StdLib/LibC/Stdio/makebuf.c

   1 /** @file
   2     Implementation of internal file buffer allocation functions.
   3
   4     Copyright (c) 2010 - 2011, Intel Corporation. All rights reserved.<BR>
   5     This program and the accompanying materials are licensed and made available
   6     under the terms and conditions of the BSD License that accompanies this
   7     distribution.  The full text of the license may be found at
   8     http://opensource.org/licenses/bsd-license.
   9
  10     THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11     WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13     Copyright (c) 1990, 1993
  14     The Regents of the University of California.  All rights reserved.
  15
  16     This code is derived from software contributed to Berkeley by
  17     Chris Torek.
  18
  19     Redistribution and use in source and binary forms, with or without
  20     modification, are permitted provided that the following conditions
  21     are met:
  22       - Redistributions of source code must retain the above copyright
  23         notice, this list of conditions and the following disclaimer.
  24       - Redistributions in binary form must reproduce the above copyright
  25         notice, this list of conditions and the following disclaimer in the
  26         documentation and/or other materials provided with the distribution.
  27       - Neither the name of the University nor the names of its contributors
  28         may be used to endorse or promote products derived from this software
  29         without specific prior written permission.
  30
  31     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  32     AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  33     IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  34     ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
  35     LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  36     CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  37     SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  38     INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  39     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  40     ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  41     POSSIBILITY OF SUCH DAMAGE.
  42
  43     NetBSD: makebuf.c,v 1.14 2003/08/07 16:43:28 agc Exp
  44     makebuf.c 8.1 (Berkeley) 6/4/93
  45 **/
  46 #include  <LibConfig.h>
  47
  48 #include  "namespace.h"
  49
  50 #include  <sys/types.h>
  51 #include  <sys/stat.h>
  52 #include  <assert.h>
  53 #include  <stdio.h>
  54 #include  <stdlib.h>
  55 #include  <unistd.h>
  56 #include  "reentrant.h"
  57 #include  "local.h"
  58 #include  <MainData.h>
  59
  60 /*
  61  * Allocate a file buffer, or switch to unbuffered I/O.
  62  * Per the ANSI C standard, ALL tty devices default to line buffered.
  63  *
  64  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
  65  * optimisation) right after the fstat() that finds the buffer size.
  66  */
  67 void
  68 __smakebuf(FILE *fp)
  69 {
  70   void *p;
  71   int flags;
  72   size_t size;
  73   int couldbetty;
  74
  75   _DIAGASSERT(fp != NULL);
  76
  77   if (fp != NULL) {
  78   if (fp->_flags & __SNBF) {
  79     fp->_bf._base = fp->_p = fp->_nbuf;
  80     fp->_bf._size = 1;
  81     return;
  82   }
  83   flags = __swhatbuf(fp, &size, &couldbetty);
  84   if ((p = malloc(size)) == NULL) {
  85     fp->_flags |= __SNBF;
  86     fp->_bf._base = fp->_p = fp->_nbuf;
  87     fp->_bf._size = 1;
  88     return;
  89   }
  90   gMD->cleanup = _cleanup;
  91   flags |= __SMBF;
  92   fp->_bf._base = fp->_p = p;
  93   fp->_bf._size = (int)size;
  94   if (couldbetty || isatty(fp->_file))
  95     flags |= __SLBF;
  96   fp->_flags |= flags;
  97   }
  98 }
  99
 100 /*
 101  * Internal routine to determine `proper' buffering for a file.
 102  */
 103 int
 104 __swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty)
 105 {
 106   struct stat st;
 107
 108   _DIAGASSERT(fp != NULL);
 109   _DIAGASSERT(bufsize != NULL);
 110   _DIAGASSERT(couldbetty != NULL);
 111   if(fp == NULL) {
 112     return (__SNPT);
 113   }
 114
 115   if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
 116     *couldbetty = 0;
 117     *bufsize = BUFSIZ;
 118     return (__SNPT);
 119   }
 120
 121   /* could be a tty iff it is a character device */
 122   *couldbetty = S_ISCHR(st.st_mode);
 123   if (st.st_blksize == 0) {
 124     *bufsize = BUFSIZ;
 125     return (__SNPT);
 126   }
 127
 128   /*
 129    * Optimise fseek() only if it is a regular file.  (The test for
 130    * __sseek is mainly paranoia.)  It is safe to set _blksize
 131    * unconditionally; it will only be used if __SOPT is also set.
 132    */
 133   *bufsize = st.st_blksize;
 134   fp->_blksize = st.st_blksize;
 135   return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
 136       __SOPT : __SNPT);
 137 }