less License, as specified in the README file.
6 *
7 * For more information about less, or for information on how to
8 * contact the author, see the README file.
9 */
10
11
12/*
13 * Routines which jump to a new location in the file.
14 */
15
16#include "less.h"
17#include "position.h"
18
19extern int jump_sline;
20extern int squished;
21extern int screen_trashed;
22extern int sc_width, sc_height;
23extern int show_attn;
24extern int top_scroll;
25
26/*
27 * Jump to the end of the file.
28 */
29	public void
30jump_forw()
31{
32	POSITION pos;
33	POSITION end_pos;
34
35	if (ch_end_seek())
36	{
37		error("Cannot seek to end of file", NULL_PARG);
38		return;
39	}
40	/*
41	 * Note; lastmark will be called later by jump_loc, but it fails
42	 * because the position table has been cleared by pos_clear below.
43	 * So call it here before calling pos_clear.
44	 */
45	lastmark();
46	/*
47	 * Position the last line in the file at the last screen line.
48	 * Go back one line from the end of the file
49	 * to get to the beginning of the last line.
50	 */
51	pos_clear();
52	end_pos = ch_tell();
53	pos = back_line(end_pos);
54	if (pos == NULL_POSITION)
55		jump_loc((POSITION)0, sc_height-1);
56	else
57	{
58		jump_loc(pos, sc_height-1);
59		if (position(sc_height-1) != end_pos)
60			repaint();
61	}
62}
63
64/*
65 * Jump to line n in the file.
66 */
67	public void
68jump_back(linenum)
69	LINENUM linenum;
70{
71	POSITION pos;
72	PARG parg;
73
74	/*
75	 * Find the position of the specified line.
76	 * If we can seek there, just jump to it.
77	 * If we can't seek, but we're trying to go to line number 1,
78	 * use ch_beg_seek() to get as close as we can.
79	 */
80	pos = find_pos(linenum);
81	if (pos != NULL_POSITION && ch_seek(pos) == 0)
82	{
83		if (show_attn)
84			set_attnpos(pos);
85		jump_loc(pos, jump_sline);
86	} else if (linenum <= 1 && ch_beg_seek() == 0)
87	{
88		jump_loc(ch_tell(), jump_sline);
89		error("Cannot seek to beginning of file", NULL_PARG);
90	} else
91	{
92		parg.p_linenum = linenum;
93		error("Cannot seek to line number %n", &parg);
94	}
95}
96
97/*
98 * Repaint the screen.
99 */
100	public void
101repaint()
102{
103	struct scrpos scrpos;
104	/*
105	 * Start at the line currently at the top of the screen
106	 * and redisplay the screen.
107	 */
108	get_scrpos(&scrpos);
109	pos_clear();
110	jump_loc(scrpos.pos, scrpos.ln);
111}
112
113/*
114 * Jump to a specified percentage into the file.
115 */
116	public void
117jump_percent(percent, fraction)
118	int percent;
119	long fraction;
120{
121	POSITION pos, len;
122
123	/*
124	 * Determine the position in the file
125	 * (the specified percentage of the file's length).
126	 */
127	if ((len = ch_length()) == NULL_POSITION)
128	{
129		ierror("Determining length of file", NULL_PARG);
130		ch_end_seek();
131	}
132	if ((len = ch_length()) == NULL_POSITION)
133	{
134		error("Don't know length of file", NULL_PARG);
135		return;
136	}
137	pos = percent_pos(len, percent, fraction);
138	if (pos >= len)
139		pos = len-1;
140
141	jump_line_loc(pos, jump_sline);
142}
143
144/*
145 * Jump to a specified position in the file.
146 * Like jump_loc, but the position need not be
147 * the first character in a line.
148 */
149	public void
150jump_line_loc(pos, sline)
151	POSITION pos;
152	int sline;
153{
154	int c;
155
156	if (ch_seek(pos) == 0)
157	{
158		/*
159		 * Back up to the beginning of the line.
