iconv/iconv_charmap.c - nest-cam/v350/glibc - Git at Google

 /* Convert using charmaps and possibly iconv().
    Copyright (C) 2001, 2005, 2006, 2008 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@redhat.com>, 2001.

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

    This program 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software Foundation,
    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

 #include <assert.h>
 #include <errno.h>
 #include <error.h>
 #include <fcntl.h>
 #include <iconv.h>
 #include <libintl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <sys/mman.h>
 #include <sys/stat.h>

 #include "iconv_prog.h"


 /* Prototypes for a few program-wide used functions.  */
 extern void *xmalloc (size_t __n);
 extern void *xcalloc (size_t __n, size_t __s);


 struct convtable
 {
   int term[256 / 8];
   union
   {
     struct convtable *sub;
     struct charseq *out;
   } val[256];
 };


 static inline struct convtable *
 allocate_table (void)
 {
   return (struct convtable *) xcalloc (1, sizeof (struct convtable));
 }


 static inline int
 is_term (struct convtable *tbl, unsigned int idx)
 {
   return tbl->term[idx / 8] & (1 << (idx % 8));
 }


 static inline void
 clear_term (struct convtable *tbl, unsigned int idx)
 {
   tbl->term[idx / 8] &= ~(1 << (idx % 8));
 }


 static inline void
 set_term (struct convtable *tbl, unsigned int idx)
 {
   tbl->term[idx / 8] |= 1 << (idx % 8);
 }


 /* Generate the conversion table.  */
 static struct convtable *use_from_charmap (struct charmap_t *from_charmap,
 					   const char *to_code);
 static struct convtable *use_to_charmap (const char *from_code,
 					 struct charmap_t *to_charmap);
 static struct convtable *use_both_charmaps (struct charmap_t *from_charmap,
 					    struct charmap_t *to_charmap);

 /* Prototypes for the functions doing the actual work.  */
 static int process_block (struct convtable *tbl, char *addr, size_t len,
 			  FILE *output);
 static int process_fd (struct convtable *tbl, int fd, FILE *output);
 static int process_file (struct convtable *tbl, FILE *input, FILE *output);


 int
 charmap_conversion (const char *from_code, struct charmap_t *from_charmap,
 		    const char *to_code, struct charmap_t *to_charmap,
 		    int argc, int remaining, char *argv[],
 		    const char *output_file)
 {
   struct convtable *cvtbl;
   int status = EXIT_SUCCESS;

   /* We have three different cases to handle:

      - both, from_charmap and to_charmap, are available.  This means we
        can assume that the symbolic names match and use them to create
        the mapping.

      - only from_charmap is available.  In this case we can only hope that
        the symbolic names used are of the <Uxxxx> form in which case we
        can use a UCS4->"to_code" iconv() conversion for the second step.

      - only to_charmap is available.  This is similar, only that we would
        use iconv() for the "to_code"->UCS4 conversion.

        We first create a table which maps input bytes into output bytes.
        Once this is done we can handle all three of the cases above
        equally.  */
   if (from_charmap != NULL)
     {
       if (to_charmap == NULL)
 	cvtbl = use_from_charmap (from_charmap, to_code);
       else
 	cvtbl = use_both_charmaps (from_charmap, to_charmap);
     }
   else
     {
       assert (to_charmap != NULL);
       cvtbl = use_to_charmap (from_code, to_charmap);
     }

   /* If we couldn't generate a table stop now.  */
   if (cvtbl == NULL)
     return EXIT_FAILURE;

   /* Determine output file.  */
   FILE *output;
   if (output_file != NULL && strcmp (output_file, "-") != 0)
     {
       output = fopen (output_file, "w");
       if (output == NULL)
 	error (EXIT_FAILURE, errno, _("cannot open output file"));
     }
   else
     output = stdout;

