[unix-history] / usr / othersrc / public / less-177 / line.c

/*
 * Routines to manipulate the "line buffer".
 * The line buffer holds a line of output as it is being built
 * in preparation for output to the screen.
 */

#include "less.h"

static char linebuf[1024];	/* Buffer which holds the current output line */
static char attr[1024];		/* Extension of linebuf to hold attributes */
static int curr;		/* Index into linebuf */
static int column;		/* Printable length, accounting for
				   backspaces, etc. */
static int overstrike;		/* Next char should overstrike previous char */
static int is_null_line;	/* There is no current line */
static char pendc;

static int do_append();

extern int bs_mode;
extern int tabstop;
extern int linenums;
extern int ctldisp;
extern int twiddle;
extern int binattr;
extern int auto_wrap, ignaw;
extern int bo_s_width, bo_e_width;
extern int ul_s_width, ul_e_width;
extern int bl_s_width, bl_e_width;
extern int sc_width, sc_height;

/*
 * Rewind the line buffer.
 */
	public void
prewind()
{
	curr = 0;
	column = 0;
	overstrike = 0;
	is_null_line = 0;
	pendc = '\0';
}

/*
 * Insert the line number (of the given position) into the line buffer.
 */
	public void
plinenum(pos)
	POSITION pos;
{
	register int lno;
	register int i;
	register int n;

	/*
	 * We display the line number at the start of each line
	 * only if the -N option is set.
	 */
	if (linenums != 2)
		return;

	/*
	 * Get the line number and put it in the current line.
	 * {{ Note: since find_linenum calls forw_raw_line,
	 *    it may seek in the input file, requiring the caller 
	 *    of plinenum to re-seek if necessary. }}
	 */
	lno = find_linenum(pos);

	sprintf(&linebuf[curr], "%6d", lno);
	n = strlen(&linebuf[curr]);
	column += n;
	for (i = 0;  i < n;  i++)
		attr[curr++] = 0;

	/*
	 * Append enough spaces to bring us to the next tab stop.
	 * {{ We could avoid this at the cost of adding some
	 *    complication to the tab stop logic in pappend(). }}
	 */
	do
	{
		linebuf[curr] = ' ';
		attr[curr++] = 0;
		column++;
	} while ((column % tabstop) != 0);
}

/*
 * Return the printing width of the start (enter) sequence
 * for a given character attribute.
 */
	int
attr_swidth(a)
	int a;
{
	switch (a)
	{
	case BOLD:	return (bo_s_width);
	case UNDERLINE:	return (ul_s_width);
	case BLINK:	return (bl_s_width);
	}
	return (0);
}

/*
 * Return the printing width of the end (exit) sequence
 * for a given character attribute.
 */
	int
attr_ewidth(a)
	int a;
{
	switch (a)
	{
	case BOLD:	return (bo_e_width);
	case UNDERLINE:	return (ul_e_width);
	case BLINK:	return (bl_e_width);
	}
	return (0);
}

/*
 * Return the printing width of a given character and attribute,
 * if the character were added to the current position in the line buffer.
 * Adding a character with a given attribute may cause an enter or exit
 * attribute sequence to be inserted, so this must be taken into account.
 */
	static int
pwidth(c, a)
	int c;
	int a;
{
	register int w;

	if (c == '\b')
		/*
		 * Backspace moves backwards one position.
		 */
		return (-1);

	if (control_char(c))
		/*
		 * Control characters do unpredicatable things,
		 * so we don't even try to guess; say it doesn't move.
		 * This can only happen if the -r flag is in effect.
		 */
		return (0);

	/*
	 * Other characters take one space,
	 * plus the width of any attribute enter/exit sequence.
	 */
	w = 1;
	if (curr > 0 && attr[curr-1] != a)
		w += attr_ewidth(attr[curr-1]);
	if (a && (curr == 0 || attr[curr-1] != a))
		w += attr_swidth(a);
	return (w);
}

/*
 * Delete the previous character in the line buffer.
 */
	static void
backc()
{
	curr--;
	column -= pwidth(linebuf[curr], attr[curr]);
}

/*
 * Append a character and attribute to the line buffer.
 */
	static int
storec(c, a)
	int c;
	int a;
{
	register int w;

	w = pwidth(c, a);
	if (ctldisp > 0 && column + w + attr_ewidth(a) > sc_width)
		/*
		 * Won't fit on screen.
		 */
		return (1);

	if (curr >= sizeof(linebuf)-2)
		/*
		 * Won't fit in line buffer.
		 */
		return (1);

