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Add an implementation of poll() written in terms of select(), to work around the lack of poll() on GNO.

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This is a BSD-licensed poll() implementation by Brian M. Clapper. Its performance characteristics aren't as good as a "native" poll() would be, but this shouldn't be a problem in practice.
This commit is contained in:
Stephen Heumann 2014-11-03 12:26:43 -06:00
parent 4e47bee9d2
commit 488a238ad7
5 changed files with 415 additions and 16 deletions
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3
Makefile
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@ -51,7 +51,8 @@ SRCS = \
libbb/appletlib.c \
libbb/bb.basename.c \
libbb/mempcpy.c \
libbb/vfork.and.run.c
libbb/vfork.and.run.c \
libbb/poll.c
OBJS = $(SRCS:.c=.o)
ROOTS = $(SRCS:.c=.root)

10
include/libbb.h
View File

@ -34,11 +34,7 @@
/* See the dirname/basename man page for details */
#undef basename
#define basename dont_use_basename
#ifndef __GNO__
# include <poll.h>
#else
//TODO Deal with lack of poll in GNO
#endif
#include "poll.h"
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
@ -755,11 +751,7 @@ void qsort_string_vector(char **sv, unsigned count) FAST_FUNC;
* On other errors complains [perror("poll")] and returns.
* Warning! May take (much) longer than timeout_ms to return!
* If this is a problem, use bare poll and open-code EINTR/ENOMEM handling */
#ifndef __GNO__
int safe_poll(struct pollfd *ufds, nfds_t nfds, int timeout_ms) FAST_FUNC;
#else
//TODO Deal with lack of poll in GNO
#endif
char *safe_gethostname(void) FAST_FUNC;

105
include/poll.h Normal file
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@ -0,0 +1,105 @@
/*---------------------------------------------------------------------------*\
$Id$
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.c", 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 BSD license, adapted from
http://opensource.org/licenses/bsd-license.php
Copyright (c) 1995-2011, Brian M. Clapper
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of the clapper.org nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
\*---------------------------------------------------------------------------*/
#ifndef _POLL_EMUL_H_
#define _POLL_EMUL_H_
#define POLLIN 0x01
#define POLLPRI 0x02
#define POLLOUT 0x04
#define POLLERR 0x08
#define POLLHUP 0x10
#define POLLNVAL 0x20
struct pollfd
{
int fd;
short events;
short revents;
};
typedef unsigned long nfds_t;
#ifdef __cplusplus
extern "C"
{
#endif
#if (__STDC__ > 0) || defined(__cplusplus)
extern int poll (struct pollfd *pArray, nfds_t n_fds, int timeout);
#else
extern int poll();
#endif
#ifdef __cplusplus
}
#endif
#endif /* _POLL_EMUL_H_ */

306
libbb/poll.c Normal file
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@ -0,0 +1,306 @@
/*---------------------------------------------------------------------------*\
$Id$
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 BSD license, adapted from
http://opensource.org/licenses/bsd-license.php
Copyright (c) 1995-2011, Brian M. Clapper
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of the clapper.org nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
\*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*\
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,
nfds_t n_fds,
fd_set *pReadSet,
fd_set *pWriteSet,
fd_set *pExceptSet)
#else
(pArray, n_fds, pReadSet, pWriteSet, pExceptSet)
struct pollfd *pArray;
nfds_t n_fds,
fd_set *pReadSet;
fd_set *pWriteSet;
fd_set *pExceptSet;
#endif
{
register nfds_t 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;
}

7
shell/shell.common.c
View File

@ -188,19 +188,14 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
* regardless of SA_RESTART-ness of that signal!
*/
errno = 0;
#ifndef __GNO__
// GNO doesn't have poll, so disable this for now. This disables the -t
// (timeout) flag and may interfere with signal handling, as mentioned above.
// TODO Do something more intelligent here.
pfd[0].fd = fd;
pfd[0].events = POLLIN;
if (poll(pfd, 1, timeout * 1000) != 1) {
if (poll(pfd, 1, timeout == -1 ? -1 : timeout * 1000) != 1) {
/* timed out, or EINTR */
err = errno;
retval = (const char *)(uintptr_t)1;
goto ret;
}
#endif
if (read(fd, &buffer[bufpos], 1) != 1) {
err = errno;
retval = (const char *)(uintptr_t)1;