gvpe/lib/poll.c

/*---------------------------------------------------------------------------*\
  $Id: poll.c,v 1.4 2003/01/01 19:02:29 bmc 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
\*---------------------------------------------------------------------------*/

#if defined(HAVE_SYS_POLL_H) && defined(HAVE_POLL)

#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:	1.1
Committed:	Tue Oct 14 17:24:19 2003 UTC (20 years, 7 months ago) by pcg
Content type:	text/plain
Branch:	MAIN
Log Message:	* empty log message *
#	User	Rev	Content
1	pcg	1.1	/---------------------------------------------------------------------------\
2			$Id: poll.c,v 1.4 2003/01/01 19:02:29 bmc Exp $
3
4			NAME
5
6			poll - select(2)-based poll() emulation function for BSD systems.
7
8			SYNOPSIS
9			#include "poll.h"
10
11			struct pollfd
12			{
13			int fd;
14			short events;
15			short revents;
16			}
17
18			int poll (struct pollfd *pArray, unsigned long n_fds, int timeout)
19
20			DESCRIPTION
21
22			This file, and the accompanying "poll.h", implement the System V
23			poll(2) system call for BSD systems (which typically do not provide
24			poll()). Poll() provides a method for multiplexing input and output
25			on multiple open file descriptors; in traditional BSD systems, that
26			capability is provided by select(). While the semantics of select()
27			differ from those of poll(), poll() can be readily emulated in terms
28			of select() -- which is how this function is implemented.
29
30			REFERENCES
31			Stevens, W. Richard. Unix Network Programming. Prentice-Hall, 1990.
32
33			NOTES
34			1. This software requires an ANSI C compiler.
35
36			LICENSE
37
38			This software is released under the following license:
39
40			Copyright (c) 1995-2002 Brian M. Clapper
41			All rights reserved.
42
43			Redistribution and use in source and binary forms are
44			permitted provided that: (1) source distributions retain
45			this entire copyright notice and comment; (2) modifications
46			made to the software are prominently mentioned, and a copy
47			of the original software (or a pointer to its location) are
48			included; and (3) distributions including binaries display
49			the following acknowledgement: "This product includes
50			software developed by Brian M. Clapper <bmc@clapper.org>"
51			in the documentation or other materials provided with the
52			distribution. The name of the author may not be used to
53			endorse or promote products derived from this software
54			without specific prior written permission.
55
56			THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS
57			OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE
58			IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
59			PARTICULAR PURPOSE.
60
61			Effectively, this means you can do what you want with the software
62			except remove this notice or take advantage of the author's name.
63			If you modify the software and redistribute your modified version,
64			you must indicate that your version is a modification of the
65			original, and you must provide either a pointer to or a copy of the
66			original.
67			\---------------------------------------------------------------------------/
68
69
70			/---------------------------------------------------------------------------\
71			Includes
72			\---------------------------------------------------------------------------/
73
74			#if defined(HAVE_SYS_POLL_H) && defined(HAVE_POLL)
75
76			#include <unistd.h> /* standard Unix definitions */
77			#include <sys/types.h> /* system types */
78			#include <sys/time.h> /* time definitions */
79			#include <assert.h> /* assertion macros */
80			#include <string.h> /* string functions */
81			#include "poll.h" /* this package */
82
83			/---------------------------------------------------------------------------\
84			Macros
85			\---------------------------------------------------------------------------/
86
87			#ifndef MAX
88			#define MAX(a,b) ((a) > (b) ? (a) : (b))
89			#endif
90
91
92			/---------------------------------------------------------------------------\
93			Private Functions
94			\---------------------------------------------------------------------------/
95
96			static int map_poll_spec
97			#if __STDC__ > 0
98			(struct pollfd *pArray,
99			unsigned long n_fds,
100			fd_set *pReadSet,
101			fd_set *pWriteSet,
102			fd_set *pExceptSet)
103			#else
104			(pArray, n_fds, pReadSet, pWriteSet, pExceptSet)
105			struct pollfd *pArray;
106			unsigned long n_fds;
107			fd_set *pReadSet;
108			fd_set *pWriteSet;
109			fd_set *pExceptSet;
110			#endif
111			{
112			register unsigned long i; /* loop control */
113			register struct pollfd pCur; / current array element */
114			register int max_fd = -1; /* return value */
115
116			/*
117			Map the poll() structures into the file descriptor sets required
118			by select().
119			*/
120			for (i = 0, pCur = pArray; i < n_fds; i++, pCur++)
