Blame libio/iofgetws_u.c

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/* Copyright (C) 1993-2018 Free Software Foundation, Inc.
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   This file is part of the GNU C Library.
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   The GNU C Library is free software; you can redistribute it and/or
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   modify it under the terms of the GNU Lesser General Public
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   License as published by the Free Software Foundation; either
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   version 2.1 of the License, or (at your option) any later version.
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   The GNU C Library is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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   Lesser General Public License for more details.
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   You should have received a copy of the GNU Lesser General Public
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   License along with the GNU C Library; if not, see
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   <http://www.gnu.org/licenses/>.
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   As a special exception, if you link the code in this file with
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   files compiled with a GNU compiler to produce an executable,
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   that does not cause the resulting executable to be covered by
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   the GNU Lesser General Public License.  This exception does not
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   however invalidate any other reasons why the executable file
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   might be covered by the GNU Lesser General Public License.
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   This exception applies to code released by its copyright holders
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   in files containing the exception.  */
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#include "libioP.h"
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#include <wchar.h>
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wchar_t *
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fgetws_unlocked (wchar_t *buf, int n, FILE *fp)
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{
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  size_t count;
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  wchar_t *result;
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  int old_error;
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  CHECK_FILE (fp, NULL);
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  if (n <= 0)
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    return NULL;
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  if (__glibc_unlikely (n == 1))
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    {
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      /* Another irregular case: since we have to store a NUL byte and
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	 there is only room for exactly one byte, we don't have to
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	 read anything.  */
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      buf[0] = L'\0';
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      return buf;
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    }
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  /* This is very tricky since a file descriptor may be in the
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     non-blocking mode. The error flag doesn't mean much in this
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     case. We return an error only when there is a new error. */
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  old_error = fp->_flags & _IO_ERR_SEEN;
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  fp->_flags &= ~_IO_ERR_SEEN;
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  count = _IO_getwline (fp, buf, n - 1, L'\n', 1);
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  /* If we read in some bytes and errno is EAGAIN, that error will
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     be reported for next read. */
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  if (count == 0 || ((fp->_flags & _IO_ERR_SEEN) && errno != EAGAIN))
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    result = NULL;
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  else
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    {
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      buf[count] = '\0';
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      result = buf;
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    }
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  fp->_flags |= old_error;
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  return result;
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}