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found one more stray '\n' that should probably be removed
[metaconfig.git] / U / compline / nblock_io.U
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1?RCS: $Id: nblock_io.U,v 3.0.1.2 1997/02/28 16:17:14 ram Exp $
2?RCS:
3?RCS: Copyright (c) 1991-1993, Raphael Manfredi
4?RCS:
5?RCS: You may redistribute only under the terms of the Artistic Licence,
6?RCS: as specified in the README file that comes with the distribution.
7?RCS: You may reuse parts of this distribution only within the terms of
8?RCS: that same Artistic Licence; a copy of which may be found at the root
9?RCS: of the source tree for dist 3.0.
10?RCS:
11?RCS: $Log: nblock_io.U,v $
12?RCS: Revision 3.0.1.2 1997/02/28 16:17:14 ram
13?RCS: patch61: simplify here document for shells that can't handle them well
14?RCS: patch61: force use of "startsh" at the head of the generated script
15?RCS: patch61: added new files to the ?F: metalint hint
16?RCS:
17?RCS: Revision 3.0.1.1 1995/07/25 14:13:22 ram
18?RCS: patch56: created
19?RCS:
20?X:
21?X: Simplify here document for shells that can't handle them well.
22?X: (Problem reported on FreeBSD; it's unclear if this helps.) --AD
23?X:
2cb64bf6 24?MAKE:o_nonblock eagain rd_nodata d_eofnblk: cat rm_try Compile run \
37a56d0d 25 d_open3 h_sysfile h_fcntl signal_t hint Oldconfig Setvar \
1273bb5e 26 startsh i_unistd i_string i_fcntl i_stdlib
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27?MAKE: -pick add $@ %<
28?S:o_nonblock:
29?S: This variable bears the symbol value to be used during open() or fcntl()
30?S: to turn on non-blocking I/O for a file descriptor. If you wish to switch
31?S: between blocking and non-blocking, you may try ioctl(FIOSNBIO) instead,
32?S: but that is only supported by some devices.
33?S:.
34?S:eagain:
35?S: This variable bears the symbolic errno code set by read() when no
36?S: data is present on the file and non-blocking I/O was enabled (otherwise,
37?S: read() blocks naturally).
38?S:.
39?S:rd_nodata:
40?S: This variable holds the return code from read() when no data is
41?S: present. It should be -1, but some systems return 0 when O_NDELAY is
42?S: used, which is a shame because you cannot make the difference between
43?S: no data and an EOF.. Sigh!
44?S:.
45?S:d_eofnblk:
46?S: This variable conditionally defines EOF_NONBLOCK if EOF can be seen
47?S: when reading from a non-blocking I/O source.
48?S:.
49?C:VAL_O_NONBLOCK:
50?C: This symbol is to be used during open() or fcntl(F_SETFL) to turn on
51?C: non-blocking I/O for the file descriptor. Note that there is no way
52?C: back, i.e. you cannot turn it blocking again this way. If you wish to
53?C: alternatively switch between blocking and non-blocking, use the
54?C: ioctl(FIOSNBIO) call instead, but that is not supported by all devices.
55?C:.
56?C:VAL_EAGAIN:
57?C: This symbol holds the errno error code set by read() when no data was
58?C: present on the non-blocking file descriptor.
59?C:.
60?C:RD_NODATA:
61?C: This symbol holds the return code from read() when no data is present
62?C: on the non-blocking file descriptor. Be careful! If EOF_NONBLOCK is
63?C: not defined, then you can't distinguish between no data and EOF by
64?C: issuing a read(). You'll have to find another way to tell for sure!
65?C:.
66?C:EOF_NONBLOCK:
67?C: This symbol, if defined, indicates to the C program that a read() on
68?C: a non-blocking file descriptor will return 0 on EOF, and not the value
69?C: held in RD_NODATA (-1 usually, in that case!).
70?C:.
