path: root/iconv/iconvconfig.c

/* Generate fastloading iconv module configuration files.
   Copyright (C) 2000, 2001 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@redhat.com>, 2000.

   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 <argp.h>
#include <assert.h>
#include <error.h>
#include <errno.h>
#include <fcntl.h>
#include <libintl.h>
#include <locale.h>
#include <mcheck.h>
#include <search.h>
#include <stdint.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/uio.h>

#include "iconvconfig.h"

/* Get libc version number.  */
#include "../version.h"

#define PACKAGE _libc_intl_domainname


/* The hashing function we use.  */
#include "../intl/hash-string.h"


/* Types used.  */
struct module
{
  char *fromname;
  struct Strent *fromname_strent;
  char *filename;
  struct Strent *filename_strent;
  const char *directory;
  struct Strent *directory_strent;
  struct module *next;
  int cost;
  struct Strent *toname_strent;
  char toname[0];
};

struct alias
{
  char *fromname;
  struct Strent *froment;
  struct module *module;
  struct Strent *toent;
  char toname[0];
};

struct name
{
  const char *name;
  struct Strent *strent;
  int module_idx;
  uint32_t hashval;
};

struct name_info
{
  const char *canonical_name;
  struct Strent *canonical_strent;

  struct module *from_internal;
  struct module *to_internal;

  struct other_conv_list
  {
    int dest_idx;
    struct other_conv
    {
      gidx_t module_idx;
      struct module *module;
      struct other_conv *next;
    } other_conv;
    struct other_conv_list *next;
  } *other_conv_list;
};


/* Name and version of program.  */
static void print_version (FILE *stream, struct argp_state *state);
void (*argp_program_version_hook) (FILE *, struct argp_state *) = print_version;

#define OPT_VERBOSE	1000

/* Definitions of arguments for argp functions.  */
static const struct argp_option options[] =
{
  { "verbose", OPT_VERBOSE, NULL, 0, N_("print progress information") },
  { NULL, 0, NULL, 0, NULL }
};

/* Short description of program.  */
static const char doc[] = N_("\
Create fastloading iconv module configuration file.");

/* Strings for arguments in help texts.  */
static const char args_doc[] = N_("[DIR...]");

/* Prototype for option handler.  */
static error_t parse_opt (int key, char *arg, struct argp_state *state);

/* Function to print some extra text in the help message.  */
static char *more_help (int key, const char *text, void *input);

/* Data structure to communicate with argp functions.  */
static struct argp argp =
{
  options, parse_opt, args_doc, doc, NULL, more_help
};


/* The function doing the actual work.  */
static int handle_dir (const char *dir);

/* Add all known builtin conversions and aliases.  */
static void add_builtins (void);

/* Create list of all aliases without circular aliases.  */
static void get_aliases (void);

/* Create list of all modules.  */
static void get_modules (void);

/* Get list of all the names and thereby indexing them.  */
static void generate_name_list (void);

/* Collect information about all the names.  */
static void generate_name_info (void);

/* Write the output file.  */
static int write_output (void);


/* Nonzero if verbose ouput is wanted.  */
static int verbose;

/* Search tree of the modules we know.  */
static void *modules;

/* Search tree of the aliases we know.  */
static void *aliases;

/* Search tree for name to index mapping.  */
static void *names;

/* Number of names we know about.  */
static int nnames;

/* List of all aliases.  */
static struct alias **alias_list;
static size_t nalias_list;
static size_t nalias_list_max;

/* List of all modules.  */
static struct module **module_list;
static size_t nmodule_list;
static size_t nmodule_list_max;

/* Names and information about them.  */
static struct name_info *name_info;
static size_t nname_info;

/* Number of translations not from or to INTERNAL.  */
static size_t nextra_modules;


/* Names and aliases for the builtin transformations.  */
static struct
{
  const char *from;
  const char *to;
} builtin_alias[] =
  {
#define BUILTIN_ALIAS(alias, real) \
    { .from = alias, .to = real },
#define BUILTIN_TRANSFORMATION(From, To, Cost, Name, Fct, MinF, MaxF, \
			       MinT, MaxT)
#include <gconv_builtin.h>
  };
#undef BUILTIN_ALIAS
#undef BUILTIN_TRANSFORMATION
#define nbuiltin_alias (sizeof (builtin_alias) / sizeof (builtin_alias[0]))

static struct
{
  const char *from;
  const char *to;
  const char *module;
  int cost;
} builtin_trans[] =
  {
#define BUILTIN_ALIAS(alias, real)
#define BUILTIN_TRANSFORMATION(From, To, Cost, Name, Fct, MinF, MaxF, \
			       MinT, MaxT) \
    { .from = From, .to = To, .module = Name, .cost = Cost },
#include <gconv_builtin.h>
  };
#define nbuiltin_trans (sizeof (builtin_trans) / sizeof (builtin_trans[0]))