	/*
	 * Special handling for "magic cookie" terminals.
	 * If an attribute enter/exit sequence has a printing width > 0,
	 * and the sequence is adjacent to a space, delete the space.
	 * We just mark the space as invisible, to avoid having too
	 * many spaces deleted.
	 * {{ Note that even if the attribute width is > 1, we
	 *    delete only one space.  It's not worth trying to do more.
	 *    It's hardly worth doing this much. }}
	 */
	if (curr > 0 && a != NORMAL && 
		linebuf[curr-1] == ' ' && attr[curr-1] == NORMAL &&
		attr_swidth(a) > 0)
	{
		/*
		 * We are about to append an enter-attribute sequence
		 * just after a space.  Delete the space.
		 */
		attr[curr-1] = INVIS;
		column--;
	} else if (curr > 0 && attr[curr-1] != NORMAL && 
		attr[curr-1] != INVIS && c == ' ' && a == NORMAL &&
		attr_ewidth(attr[curr-1]) > 0)
	{
		/*
		 * We are about to append a space just after an 
		 * exit-attribute sequence.  Delete the space.
		 */
		a = INVIS;
		column--;
	}
	/* End of magic cookie handling. */

	linebuf[curr] = c;
	attr[curr] = a;
	column += w;
	return (0);
}

/*
 * Append a character to the line buffer.
 * Expand tabs into spaces, handle underlining, boldfacing, etc.
 * Returns 0 if ok, 1 if couldn't fit in buffer.
 */
	public int
pappend(c)
	register int c;
{
	if (pendc)
	{
		if (do_append(pendc))
			/*
			 * Oops.  We've probably lost the char which
			 * was in pendc, since caller won't back up.
			 */
			return (1);
		pendc = '\0';
	}

	if (c == '\r' && bs_mode == BS_SPECIAL)
	{
		/*
		 * Don't put the CR into the buffer until we see 
		 * the next char.  If the next char is a newline,
		 * discard the CR.
		 */
		pendc = c;
		return (0);
	}

	return (do_append(c));
}

	static int
do_append(c)
	int c;
{
	register char *s;
	register int a;

#define	STOREC(c,a)	if (storec((c),(a))) return (1); else curr++

	if (overstrike)
	{
		/*
		 * Overstrike the character at the current position
		 * in the line buffer.  This will cause either 
		 * underline (if a "_" is overstruck), 
		 * bold (if an identical character is overstruck),
		 * or just deletion of the character in the buffer.
		 */
		overstrike = 0;
		if (c == linebuf[curr])
			STOREC(linebuf[curr], BOLD);
		else if (c == '_')
			STOREC(linebuf[curr], UNDERLINE);
		else if (linebuf[curr] == '_')
			STOREC(c, UNDERLINE);
		else if (control_char(c))
			goto do_control_char;
		else
			STOREC(c, NORMAL);
	} else if (c == '\b')
	{
		switch (bs_mode)
		{
		case BS_NORMAL:
			STOREC(c, NORMAL);
			break;
		case BS_CONTROL:
			goto do_control_char;
		case BS_SPECIAL:
			if (curr == 0)
				break;
			backc();
			overstrike = 1;
			break;
		}
	} else if (c == '\t') 
	{
		/*
		 * Expand a tab into spaces.
		 */
		do
		{
			STOREC(' ', NORMAL);
		} while ((column % tabstop) != 0);
	} else if (control_char(c))
	{
	do_control_char:
		if (ctldisp == 0)
		{
			/*
			 * Output as a normal character.
			 */
			STOREC(c, NORMAL);
		} else 
		{
			/*
			 * Output in the (blinking) ^X format.
			 */
			s = prchar(c);  
			a = binattr;

			/*
			 * Make sure we can get the entire representation
			 * the character on this line.
			 */
			if (column + strlen(s) + 
			    attr_swidth(a) + attr_ewidth(a) > sc_width)
				return (1);

			for ( ;  *s != 0;  s++)
				STOREC(*s, a);
		}
	} else
	{
		STOREC(c, NORMAL);
	}

	return (0);
}

/*
 * Terminate the line in the line buffer.
 */
	public void
pdone(endline)
	int endline;
{
	if (pendc && (pendc != '\r' || !endline))
		/*
		 * If we had a pending character, put it in the buffer.
		 * But discard a pending CR if we are at end of line
		 * (that is, discard the CR in a CR/LF sequence).
		 */
		(void) do_append(pendc);

