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makebuf.c revision 1.1 
      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[] = "@(#)makebuf.c	5.2 (Berkeley) 2/24/91";
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include <sys/types.h>
     42 #include <sys/stat.h>
     43 #include <unistd.h>
     44 #include <stdio.h>
     45 #include <stdlib.h>
     46 #include "local.h"
     47 
     48 /*
     49  * Allocate a file buffer, or switch to unbuffered I/O.
     50  * Per the ANSI C standard, ALL tty devices default to line buffered.
     51  *
     52  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
     53  * optimisation) right after the fstat() that finds the buffer size.
     54  */
     55 void
     56 __smakebuf(fp)
     57 	register FILE *fp;
     58 {
     59 	register size_t size, couldbetty;
     60 	register void *p;
     61 	struct stat st;
     62 
     63 	if (fp->_flags & __SNBF) {
     64 		fp->_bf._base = fp->_p = fp->_nbuf;
     65 		fp->_bf._size = 1;
     66 		return;
     67 	}
     68 	if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
     69 		couldbetty = 0;
     70 		size = BUFSIZ;
     71 		/* do not try to optimise fseek() */
     72 		fp->_flags |= __SNPT;
     73 	} else {
     74 		couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
     75 		size = st.st_blksize <= 0 ? BUFSIZ : st.st_blksize;
     76 		/*
     77 		 * Optimise fseek() only if it is a regular file.
     78 		 * (The test for __sseek is mainly paranoia.)
     79 		 */
     80 		if ((st.st_mode & S_IFMT) == S_IFREG &&
     81 		    fp->_seek == __sseek) {
     82 			fp->_flags |= __SOPT;
     83 			fp->_blksize = st.st_blksize;
     84 		} else
     85 			fp->_flags |= __SNPT;
     86 	}
     87 	if ((p = malloc(size)) == NULL) {
     88 		fp->_flags |= __SNBF;
     89 		fp->_bf._base = fp->_p = fp->_nbuf;
     90 		fp->_bf._size = 1;
     91 	} else {
     92 		__cleanup = _cleanup;
     93 		fp->_flags |= __SMBF;
     94 		fp->_bf._base = fp->_p = p;
     95 		fp->_bf._size = size;
     96 		if (couldbetty && isatty(fp->_file))
     97 			fp->_flags |= __SLBF;
     98 	}
     99 }
    100