/* Filename extension for the modules.  */
#ifndef MODULE_EXT
# define MODULE_EXT ".so"
#endif
static const char gconv_module_ext[] = MODULE_EXT;


extern void *xmalloc (size_t n) __attribute__ ((__malloc__));
extern void *xcalloc (size_t n, size_t m) __attribute__ ((__malloc__));
extern void *xrealloc (void *p, size_t n);


/* C string table handling.  */
struct Strtab;
struct Strent;

/* Create new C string table object in memory.  */
extern struct Strtab *strtabinit (void);

/* Free resources allocated for C string table ST.  */
extern void strtabfree (struct Strtab *st);

/* Add string STR (length LEN is != 0) to C string table ST.  */
extern struct Strent *strtabadd (struct Strtab *st, const char *str,
				 size_t len);

/* Finalize string table ST and store size in *SIZE and return a pointer.  */
extern void *strtabfinalize (struct Strtab *st, size_t *size);

/* Get offset in string table for string associated with SE.  */
extern size_t strtaboffset (struct Strent *se);

/* String table we construct.  */
static struct Strtab *strtab;



int
main (int argc, char *argv[])
{
  int remaining;
  int status = 0;
  char *path;
  char *tp;

  /* Enable memory use testing.  */
  mcheck_pedantic (NULL);

  /* Set locale via LC_ALL.  */
  setlocale (LC_ALL, "");

  /* Set the text message domain.  */
  textdomain (_libc_intl_domainname);

  /* Parse and process arguments.  */
  argp_parse (&argp, argc, argv, 0, &remaining, NULL);

  /* Initialize the string table.  */
  strtab = strtabinit ();

  /* Handle all directories mentioned.  */
  while (remaining < argc)
    status |= handle_dir (argv[remaining++]);

  /* In any case also handle the standard directory.  */
  path = strdupa (GCONV_PATH);
  tp = strtok (path, ":");
  while (tp != NULL)
    {
      status |= handle_dir (tp);

      tp = strtok (NULL, ":");
    }

  /* Add the builtin transformations and aliases without overwriting
     anything.  */
  add_builtins ();

  /* Store aliases in an array.  */
  get_aliases ();

  /* Get list of all modules.  */
  get_modules ();

  /* Generate list of all the names we know to handle in some way.  */
  generate_name_list ();

  /* Now we know all the names we will handle, collect information
     about them.  */
  generate_name_info ();

  /* Write the output file.  */
  status = write_output ();

  return status;
}


/* Handle program arguments.  */
static error_t
parse_opt (int key, char *arg, struct argp_state *state)
{
  switch (key)
    {
    case OPT_VERBOSE:
      verbose = 1;
      break;
    default:
      return ARGP_ERR_UNKNOWN;
    }
  return 0;
}


static char *
more_help (int key, const char *text, void *input)
{
  switch (key)
    {
    case ARGP_KEY_HELP_EXTRA:
      /* We print some extra information.  */
      return strdup (gettext ("\
Report bugs using the `glibcbug' script to <bugs@gnu.org>.\n"));
    default:
      break;
    }
  return (char *) text;
}


/* Print the version information.  */
static void
print_version (FILE *stream, struct argp_state *state)
{
  fprintf (stream, "iconvconfig (GNU %s) %s\n", PACKAGE, VERSION);
  fprintf (stream, gettext ("\
Copyright (C) %s Free Software Foundation, Inc.\n\
This is free software; see the source for copying conditions.  There is NO\n\
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
"), "2001");
  fprintf (stream, gettext ("Written by %s.\n"), "Ulrich Drepper");
}


static int
alias_compare (const void *p1, const void *p2)
{
  const struct alias *a1 = (const struct alias *) p1;
  const struct alias *a2 = (const struct alias *) p2;

  return strcmp (a1->fromname, a2->fromname);
}


static void
new_alias (const char *fromname, size_t fromlen, const char *toname,
	   size_t tolen)
{
  struct alias *newp;
  void **inserted;

  newp = (struct alias *) xmalloc (sizeof (struct alias) + fromlen + tolen);

  newp->fromname = mempcpy (newp->toname, toname, tolen);
  memcpy (newp->fromname, fromname, fromlen);
  newp->module = NULL;

  inserted = (void **) tsearch (newp, &aliases, alias_compare);
  if (inserted == NULL)
    error (EXIT_FAILURE, errno, gettext ("while inserting in search tree"));
  if (*inserted != newp)
    /* Something went wrong, free this entry.  */
    free (newp);
  else
    {
      newp->froment = strtabadd (strtab, newp->fromname, fromlen);
      newp->toent = strtabadd (strtab, newp->toname, tolen);
    }
}