	/*
	 * Add a newline if necessary,
	 * and append a '\0' to the end of the line.
	 */
	if (column < sc_width || !auto_wrap || ignaw || ctldisp == 0)
	{
		linebuf[curr] = '\n';
		attr[curr] = NORMAL;
		curr++;
	}
	linebuf[curr] = '\0';
	attr[curr] = NORMAL;
}

/*
 * Get a character from the current line.
 * Return the character as the function return value,
 * and the character attribute in *ap.
 */
	public int
gline(i, ap)
	register int i;
	register int *ap;
{
	if (is_null_line)
	{
		/*
		 * If there is no current line, we pretend the line is
		 * either "~" or "", depending on the "twiddle" flag.
		 */
		*ap = NORMAL;
		if (twiddle)
			return ("~\n"[i]);
		return ("\n"[i]);
	}

	*ap = attr[i];
	return (linebuf[i] & 0377);
}

/*
 * Indicate that there is no current line.
 */
	public void
null_line()
{
	is_null_line = 1;
}

/*
 * Analogous to forw_line(), but deals with "raw lines":
 * lines which are not split for screen width.
 * {{ This is supposed to be more efficient than forw_line(). }}
 */
	public POSITION
forw_raw_line(curr_pos, linep)
	POSITION curr_pos;
	char **linep;
{
	register char *p;
	register int c;
	POSITION new_pos;

	if (curr_pos == NULL_POSITION || ch_seek(curr_pos) ||
		(c = ch_forw_get()) == EOI)
		return (NULL_POSITION);

	p = linebuf;

	for (;;)
	{
		if (c == '\n' || c == EOI)
		{
			new_pos = ch_tell();
			break;
		}
		if (p >= &linebuf[sizeof(linebuf)-1])
		{
			/*
			 * Overflowed the input buffer.
			 * Pretend the line ended here.
			 * {{ The line buffer is supposed to be big
			 *    enough that this never happens. }}
			 */
			new_pos = ch_tell() - 1;
			break;
		}
		*p++ = c;
		c = ch_forw_get();
	}
	*p = '\0';
	if (linep != NULL)
		*linep = linebuf;
	return (new_pos);
}

/*
 * Analogous to back_line(), but deals with "raw lines".
 * {{ This is supposed to be more efficient than back_line(). }}
 */
	public POSITION
back_raw_line(curr_pos, linep)
	POSITION curr_pos;
	char **linep;
{
	register char *p;
	register int c;
	POSITION new_pos;

	if (curr_pos == NULL_POSITION || curr_pos <= ch_zero() ||
		ch_seek(curr_pos-1))
		return (NULL_POSITION);

	p = &linebuf[sizeof(linebuf)];
	*--p = '\0';

