usr/src/lib/libcurses/screen/typeahead.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 1997 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1988 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 /*
  31  * University Copyright- Copyright (c) 1982, 1986, 1988
  32  * The Regents of the University of California
  33  * All Rights Reserved
  34  *
  35  * University Acknowledgment- Portions of this document are derived from
  36  * software developed by the University of California, Berkeley, and its
  37  * contributors.
  38  */
  39
  40 #pragma ident   "%Z%%M% %I%     %E% SMI"
  41
  42 /*LINTLIBRARY*/
  43
  44 #include        <unistd.h>
  45 #include        <sys/types.h>
  46 #include        "curses_inc.h"
  47
  48 /*
  49  * Set the file descriptor for typeahead checks to fd.  fd can be -1
  50  * to disable the checking.
  51  */
  52
  53 int
  54 typeahead(int fd)
  55 {
  56 #ifdef  SYSV
  57         /*
  58          * Doing fcntls before and after each typeahead check
  59          * read is a serious problem on the 3b2. Profiling
  60          * results indicated that a simple program(edit.c from
  61          * "The New Curses and Terminfo Package") was spending
  62          * 9.2% of the time in fcntl().
  63          */
  64
  65 #include        <fcntl.h>
  66         int     savefd = cur_term->_check_fd;
  67
  68         /* Close the previous duped file descriptor. */
  69         if (savefd >= 0)
  70                 (void) close(savefd);
  71
  72         /*
  73          * Duplicate the file descriptor so we have one to play with.
  74          * We cannot use dup(2), unfortunately, so we do typeahead checking
  75          * on terminals only. Besides, if typeahead is done when input is
  76          * coming from a file, nothing would EVER get drawn on the screen!
  77          */
  78
  79         /* MODIFIED: DRS 3/26/89 */
  80
  81         /*
  82          * a couple of notes by DRS:  first, a new file descriptor is
  83          * required, since O_NDELAY must be set.  calling fcntl() or dup()
  84          * would provide a new file descriptor, but NOT a new file pointer
  85          * for the open file (by file pointer, i mean a unix kernal file
  86          * ptr).  if a new underlying unix file ptr. is not allocated,
  87          * setting O_NDELAY will cause all normal terminal i/o to return
  88          * prematurely without blocking.
  89          *
  90          * second, the call to ttyname is NOT necessary, /dev/tty can be
  91          * used instead.  calling ttyname is quite expensive -- especially
  92          * for large /dev directories.
  93          *
  94          * note also that the code for the '#else' clause will not work
  95          * since the new file descriptor MUST have O_NDELAY set for the
  96          * rest of libcurses code to function properly.
  97          *
  98          * 4/24/89:  modified to set the close on exec() flag of the newly
  99          *              opened file descriptor
 100          */
 101
 102         /*
 103          *      cur_term->_check_fd = (tty = ttyname(fd)) ?
 104          *          open(tty, O_RDONLY | O_NDELAY) : -1;
 105          */
 106         if (isatty(fd)) {
 107                 if ((cur_term->_check_fd = open("/dev/tty", O_RDONLY |
 108                     O_NDELAY)) >= 0)
 109                         (void) fcntl(cur_term->_check_fd, F_SETFD, 1);
 110         } else
 111                 cur_term->_check_fd = -1;
 112
 113 #else   /* SYSV */
 114         int savefd = cur_term->_check_fd;
 115         /* Only do typeahead checking if the input is a tty. */
 116         if (isatty(fd))
 117                 cur_term->_check_fd = fd;
 118         else
 119                 cur_term->_check_fd = -1;
 120 #endif  /* SYSV */
 121         return (savefd);
 122 }