   /* We can now start the conversion.  */
   if (remaining == argc)
     {
       if (process_file (cvtbl, stdin, output) != 0)
 	status = EXIT_FAILURE;
     }
   else
     do
       {
 	struct stat st;
 	char *addr;
 	int fd;

 	if (verbose)
 	  printf ("%s:\n", argv[remaining]);
 	if (strcmp (argv[remaining], "-") == 0)
 	  fd = 0;
 	else
 	  {
 	    fd = open (argv[remaining], O_RDONLY);

 	    if (fd == -1)
 	      {
 		error (0, errno, _("cannot open input file `%s'"),
 		       argv[remaining]);
 		status = EXIT_FAILURE;
 		continue;
 	      }
 	  }

 #ifdef _POSIX_MAPPED_FILES
 	/* We have possibilities for reading the input file.  First try
 	   to mmap() it since this will provide the fastest solution.  */
 	if (fstat (fd, &st) == 0
 	    && ((addr = mmap (NULL, st.st_size, PROT_READ, MAP_PRIVATE,
 			      fd, 0)) != MAP_FAILED))
 	  {
 	    /* Yes, we can use mmap().  The descriptor is not needed
 	       anymore.  */
 	    if (close (fd) != 0)
 	      error (EXIT_FAILURE, errno,
 		     _("error while closing input `%s'"), argv[remaining]);

 	    if (process_block (cvtbl, addr, st.st_size, output) < 0)
 	      {
 		/* Something went wrong.  */
 		status = EXIT_FAILURE;

 		/* We don't need the input data anymore.  */
 		munmap ((void *) addr, st.st_size);

 		/* We cannot go on with producing output since it might
 		   lead to problem because the last output might leave
 		   the output stream in an undefined state.  */
 		break;
 	      }

 	    /* We don't need the input data anymore.  */
 	    munmap ((void *) addr, st.st_size);
 	  }
 	else
 #endif	/* _POSIX_MAPPED_FILES */
 	  {
 	    /* Read the file in pieces.  */
 	    if (process_fd (cvtbl, fd, output) != 0)
 	      {
 		/* Something went wrong.  */
 		status = EXIT_FAILURE;

 		/* We don't need the input file anymore.  */
 		close (fd);

 		/* We cannot go on with producing output since it might
 		   lead to problem because the last output might leave
 		   the output stream in an undefined state.  */
 		break;
 	      }

 	    /* Now close the file.  */
 	    close (fd);
 	  }
       }
     while (++remaining < argc);

   /* All done.  */
   return status;
 }


 static void
 add_bytes (struct convtable *tbl, struct charseq *in, struct charseq *out)
 {
   int n = 0;
   unsigned int byte;

   assert (in->nbytes > 0);

   byte = ((unsigned char *) in->bytes)[n];
   while (n + 1 < in->nbytes)
     {
       if (is_term (tbl, byte) || tbl->val[byte].sub == NULL)
 	{
 	  /* Note that we simply ignore a definition for a byte sequence
 	     which is also the prefix for a longer one.  */
 	  clear_term (tbl, byte);
 	  tbl->val[byte].sub =
 	    (struct convtable *) xcalloc (1, sizeof (struct convtable));
 	}

       tbl = tbl->val[byte].sub;

       byte = ((unsigned char *) in->bytes)[++n];
     }

   /* Only add the new sequence if there is none yet and the byte sequence
      is not part of an even longer one.  */
   if (! is_term (tbl, byte) && tbl->val[byte].sub == NULL)
     {
       set_term (tbl, byte);
       tbl->val[byte].out = out;
     }
 }


 static struct convtable *
 use_from_charmap (struct charmap_t *from_charmap, const char *to_code)
 {
   /* We iterate over all entries in the from_charmap and for those which
      have a known UCS4 representation we use an iconv() call to determine
      the mapping to the to_code charset.  */
   struct convtable *rettbl;
   iconv_t cd;
   void *ptr = NULL;
   const void *key;
   size_t keylen;
   void *data;

   cd = iconv_open (to_code, "WCHAR_T");
   if (cd == (iconv_t) -1)
     /* We cannot do anything.  */
     return NULL;

