demux.h

早期freebsd实现

/******************************************************************************
 *  Copyright 1990, 1992 Free Software Foundation, Inc.
 *
 *  This code was donated by Intel Corp.
 *
 * This include file supports demultiplexing of input from two sources:
 * stdin and one external source (normally the NINDY monitor).
 *
 * Its purpose is to promote portability of applications between different
 * flavors (BSD and USG/SysV) of Unix.  As of this writing, it is used by the
 * gdb960 remote communications module (remote.c) and the comm960 utility.
 * 
 * It is assumed that 'USG' is defined on the compiler invocation line if the
 * code should compile and run on a USG/SysV system.  Otherwise, BSD is assumed.
 *
 * The application code must use all three of these macros:
 *
 *	DEMUX_DECL	Declares data structures needed by the other macros.
 *
 *	DEMUX_WAIT(fd)	Waits until input is available on either stdin or
 *			file descriptor 'fd'.
 *
 *	DEMUX_READ(fd,bufp,bufsz)
 *			Reads up to 'bufsz' bytes from file descriptor 'fd'
 *			into buffer pointed at by character pointer 'bufp'.
 *			Returns the number of bytes read, which will be 0
 *			if there was no input pending on 'fd'. 'fd' should be
 *			either 0 (stdin) or the same descriptor that was used
 *			in the invocation of 'DEMUX_WAIT'.
 *
 * The following macro is also included:
 *
 *	TIME_INPUT(fd,timeout,retp)
 *			Waits up to 'timeout' seconds for input on file
 *			descriptor 'fd'.  Sets (*retp) to:
 *				 1 if input is ready
 *				 0 if timeout occurred
 *				-1 if wait was interrupted by a signal
 *
 * WARNINGS ABOUT USG (System V) UNIX!!
 *
 *	The TIME_INPUT macro isn't implemented: it's a no-op.
 *
 *	The damned 'poll' call can't be used on normal tty's, so DEMUX_WAIT is
 *	also a no-op: DEMUX_READ uses the FIONREAD ioctl if it's available;
 *	otherwise the file descriptor is temporarily set for non-blocking input
 *	and a read it done.
 *
 ******************************************************************************/

#ifdef USG
#	include <fcntl.h>

#	define DEMUX_DECL		int _saveflags_; int _n_
#	define DEMUX_WAIT(fd)

	/* Use non-blocking I/O */
#	define DEMUX_READ(fd,bufp,bufsz) (			\
			_saveflags_ = fcntl( fd, F_GETFL, 0 ),		\
			fcntl( fd, F_SETFL, _saveflags_ | O_NDELAY ),	\
			_n_ = read( fd, bufp, bufsz ),			\
			fcntl( fd, F_SETFL, _saveflags_ ),		\
			_n_ )

#	define TIME_INPUT(fd,timeout,retp)
 
#else	/* BSD */

#	include <sys/types.h>
#	include <sys/time.h>

#	define DEMUX_DECL	fd_set _mux_

#	define DEMUX_WAIT(fd)	{					\
			FD_ZERO( &_mux_ );				\
			FD_SET( 0, &_mux_ );				\
			FD_SET( fd, &_mux_ );				\
			if (select(fd+1,&_mux_,0,0,0) <= 0){		\
				FD_ZERO(&_mux_);			\
			}						\
	}
			/* Check return value of select in case of
			 * premature termination due to signal:  clear
			 * file descriptors in this case so DEMUX_READ
			 * doesn't mistakenly say there's input on them.
			 */

#	define DEMUX_READ(fd,bufp,bufsz) \
			( FD_ISSET(fd,&_mux_) ?	read(fd,bufp,bufsz) : 0 )

#	define TIME_INPUT(fd,timeout,retp)	{			\
			fd_set _fds_;					\
			struct timeval _timeout_;			\
			FD_ZERO( &_fds_ );				\
			FD_SET( fd, &_fds_ );				\
			_timeout_.tv_sec  = timeout;			\
			_timeout_.tv_usec = 0;				\
			*(retp) = select(fd+1,&_fds_,0,0,&_timeout_);	\
	}

#endif