os.c revision 63128 
1/*
2 * Copyright (C) 1984-2000  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 * Operating system dependent routines.
14 *
15 * Most of the stuff in here is based on Unix, but an attempt
16 * has been made to make things work on other operating systems.
17 * This will sometimes result in a loss of functionality, unless
18 * someone rewrites code specifically for the new operating system.
19 *
20 * The makefile provides defines to decide whether various
21 * Unix features are present.
22 */
23
24#include "less.h"
25#include <signal.h>
26#include <setjmp.h>
27#if HAVE_TIME_H
28#include <time.h>
29#endif
30#if HAVE_ERRNO_H
31#include <errno.h>
32#endif
33#if HAVE_VALUES_H
34#include <values.h>
35#endif
36#if HAVE_LIMITS_H
37#include <limits.h>
38#endif
39
40#if HAVE_TIME_T
41#define time_type	time_t
42#else
43#define	time_type	long
44#endif
45
46/*
47 * BSD setjmp() saves (and longjmp() restores) the signal mask.
48 * This costs a system call or two per setjmp(), so if possible we clear the
49 * signal mask with sigsetmask(), and use _setjmp()/_longjmp() instead.
50 * On other systems, setjmp() doesn't affect the signal mask and so
51 * _setjmp() does not exist; we just use setjmp().
52 */
53#if HAVE__SETJMP && HAVE_SIGSETMASK
54#define SET_JUMP	_setjmp
55#define LONG_JUMP	_longjmp
56#else
57#define SET_JUMP	setjmp
58#define LONG_JUMP	longjmp
59#endif
60
61public int reading;
62
63static jmp_buf read_label;
64
65extern int sigs;
66
67/*
68 * Like read() system call, but is deliberately interruptible.
69 * A call to intread() from a signal handler will interrupt
70 * any pending iread().
71 */
72	public int
73iread(fd, buf, len)
74	int fd;
75	char *buf;
76	unsigned int len;
77{
78	register int n;
79
80#if MSDOS_COMPILER==WIN32C
81	if (ABORT_SIGS())
82		return (READ_INTR);
83#else
84#if MSDOS_COMPILER && MSDOS_COMPILER != DJGPPC
85	if (kbhit())
86	{
87		int c;
88
89		c = getch();
90		if (c == '\003')
91			return (READ_INTR);
92		ungetch(c);
93	}
94#endif
95#endif
96	if (SET_JUMP(read_label))
97	{
98		/*
99		 * We jumped here from intread.
100		 */
101		reading = 0;
102#if HAVE_SIGPROCMASK
103		{
104		  sigset_t mask;
105		  sigemptyset(&mask);
106		  sigprocmask(SIG_SETMASK, &mask, NULL);
107		}
108#else
109#if HAVE_SIGSETMASK
110		sigsetmask(0);
111#else
112#ifdef _OSK
113		sigmask(~0);
114#endif
115#endif
116#endif
117		return (READ_INTR);
118	}
119
120	flush();
121	reading = 1;
122#if MSDOS_COMPILER==DJGPPC
123	if (isatty(fd))
124	{
125		/*
126		 * Don't try reading from a TTY until a character is
127		 * available, because that makes some background programs
128		 * believe DOS is busy in a way that prevents those
129		 * programs from working while "less" waits.
130		 */
131		fd_set readfds;
132
133		FD_ZERO(&readfds);
134		FD_SET(fd, &readfds);
135		if (select(fd+1, &readfds, 0, 0, 0) == -1)
136			return (-1);
137	}
138#endif
139	n = read(fd, buf, len);
140#if 1
141	/*
142	 * This is a kludge to workaround a problem on some systems
143	 * where terminating a remote tty connection causes read() to
144	 * start returning 0 forever, instead of -1.
145	 */
146	{
147		extern int ignore_eoi;
148		if (!ignore_eoi)
149		{
150			static int consecutive_nulls = 0;
151			if (n == 0)
152				consecutive_nulls++;
153			else
154				consecutive_nulls = 0;
155			if (consecutive_nulls > 20)
156				quit(QUIT_ERROR);
157		}
158	}
159#endif
160	reading = 0;
161	if (n < 0)
162		return (-1);
163	return (n);
164}
165
166/*
167 * Interrupt a pending iread().
168 */
169	public void
170intread()
171{
172	LONG_JUMP(read_label, 1);
173}
174
175/*
176 * Return the current time.
177 */
178#if HAVE_TIME
179	public long
180get_time()
181{
182	time_type t;
183
184	time(&t);
185	return (t);
186}
187#endif
188
189
190#if !HAVE_STRERROR
191/*
192 * Local version of strerror, if not available from the system.
193 */
194	static char *
195strerror(err)
196	int err;
197{
198#if HAVE_SYS_ERRLIST
199	static char buf[16];
200	extern char *sys_errlist[];
201	extern int sys_nerr;
202
203	if (err < sys_nerr)
204		return sys_errlist[err];
205	sprintf(buf, "Error %d", err);
206	return buf;
207#else
208	return ("cannot open");
209#endif
210}
211#endif
212
213/*
214 * errno_message: Return an error message based on the value of "errno".
215 */
216	public char *
217errno_message(filename)
218	char *filename;
219{
220	register char *p;
221	register char *m;
222#if HAVE_ERRNO
223#if MUST_DEFINE_ERRNO
224	extern int errno;
225#endif
226	p = strerror(errno);
227#else
228	p = "cannot open";
229#endif
230	m = (char *) ecalloc(strlen(filename) + strlen(p) + 3, sizeof(char));
231	sprintf(m, "%s: %s", filename, p);
232	return (m);
233}
234
235/*
236 * Return the largest possible number that can fit in a long.
237 */
238	static long
239get_maxlong()
240{
241#ifdef LONG_MAX
242	return (LONG_MAX);
243#else
244#ifdef MAXLONG
245	return (MAXLONG);
246#else
247	long n, n2;
248
249	/*
250	 * Keep doubling n until we overflow.
251	 * {{ This actually only returns the largest power of two that
252	 *    can fit in a long, but percentage() doesn't really need
253	 *    it any more accurate than that. }}
254	 */
255	n2 = 128;  /* Hopefully no maxlong is less than 128! */
256	do {
257		n = n2;
258		n2 *= 2;
259	} while (n2 / 2 == n);
260	return (n);
261#endif
262#endif
263}
264
265/*
266 * Return the ratio of two POSITIONS, as a percentage.
267 * {{ Assumes a POSITION is a long int. }}
268 */
269	public int
270percentage(num, den)
271	POSITION num, den;
272{
273	if (num <= get_maxlong() / 100)
274		return ((100 * num) / den);
275	else
276		return (num / (den / 100));
277}
278
279/*
280 * Return the specified percentage of a POSITION.
281 * {{ Assumes a POSITION is a long int. }}
282 */
283	public POSITION
284percent_pos(pos, percent)
285	POSITION pos;
286	int percent;
287{
288	if (pos <= get_maxlong() / 100)
289		return ((percent * pos) / 100);
290	else
291		return (percent * (pos / 100));
292}
293
294#ifdef _OSK_MWC32
295
296/*
297 * This implements an ANSI-style intercept setup for Microware C 3.2
298 */
299	public int
300os9_signal(type, handler)
301	int type;
302	RETSIGTYPE (*handler)();
303{
304	intercept(handler);
305}
306
307#include <sgstat.h>
308
309	public int
310isatty(f)
311	int f;
312{
313	struct sgbuf sgbuf;
314
315	if (_gs_opt(f, &sgbuf) < 0)
316		return -1;
317	return (sgbuf.sg_class == 0);
318}
319
320#endif
321