| 1 |
#if defined(HAVE_SYS_POLL_H) && defined(HAVE_POLL) |
| 2 |
/* nothing to do, all is well, gore is president. */ |
| 3 |
#else |
| 4 |
|
| 5 |
/*---------------------------------------------------------------------------*\ |
| 6 |
$Id: poll.c,v 1.1 2003/10/14 17:24:19 pcg Exp $ |
| 7 |
|
| 8 |
NAME |
| 9 |
|
| 10 |
poll - select(2)-based poll() emulation function for BSD systems. |
| 11 |
|
| 12 |
SYNOPSIS |
| 13 |
#include "poll.h" |
| 14 |
|
| 15 |
struct pollfd |
| 16 |
{ |
| 17 |
int fd; |
| 18 |
short events; |
| 19 |
short revents; |
| 20 |
} |
| 21 |
|
| 22 |
int poll (struct pollfd *pArray, unsigned long n_fds, int timeout) |
| 23 |
|
| 24 |
DESCRIPTION |
| 25 |
|
| 26 |
This file, and the accompanying "poll.h", implement the System V |
| 27 |
poll(2) system call for BSD systems (which typically do not provide |
| 28 |
poll()). Poll() provides a method for multiplexing input and output |
| 29 |
on multiple open file descriptors; in traditional BSD systems, that |
| 30 |
capability is provided by select(). While the semantics of select() |
| 31 |
differ from those of poll(), poll() can be readily emulated in terms |
| 32 |
of select() -- which is how this function is implemented. |
| 33 |
|
| 34 |
REFERENCES |
| 35 |
Stevens, W. Richard. Unix Network Programming. Prentice-Hall, 1990. |
| 36 |
|
| 37 |
NOTES |
| 38 |
1. This software requires an ANSI C compiler. |
| 39 |
|
| 40 |
LICENSE |
| 41 |
|
| 42 |
This software is released under the following license: |
| 43 |
|
| 44 |
Copyright (c) 1995-2002 Brian M. Clapper |
| 45 |
All rights reserved. |
| 46 |
|
| 47 |
Redistribution and use in source and binary forms are |
| 48 |
permitted provided that: (1) source distributions retain |
| 49 |
this entire copyright notice and comment; (2) modifications |
| 50 |
made to the software are prominently mentioned, and a copy |
| 51 |
of the original software (or a pointer to its location) are |
| 52 |
included; and (3) distributions including binaries display |
| 53 |
the following acknowledgement: "This product includes |
| 54 |
software developed by Brian M. Clapper <bmc@clapper.org>" |
| 55 |
in the documentation or other materials provided with the |
| 56 |
distribution. The name of the author may not be used to |
| 57 |
endorse or promote products derived from this software |
| 58 |
without specific prior written permission. |
| 59 |
|
| 60 |
THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS |
| 61 |
OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE |
| 62 |
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A |
| 63 |
PARTICULAR PURPOSE. |
| 64 |
|
| 65 |
Effectively, this means you can do what you want with the software |
| 66 |
except remove this notice or take advantage of the author's name. |
| 67 |
If you modify the software and redistribute your modified version, |
| 68 |
you must indicate that your version is a modification of the |
| 69 |
original, and you must provide either a pointer to or a copy of the |
| 70 |
original. |
| 71 |
\*---------------------------------------------------------------------------*/ |
| 72 |
|
| 73 |
|
| 74 |
/*---------------------------------------------------------------------------*\ |
| 75 |
Includes |
| 76 |
\*---------------------------------------------------------------------------*/ |
| 77 |
|
| 78 |
#include <unistd.h> /* standard Unix definitions */ |
| 79 |
#include <sys/types.h> /* system types */ |
| 80 |
#include <sys/time.h> /* time definitions */ |
| 81 |
#include <assert.h> /* assertion macros */ |
| 82 |
#include <string.h> /* string functions */ |
| 83 |