71?H:#define VAL_O_NONBLOCK $o_nonblock
72?H:#define VAL_EAGAIN $eagain
73?H:#define RD_NODATA $rd_nodata
74?H:#$d_eofnblk EOF_NONBLOCK
75?H:.
0f00356b 76?F:!try.out !try.ret !try.err
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77?T:status
78?LINT:use d_open3
79: check for non-blocking I/O stuff
80case "$h_sysfile" in
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81true) echo "#include <sys/file.h>" > head.c;;
82*)
83 case "$h_fcntl" in
84 true) echo "#include <fcntl.h>" > head.c;;
85 *) echo "#include <sys/fcntl.h>" > head.c;;
86 esac
87 ;;
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88esac
89echo " "
90echo "Figuring out the flag used by open() for non-blocking I/O..." >&4
91case "$o_nonblock" in
92'')
93 $cat head.c > try.c
e8970d08 94 $cat >>try.c <<EOCP
37a56d0d 95#include <stdio.h>
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96#$i_stdlib I_STDLIB
97#ifdef I_STDLIB
d0abe53c 98#include <stdlib.h>
1273bb5e 99#endif
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100#$i_fcntl I_FCNTL
101#ifdef I_FCNTL
102#include <fcntl.h>
103#endif
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104int main() {
105#ifdef O_NONBLOCK
106 printf("O_NONBLOCK\n");
107 exit(0);
108#endif
109#ifdef O_NDELAY
110 printf("O_NDELAY\n");
111 exit(0);
112#endif
113?X: Stevens "Advanced Programming in the UNIX Environment" page 364 mentions
8411e286 114?X: the FNDELAY symbol, used in 4.3BSD (source: Paul Marquess).
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115#ifdef FNDELAY
116 printf("FNDELAY\n");
117 exit(0);
118#endif
119 exit(0);
120}
121EOCP
122 set try
123 if eval $compile_ok; then
0f00356b 124 o_nonblock=`$run ./try`
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125 case "$o_nonblock" in
126 '') echo "I can't figure it out, assuming O_NONBLOCK will do.";;
127 *) echo "Seems like we can use $o_nonblock.";;
128 esac
129 else
130 echo "(I can't compile the test program; pray O_NONBLOCK is right!)"
131 fi
132 ;;
133*) echo "Using $hint value $o_nonblock.";;
134esac
2cb64bf6 135$rm_try
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136
137echo " "
138echo "Let's see what value errno gets from read() on a $o_nonblock file..." >&4
139case "$eagain" in
140'')
141 $cat head.c > try.c
142 $cat >>try.c <<EOCP
143#include <errno.h>
144#include <sys/types.h>
145#include <signal.h>
2cb64bf6 146#include <stdio.h>
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147#$i_stdlib I_STDLIB
148#ifdef I_STDLIB
149#include <stdlib.h>
150#endif
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151#$i_fcntl I_FCNTL
152#ifdef I_FCNTL
153#include <fcntl.h>
154#endif
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155#define MY_O_NONBLOCK $o_nonblock
156#ifndef errno /* XXX need better Configure test */
157extern int errno;
158#endif
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159#$i_unistd I_UNISTD
160#ifdef I_UNISTD
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161#include <unistd.h>
162#endif
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163#$i_string I_STRING
164#ifdef I_STRING
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165#include <string.h>
166#else
167#include <strings.h>
168#endif
dc952a08 169$signal_t blech(int x) { exit(3); }
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170EOCP
171 $cat >> try.c <<'EOCP'
172int main()
173{
174 int pd[2];
175 int pu[2];
176 char buf[1];
177 char string[100];
178
179 pipe(pd); /* Down: child -> parent */
180 pipe(pu); /* Up: parent -> child */
181 if (0 != fork()) {
182 int ret;
183 close(pd[1]); /* Parent reads from pd[0] */