	for (;;)
	{
		c = ch_back_get();
		if (c == '\n')
		{
			/*
			 * This is the newline ending the previous line.
			 * We have hit the beginning of the line.
			 */
			new_pos = ch_tell() + 1;
			break;
		}
		if (c == EOI)
		{
			/*
			 * We have hit the beginning of the file.
			 * This must be the first line in the file.
			 * This must, of course, be the beginning of the line.
			 */
			new_pos = ch_zero();
			break;
		}
		if (p <= linebuf)
		{
			/*
			 * Overflowed the input buffer.
			 * Pretend the line ended here.
			 */
			new_pos = ch_tell() + 1;
			break;
		}
		*--p = c;
	}
	if (linep != NULL)
		*linep = p;
	return (new_pos);
}
Commit	Line	Data
89edd2cf WJ	1	/*
	2	* Routines to manipulate the "line buffer".
	3	* The line buffer holds a line of output as it is being built
	4	* in preparation for output to the screen.
	5	*/
	6
	7	#include "less.h"
	8
	9	static char linebuf[1024]; /* Buffer which holds the current output line */
	10	static char attr[1024]; /* Extension of linebuf to hold attributes */
	11	static int curr; /* Index into linebuf */
	12	static int column; /* Printable length, accounting for
	13	backspaces, etc. */
	14	static int overstrike; /* Next char should overstrike previous char */
	15	static int is_null_line; /* There is no current line */
	16	static char pendc;
	17
	18	static int do_append();
	19
	20	extern int bs_mode;
	21	extern int tabstop;
	22	extern int linenums;
	23	extern int ctldisp;
	24	extern int twiddle;
	25	extern int binattr;
	26	extern int auto_wrap, ignaw;
	27	extern int bo_s_width, bo_e_width;
	28	extern int ul_s_width, ul_e_width;
	29	extern int bl_s_width, bl_e_width;
	30	extern int sc_width, sc_height;
	31
	32	/*
	33	* Rewind the line buffer.
	34	*/
	35	public void
	36	prewind()
	37	{
	38	curr = 0;
	39	column = 0;
	40	overstrike = 0;
	41	is_null_line = 0;
	42	pendc = '\0';
	43	}
	44
	45	/*
	46	* Insert the line number (of the given position) into the line buffer.
	47	*/
	48	public void
	49	plinenum(pos)
	50	POSITION pos;
	51	{
	52	register int lno;
	53	register int i;
	54	register int n;
	55
	56	/*
	57	* We display the line number at the start of each line
	58	* only if the -N option is set.
	59	*/
	60	if (linenums != 2)
	61	return;
	62
	63	/*
	64	* Get the line number and put it in the current line.
65	* {{ Note: since find_linenum calls forw_raw_line,
66	* it may seek in the input file, requiring the caller
67	* of plinenum to re-seek if necessary. }}
68	*/
69	lno = find_linenum(pos);
70
71	sprintf(&linebuf[curr], "%6d", lno);
72	n = strlen(&linebuf[curr]);
73	column += n;
74	for (i = 0; i < n; i++)
75	attr[curr++] = 0;
76
77	/*
78	* Append enough spaces to bring us to the next tab stop.
79	* {{ We could avoid this at the cost of adding some
80	* complication to the tab stop logic in pappend(). }}
81	*/
82	do
83	{
84	linebuf[curr] = ' ';
85	attr[curr++] = 0;
86	column++;
87	} while ((column % tabstop) != 0);
88	}
89
90	/*
91	* Return the printing width of the start (enter) sequence
92	* for a given character attribute.
93	*/
94	int
95	attr_swidth(a)
96	int a;
97	{
98	switch (a)
99	{
100	case BOLD: return (bo_s_width);
101	case UNDERLINE: return (ul_s_width);
102	case BLINK: return (bl_s_width);
103	}
104	return (0);
105	}
106
107	/*
108	* Return the printing width of the end (exit) sequence
109	* for a given character attribute.
110	*/
111	int
112	attr_ewidth(a)
113	int a;
114	{
115	switch (a)
116	{
117	case BOLD: return (bo_e_width);
118	case UNDERLINE: return (ul_e_width);
119	case BLINK: return (bl_e_width);
120	}
121	return (0);
122	}
123
124	/*
125	* Return the printing width of a given character and attribute,
126	* if the character were added to the current position in the line buffer.
127	* Adding a character with a given attribute may cause an enter or exit
128	* attribute sequence to be inserted, so this must be taken into account.
129	*/
130	static int
131	pwidth(c, a)
132	int c;
133	int a;
134	{
135	register int w;
136
137	if (c == '\b')
138	/*
139	* Backspace moves backwards one position.
140	*/
141	return (-1);
142
143	if (control_char(c))
144	/*
145	* Control characters do unpredicatable things,
