gvpe/lib/poll.c

#if defined(HAVE_SYS_POLL_H) && defined(HAVE_POLL)
/* nothing to do, all is well, gore is president. */
#else

/*---------------------------------------------------------------------------*\
  $Id: poll.c,v 1.2 2003/10/14 19:14:27 pcg Exp $

  NAME

        poll - select(2)-based poll() emulation function for BSD systems.

  SYNOPSIS
        #include "poll.h"

        struct pollfd
        {
            int     fd;
            short   events;
            short   revents;
        }

        int poll (struct pollfd *pArray, unsigned long n_fds, int timeout)

  DESCRIPTION

        This file, and the accompanying "poll.h", implement the System V
        poll(2) system call for BSD systems (which typically do not provide
        poll()).  Poll() provides a method for multiplexing input and output
        on multiple open file descriptors; in traditional BSD systems, that
        capability is provided by select().  While the semantics of select()
        differ from those of poll(), poll() can be readily emulated in terms
        of select() -- which is how this function is implemented.

  REFERENCES
        Stevens, W. Richard. Unix Network Programming.  Prentice-Hall, 1990.

  NOTES
        1. This software requires an ANSI C compiler.

  LICENSE

        This software is released under the following license:

                Copyright (c) 1995-2002 Brian M. Clapper
                All rights reserved.

                Redistribution and use in source and binary forms are
                permitted provided that: (1) source distributions retain
                this entire copyright notice and comment; (2) modifications
                made to the software are prominently mentioned, and a copy
                of the original software (or a pointer to its location) are
                included; and (3) distributions including binaries display
                the following acknowledgement: "This product includes
                software developed by Brian M. Clapper <bmc@clapper.org>"
                in the documentation or other materials provided with the
                distribution. The name of the author may not be used to
                endorse or promote products derived from this software
                without specific prior written permission.

                THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS
                OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE
                IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
                PARTICULAR PURPOSE.

        Effectively, this means you can do what you want with the software
        except remove this notice or take advantage of the author's name.
        If you modify the software and redistribute your modified version,
        you must indicate that your version is a modification of the
        original, and you must provide either a pointer to or a copy of the
        original.
\*---------------------------------------------------------------------------*/


/*---------------------------------------------------------------------------*\
                                 Includes
\*---------------------------------------------------------------------------*/

#include <unistd.h>                          /* standard Unix definitions */
#include <sys/types.h>                       /* system types */
#include <sys/time.h>                        /* time definitions */
#include <assert.h>                          /* assertion macros */
#include <string.h>                          /* string functions */
#include "poll.h"                            /* this package */

/*---------------------------------------------------------------------------*\
                                  Macros
\*---------------------------------------------------------------------------*/

#ifndef MAX
#define MAX(a,b)        ((a) > (b) ? (a) : (b))
#endif


/*---------------------------------------------------------------------------*\
                             Private Functions
\*---------------------------------------------------------------------------*/

static int map_poll_spec
#if __STDC__ > 0
                        (struct pollfd *pArray,
                          unsigned long  n_fds,
                          fd_set        *pReadSet,
                          fd_set        *pWriteSet,
                          fd_set        *pExceptSet)
#else
                         (pArray, n_fds, pReadSet, pWriteSet, pExceptSet)
                          struct pollfd *pArray;
                          unsigned long  n_fds;
                          fd_set        *pReadSet;
                          fd_set        *pWriteSet;
                          fd_set        *pExceptSet;
#endif
{
    register unsigned long  i;                   /* loop control */
    register struct         pollfd *pCur;        /* current array element */
    register int            max_fd = -1;         /* return value */

    /*
       Map the poll() structures into the file descriptor sets required
       by select().
    */
    for (i = 0, pCur = pArray; i < n_fds; i++, pCur++)
    {
        /* Skip any bad FDs in the array. */

        if (pCur->fd < 0)
            continue;

        if (pCur->events & POLLIN)
        {
            /* "Input Ready" notification desired. */
            FD_SET (pCur->fd, pReadSet);
        }

        if (pCur->events & POLLOUT)
        {
            /* "Output Possible" notification desired. */
            FD_SET (pCur->fd, pWriteSet);
        }

        if (pCur->events & POLLPRI)
        {
            /*
               "Exception Occurred" notification desired.  (Exceptions
               include out of band data.
            */
            FD_SET (pCur->fd, pExceptSet);
        }

        max_fd = MAX (max_fd, pCur->fd);
    }

    return max_fd;
}

static struct timeval *map_timeout
#if __STDC__ > 0
                        (int poll_timeout, struct timeval *pSelTimeout)
#else
                        (poll_timeout, pSelTimeout)
                         int             poll_timeout;
                         struct timeval *pSelTimeout;
#endif
{
    struct timeval *pResult;