   rettbl = allocate_table ();

   while (iterate_table (&from_charmap->char_table, &ptr, &key, &keylen, &data)
 	 >= 0)
     {
       struct charseq *in = (struct charseq *) data;

       if (in->ucs4 != UNINITIALIZED_CHAR_VALUE)
 	{
 	  /* There is a chance.  Try the iconv module.  */
 	  wchar_t inbuf[1] = { in->ucs4 };
 	  unsigned char outbuf[64];
 	  char *inptr = (char *) inbuf;
 	  size_t inlen = sizeof (inbuf);
 	  char *outptr = (char *) outbuf;
 	  size_t outlen = sizeof (outbuf);

 	  (void) iconv (cd, &inptr, &inlen, &outptr, &outlen);

 	  if (outptr != (char *) outbuf)
 	    {
 	      /* We got some output.  Good, use it.  */
 	      struct charseq *newp;

 	      outlen = sizeof (outbuf) - outlen;
 	      assert ((char *) outbuf + outlen == outptr);

 	      newp = (struct charseq *) xmalloc (sizeof (struct charseq)
 						 + outlen);
 	      newp->name = in->name;
 	      newp->ucs4 = in->ucs4;
 	      newp->nbytes = outlen;
 	      memcpy (newp->bytes, outbuf, outlen);

 	      add_bytes (rettbl, in, newp);
 	    }

 	  /* Clear any possible state left behind.  */
 	  (void) iconv (cd, NULL, NULL, NULL, NULL);
 	}
     }

   iconv_close (cd);

   return rettbl;
 }


 static struct convtable *
 use_to_charmap (const char *from_code, struct charmap_t *to_charmap)
 {
   /* We iterate over all entries in the to_charmap and for those which
      have a known UCS4 representation we use an iconv() call to determine
      the mapping to the from_code charset.  */
   struct convtable *rettbl;
   iconv_t cd;
   void *ptr = NULL;
   const void *key;
   size_t keylen;
   void *data;

   /* Note that the conversion we use here is the reverse direction.  Without
      exhaustive search we cannot figure out which input yields the UCS4
      character we are looking for.  Therefore we determine it the other
      way round.  */
   cd = iconv_open (from_code, "WCHAR_T");
   if (cd == (iconv_t) -1)
     /* We cannot do anything.  */
     return NULL;

   rettbl = allocate_table ();

   while (iterate_table (&to_charmap->char_table, &ptr, &key, &keylen, &data)
 	 >= 0)
     {
       struct charseq *out = (struct charseq *) data;

       if (out->ucs4 != UNINITIALIZED_CHAR_VALUE)
 	{
 	  /* There is a chance.  Try the iconv module.  */
 	  wchar_t inbuf[1] = { out->ucs4 };
 	  unsigned char outbuf[64];
 	  char *inptr = (char *) inbuf;
 	  size_t inlen = sizeof (inbuf);
 	  char *outptr = (char *) outbuf;
 	  size_t outlen = sizeof (outbuf);

 	  (void) iconv (cd, &inptr, &inlen, &outptr, &outlen);

 	  if (outptr != (char *) outbuf)
 	    {
 	      /* We got some output.  Good, use it.  */
 	      union
 	      {
 		struct charseq seq;
 		struct
 		{
 		  const char *name;
 		  uint32_t ucs4;
 		  int nbytes;
 		  unsigned char bytes[outlen];
 		} mem;
 	      } new;

 	      outlen = sizeof (outbuf) - outlen;
 	      assert ((char *) outbuf + outlen == outptr);

 	      new.mem.name = out->name;
 	      new.mem.ucs4 = out->ucs4;
 	      new.mem.nbytes = outlen;
 	      memcpy (new.mem.bytes, outbuf, outlen);

 	      add_bytes (rettbl, &new.seq, out);
 	    }

 	  /* Clear any possible state left behind.  */
 	  (void) iconv (cd, NULL, NULL, NULL, NULL);
 	}
     }

   iconv_close (cd);