/* Add new alias.  */
static void
add_alias (char *rp)
{
  /* We now expect two more string.  The strings are normalized
     (converted to UPPER case) and strored in the alias database.  */
  char *from;
  char *to;
  char *wp;

  while (isspace (*rp))
    ++rp;
  from = wp = rp;
  while (*rp != '\0' && !isspace (*rp))
    *wp++ = toupper (*rp++);
  if (*rp == '\0')
    /* There is no `to' string on the line.  Ignore it.  */
    return;
  *wp++ = '\0';
  to = ++rp;
  while (isspace (*rp))
    ++rp;
  while (*rp != '\0' && !isspace (*rp))
    *wp++ = toupper (*rp++);
  if (to == wp)
    /* No `to' string, ignore the line.  */
    return;
  *wp++ = '\0';

  new_alias (from, to - from, to, wp - to);
}


static void
append_alias (const void *nodep, VISIT value, int level)
{
  if (value != leaf && value != postorder)
    return;

  if (nalias_list_max == nalias_list)
    {
      nalias_list_max += 50;
      alias_list = (struct alias **) xrealloc (alias_list,
					       (nalias_list_max
						* sizeof (struct alias *)));
    }

  alias_list[nalias_list++] = *(struct alias **) nodep;
}


static void
get_aliases (void)
{
  twalk (aliases, append_alias);
}


static int
module_compare (const void *p1, const void *p2)
{
  const struct module *m1 = (const struct module *) p1;
  const struct module *m2 = (const struct module *) p2;
  int result;

  result = strcmp (m1->fromname, m2->fromname);
  if (result == 0)
    result = strcmp (m1->toname, m2->toname);

  return result;
}


/* Create new module record.  */
static void
new_module (const char *fromname, size_t fromlen, const char *toname,
	    size_t tolen, const char *directory,
	    const char *filename, size_t filelen, int cost, size_t need_ext)
{
  struct module *new_module;
  size_t dirlen = strlen (directory) + 1;
  char *tmp;
  void **inserted;

  new_module = (struct module *) xmalloc (sizeof (struct module)
					  + fromlen + tolen + filelen
					  + need_ext);

  new_module->fromname = mempcpy (new_module->toname, toname, tolen);

  new_module->filename = mempcpy (new_module->fromname, fromname, fromlen);

  new_module->cost = cost;
  new_module->next = NULL;

  tmp = mempcpy (new_module->filename, filename, filelen);
  if (need_ext)
    {
      memcpy (tmp - 1, gconv_module_ext, sizeof (gconv_module_ext));
      filelen += sizeof (gconv_module_ext) - 1;
    }
  new_module->directory = directory;

  /* Now insert the new module data structure in our search tree.  */
  inserted = (void **) tsearch (new_module, &modules, module_compare);
  if (inserted == NULL)
    error (EXIT_FAILURE, errno, "while inserting in search tree");
  if (*inserted != new_module)
    free (new_module);
  else
    {
      new_module->fromname_strent = strtabadd (strtab, new_module->fromname,
					       fromlen);
      new_module->toname_strent = strtabadd (strtab, new_module->toname,
					     tolen);
      new_module->filename_strent = strtabadd (strtab, new_module->filename,
					       filelen);
      new_module->directory_strent = strtabadd (strtab, directory, dirlen);
    }
}


/* Add new module.  */
static void
internal_function
add_module (char *rp, const char *directory)
{
  /* We expect now
     1. `from' name
     2. `to' name
     3. filename of the module
     4. an optional cost value
  */
  char *from;
  char *to;
  char *module;
  char *wp;
  int need_ext;
  int cost;

  while (isspace (*rp))
    ++rp;
  from = rp;
  while (*rp != '\0' && !isspace (*rp))
    {
      *rp = toupper (*rp);
      ++rp;
    }
  if (*rp == '\0')
    return;
  *rp++ = '\0';
  to = wp = rp;
  while (isspace (*rp))
    ++rp;
  while (*rp != '\0' && !isspace (*rp))
    *wp++ = toupper (*rp++);
  if (*rp == '\0')
    return;
  *wp++ = '\0';
  do
    ++rp;
  while (isspace (*rp));
  module = wp;
  while (*rp != '\0' && !isspace (*rp))
    *wp++ = *rp++;
  if (*rp == '\0')
    {
      /* There is no cost, use one by default.  */
      *wp++ = '\0';
      cost = 1;
    }
  else
    {
      /* There might be a cost value.  */
      char *endp;