#include "poll.h" /* this package */ |
| 84 |
|
| 85 |
/*---------------------------------------------------------------------------*\ |
| 86 |
Macros |
| 87 |
\*---------------------------------------------------------------------------*/ |
| 88 |
|
| 89 |
#ifndef MAX |
| 90 |
#define MAX(a,b) ((a) > (b) ? (a) : (b)) |
| 91 |
#endif |
| 92 |
|
| 93 |
|
| 94 |
/*---------------------------------------------------------------------------*\ |
| 95 |
Private Functions |
| 96 |
\*---------------------------------------------------------------------------*/ |
| 97 |
|
| 98 |
static int map_poll_spec |
| 99 |
#if __STDC__ > 0 |
| 100 |
(struct pollfd *pArray, |
| 101 |
unsigned long n_fds, |
| 102 |
fd_set *pReadSet, |
| 103 |
fd_set *pWriteSet, |
| 104 |
fd_set *pExceptSet) |
| 105 |
#else |
| 106 |
(pArray, n_fds, pReadSet, pWriteSet, pExceptSet) |
| 107 |
struct pollfd *pArray; |
| 108 |
unsigned long n_fds; |
| 109 |
fd_set *pReadSet; |
| 110 |
fd_set *pWriteSet; |
| 111 |
fd_set *pExceptSet; |
| 112 |
#endif |
| 113 |
{ |
| 114 |
register unsigned long i; /* loop control */ |
| 115 |
register struct pollfd *pCur; /* current array element */ |
| 116 |
register int max_fd = -1; /* return value */ |
| 117 |
|
| 118 |
/* |
| 119 |
Map the poll() structures into the file descriptor sets required |
| 120 |
by select(). |
| 121 |
*/ |
| 122 |
for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) |
| 123 |
{ |
| 124 |
/* Skip any bad FDs in the array. */ |
| 125 |
|
| 126 |
if (pCur->fd < 0) |
| 127 |
continue; |
| 128 |
|
| 129 |
if (pCur->events & POLLIN) |
| 130 |
{ |
| 131 |
/* "Input Ready" notification desired. */ |
| 132 |
FD_SET (pCur->fd, pReadSet); |
| 133 |
} |
| 134 |
|
| 135 |
if (pCur->events & POLLOUT) |
| 136 |
{ |
| 137 |
/* "Output Possible" notification desired. */ |
| 138 |
FD_SET (pCur->fd, pWriteSet); |
| 139 |
} |
| 140 |
|
| 141 |
if (pCur->events & POLLPRI) |
| 142 |
{ |
| 143 |
/* |
| 144 |
"Exception Occurred" notification desired. (Exceptions |
| 145 |
include out of band data. |
| 146 |
*/ |
| 147 |
FD_SET (pCur->fd, pExceptSet); |
| 148 |
} |
| 149 |
|
| 150 |
max_fd = MAX (max_fd, pCur->fd); |
| 151 |
} |
| 152 |
|
| 153 |
return max_fd; |
| 154 |
} |
| 155 |
|
| 156 |
static struct timeval *map_timeout |
| 157 |
#if __STDC__ > 0 |
| 158 |
(int poll_timeout, struct timeval *pSelTimeout) |
| 159 |
#else |
| 160 |
(poll_timeout, pSelTimeout) |
| 161 |
int poll_timeout; |
| 162 |
struct timeval *pSelTimeout; |
| 163 |
#endif |
| 164 |
{ |
| 165 |
struct timeval *pResult; |
| 166 |
|
| 167 |
/* |
| 168 |
Map the poll() timeout value into a select() timeout. The possible |
| 169 |
values of the poll() timeout value, and their meanings, are: |
| 170 |
|
| 171 |
VALUE MEANING |
| 172 |
|
| 173 |
-1 wait indefinitely (until signal occurs) |
| 174 |
0 return immediately, don't block |
| 175 |
>0 wait specified number of milliseconds |
| 176 |
|
| 177 |
select() uses a "struct timeval", which specifies the timeout in |
| 178 |
seconds and microseconds, so the milliseconds value has to be mapped |
| 179 |
accordingly. |
| 180 |
*/ |
| 181 |
|
| 182 |
assert (pSelTimeout != (struct timeval *) NULL); |
| 183 |
|
| 184 |
switch (poll_timeout) |
| 185 |
{ |
| 186 |
case -1: |
| 187 |
/* |
| 188 |
A NULL timeout structure tells select() to wait indefinitely. |
| 189 |
*/ |
| 190 |
pResult = (struct timeval *) NULL; |
| 191 |
break; |
| 192 |
|
| 193 |
case 0: |
| 194 |
/* |
| 195 |
"Return immediately" (test) is specified by all zeros in |
| 196 |
a timeval structure. |
| 197 |
*/ |
| 198 |
pSelTimeout->tv_sec = 0; |
| 199 |