   return rettbl;
 }


 static struct convtable *
 use_both_charmaps (struct charmap_t *from_charmap,
 		   struct charmap_t *to_charmap)
 {
   /* In this case we iterate over all the entries in the from_charmap,
      determine the internal name, and find an appropriate entry in the
      to_charmap (if it exists).  */
   struct convtable *rettbl = allocate_table ();
   void *ptr = NULL;
   const void *key;
   size_t keylen;
   void *data;

   while (iterate_table (&from_charmap->char_table, &ptr, &key, &keylen, &data)
 	 >= 0)
     {
       struct charseq *in = (struct charseq *) data;
       struct charseq *out = charmap_find_value (to_charmap, key, keylen);

       if (out != NULL)
 	add_bytes (rettbl, in, out);
     }

   return rettbl;
 }


 static int
 process_block (struct convtable *tbl, char *addr, size_t len, FILE *output)
 {
   size_t n = 0;

   while (n < len)
     {
       struct convtable *cur = tbl;
       unsigned char *curp = (unsigned char *) addr;
       unsigned int byte = *curp;
       int cnt;
       struct charseq *out;

       while (! is_term (cur, byte))
 	if (cur->val[byte].sub == NULL)
 	  {
 	    /* This is a invalid sequence.  Skip the first byte if we are
 	       ignoring errors.  Otherwise punt.  */
 	    if (! omit_invalid)
 	      {
 		error (0, 0, _("illegal input sequence at position %Zd"), n);
 		return -1;
 	      }

 	    n -= curp - (unsigned char *) addr;

 	    byte = *(curp = (unsigned char *) ++addr);
 	    if (++n >= len)
 	      /* All converted.  */
 	      return 0;

 	    cur = tbl;
 	  }
 	else
 	  {
 	    cur = cur->val[byte].sub;

 	    if (++n >= len)
 	      {
 		error (0, 0, _("\
 incomplete character or shift sequence at end of buffer"));
 		return -1;
 	      }

 	    byte = *++curp;
 	  }

       /* We found a final byte.  Write the output bytes.  */
       out = cur->val[byte].out;
       for (cnt = 0; cnt < out->nbytes; ++cnt)
 	fputc_unlocked (out->bytes[cnt], output);

       addr = (char *) curp + 1;
       ++n;
     }

   return 0;
 }


 static int
 process_fd (struct convtable *tbl, int fd, FILE *output)
 {
   /* We have a problem with reading from a descriptor since we must not
      provide the iconv() function an incomplete character or shift
      sequence at the end of the buffer.  Since we have to deal with
      arbitrary encodings we must read the whole text in a buffer and
      process it in one step.  */
   static char *inbuf = NULL;
   static size_t maxlen = 0;
   char *inptr = inbuf;
   size_t actlen = 0;

   while (actlen < maxlen)
     {
       ssize_t n = read (fd, inptr, maxlen - actlen);

       if (n == 0)
 	/* No more text to read.  */
 	break;

       if (n == -1)
 	{
 	  /* Error while reading.  */
 	  error (0, errno, _("error while reading the input"));
 	  return -1;
 	}

       inptr += n;
       actlen += n;
     }

   if (actlen == maxlen)
     while (1)
       {
 	ssize_t n;
 	char *new_inbuf;

 	/* Increase the buffer.  */
 	new_inbuf = (char *) realloc (inbuf, maxlen + 32768);
 	if (new_inbuf == NULL)
 	  {
 	    error (0, errno, _("unable to allocate buffer for input"));
 	    return -1;
 	  }
 	inbuf = new_inbuf;
 	maxlen += 32768;
 	inptr = inbuf + actlen;

 	do
 	  {
 	    n = read (fd, inptr, maxlen - actlen);

 	    if (n == 0)
 	      /* No more text to read.  */
 	      break;

 	    if (n == -1)
 	      {
 		/* Error while reading.  */
 		error (0, errno, _("error while reading the input"));
 		return -1;
 	      }