146	* so we don't even try to guess; say it doesn't move.
147	* This can only happen if the -r flag is in effect.
148	*/
149	return (0);
150
151	/*
152	* Other characters take one space,
153	* plus the width of any attribute enter/exit sequence.
154	*/
155	w = 1;
156	if (curr > 0 && attr[curr-1] != a)
157	w += attr_ewidth(attr[curr-1]);
158	if (a && (curr == 0 \|\| attr[curr-1] != a))
159	w += attr_swidth(a);
160	return (w);
161	}
162
163	/*
164	* Delete the previous character in the line buffer.
165	*/
166	static void
167	backc()
168	{
169	curr--;
170	column -= pwidth(linebuf[curr], attr[curr]);
171	}
172
173	/*
174	* Append a character and attribute to the line buffer.
175	*/
176	static int
177	storec(c, a)
178	int c;
179	int a;
180	{
181	register int w;
182
183	w = pwidth(c, a);
184	if (ctldisp > 0 && column + w + attr_ewidth(a) > sc_width)
185	/*
186	* Won't fit on screen.
187	*/
188	return (1);
189
190	if (curr >= sizeof(linebuf)-2)
191	/*
192	* Won't fit in line buffer.
193	*/
194	return (1);
195
196	/*
197	* Special handling for "magic cookie" terminals.
198	* If an attribute enter/exit sequence has a printing width > 0,
199	* and the sequence is adjacent to a space, delete the space.
200	* We just mark the space as invisible, to avoid having too
201	* many spaces deleted.
202	* {{ Note that even if the attribute width is > 1, we
203	* delete only one space. It's not worth trying to do more.
204	* It's hardly worth doing this much. }}
205	*/
206	if (curr > 0 && a != NORMAL &&
207	linebuf[curr-1] == ' ' && attr[curr-1] == NORMAL &&
208	attr_swidth(a) > 0)
209	{
210	/*
211	* We are about to append an enter-attribute sequence
212	* just after a space. Delete the space.
213	*/
214	attr[curr-1] = INVIS;
215	column--;
216	} else if (curr > 0 && attr[curr-1] != NORMAL &&
217	attr[curr-1] != INVIS && c == ' ' && a == NORMAL &&
218	attr_ewidth(attr[curr-1]) > 0)
219	{
220	/*
221	* We are about to append a space just after an
222	* exit-attribute sequence. Delete the space.
223	*/
224	a = INVIS;
225	column--;
226	}
227	/* End of magic cookie handling. */
228
229	linebuf[curr] = c;
230	attr[curr] = a;
231	column += w;
232	return (0);
233	}
234
235	/*
236	* Append a character to the line buffer.
237	* Expand tabs into spaces, handle underlining, boldfacing, etc.
238	* Returns 0 if ok, 1 if couldn't fit in buffer.
239	*/
240	public int
241	pappend(c)
242	register int c;
243	{
244	if (pendc)
245	{
246	if (do_append(pendc))
247	/*
248	* Oops. We've probably lost the char which
249	* was in pendc, since caller won't back up.
250	*/
251	return (1);
252	pendc = '\0';
253	}
254
255	if (c == '\r' && bs_mode == BS_SPECIAL)
256	{
257	/*
258	* Don't put the CR into the buffer until we see
259	* the next char. If the next char is a newline,
260	* discard the CR.
261	*/
262	pendc = c;
263	return (0);
264	}
265
266	return (do_append(c));
267	}
268
269	static int
270	do_append(c)
271	int c;
272	{
273	register char *s;
274	register int a;
275
276	#define STOREC(c,a) if (storec((c),(a))) return (1); else curr++
277
278	if (overstrike)
279	{
280	/*
281	* Overstrike the character at the current position
282	* in the line buffer. This will cause either
283	* underline (if a "_" is overstruck),
284	* bold (if an identical character is overstruck),
285	* or just deletion of the character in the buffer.
286	*/
287	overstrike = 0;
288	if (c == linebuf[curr])
289	STOREC(linebuf[curr], BOLD);
290	else if (c == '_')
291	STOREC(linebuf[curr], UNDERLINE);
292	else if (linebuf[curr] == '_')
293	STOREC(c, UNDERLINE);
294	else if (control_char(c))
295	goto do_control_char;
296	else
297	STOREC(c, NORMAL);
298	} else if (c == '\b')
299	{
300	switch (bs_mode)
301	{
302	case BS_NORMAL:
303	STOREC(c, NORMAL);
304	break;
305	case BS_CONTROL:
306	goto do_control_char;
307	case BS_SPECIAL:
308	if (curr == 0)
309	break;
310	backc();
311	overstrike = 1;
312	break;
313	}
314	} else if (c == '\t')
315	{
316	/*
317	* Expand a tab into spaces.
318	*/
319	do
320	{
321	STOREC(' ', NORMAL);
322	} while ((column % tabstop) != 0);
323	} else if (control_char(c))
324	{
