gonzui

    1: /*      $OpenBSD: makebuf.c,v 1.8 2005/12/28 18:50:22 millert Exp $ */
    2: /*-
    3:  * Copyright (c) 1990, 1993
    4:  *      The Regents of the University of California.  All rights reserved.
    5:  *
    6:  * This code is derived from software contributed to Berkeley by
    7:  * Chris Torek.
    8:  *
    9:  * Redistribution and use in source and binary forms, with or without
   10:  * modification, are permitted provided that the following conditions
   11:  * are met:
   12:  * 1. Redistributions of source code must retain the above copyright
   13:  *    notice, this list of conditions and the following disclaimer.
   14:  * 2. Redistributions in binary form must reproduce the above copyright
   15:  *    notice, this list of conditions and the following disclaimer in the
   16:  *    documentation and/or other materials provided with the distribution.
   17:  * 3. Neither the name of the University nor the names of its contributors
   18:  *    may be used to endorse or promote products derived from this software
   19:  *    without specific prior written permission.
   20:  *
   21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31:  * SUCH DAMAGE.
   32:  */
   33: 
   34: #include <sys/types.h>
   35: #include <sys/stat.h>
   36: #include <unistd.h>
   37: #include <stdio.h>
   38: #include <stdlib.h>
   39: #include "local.h"
   40: 
   41: /*
   42:  * Allocate a file buffer, or switch to unbuffered I/O.
   43:  * Per the ANSI C standard, ALL tty devices default to line buffered.
   44:  *
   45:  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
   46:  * optimisation) right after the __libc_fstat() that finds the buffer size.
   47:  */
   48: void
   49: __smakebuf(FILE *fp)
   50: {
   51:         void *p;
   52:         int flags;
   53:         size_t size;
   54:         int couldbetty;
   55: 
   56:         if (fp->_flags & __SNBF) {
   57:                 fp->_bf._base = fp->_p = fp->_nbuf;
   58:                 fp->_bf._size = 1;
   59:                 return;
   60:         }
   61:         flags = __swhatbuf(fp, &size, &couldbetty);
   62:         if ((p = malloc(size)) == NULL) {
   63:                 fp->_flags |= __SNBF;
   64:                 fp->_bf._base = fp->_p = fp->_nbuf;
   65:                 fp->_bf._size = 1;
   66:                 return;
   67:         }
   68:         __atexit_register_cleanup(_cleanup);
   69:         flags |= __SMBF;
   70:         fp->_bf._base = fp->_p = p;
   71:         fp->_bf._size = size;
   72:         if (couldbetty && isatty(fp->_file))
   73:                 flags |= __SLBF;
   74:         fp->_flags |= flags;
   75: }
   76: 
   77: /*
   78:  * Internal routine to determine `proper' buffering for a file.
   79:  */
   80: int
   81: __swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty)
   82: {
   83:         struct stat st;
   84: 
   85:         if (fp->_file < 0 || __libc_fstat(fp->_file, &st) < 0) {
   86:                 *couldbetty = 0;
   87:                 *bufsize = BUFSIZ;
   88:                 return (__SNPT);
   89:         }
   90: 
   91:         /* could be a tty iff it is a character device */
   92:         *couldbetty = S_ISCHR(st.st_mode);
   93:         if (st.st_blksize == 0) {
   94:                 *bufsize = BUFSIZ;
   95:                 return (__SNPT);
   96:         }
   97: 
   98:         /*
   99:          * Optimise fseek() only if it is a regular file.  (The test for
  100:          * __sseek is mainly paranoia.)  It is safe to set _blksize
  101:          * unconditionally; it will only be used if __SOPT is also set.
  102:          */
  103:         *bufsize = st.st_blksize;
  104:         fp->_blksize = st.st_blksize;
  105:         return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
  106:             __SOPT : __SNPT);
  107: }