gonzui

    1: /*      $OpenBSD: freopen.c,v 1.13 2009/11/09 00:18:27 kurt 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 <fcntl.h>
   37: #include <errno.h>
   38: #include <limits.h>
   39: #include <unistd.h>
   40: #include <stdio.h>
   41: #include <stdlib.h>
   42: #include "local.h"
   43: 
   44: /* 
   45:  * Re-direct an existing, __libc_open(probably) file to some other file. 
   46:  * ANSI is written such that the original file gets closed if at
   47:  * all possible, no matter what.
   48:  */
   49: FILE *
   50: freopen_eno(const char *file, const char *mode, FILE *fp, int *eno)
   51: {
   52:         int f;
   53:         int flags, isopen, oflags, sverrno, wantfd;
   54: 
   55:         if ((flags = __sflags(mode, &oflags)) == 0) {
   56:                 (void) fclose(fp);
   57:                 f = EINVAL; goto e1;
   58:         }
   59: 
   60:         if (!__sdidinit)
   61:                 __sinit();
   62: 
   63:         FLOCKFILE(fp);
   64: 
   65:         /*
   66:          * There are actually programs that depend on being able to "freopen"
   67:          * descriptors that weren't originally open.  Keep this from breaking.
   68:          * Remember whether the stream was open to begin with, and which file
   69:          * descriptor (if any) was associated with it.  If it was attached to
   70:          * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
   71:          * should work.  This is unnecessary if it was not a Unix file.
   72:          */
   73:         if (fp->_flags == 0) {
   74:                 fp->_flags = __SEOF;  /* hold on to it */
   75:                 isopen = 0;
   76:                 wantfd = -1;
   77:         } else {
   78:                 /* flush the stream; ANSI doesn't require this. */
   79:                 if (fp->_flags & __SWR)
   80:                         (void) __sflush(fp);
   81:                 /* if close is NULL, closing is a no-op, hence pointless */
   82:                 isopen = fp->_close != NULL;
   83:                 if ((wantfd = fp->_file) < 0 && isopen) {
   84:                         (void) (*fp->_close)(fp->_cookie);
   85:                         isopen = 0;
   86:                 }
   87:         }
   88: 
   89:         /* Get a new descriptor to refer to the new file. */
   90:         f = __libc_open(file, oflags, DEFFILEMODE);
   91:         if (f < 0 && isopen) {
   92:                 /* If out of fd's close the old one and try again. */
   93:                 if (/*errno == ENFILE || errno == EMFILE*/(f & 0xffff) == ENFILE) {
   94:                         (void) (*fp->_close)(fp->_cookie);
   95:                         isopen = 0;
   96:                         f = __libc_open(file, oflags, DEFFILEMODE);
   97:                 }
   98:         }
   99:         sverrno = /*errno*/f & 0xffff;
  100: 
  101:         /*
  102:          * Finish closing fp.  Even if the open succeeded above, we cannot
  103:          * keep fp->_base: it may be the wrong size.  This loses the effect
  104:          * of any setbuffer calls, but stdio has always done this before.
  105:          */
  106:         if (isopen && f != wantfd)
  107:                 (void) (*fp->_close)(fp->_cookie);
  108:         if (fp->_flags & __SMBF)
  109:                 free((char *)fp->_bf._base);
  110:         fp->_w = 0;
  111:         fp->_r = 0;
  112:         fp->_p = NULL;
  113:         fp->_bf._base = NULL;
  114:         fp->_bf._size = 0;
  115:         fp->_lbfsize = 0;
  116:         if (HASUB(fp))
  117:                 FREEUB(fp);
  118:         _UB(fp)._size = 0;
  119:         WCIO_FREE(fp);
  120:         if (HASLB(fp))
  121:                 FREELB(fp);
  122:         fp->_lb._size = 0;
  123: 
  124:         if (f < 0) {                   /* did not get it after all */
  125:                 fp->_flags = 0;               /* set it free */
  126:                 FUNLOCKFILE(fp);
  127:                 /*errno*/f = sverrno; /* restore in case _close clobbered */
  128:                 goto e1;
  129:         }
  130: 
  131:         /*
  132:          * If reopening something that was open before on a real file, try
  133:          * to maintain the descriptor.  Various C library routines (perror)
  134:          * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
  135:          */
  136:         if (wantfd >= 0 && f != wantfd) {
  137:                 if (/*dup2(f, wantfd) >= 0*/0) {
  138:                         (void) __libc_close(f);
  139:                         f = wantfd;
  140:                 }
  141:         }
  142: 
  143:         /* _file is only a short */
  144:         if (f > SHRT_MAX) {
  145:                 fp->_flags = 0;               /* set it free */
  146:                 FUNLOCKFILE(fp);
  147:                 /*errno*/f = EMFILE;
  148:                 goto e1;
  149:         }
  150: 
  151:         fp->_flags = flags;
  152:         fp->_file = f;
  153:         fp->_cookie = fp;
  154:         fp->_read = __sread;
  155:         fp->_write = __swrite;
  156:         fp->_seek = __sseek;
  157:         fp->_close = __sclose;
  158: 
  159:         /*
  160:          * When opening in append mode, even though we use O_APPEND,
  161:          * we need to seek to the end so that ftell() gets the right
  162:          * answer.  If the user then alters the seek pointer, or
  163:          * the file extends, this will fail, but there is not much
  164:          * we can do about this.  (We could set __SAPP and check in
  165:          * fseek and ftell.)
  166:          */
  167:         if (oflags & O_APPEND)
  168:                 (void) __sseek((void *)fp, (fpos_t)0, SEEK_END);
  169:         FUNLOCKFILE(fp);
  170:         return (fp); e1: if (eno) *eno = f; return NULL;
  171: }
  172: FILE *freopen(const char *path, const char *mode, FILE *fp){ return freopen_eno(path, mode, fp, NULL); }