160		 */
161		while ((c = ch_back_get()) != '\n' && c != EOI)
162			;
163		if (c == '\n')
164			(void) ch_forw_get();
165		pos = ch_tell();
166	}
167	if (show_attn)
168		set_attnpos(pos);
169	jump_loc(pos, sline);
170}
171
172/*
173 * Jump to a specified position in the file.
174 * The position must be the first character in a line.
175 * Place the target line on a specified line on the screen.
176 */
177	public void
178jump_loc(pos, sline)
179	POSITION pos;
180	int sline;
181{
182	register int nline;
183	POSITION tpos;
184	POSITION bpos;
185
186	/*
187	 * Normalize sline.
188	 */
189	sline = adjsline(sline);
190
191	if ((nline = onscreen(pos)) >= 0)
192	{
193		/*
194		 * The line is currently displayed.
195		 * Just scroll there.
196		 */
197		nline -= sline;
198		if (nline > 0)
199			forw(nline, position(BOTTOM_PLUS_ONE), 1, 0, 0);
200		else
201			back(-nline, position(TOP), 1, 0);
202#if HILITE_SEARCH
203		if (show_attn)
204			repaint_hilite(1);
205#endif
206		return;
207	}
208
209	/*
210	 * Line is not on screen.
211	 * Seek to the desired location.
212	 */
213	if (ch_seek(pos))
214	{
215		error("Cannot seek to that file position", NULL_PARG);
216		return;
217	}
218
219	/*
220	 * See if the desired line is before or after
221	 * the currently displayed screen.
222	 */
223	tpos = position(TOP);
224	bpos = position(BOTTOM_PLUS_ONE);
225	if (tpos == NULL_POSITION || pos >= tpos)
226	{
227		/*
228		 * The desired line is after the current screen.
229		 * Move back in the file far enough so that we can
230		 * call forw() and put the desired line at the
231		 * sline-th line on the screen.
232		 */
233		for (nline = 0;  nline < sline;  nline++)
234		{
235			if (bpos != NULL_POSITION && pos <= bpos)
236			{
237				/*
238				 * Surprise!  The desired line is
239				 * close enough to the current screen
240				 * that we can just scroll there after all.
241				 */
242				forw(sc_height-sline+nline-1, bpos, 1, 0, 0);
243#if HILITE_SEARCH
244				if (show_attn)
245					repaint_hilite(1);
246#endif
247				return;
248			}
249			pos = back_line(pos);
250			if (pos == NULL_POSITION)
251			{
252				/*
253				 * Oops.  Ran into the beginning of the file.
254				 * Exit the loop here and rely on forw()
255				 * below to draw the required number of
256				 * blank lines at the top of the screen.
257				 */
258				break;
259			}
260		}
261		lastmark();
262		squished = 0;
263		screen_trashed = 0;
264		forw(sc_height-1, pos, 1, 0, sline-nline);
265	} else
266	{
267		/*
268		 * The desired line is before the current screen.
269		 * Move forward in the file far enough so that we
270		 * can call back() and put the desired line at the
271		 * sline-th line on the screen.
272		 */
273		for (nline = sline;  nline < sc_height - 1;  nline++)
274		{
275			pos = forw_line(pos);
276			if (pos == NULL_POSITION)
277			{
278				/*
279				 * Ran into end of file.
280				 * This shouldn't normally happen,
281				 * but may if there is some kind of read error.
282				 */
283				break;
284			}
285			if (pos >= tpos)
286			{
287				/*
288				 * Surprise!  The desired line is
289				 * close enough to the current screen
290				 * that we can just scroll there after all.
291				 */
292				back(nline+1, tpos, 1, 0);
293#if HILITE_SEARCH
294				if (show_attn)
295					repaint_hilite(1);
296#endif
297				return;
298			}
299		}
300		lastmark();
301		if (!top_scroll)
302			clear();
303		else
304			home();
305		screen_trashed = 0;
306		add_back_pos(pos);
307		back(sc_height-1, pos, 1, 0);
308	}
309}
310