glibc/wcsmbs/wmemrtombs.c

/* Copyright (C) 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@gnu.org>, 1997.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <wchar.h>

#ifndef EILSEQ
#define EILSEQ EINVAL
#endif


static const wchar_t encoding_mask[] =
{
  ~0x7ff, ~0xffff, ~0x1fffff, ~0x3ffffff
};

static const unsigned char encoding_byte[] =
{
  0xc0, 0xe0, 0xf0, 0xf8, 0xfc
};

/* We don't need the state really because we don't have shift states
   to maintain between calls to this function.  */
static mbstate_t internal;

/* This is a non-standard function but it is very useful in the
   implementation of stdio because we have to deal with unterminated
   buffers.  At most NWC wide character will be converted.  */
size_t
__wmemrtombs (dst, src, nwc, len, ps)
     char *dst;
     const wchar_t **src;
     size_t nwc;
     size_t len;
     mbstate_t *ps;
{
  size_t written = 0;
  const wchar_t *run = *src;

  if (ps == NULL)
    ps = &internal;

  if (dst == NULL)
    /* The LEN parameter has to be ignored if we don't actually write
       anything.  */
    len = ~0;

  while (written < len && nwc-- > 0)
    {
      wchar_t wc;

      /* Store position of first unprocessed word.  */
      *src = run;

      wc = *run++;

      if (wc < 0 || wc > 0x7fffffff)
	{
	  /* This is no correct ISO 10646 character.  */
	  __set_errno (EILSEQ);
	  return (size_t) -1;
	}

      if (wc < 0x80)
	{
	  /* It's an one byte sequence.  */
	  if (dst != NULL)
	    *dst++ = (char) wc;
	  ++written;
	}
      else
	{
	  size_t step;

	  for (step = 2; step < 6; ++step)
	    if ((wc & encoding_mask[step - 2]) == 0)
	      break;

	  if (written + step >= len)
	    /* Too long.  */
	    break;

	  if (dst != NULL)
	    {
	      size_t cnt = step;

	      dst[0] = encoding_byte[cnt - 2];

	      --cnt;
	      do
		{
		  dst[cnt] = 0x80 | (wc & 0x3f);
		  wc >>= 6;
		}
	      while (--cnt > 0);
	      dst[0] |= wc;

	      dst += step;
	    }

	  written += step;
	}
    }

  /* Store position of first unprocessed word.  */
  *src = run;

  return written;
}
weak_alias (__wmemrtombs, wmemrtombs)