libc/stdio/_trans2w.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 /* Function to handle transition to writing.
  12  *   Initialize or verify the stream's orientation (even if readonly).
  13  *   Check that the stream is writable.
  14  *   If currently reading, check that we can transition to writing.
  15  *      C99 requires that the stream is at EOF, but attempting to
  16  *      auto-transition via fseek() is a configurable option.
  17  *   Returns 0 on success and EOF otherwise.
  18  *
  19  * Notes:
  20  *   There are two function signatures, depending on wchar support,
  21  *   since with no wchar support the orientation is narrow by default.
  22  */
  23
  24 #ifdef __UCLIBC_HAS_WCHAR__
  25 int attribute_hidden __stdio_trans2w_o(FILE * __restrict stream, int oflag)
  26 #else
  27 int attribute_hidden __stdio_trans2w(FILE * __restrict stream)
  28 #endif
  29 {
  30         __STDIO_STREAM_VALIDATE(stream);
  31         assert(!__STDIO_STREAM_IS_WRITING(stream));
  32
  33 #ifdef __UCLIBC_HAS_WCHAR__
  34         if (!(stream->__modeflags & oflag)) {
  35                 if (stream->__modeflags & (__FLAG_NARROW|__FLAG_WIDE)) {
  36                         __UNDEFINED_OR_NONPORTABLE;
  37                         goto DO_EBADF;
  38                 }
  39                 stream->__modeflags |= oflag;
  40         }
  41 #endif
  42
  43         if (stream->__modeflags & __FLAG_READONLY) {
  44 #if defined(__UCLIBC_HAS_WCHAR__) || !defined(__UCLIBC_HAS_STDIO_AUTO_RW_TRANSITION__)
  45         DO_EBADF:
  46 #endif
  47                 __set_errno(EBADF);
  48 #ifdef __UCLIBC_HAS_STDIO_AUTO_RW_TRANSITION__
  49         ERROR:
  50 #endif
  51                 __STDIO_STREAM_SET_ERROR(stream);
  52                 __STDIO_STREAM_VALIDATE(stream);
  53                 return EOF;
  54         }
  55
  56         if (__STDIO_STREAM_IS_READING(stream)) {
  57                 if (!__FEOF_UNLOCKED(stream)) {
  58 #ifdef __UCLIBC_HAS_STDIO_AUTO_RW_TRANSITION__
  59                         /* Need to seek to correct position if we have buffered
  60                          * read data or ungots.  If appending, we might as well
  61                          * seek to the end.
  62                          *
  63                          * NOTE: If the OS does not handle append files correctly,
  64                          *   this is insufficient since we would need to seek to
  65                          *   the end even if not reading.*/
  66                         if (((__STDIO_STREAM_BUFFER_RAVAIL(stream))
  67                                  || (stream->__modeflags & __FLAG_UNGOT))
  68                                 && fseek(stream, 0L,
  69                                                  ((stream->__modeflags & __FLAG_APPEND)
  70                                                   ? SEEK_END : SEEK_CUR))
  71                                 ) {
  72                                 /* fseek() only sets error indicator on read/write error. */
  73                                 goto ERROR;
  74                         }
  75 #else
  76                         /* C99 requires either at EOF or currently not reading. */
  77                         __UNDEFINED_OR_NONPORTABLE;
  78                         goto DO_EBADF;
  79 #endif
  80                 }
  81                 __STDIO_STREAM_CLEAR_READING_AND_UNGOTS(stream);
  82                 __STDIO_STREAM_DISABLE_GETC(stream);
  83                 /* Reaching EOF does not reset buffer pointers... */
  84                 __STDIO_STREAM_INIT_BUFREAD_BUFPOS(stream);
  85         }
  86
  87         __STDIO_STREAM_SET_WRITING(stream);
  88         if (__STDIO_STREAM_IS_NARROW_FBF(stream)) {
  89                 __STDIO_STREAM_ENABLE_PUTC(stream);
  90         }
  91
  92         __STDIO_STREAM_VALIDATE(stream);
  93         return 0;
  94 }