 	    inptr += n;
 	    actlen += n;
 	  }
 	while (actlen < maxlen);

 	if (n == 0)
 	  /* Break again so we leave both loops.  */
 	  break;
       }

   /* Now we have all the input in the buffer.  Process it in one run.  */
   return process_block (tbl, inbuf, actlen, output);
 }


 static int
 process_file (struct convtable *tbl, FILE *input, FILE *output)
 {
   /* This should be safe since we use this function only for `stdin' and
      we haven't read anything so far.  */
   return process_fd (tbl, fileno (input), output);
 }
	/* Convert using charmaps and possibly iconv().
	Copyright (C) 2001, 2005, 2006, 2008 Free Software Foundation, Inc.
	This file is part of the GNU C Library.
	Contributed by Ulrich Drepper <drepper@redhat.com>, 2001.

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

	This program 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 General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software Foundation,
	Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */

	#include <assert.h>
	#include <errno.h>
	#include <error.h>
	#include <fcntl.h>
	#include <iconv.h>
	#include <libintl.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <sys/mman.h>
	#include <sys/stat.h>

	#include "iconv_prog.h"


	/* Prototypes for a few program-wide used functions. */
	extern void *xmalloc (size_t __n);
	extern void *xcalloc (size_t __n, size_t __s);


	struct convtable
	{
	int term[256 / 8];
	union
	{
	struct convtable *sub;
	struct charseq *out;
	} val[256];
	};


	static inline struct convtable *
	allocate_table (void)
	{
	return (struct convtable *) xcalloc (1, sizeof (struct convtable));
	}


	static inline int
	is_term (struct convtable *tbl, unsigned int idx)
	{
	return tbl->term[idx / 8] & (1 << (idx % 8));
	}


	static inline void
	clear_term (struct convtable *tbl, unsigned int idx)
	{
	tbl->term[idx / 8] &= ~(1 << (idx % 8));
	}


	static inline void
	set_term (struct convtable *tbl, unsigned int idx)
	{
	tbl->term[idx / 8] \|= 1 << (idx % 8);
	}


	/* Generate the conversion table. */
	static struct convtable use_from_charmap (struct charmap_t from_charmap,
	const char *to_code);
	static struct convtable use_to_charmap (const char from_code,
	struct charmap_t *to_charmap);
	static struct convtable use_both_charmaps (struct charmap_t from_charmap,
	struct charmap_t *to_charmap);

	/* Prototypes for the functions doing the actual work. */
	static int process_block (struct convtable tbl, char addr, size_t len,
	FILE *output);
	static int process_fd (struct convtable tbl, int fd, FILE output);
	static int process_file (struct convtable tbl, FILE input, FILE *output);


	int
	charmap_conversion (const char from_code, struct charmap_t from_charmap,
	const char to_code, struct charmap_t to_charmap,
	int argc, int remaining, char *argv[],
	const char *output_file)
	{
	struct convtable *cvtbl;
	int status = EXIT_SUCCESS;

	/* We have three different cases to handle:

	- both, from_charmap and to_charmap, are available. This means we
	can assume that the symbolic names match and use them to create
	the mapping.

	- only from_charmap is available. In this case we can only hope that
	the symbolic names used are of the <Uxxxx> form in which case we
	can use a UCS4->"to_code" iconv() conversion for the second step.

	- only to_charmap is available. This is similar, only that we would
	use iconv() for the "to_code"->UCS4 conversion.