184 close(pu[0]); /* Parent writes (blocking) to pu[1] */
cede5cd9 185#ifdef F_SETFL
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186 if (-1 == fcntl(pd[0], F_SETFL, MY_O_NONBLOCK))
187 exit(1);
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188#else
189 exit(4);
190#endif
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191 signal(SIGALRM, blech);
192 alarm(5);
193 if ((ret = read(pd[0], buf, 1)) > 0) /* Nothing to read! */
194 exit(2);
195 sprintf(string, "%d\n", ret);
196 write(2, string, strlen(string));
197 alarm(0);
198#ifdef EAGAIN
199 if (errno == EAGAIN) {
200 printf("EAGAIN\n");
201 goto ok;
202 }
203#endif
204#ifdef EWOULDBLOCK
205 if (errno == EWOULDBLOCK)
206 printf("EWOULDBLOCK\n");
207#endif
208 ok:
209 write(pu[1], buf, 1); /* Unblocks child, tell it to close our pipe */
210 sleep(2); /* Give it time to close our pipe */
211 alarm(5);
212 ret = read(pd[0], buf, 1); /* Should read EOF */
213 alarm(0);
214 sprintf(string, "%d\n", ret);
26470d78 215 write(4, string, strlen(string));
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216 exit(0);
217 }
218
219 close(pd[0]); /* We write to pd[1] */
220 close(pu[1]); /* We read from pu[0] */
221 read(pu[0], buf, 1); /* Wait for parent to signal us we may continue */
222 close(pd[1]); /* Pipe pd is now fully closed! */
223 exit(0); /* Bye bye, thank you for playing! */
224}
225EOCP
226 set try
227 if eval $compile_ok; then
228?X: Use script to avoid the possible 'alarm call' message
229 echo "$startsh" >mtry
26470d78 230 echo "$run ./try >try.out 2>try.ret 4>try.err || exit 4" >>mtry
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231 chmod +x mtry
232 ./mtry >/dev/null 2>&1
233 case $? in
234 0) eagain=`$cat try.out`;;
235 1) echo "Could not perform non-blocking setting!";;
236 2) echo "I did a successful read() for something that was not there!";;
237 3) echo "Hmm... non-blocking I/O does not seem to be working!";;
cede5cd9 238 4) echo "Could not find F_SETFL!";;
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239 *) echo "Something terribly wrong happened during testing.";;
240 esac
241 rd_nodata=`$cat try.ret`
242 echo "A read() system call with no data present returns $rd_nodata."
243 case "$rd_nodata" in
244 0|-1) ;;
245 *)
246 echo "(That's peculiar, fixing that to be -1.)"
247 rd_nodata=-1
248 ;;
249 esac
250 case "$eagain" in
251 '')
252 echo "Forcing errno EAGAIN on read() with no data available."
253 eagain=EAGAIN
254 ;;
255 *)
256 echo "Your read() sets errno to $eagain when no data is available."
257 ;;
258 esac
259 status=`$cat try.err`
260 case "$status" in
261 0) echo "And it correctly returns 0 to signal EOF.";;
262 -1) echo "But it also returns -1 to signal EOF, so be careful!";;
263 *) echo "However, your read() returns '$status' on EOF??";;
264 esac
265 val="$define"
266 if test "$status" = "$rd_nodata"; then
267 echo "WARNING: you can't distinguish between EOF and no data!"
268 val="$undef"
269 fi
270 else
271 echo "I can't compile the test program--assuming errno EAGAIN will do."
272 eagain=EAGAIN
273 fi
274 set d_eofnblk
275 eval $setvar
276 ;;
277*)
278 echo "Using $hint value $eagain."
279 echo "Your read() returns $rd_nodata when no data is present."
280 case "$d_eofnblk" in
281 "$define") echo "And you can see EOF because read() returns 0.";;
282 "$undef") echo "But you can't see EOF status from read() returned value.";;
283 *)
284?X: Should not happen, but if it does, assume the worst!
285 echo "(Assuming you can't see EOF status from read anyway.)"
286 d_eofnblk=$undef
287 ;;
288 esac
289 ;;
290esac
2cb64bf6 291$rm_try head.c mtry
959f3c4c 292