1 /* Copyright (C) 2010, 2013 Free Software Foundation, Inc.
3 * This library is free software; you can redistribute it and/or
4 * modify it under the terms of the GNU Lesser General Public License
5 * as published by the Free Software Foundation; either version 3 of
6 * the License, or (at your option) any later version.
8 * This library is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * Lesser General Public License for more details.
13 * You should have received a copy of the GNU Lesser General Public
14 * License along with this library; if not, write to the Free Software
15 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
30 #include "libguile/_scm.h"
31 #include "libguile/bytevectors.h"
32 #include "libguile/numbers.h"
33 #include "libguile/error.h"
34 #include "libguile/validate.h"
36 #include "libguile/poll.h"
43 /* Poll a set of file descriptors, waiting until one or more of them is
44 ready to perform input or output.
46 This is a low-level interface. See the `(ice-9 poll)' module for a more
49 `pollfds' is expected to be a bytevector, laid out in contiguous blocks of 64
50 bits. Each block has the format of one `struct pollfd': a 32-bit int file
51 descriptor, a 16-bit int events mask, and a 16-bit int revents mask.
53 The number of pollfd structures in `pollfds' is specified in
54 `nfds'. `pollfds' must be at least long enough to support that number of
55 structures. It may be longer, in which case the trailing entries are left
58 The pollfds bytevector is modified directly, setting the returned events in
59 the final two bytes (the revents member).
61 Since Scheme ports can buffer input or output in userspace, a Scheme
62 poll interface needs to take that into account as well. The `ports'
63 argument, a vector big enough for `nfds' elements, is given for this
64 purpose. If a pollfd entry has a corresponding open port, that port
65 is scanned for available input or output before dropping into the
66 poll. If any port has buffered I/O available, the poll syscall is
67 still issued, but with a timeout of 0 milliseconds, and a full port
68 scan occurs after the poll returns.
70 If timeout is given and is non-negative, the poll will return after that
71 number of milliseconds if no fd became active.
74 scm_primitive_poll (SCM pollfds
, SCM nfds
, SCM ports
, SCM timeout
)
75 #define FUNC_NAME "primitive-poll"
81 int have_buffered_io
= 0;
84 SCM_VALIDATE_BYTEVECTOR (SCM_ARG1
, pollfds
);
85 c_nfds
= scm_to_uint32 (nfds
);
86 c_timeout
= scm_to_int (timeout
);
88 if (SCM_UNLIKELY (SCM_BYTEVECTOR_LENGTH (pollfds
)
89 < c_nfds
* sizeof(struct pollfd
)))
90 SCM_OUT_OF_RANGE (SCM_ARG2
, nfds
);
92 SCM_VALIDATE_VECTOR (SCM_ARG3
, ports
);
93 if (SCM_UNLIKELY (SCM_SIMPLE_VECTOR_LENGTH (ports
) < c_nfds
))
94 SCM_OUT_OF_RANGE (SCM_ARG3
, ports
);
96 fds
= (struct pollfd
*)SCM_BYTEVECTOR_CONTENTS (pollfds
);
98 for (i
= 0; i
< c_nfds
; i
++)
100 SCM port
= SCM_SIMPLE_VECTOR_REF (ports
, i
);
101 short int revents
= 0;
103 if (SCM_PORTP (port
))
105 if (SCM_CLOSEDP (port
))
109 scm_t_port
*pt
= SCM_PTAB_ENTRY (port
);
111 if (pt
->read_pos
< pt
->read_end
)
112 /* Buffered input waiting to be read. */
114 if (pt
->write_pos
< pt
->write_end
)
115 /* Buffered output possible. */
120 if (revents
& fds
[i
].events
)
122 have_buffered_io
= 1;
128 SCM_SYSCALL (rv
= poll (fds
, c_nfds
, c_timeout
));
133 if (have_buffered_io
)
134 for (i
= 0; i
< c_nfds
; i
++)
136 SCM port
= SCM_SIMPLE_VECTOR_REF (ports
, i
);
137 short int revents
= 0;
139 if (SCM_PORTP (port
))
141 if (SCM_CLOSEDP (port
))
145 scm_t_port
*pt
= SCM_PTAB_ENTRY (port
);
147 if (pt
->read_pos
< pt
->read_end
)
148 /* Buffered input waiting to be read. */
150 if (SCM_OUTPUT_PORT_P (port
) && pt
->write_pos
< pt
->write_end
)
151 /* Buffered output possible. */
156 /* Mask in the events we are interested, and test if any are
158 if ((revents
&= fds
[i
].events
))
160 /* Could be the underlying fd is also ready for reading. */
164 /* In any case, add these events to whatever the syscall
166 fds
[i
].revents
|= revents
;
170 return scm_from_int (rv
);
180 scm_c_define_gsubr ("primitive-poll", 4, 0, 0, scm_primitive_poll
);
181 scm_c_define ("%sizeof-struct-pollfd", scm_from_size_t (sizeof (struct pollfd
)));
184 scm_c_define ("POLLIN", scm_from_int (POLLIN
));
187 scm_c_define ("POLLPRI", scm_from_int (POLLPRI
));
190 scm_c_define ("POLLOUT", scm_from_int (POLLOUT
));
193 scm_c_define ("POLLRDHUP", scm_from_int (POLLRDHUP
));
196 scm_c_define ("POLLERR", scm_from_int (POLLERR
));
199 scm_c_define ("POLLHUP", scm_from_int (POLLHUP
));
202 scm_c_define ("POLLNVAL", scm_from_int (POLLNVAL
));
208 scm_register_poll (void)
210 scm_c_register_extension ("libguile-" SCM_EFFECTIVE_VERSION
,
212 (scm_t_extension_init_func
) scm_init_poll
,