	We first create a table which maps input bytes into output bytes.
	Once this is done we can handle all three of the cases above
	equally. */
	if (from_charmap != NULL)
	{
	if (to_charmap == NULL)
	cvtbl = use_from_charmap (from_charmap, to_code);
	else
	cvtbl = use_both_charmaps (from_charmap, to_charmap);
	}
	else
	{
	assert (to_charmap != NULL);
	cvtbl = use_to_charmap (from_code, to_charmap);
	}

	/* If we couldn't generate a table stop now. */
	if (cvtbl == NULL)
	return EXIT_FAILURE;

	/* Determine output file. */
	FILE *output;
	if (output_file != NULL && strcmp (output_file, "-") != 0)
	{
	output = fopen (output_file, "w");
	if (output == NULL)
	error (EXIT_FAILURE, errno, _("cannot open output file"));
	}
	else
	output = stdout;

	/* We can now start the conversion. */
	if (remaining == argc)
	{
	if (process_file (cvtbl, stdin, output) != 0)
	status = EXIT_FAILURE;
	}
	else
	do
	{
	struct stat st;
	char *addr;
	int fd;

	if (verbose)
	printf ("%s:\n", argv[remaining]);
	if (strcmp (argv[remaining], "-") == 0)
	fd = 0;
	else
	{
	fd = open (argv[remaining], O_RDONLY);

	if (fd == -1)
	{
	error (0, errno, _("cannot open input file `%s'"),
	argv[remaining]);
	status = EXIT_FAILURE;
	continue;
	}
	}

	#ifdef _POSIX_MAPPED_FILES
	/* We have possibilities for reading the input file. First try
	to mmap() it since this will provide the fastest solution. */
	if (fstat (fd, &st) == 0
	&& ((addr = mmap (NULL, st.st_size, PROT_READ, MAP_PRIVATE,
	fd, 0)) != MAP_FAILED))
	{
	/* Yes, we can use mmap(). The descriptor is not needed
	anymore. */
	if (close (fd) != 0)
	error (EXIT_FAILURE, errno,
	_("error while closing input `%s'"), argv[remaining]);

	if (process_block (cvtbl, addr, st.st_size, output) < 0)
	{
	/* Something went wrong. */
	status = EXIT_FAILURE;

	/* We don't need the input data anymore. */
	munmap ((void *) addr, st.st_size);

	/* We cannot go on with producing output since it might
	lead to problem because the last output might leave
	the output stream in an undefined state. */
	break;
	}

	/* We don't need the input data anymore. */
	munmap ((void *) addr, st.st_size);
	}
	else
	#endif /* _POSIX_MAPPED_FILES */
	{
	/* Read the file in pieces. */
	if (process_fd (cvtbl, fd, output) != 0)
	{
	/* Something went wrong. */
	status = EXIT_FAILURE;

	/* We don't need the input file anymore. */
	close (fd);

	/* We cannot go on with producing output since it might
	lead to problem because the last output might leave
	the output stream in an undefined state. */
	break;
	}

	/* Now close the file. */
	close (fd);
	}
	}
	while (++remaining < argc);

	/* All done. */
	return status;
	}


	static void
	add_bytes (struct convtable tbl, struct charseq in, struct charseq *out)
	{
	int n = 0;
	unsigned int byte;

	assert (in->nbytes > 0);

	byte = ((unsigned char *) in->bytes)[n];
	while (n + 1 < in->nbytes)
	{
	if (is_term (tbl, byte) \|\| tbl->val[byte].sub == NULL)
	{
	/* Note that we simply ignore a definition for a byte sequence
	which is also the prefix for a longer one. */
	clear_term (tbl, byte);
	tbl->val[byte].sub =
	(struct convtable *) xcalloc (1, sizeof (struct convtable));
	}

	tbl = tbl->val[byte].sub;

	byte = ((unsigned char *) in->bytes)[++n];
	}

	/* Only add the new sequence if there is none yet and the byte sequence
	is not part of an even longer one. */
	if (! is_term (tbl, byte) && tbl->val[byte].sub == NULL)
	{
	set_term (tbl, byte);
	tbl->val[byte].out = out;
	}
	}


	static struct convtable *
	use_from_charmap (struct charmap_t from_charmap, const char to_code)
	{
	/* We iterate over all entries in the from_charmap and for those which
	have a known UCS4 representation we use an iconv() call to determine
	the mapping to the to_code charset. */
	struct convtable *rettbl;
	iconv_t cd;
	void *ptr = NULL;
	const void *key;
	size_t keylen;
	void *data;