325	do_control_char:
326	if (ctldisp == 0)
327	{
328	/*
329	* Output as a normal character.
330	*/
331	STOREC(c, NORMAL);
332	} else
333	{
334	/*
335	* Output in the (blinking) ^X format.
336	*/
337	s = prchar(c);
338	a = binattr;
339
340	/*
341	* Make sure we can get the entire representation
342	* the character on this line.
343	*/
344	if (column + strlen(s) +
345	attr_swidth(a) + attr_ewidth(a) > sc_width)
346	return (1);
347
348	for ( ; *s != 0; s++)
349	STOREC(*s, a);
350	}
351	} else
352	{
353	STOREC(c, NORMAL);
354	}
355
356	return (0);
357	}
358
359	/*
360	* Terminate the line in the line buffer.
361	*/
362	public void
363	pdone(endline)
364	int endline;
365	{
366	if (pendc && (pendc != '\r' \|\| !endline))
367	/*
368	* If we had a pending character, put it in the buffer.
369	* But discard a pending CR if we are at end of line
370	* (that is, discard the CR in a CR/LF sequence).
371	*/
372	(void) do_append(pendc);
373
374	/*
375	* Add a newline if necessary,
376	* and append a '\0' to the end of the line.
377	*/
378	if (column < sc_width \|\| !auto_wrap \|\| ignaw \|\| ctldisp == 0)
379	{
380	linebuf[curr] = '\n';
381	attr[curr] = NORMAL;
382	curr++;
383	}
384	linebuf[curr] = '\0';
385	attr[curr] = NORMAL;
386	}
387
388	/*
389	* Get a character from the current line.
390	* Return the character as the function return value,
391	* and the character attribute in *ap.
392	*/
393	public int
394	gline(i, ap)
395	register int i;
396	register int *ap;
397	{
398	if (is_null_line)
399	{
400	/*
401	* If there is no current line, we pretend the line is
402	* either "~" or "", depending on the "twiddle" flag.
403	*/
404	*ap = NORMAL;
405	if (twiddle)
406	return ("~\n"[i]);
407	return ("\n"[i]);
408	}
409
410	*ap = attr[i];
411	return (linebuf[i] & 0377);
412	}
413
414	/*
415	* Indicate that there is no current line.
416	*/
417	public void
418	null_line()
419	{
420	is_null_line = 1;
421	}
422
423	/*
424	* Analogous to forw_line(), but deals with "raw lines":
425	* lines which are not split for screen width.
426	* {{ This is supposed to be more efficient than forw_line(). }}
427	*/
428	public POSITION
429	forw_raw_line(curr_pos, linep)
430	POSITION curr_pos;
431	char **linep;
432	{
433	register char *p;
434	register int c;
435	POSITION new_pos;
436
437	if (curr_pos == NULL_POSITION \|\| ch_seek(curr_pos) \|\|
438	(c = ch_forw_get()) == EOI)
439	return (NULL_POSITION);
440
441	p = linebuf;
442
443	for (;;)
444	{
445	if (c == '\n' \|\| c == EOI)
446	{
447	new_pos = ch_tell();
448	break;
449	}
450	if (p >= &linebuf[sizeof(linebuf)-1])
451	{
452	/*
453	* Overflowed the input buffer.
454	* Pretend the line ended here.
455	* {{ The line buffer is supposed to be big
456	* enough that this never happens. }}
457	*/
458	new_pos = ch_tell() - 1;
459	break;
460	}
461	*p++ = c;
462	c = ch_forw_get();
463	}
464	*p = '\0';
465	if (linep != NULL)
466	*linep = linebuf;
467	return (new_pos);
468	}
469
470	/*
471	* Analogous to back_line(), but deals with "raw lines".
472	* {{ This is supposed to be more efficient than back_line(). }}
473	*/
474	public POSITION
475	back_raw_line(curr_pos, linep)
476	POSITION curr_pos;
477	char **linep;
478	{
479	register char *p;
480	register int c;
481	POSITION new_pos;
482
483	if (curr_pos == NULL_POSITION \|\| curr_pos <= ch_zero() \|\|
484	ch_seek(curr_pos-1))
485	return (NULL_POSITION);
486
487	p = &linebuf[sizeof(linebuf)];
488	*--p = '\0';
489
490	for (;;)
491	{
492	c = ch_back_get();
493	if (c == '\n')
494	{
495	/*
496	* This is the newline ending the previous line.
497	* We have hit the beginning of the line.
498	*/
499	new_pos = ch_tell() + 1;
500	break;
501	}
502	if (c == EOI)
503	{
504	/*
505	* We have hit the beginning of the file.
506	* This must be the first line in the file.
507	* This must, of course, be the beginning of the line.
508	*/
509	new_pos = ch_zero();
510	break;
511	}
512	if (p <= linebuf)
513	{
514	/*
515	* Overflowed the input buffer.
516	* Pretend the line ended here.
517	*/
518	new_pos = ch_tell() + 1;
519	break;
520	}
521	*--p = c;
522	}
523	if (linep != NULL)
524	*linep = p;
525	return (new_pos);
526	}