121			{
122			/* Skip any bad FDs in the array. */
123
124			if (pCur->fd < 0)
125			continue;
126
127			if (pCur->events & POLLIN)
128			{
129			/* "Input Ready" notification desired. */
130			FD_SET (pCur->fd, pReadSet);
131			}
132
133			if (pCur->events & POLLOUT)
134			{
135			/* "Output Possible" notification desired. */
136			FD_SET (pCur->fd, pWriteSet);
137			}
138
139			if (pCur->events & POLLPRI)
140			{
141			/*
142			"Exception Occurred" notification desired. (Exceptions
143			include out of band data.
144			*/
145			FD_SET (pCur->fd, pExceptSet);
146			}
147
148			max_fd = MAX (max_fd, pCur->fd);
149			}
150
151			return max_fd;
152			}
153
154			static struct timeval *map_timeout
155			#if __STDC__ > 0
156			(int poll_timeout, struct timeval *pSelTimeout)
157			#else
158			(poll_timeout, pSelTimeout)
159			int poll_timeout;
160			struct timeval *pSelTimeout;
161			#endif
162			{
163			struct timeval *pResult;
164
165			/*
166			Map the poll() timeout value into a select() timeout. The possible
167			values of the poll() timeout value, and their meanings, are:
168
169			VALUE MEANING
170
171			-1 wait indefinitely (until signal occurs)
172			0 return immediately, don't block
173			>0 wait specified number of milliseconds
174
175			select() uses a "struct timeval", which specifies the timeout in
176			seconds and microseconds, so the milliseconds value has to be mapped
177			accordingly.
178			*/
179
180			assert (pSelTimeout != (struct timeval *) NULL);
181
182			switch (poll_timeout)
183			{
184			case -1:
185			/*
186			A NULL timeout structure tells select() to wait indefinitely.
187			*/
188			pResult = (struct timeval *) NULL;
189			break;
190
191			case 0:
192			/*
193			"Return immediately" (test) is specified by all zeros in
194			a timeval structure.
195			*/
196			pSelTimeout->tv_sec = 0;
197			pSelTimeout->tv_usec = 0;
198			pResult = pSelTimeout;
199			break;
200
201			default:
202			/* Wait the specified number of milliseconds. */
203			pSelTimeout->tv_sec = poll_timeout / 1000; /* get seconds */
204			poll_timeout %= 1000; /* remove seconds */
205			pSelTimeout->tv_usec = poll_timeout * 1000; /* get microseconds */
206			pResult = pSelTimeout;
207			break;
208			}
209
210
211			return pResult;
212			}
213
214			static void map_select_results
215			#if __STDC__ > 0
216			(struct pollfd *pArray,
217			unsigned long n_fds,
218			fd_set *pReadSet,
219			fd_set *pWriteSet,
220			fd_set *pExceptSet)
221			#else
222			(pArray, n_fds, pReadSet, pWriteSet, pExceptSet)
223			struct pollfd *pArray;
224			unsigned long n_fds;
225			fd_set *pReadSet;
226			fd_set *pWriteSet;
227			fd_set *pExceptSet;
228			#endif
229			{
230			register unsigned long i; /* loop control */
231			register struct pollfd pCur; / current array element */
232
233			for (i = 0, pCur = pArray; i < n_fds; i++, pCur++)
234			{
235			/* Skip any bad FDs in the array. */
236
237			if (pCur->fd < 0)
238			continue;
239
240			/* Exception events take priority over input events. */
241
242			pCur->revents = 0;
243			if (FD_ISSET (pCur->fd, pExceptSet))
244			pCur->revents \|= POLLPRI;
245
246			else if (FD_ISSET (pCur->fd, pReadSet))
247			pCur->revents \|= POLLIN;
248
249			if (FD_ISSET (pCur->fd, pWriteSet))
250			pCur->revents \|= POLLOUT;
251			}
252
253			return;
254			}
255
256			/---------------------------------------------------------------------------\
257			Public Functions
258			\---------------------------------------------------------------------------/
259
260			int poll
261
262			#if __STDC__ > 0
263			(struct pollfd *pArray, unsigned long n_fds, int timeout)
264			#else
265			(pArray, n_fds, timeout)
266			struct pollfd *pArray;
267			unsigned long n_fds;
268			int timeout;
269			#endif
270
271			{
272			fd_set read_descs; /* input file descs */
273			fd_set write_descs; /* output file descs */
274			fd_set except_descs; /* exception descs */
275			struct timeval stime; /* select() timeout value */
276			int ready_descriptors; /* function result */
277			int max_fd; /* maximum fd value */
278			struct timeval pTimeout; / actually passed */
279
280			FD_ZERO (&read_descs);
281			FD_ZERO (&write_descs);
282			FD_ZERO (&except_descs);
283
284			assert (pArray != (struct pollfd *) NULL);
285
286			/* Map the poll() file descriptor list in the select() data structures. */
287
288			max_fd = map_poll_spec (pArray, n_fds,
289			&read_descs, &write_descs, &except_descs);
290
291			/* Map the poll() timeout value in the select() timeout structure. */
292
293			pTimeout = map_timeout (timeout, &stime);
294
295			/* Make the select() call. */
296
297			ready_descriptors = select (max_fd + 1, &read_descs, &write_descs,
298			&except_descs, pTimeout);
299
300			if (ready_descriptors >= 0)
301			{
302			map_select_results (pArray, n_fds,
303			&read_descs, &write_descs, &except_descs);
304			}
305
306			return ready_descriptors;
307			}
308
309			#endif
310