	cd = iconv_open (to_code, "WCHAR_T");
	if (cd == (iconv_t) -1)
	/* We cannot do anything. */
	return NULL;

	rettbl = allocate_table ();

	while (iterate_table (&from_charmap->char_table, &ptr, &key, &keylen, &data)
	>= 0)
	{
	struct charseq in = (struct charseq ) data;

	if (in->ucs4 != UNINITIALIZED_CHAR_VALUE)
	{
	/* There is a chance. Try the iconv module. */
	wchar_t inbuf[1] = { in->ucs4 };
	unsigned char outbuf[64];
	char inptr = (char ) inbuf;
	size_t inlen = sizeof (inbuf);
	char outptr = (char ) outbuf;
	size_t outlen = sizeof (outbuf);

	(void) iconv (cd, &inptr, &inlen, &outptr, &outlen);

	if (outptr != (char *) outbuf)
	{
	/* We got some output. Good, use it. */
	struct charseq *newp;

	outlen = sizeof (outbuf) - outlen;
	assert ((char *) outbuf + outlen == outptr);

	newp = (struct charseq *) xmalloc (sizeof (struct charseq)
	+ outlen);
	newp->name = in->name;
	newp->ucs4 = in->ucs4;
	newp->nbytes = outlen;
	memcpy (newp->bytes, outbuf, outlen);

	add_bytes (rettbl, in, newp);
	}

	/* Clear any possible state left behind. */
	(void) iconv (cd, NULL, NULL, NULL, NULL);
	}
	}

	iconv_close (cd);

	return rettbl;
	}


	static struct convtable *
	use_to_charmap (const char from_code, struct charmap_t to_charmap)
	{
	/* We iterate over all entries in the to_charmap and for those which
	have a known UCS4 representation we use an iconv() call to determine
	the mapping to the from_code charset. */
	struct convtable *rettbl;
	iconv_t cd;
	void *ptr = NULL;
	const void *key;
	size_t keylen;
	void *data;

	/* Note that the conversion we use here is the reverse direction. Without
	exhaustive search we cannot figure out which input yields the UCS4
	character we are looking for. Therefore we determine it the other
	way round. */
	cd = iconv_open (from_code, "WCHAR_T");
	if (cd == (iconv_t) -1)
	/* We cannot do anything. */
	return NULL;

	rettbl = allocate_table ();

	while (iterate_table (&to_charmap->char_table, &ptr, &key, &keylen, &data)
	>= 0)
	{
	struct charseq out = (struct charseq ) data;

	if (out->ucs4 != UNINITIALIZED_CHAR_VALUE)
	{
	/* There is a chance. Try the iconv module. */
	wchar_t inbuf[1] = { out->ucs4 };
	unsigned char outbuf[64];
	char inptr = (char ) inbuf;
	size_t inlen = sizeof (inbuf);
	char outptr = (char ) outbuf;
	size_t outlen = sizeof (outbuf);

	(void) iconv (cd, &inptr, &inlen, &outptr, &outlen);

	if (outptr != (char *) outbuf)
	{
	/* We got some output. Good, use it. */
	union
	{
	struct charseq seq;
	struct
	{
	const char *name;
	uint32_t ucs4;
	int nbytes;
	unsigned char bytes[outlen];
	} mem;
	} new;

	outlen = sizeof (outbuf) - outlen;
	assert ((char *) outbuf + outlen == outptr);

	new.mem.name = out->name;
	new.mem.ucs4 = out->ucs4;
	new.mem.nbytes = outlen;
	memcpy (new.mem.bytes, outbuf, outlen);

	add_bytes (rettbl, &new.seq, out);
	}

	/* Clear any possible state left behind. */
	(void) iconv (cd, NULL, NULL, NULL, NULL);
	}
	}

	iconv_close (cd);