    /*
       Map the poll() timeout value into a select() timeout.  The possible
       values of the poll() timeout value, and their meanings, are:

       VALUE    MEANING

       -1       wait indefinitely (until signal occurs)
        0       return immediately, don't block
       >0       wait specified number of milliseconds

       select() uses a "struct timeval", which specifies the timeout in
       seconds and microseconds, so the milliseconds value has to be mapped
       accordingly.
    */

    assert (pSelTimeout != (struct timeval *) NULL);

    switch (poll_timeout)
    {
        case -1:
            /*
               A NULL timeout structure tells select() to wait indefinitely.
            */
            pResult = (struct timeval *) NULL;
            break;

        case 0:
            /*
               "Return immediately" (test) is specified by all zeros in
               a timeval structure.
            */
            pSelTimeout->tv_sec  = 0;
            pSelTimeout->tv_usec = 0;
            pResult = pSelTimeout;
            break;

        default:
            /* Wait the specified number of milliseconds. */
            pSelTimeout->tv_sec  = poll_timeout / 1000; /* get seconds */
            poll_timeout        %= 1000;                /* remove seconds */
            pSelTimeout->tv_usec = poll_timeout * 1000; /* get microseconds */
            pResult = pSelTimeout;
            break;
    }


    return pResult;
}

static void map_select_results
#if __STDC__ > 0
                         (struct pollfd *pArray,
                          unsigned long  n_fds,
                          fd_set        *pReadSet,
                          fd_set        *pWriteSet,
                          fd_set        *pExceptSet)
#else
                         (pArray, n_fds, pReadSet, pWriteSet, pExceptSet)
                          struct pollfd *pArray;
                          unsigned long  n_fds;
                          fd_set        *pReadSet;
                          fd_set        *pWriteSet;
                          fd_set        *pExceptSet;
#endif
{
    register unsigned long  i;                   /* loop control */
    register struct         pollfd *pCur;        /* current array element */

    for (i = 0, pCur = pArray; i < n_fds; i++, pCur++)
    {
        /* Skip any bad FDs in the array. */

        if (pCur->fd < 0)
            continue;

        /* Exception events take priority over input events. */

        pCur->revents = 0;
        if (FD_ISSET (pCur->fd, pExceptSet))
            pCur->revents |= POLLPRI;

        else if (FD_ISSET (pCur->fd, pReadSet))
            pCur->revents |= POLLIN;

        if (FD_ISSET (pCur->fd, pWriteSet))
            pCur->revents |= POLLOUT;
    }

    return;
}

/*---------------------------------------------------------------------------*\
                             Public Functions
\*---------------------------------------------------------------------------*/

int poll

#if __STDC__ > 0
        (struct pollfd *pArray, unsigned long n_fds, int timeout)
#else
        (pArray, n_fds, timeout)
         struct        pollfd *pArray;
         unsigned long n_fds;
         int           timeout;
#endif

{
    fd_set  read_descs;                          /* input file descs */
    fd_set  write_descs;                         /* output file descs */
    fd_set  except_descs;                        /* exception descs */
    struct  timeval stime;                       /* select() timeout value */
    int     ready_descriptors;                   /* function result */
    int     max_fd;                              /* maximum fd value */
    struct  timeval *pTimeout;                   /* actually passed */

    FD_ZERO (&read_descs);
    FD_ZERO (&write_descs);
    FD_ZERO (&except_descs);

    assert (pArray != (struct pollfd *) NULL);

    /* Map the poll() file descriptor list in the select() data structures. */

    max_fd = map_poll_spec (pArray, n_fds,
                            &read_descs, &write_descs, &except_descs);

    /* Map the poll() timeout value in the select() timeout structure. */

    pTimeout = map_timeout (timeout, &stime);

    /* Make the select() call. */

    ready_descriptors = select (max_fd + 1, &read_descs, &write_descs,
                                &except_descs, pTimeout);

    if (ready_descriptors >= 0)
    {
        map_select_results (pArray, n_fds,
                            &read_descs, &write_descs, &except_descs);
    }

    return ready_descriptors;
}

#endif

Revision:	1.3
Committed:	Sat Jan 17 01:18:36 2004 UTC (20 years, 4 months ago) by pcg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.2:	+1 -1 lines
State:	*FILE REMOVED*
Log Message:	* empty log message *
#	User	Rev	Content
1	pcg	1.2	#if defined(HAVE_SYS_POLL_H) && defined(HAVE_POLL)
2			/* nothing to do, all is well, gore is president. */
3			#else
4
5	pcg	1.1	/---------------------------------------------------------------------------\
6	pcg	1.3	$Id: poll.c,v 1.2 2003/10/14 19:14:27 pcg Exp $
7	pcg	1.1
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