poll.c

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/*---------------------------------------------------------------------------*\
  $Id$
 
  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 "asterisk.h"
 
#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 <errno.h>
 
#include "asterisk/utils.h"                            /* this package */
#include "asterisk/poll-compat.h"                            /* this package */
 
unsigned int ast_FD_SETSIZE = FD_SETSIZE;
 
#ifndef MAX
#define MAX(a,b)    a > b ? a : b
#endif
 
/*---------------------------------------------------------------------------*\
                 Private Functions
\*---------------------------------------------------------------------------*/
 
#if defined(AST_POLL_COMPAT)
static int map_poll_spec(struct pollfd *pArray, unsigned long n_fds,
        ast_fdset *pReadSet, ast_fdset *pWriteSet, ast_fdset *pExceptSet)
{
    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) {
            /*!\note
             * "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;
}
 
#ifdef AST_POLL_COMPAT
static struct timeval *map_timeout(int poll_timeout, struct timeval *pSelTimeout)
{
    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 != 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;
}
#endif /* AST_POLL_COMPAT */
 
static void map_select_results(struct pollfd *pArray, unsigned long n_fds,
              ast_fdset *pReadSet, ast_fdset *pWriteSet, ast_fdset *pExceptSet)
{
    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, (fd_set *) pExceptSet)) {
            pCur->revents |= POLLPRI;
        } else if (FD_ISSET(pCur->fd, (fd_set *) pReadSet)) {
            pCur->revents |= POLLIN;
        }
 
        if (FD_ISSET(pCur->fd, (fd_set *) pWriteSet)) {
            pCur->revents |= POLLOUT;
        }
    }
 
    return;
}
#endif /* defined(AST_POLL_COMPAT) || !defined(HAVE_PPOLL) */
 
/*---------------------------------------------------------------------------*\
                 Public Functions
\*---------------------------------------------------------------------------*/
#ifdef AST_POLL_COMPAT
int ast_internal_poll(struct pollfd *pArray, unsigned long n_fds, int timeout)
{
    ast_fdset  read_descs;                       /* input file descs */
    ast_fdset  write_descs;                      /* output file descs */
    ast_fdset  except_descs;                     /* exception descs */
    struct  timeval stime;                       /* select() timeout value */
    int     ready_descriptors;                   /* function result */
    int     max_fd = 0;                          /* maximum fd value */
    struct  timeval *pTimeout;                   /* actually passed */
    int save_errno;
 
    FD_ZERO(&read_descs);
    FD_ZERO(&write_descs);
    FD_ZERO(&except_descs);
 
    /* Map the poll() file descriptor list in the select() data structures. */
 
    if (pArray) {
        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 = ast_select(max_fd + 1, &read_descs, &write_descs,
                &except_descs, pTimeout);
    save_errno = errno;
 
    if (ready_descriptors >= 0) {
        map_select_results (pArray, n_fds,
                &read_descs, &write_descs, &except_descs);
    }
 
    errno = save_errno;
    return ready_descriptors;
}
#endif /* AST_POLL_COMPAT */
 
int ast_poll2(struct pollfd *pArray, unsigned long n_fds, struct timeval *tv)
{
#if !defined(AST_POLL_COMPAT)
    struct timeval start = ast_tvnow();
#if defined(HAVE_PPOLL)
    struct timespec ts = { tv ? tv->tv_sec : 0, tv ? tv->tv_usec * 1000 : 0 };
    int res = ppoll(pArray, n_fds, tv ? &ts : NULL, NULL);
#else
    int res = poll(pArray, n_fds, tv ? tv->tv_sec * 1000 + tv->tv_usec / 1000 : -1);
#endif
    struct timeval after = ast_tvnow();
    if (res > 0 && tv && ast_tvdiff_ms(ast_tvadd(*tv, start), after) > 0) {
        *tv = ast_tvsub(*tv, ast_tvsub(after, start));
    } else if (res > 0 && tv) {
        *tv = ast_tv(0, 0);
    }
    return res;
#else
    ast_fdset read_descs, write_descs, except_descs;
    int ready_descriptors, max_fd = 0;
 
    FD_ZERO(&read_descs);
    FD_ZERO(&write_descs);
    FD_ZERO(&except_descs);
 
    if (pArray) {
        max_fd = map_poll_spec(pArray, n_fds, &read_descs, &write_descs, &except_descs);
    }
 
    ready_descriptors = ast_select(max_fd + 1, &read_descs, &write_descs, &except_descs, tv);
 
    if (ready_descriptors >= 0) {
        map_select_results(pArray, n_fds, &read_descs, &write_descs, &except_descs);
    }
 
    return ready_descriptors;
#endif
}