lib/libc/stdio/refill.c

   1 /*      $NetBSD: refill.c,v 1.16 2012/03/27 15:05:42 christos Exp $     */
   2
   3 /*-
   4  * Copyright (c) 1990, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Chris Torek.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/cdefs.h>
  36 #if defined(LIBC_SCCS) && !defined(lint)
  37 #if 0
  38 static char sccsid[] = "@(#)refill.c    8.1 (Berkeley) 6/4/93";
  39 #else
  40 __RCSID("$NetBSD: refill.c,v 1.16 2012/03/27 15:05:42 christos Exp $");
  41 #endif
  42 #endif /* LIBC_SCCS and not lint */
  43
  44 #include <assert.h>
  45 #include <errno.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include "reentrant.h"
  49 #include "local.h"
  50
  51 #ifdef _REENTRANT
  52 extern rwlock_t __sfp_lock;
  53 #endif
  54
  55 static int
  56 lflush(FILE *fp)
  57 {
  58
  59         _DIAGASSERT(fp != NULL);
  60
  61         if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
  62                 return __sflush(fp);
  63         return 0;
  64 }
  65
  66 /*
  67  * Refill a stdio buffer.
  68  * Return EOF on eof or error, 0 otherwise.
  69  */
  70 int
  71 __srefill(FILE *fp)
  72 {
  73
  74         _DIAGASSERT(fp != NULL);
  75
  76         /* make sure stdio is set up */
  77         if (!__sdidinit)
  78                 __sinit();
  79
  80         fp->_r = 0;             /* largely a convenience for callers */
  81
  82         /* SysV does not make this test; take it out for compatibility */
  83         if (fp->_flags & __SEOF)
  84                 return EOF;
  85
  86         /* if not already reading, have to be reading and writing */
  87         if ((fp->_flags & __SRD) == 0) {
  88                 if ((fp->_flags & __SRW) == 0) {
  89                         errno = EBADF;
  90                         fp->_flags |= __SERR;
  91                         return EOF;
  92                 }
  93                 /* switch to reading */
  94                 if (fp->_flags & __SWR) {
  95                         if (__sflush(fp))
  96                                 return EOF;
  97                         fp->_flags &= ~__SWR;
  98                         fp->_w = 0;
  99                         fp->_lbfsize = 0;
 100                 }
 101                 fp->_flags |= __SRD;
 102         } else {
 103                 /*
 104                  * We were reading.  If there is an ungetc buffer,
 105                  * we must have been reading from that.  Drop it,
 106                  * restoring the previous buffer (if any).  If there
 107                  * is anything in that buffer, return.
 108                  */
 109                 if (HASUB(fp)) {
 110                         FREEUB(fp);
 111                         if ((fp->_r = fp->_ur) != 0) {
 112                                 fp->_p = fp->_up;
 113                                 return 0;
 114                         }
 115                 }
 116         }
 117
 118         if (fp->_bf._base == NULL)
 119                 __smakebuf(fp);
 120
 121         /*
 122          * Before reading from a line buffered or unbuffered file,
 123          * flush all line buffered output files, per the ANSI C
 124          * standard.
 125          */
 126         if (fp->_flags & (__SLBF|__SNBF)) {
 127                 rwlock_rdlock(&__sfp_lock);
 128                 (void) _fwalk(lflush);
 129                 rwlock_unlock(&__sfp_lock);
 130         }
 131         fp->_p = fp->_bf._base;
 132         fp->_r = (int)(*fp->_read)(fp->_cookie, (char *)fp->_p,
 133             (size_t)fp->_bf._size);
 134         fp->_flags &= ~__SMOD;  /* buffer contents are again pristine */
 135         if (fp->_r <= 0) {
 136                 if (fp->_r == 0)
 137                         fp->_flags |= __SEOF;
 138                 else {
 139                         fp->_r = 0;
 140                         fp->_flags |= __SERR;
 141                 }
 142                 return EOF;
 143         }
 144         return 0;
 145 }