	return rettbl;
	}


	static struct convtable *
	use_both_charmaps (struct charmap_t *from_charmap,
	struct charmap_t *to_charmap)
	{
	/* In this case we iterate over all the entries in the from_charmap,
	determine the internal name, and find an appropriate entry in the
	to_charmap (if it exists). */
	struct convtable *rettbl = allocate_table ();
	void *ptr = NULL;
	const void *key;
	size_t keylen;
	void *data;

	while (iterate_table (&from_charmap->char_table, &ptr, &key, &keylen, &data)
	>= 0)
	{
	struct charseq in = (struct charseq ) data;
	struct charseq *out = charmap_find_value (to_charmap, key, keylen);

	if (out != NULL)
	add_bytes (rettbl, in, out);
	}

	return rettbl;
	}


	static int
	process_block (struct convtable tbl, char addr, size_t len, FILE *output)
	{
	size_t n = 0;

	while (n < len)
	{
	struct convtable *cur = tbl;
	unsigned char curp = (unsigned char ) addr;
	unsigned int byte = *curp;
	int cnt;
	struct charseq *out;

	while (! is_term (cur, byte))
	if (cur->val[byte].sub == NULL)
	{
	/* This is a invalid sequence. Skip the first byte if we are
	ignoring errors. Otherwise punt. */
	if (! omit_invalid)
	{
	error (0, 0, _("illegal input sequence at position %Zd"), n);
	return -1;
	}

	n -= curp - (unsigned char *) addr;

	byte = (curp = (unsigned char ) ++addr);
	if (++n >= len)
	/* All converted. */
	return 0;

	cur = tbl;
	}
	else
	{
	cur = cur->val[byte].sub;

	if (++n >= len)
	{
	error (0, 0, _("\
	incomplete character or shift sequence at end of buffer"));
	return -1;
	}

	byte = *++curp;
	}

	/* We found a final byte. Write the output bytes. */
	out = cur->val[byte].out;
	for (cnt = 0; cnt < out->nbytes; ++cnt)
	fputc_unlocked (out->bytes[cnt], output);

	addr = (char *) curp + 1;
	++n;
	}

	return 0;
	}


	static int
	process_fd (struct convtable tbl, int fd, FILE output)
	{
	/* We have a problem with reading from a descriptor since we must not
	provide the iconv() function an incomplete character or shift
	sequence at the end of the buffer. Since we have to deal with
	arbitrary encodings we must read the whole text in a buffer and
	process it in one step. */
	static char *inbuf = NULL;
	static size_t maxlen = 0;
	char *inptr = inbuf;
	size_t actlen = 0;

	while (actlen < maxlen)
	{
	ssize_t n = read (fd, inptr, maxlen - actlen);

	if (n == 0)
	/* No more text to read. */
	break;

	if (n == -1)
	{
	/* Error while reading. */
	error (0, errno, _("error while reading the input"));
	return -1;
	}

	inptr += n;
	actlen += n;
	}

	if (actlen == maxlen)
	while (1)
	{
	ssize_t n;
	char *new_inbuf;

	/* Increase the buffer. */
	new_inbuf = (char *) realloc (inbuf, maxlen + 32768);
	if (new_inbuf == NULL)
	{
	error (0, errno, _("unable to allocate buffer for input"));
	return -1;
	}
	inbuf = new_inbuf;
	maxlen += 32768;
	inptr = inbuf + actlen;

	do
	{
	n = read (fd, inptr, maxlen - actlen);

	if (n == 0)
	/* No more text to read. */
	break;

	if (n == -1)
	{
	/* Error while reading. */
	error (0, errno, _("error while reading the input"));
	return -1;
	}

	inptr += n;
	actlen += n;
	}
	while (actlen < maxlen);

	if (n == 0)
	/* Break again so we leave both loops. */
	break;
	}

	/* Now we have all the input in the buffer. Process it in one run. */
	return process_block (tbl, inbuf, actlen, output);
	}


	static int
	process_file (struct convtable tbl, FILE input, FILE *output)
	{
	/* This should be safe since we use this function only for `stdin' and
	we haven't read anything so far. */
	return process_fd (tbl, fileno (input), output);
	}