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flags.c revision 1.4 
      1 /*-
      2  * Copyright (c) 1990 The Regents of the University of California.
      3  * All rights reserved.
      4  *
      5  * This code is derived from software contributed to Berkeley by
      6  * Chris Torek.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by the University of
     19  *	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 /*static char *sccsid = "from: @(#)flags.c	5.1 (Berkeley) 1/20/91";*/
     39 static char *rcsid = "$Id: flags.c,v 1.4 1993/12/31 19:14:15 jtc Exp $";
     40 #endif /* LIBC_SCCS and not lint */
     41 
     42 #include <sys/types.h>
     43 #include <sys/file.h>
     44 #include <stdio.h>
     45 #include <errno.h>
     46 
     47 /*
     48  * Return the (stdio) flags for a given mode.  Store the flags
     49  * to be passed to an open() syscall through *optr.
     50  * Return 0 on error.
     51  */
     52 int
     53 __sflags(mode, optr)
     54 	register char *mode;
     55 	int *optr;
     56 {
     57 	register int ret, m, o;
     58 
     59 	switch (*mode++) {
     60 
     61 	case 'r':	/* open for reading */
     62 		ret = __SRD;
     63 		m = O_RDONLY;
     64 		o = 0;
     65 		break;
     66 
     67 	case 'w':	/* open for writing */
     68 		ret = __SWR;
     69 		m = O_WRONLY;
     70 		o = O_CREAT | O_TRUNC;
     71 		break;
     72 
     73 	case 'a':	/* open for appending */
     74 		ret = __SWR;
     75 		m = O_WRONLY;
     76 		o = O_CREAT | O_APPEND;
     77 		break;
     78 
     79 	default:	/* illegal mode */
     80 		errno = EINVAL;
     81 		return (0);
     82 	}
     83 
     84 	/* [rwa]\+ or [rwa]b\+ means read and write */
     85 	if (*mode == '+' || (*mode == 'b' && mode[1] == '+')) {
     86 		ret = __SRW;
     87 		m = O_RDWR;
     88 	}
     89 	*optr = m | o;
     90 	return (ret);
     91 }
     92