pSelTimeout->tv_usec = 0; |
| 200 |
pResult = pSelTimeout; |
| 201 |
break; |
| 202 |
|
| 203 |
default: |
| 204 |
/* Wait the specified number of milliseconds. */ |
| 205 |
pSelTimeout->tv_sec = poll_timeout / 1000; /* get seconds */ |
| 206 |
poll_timeout %= 1000; /* remove seconds */ |
| 207 |
pSelTimeout->tv_usec = poll_timeout * 1000; /* get microseconds */ |
| 208 |
pResult = pSelTimeout; |
| 209 |
break; |
| 210 |
} |
| 211 |
|
| 212 |
|
| 213 |
return pResult; |
| 214 |
} |
| 215 |
|
| 216 |
static void map_select_results |
| 217 |
#if __STDC__ > 0 |
| 218 |
(struct pollfd *pArray, |
| 219 |
unsigned long n_fds, |
| 220 |
fd_set *pReadSet, |
| 221 |
fd_set *pWriteSet, |
| 222 |
fd_set *pExceptSet) |
| 223 |
#else |
| 224 |
(pArray, n_fds, pReadSet, pWriteSet, pExceptSet) |
| 225 |
struct pollfd *pArray; |
| 226 |
unsigned long n_fds; |
| 227 |
fd_set *pReadSet; |
| 228 |
fd_set *pWriteSet; |
| 229 |
fd_set *pExceptSet; |
| 230 |
#endif |
| 231 |
{ |
| 232 |
register unsigned long i; /* loop control */ |
| 233 |
register struct pollfd *pCur; /* current array element */ |
| 234 |
|
| 235 |
for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) |
| 236 |
{ |
| 237 |
/* Skip any bad FDs in the array. */ |
| 238 |
|
| 239 |
if (pCur->fd < 0) |
| 240 |
continue; |
| 241 |
|
| 242 |
/* Exception events take priority over input events. */ |
| 243 |
|
| 244 |
pCur->revents = 0; |
| 245 |
if (FD_ISSET (pCur->fd, pExceptSet)) |
| 246 |
pCur->revents |= POLLPRI; |
| 247 |
|
| 248 |
else if (FD_ISSET (pCur->fd, pReadSet)) |
| 249 |
pCur->revents |= POLLIN; |
| 250 |
|
| 251 |
if (FD_ISSET (pCur->fd, pWriteSet)) |
| 252 |
pCur->revents |= POLLOUT; |
| 253 |
} |
| 254 |
|
| 255 |
return; |
| 256 |
} |
| 257 |
|
| 258 |
/*---------------------------------------------------------------------------*\ |
| 259 |
Public Functions |
| 260 |
\*---------------------------------------------------------------------------*/ |
| 261 |
|
| 262 |
int poll |
| 263 |
|
| 264 |
#if __STDC__ > 0 |
| 265 |
(struct pollfd *pArray, unsigned long n_fds, int timeout) |
| 266 |
#else |
| 267 |
(pArray, n_fds, timeout) |
| 268 |
struct pollfd *pArray; |
| 269 |
unsigned long n_fds; |
| 270 |
int timeout; |
| 271 |
#endif |
| 272 |
|
| 273 |
{ |
| 274 |
fd_set read_descs; /* input file descs */ |
| 275 |
fd_set write_descs; /* output file descs */ |
| 276 |
fd_set except_descs; /* exception descs */ |
| 277 |
struct timeval stime; /* select() timeout value */ |
| 278 |
int ready_descriptors; /* function result */ |
| 279 |
int max_fd; /* maximum fd value */ |
| 280 |
struct timeval *pTimeout; /* actually passed */ |
| 281 |
|
| 282 |
FD_ZERO (&read_descs); |
| 283 |
FD_ZERO (&write_descs); |
| 284 |
FD_ZERO (&except_descs); |
| 285 |
|
| 286 |
assert (pArray != (struct pollfd *) NULL); |
| 287 |
|
| 288 |
/* Map the poll() file descriptor list in the select() data structures. */ |
| 289 |
|
| 290 |
max_fd = map_poll_spec (pArray, n_fds, |
| 291 |
&read_descs, &write_descs, &except_descs); |
| 292 |
|
| 293 |
/* Map the poll() timeout value in the select() timeout structure. */ |
| 294 |
|
| 295 |
pTimeout = map_timeout (timeout, &stime); |
| 296 |
|
| 297 |
/* Make the select() call. */ |
| 298 |
|
| 299 |
ready_descriptors = select (max_fd + 1, &read_descs, &write_descs, |
| 300 |
&except_descs, pTimeout); |
| 301 |
|
| 302 |
if (ready_descriptors >= 0) |
| 303 |
{ |
| 304 |
map_select_results (pArray, n_fds, |
| 305 |
&read_descs, &write_descs, &except_descs); |
| 306 |
} |
| 307 |
|
| 308 |
return ready_descriptors; |
| 309 |
} |
| 310 |
|
| 311 |
#endif |
| 312 |
|
