libc/stdio/freopen.c

   1 /* Copyright (C) 2004       Manuel Novoa III    <mjn3@codepoet.org>
   2  *
   3  * GNU Library General Public License (LGPL) version 2 or later.
   4  *
   5  * Dedicated to Toni.  See uClibc/DEDICATION.mjn3 for details.
   6  */
   7
   8 #include "_stdio.h"
   9
  10
  11 #ifndef __DO_LARGEFILE
  12 # define FILEDES_ARG    (-1)
  13 #endif
  14
  15 FILE *freopen(const char * __restrict filename, const char * __restrict mode,
  16                           register FILE * __restrict stream)
  17 {
  18         /*
  19          * ANSI/ISO allow (implementation-defined) change of mode for an
  20          * existing file if filename is NULL.  It doesn't look like Linux
  21          * supports this, so we don't here.
  22          *
  23          * NOTE: Whether or not the stream is free'd on failure is unclear
  24          *       w.r.t. ANSI/ISO.  This implementation chooses to NOT free
  25          *       the stream and associated buffer if they were dynamically
  26          *       allocated.
  27          * NOTE: Previous versions of uClibc did free dynamic storage.
  28          *
  29          * TODO: Apparently linux allows setting append mode.  Implement?
  30          */
  31         unsigned short dynmode;
  32         register FILE *fp;
  33         __STDIO_AUTO_THREADLOCK_VAR;
  34
  35         __STDIO_AUTO_THREADLOCK(stream);
  36
  37         __STDIO_STREAM_VALIDATE(stream);
  38
  39         __STDIO_OPENLIST_INC_USE;       /* Do not remove the file from the list. */
  40
  41         /* First, flush and close, but don't deallocate, the stream. */
  42         /* This also removes the stream for the open file list. */
  43         dynmode = (stream->__modeflags & (__FLAG_FREEBUF|__FLAG_FREEFILE));
  44
  45         stream->__modeflags &= ~(__FLAG_FREEBUF|__FLAG_FREEFILE);
  46
  47         /* Only call fclose on the stream if it is not already closed. */
  48         if ((stream->__modeflags & (__FLAG_READONLY|__FLAG_WRITEONLY))
  49                 != (__FLAG_READONLY|__FLAG_WRITEONLY)
  50                 ) {
  51                 fclose(stream);                 /* Failures are ignored. */
  52                 /* NOTE: fclose always does __STDIO_OPENLIST_INC_DEL_CNT.  But we don't
  53                  * want to remove this FILE from the open list, even if the freopen fails.
  54                  * Consider the case of a failed freopen() on stdin.  You probably still
  55                  * want to be able to call freopen() again.  Similarly for other "malloc'd"
  56                  * streams. */
  57                 __STDIO_OPENLIST_DEC_DEL_CNT;
  58         }
  59
  60         fp = _stdio_fopen(((intptr_t) filename), mode, stream, FILEDES_ARG);
  61         if (!fp) {
  62                 /* Don't remove stream from the open file list and (potentially) free it.
  63                  * See _stdio_openlist_dec_use() in fflush.c. */
  64                 stream->__modeflags = __FLAG_READONLY|__FLAG_WRITEONLY|__FLAG_FAILED_FREOPEN;
  65         }
  66
  67         /* Reset the allocation flags. */
  68         stream->__modeflags |= dynmode;
  69
  70         __STDIO_OPENLIST_DEC_USE;
  71
  72         __STDIO_AUTO_THREADUNLOCK(stream);
  73
  74         return fp;
  75 }