usr/src/lib/libc/port/stdio/_findbuf.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 (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 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 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32
  33 #define _LARGEFILE64_SOURCE     1
  34
  35 #include "lint.h"
  36 #include "file64.h"
  37 #include <stdlib.h>
  38 #include <stdio.h>
  39 #include <sys/types.h>
  40 #include <sys/stat.h>
  41 #include "stdiom.h"
  42
  43 /*
  44  * If buffer space has been pre-allocated use it otherwise malloc space.
  45  * PUSHBACK causes the base pointer to be bumped forward. At least 4 bytes
  46  * of pushback are required to meet international specifications.
  47  * Extra space at the end of the buffer allows for synchronization problems.
  48  * If malloc() fails stdio bails out; assumption being the system is in trouble.
  49  * Associate a buffer with stream; return NULL on error.
  50  */
  51 Uchar *
  52 _findbuf(FILE *iop)
  53 {
  54         int fd = GET_FD(iop);
  55         Uchar *buf;
  56         int size = BUFSIZ;
  57         Uchar *endbuf;
  58         int tty = -1;
  59
  60         struct stat64 stbuf;            /* used to get file system block size */
  61
  62         if (iop->_flag & _IONBF)        /* need a small buffer, at least */
  63         {
  64         trysmall:;
  65                 size = _SMBFSZ - PUSHBACK;
  66                 if (fd < _NFILE)
  67                         buf = _smbuf[fd];
  68                 else if ((buf = (Uchar *)malloc(_SMBFSZ * sizeof (Uchar))) !=
  69                     NULL)
  70                         iop->_flag |= _IOMYBUF;
  71         }
  72 #ifndef _STDIO_ALLOCATE
  73         else if (fd < 2 && (tty = isatty(fd))) {
  74                 buf = (fd == 0) ? _sibuf : _sobuf; /* special buffer */
  75                                                 /* for std{in,out} */
  76         }
  77 #endif
  78         else {
  79                 /*
  80                  * The operating system can tell us the
  81                  * right size for a buffer;
  82                  * avoid 0-size buffers as returned for some
  83                  * special files (doors)
  84                  */
  85                 if (fstat64(fd, &stbuf) == 0 && stbuf.st_blksize > 0)
  86                         size = stbuf.st_blksize;
  87
  88                 if ((buf = (Uchar *)malloc(sizeof (Uchar)*(size+_SMBFSZ))) !=
  89                     NULL)
  90                         iop->_flag |= _IOMYBUF;
  91                 else
  92                         goto trysmall;
  93         }
  94         if (buf == NULL)
  95                 return (NULL);  /* malloc() failed */
  96         iop->_base = buf + PUSHBACK;    /* bytes for pushback */
  97         iop->_ptr = buf + PUSHBACK;
  98         endbuf = iop->_base + size;
  99         _setbufend(iop, endbuf);
 100         if (!(iop->_flag & _IONBF) && ((tty != -1) ? tty : isatty(fd)))
 101                 iop->_flag |= _IOLBF;
 102         return (endbuf);
 103 }