      *wp++ = '\0';
      cost = strtol (rp, &endp, 10);
      if (rp == endp || cost < 1)
	/* No useful information.  */
	cost = 1;
    }

  if (module[0] == '\0')
    /* No module name given.  */
    return;

  /* See whether we must add the ending.  */
  need_ext = 0;
  if (wp - module < sizeof (gconv_module_ext)
      || memcmp (wp - sizeof (gconv_module_ext), gconv_module_ext,
		 sizeof (gconv_module_ext)) != 0)
    /* We must add the module extension.  */
    need_ext = sizeof (gconv_module_ext) - 1;

  assert (strlen (from) + 1 == to - from);
  assert (strlen (to) + 1 == module - to);
  assert (strlen (module) + 1 == wp - module);

  new_module (from, to - from, to, module - to, directory, module, wp - module,
	      cost, need_ext);
}


/* Read the config file and add the data for this directory to that.  */
static int
handle_dir (const char *dir)
{
  char *infile;
  FILE *fp;
  char *line = NULL;
  size_t linelen = 0;
  size_t dirlen = strlen (dir);

  if (dir[dirlen - 1] != '/')
    {
      char *newp = (char *) xmalloc (dirlen + 2);
      dir = memcpy (newp, dir, dirlen);
      newp[dirlen++] = '/';
      newp[dirlen] = '\0';
    }

  infile = (char *) alloca (dirlen + sizeof "gconv-modules");
  strcpy (mempcpy (infile, dir, dirlen), "gconv-modules");

  fp = fopen (infile, "r");
  if (fp == NULL)
    {
      error (0, errno, "cannot open `%s'", infile);
      return 1;
    }

  /* No threads present.  */
  __fsetlocking (fp, FSETLOCKING_BYCALLER);

  while (!feof_unlocked (fp))
    {
      char *rp, *endp, *word;
      ssize_t n = __getdelim (&line, &linelen, '\n', fp);

      if (n < 0)
	/* An error occurred.  */
	break;

      rp = line;
      /* Terminate the line (excluding comments or newline) with a NUL
	 byte to simplify the following code.  */
      endp = strchr (rp, '#');
      if (endp != NULL)
	*endp = '\0';
      else
	if (rp[n - 1] == '\n')
	  rp[n - 1] = '\0';

      while (isspace (*rp))
	++rp;

      /* If this is an empty line go on with the next one.  */
      if (rp == endp)
	continue;

      word = rp;
      while (*rp != '\0' && !isspace (*rp))
	++rp;

      if (rp - word == sizeof ("alias") - 1
	  && memcmp (word, "alias", sizeof ("alias") - 1) == 0)
	add_alias (rp);
      else if (rp - word == sizeof ("module") - 1
	       && memcmp (word, "module", sizeof ("module") - 1) == 0)
	add_module (rp, dir);
      /* else */
	/* Otherwise ignore the line.  */
    }

  free (line);

  fclose (fp);

  return 0;
}


static void
append_module (const void *nodep, VISIT value, int level)
{
  struct module *mo;

  if (value != leaf && value != postorder)
    return;

  mo = *(struct module **) nodep;

  if (nmodule_list > 0
      && strcmp (module_list[nmodule_list - 1]->fromname, mo->fromname) == 0)
    {
      /* Same name.  */
      mo->next = module_list[nmodule_list - 1];
      module_list[nmodule_list - 1] = mo;

      return;
    }

  if (nmodule_list_max == nmodule_list)
    {
      nmodule_list_max += 50;
      module_list = (struct module **) xrealloc (module_list,
						 (nmodule_list_max
						  * sizeof (struct module *)));
    }

  module_list[nmodule_list++] = mo;
}


static void
get_modules (void)
{
  twalk (modules, append_module);
}


static void
add_builtins (void)
{
  size_t cnt;

  /* Add all aliases.  */
  for (cnt = 0; cnt < nbuiltin_alias; ++cnt)
    new_alias (builtin_alias[cnt].from,
	       strlen (builtin_alias[cnt].from) + 1,
	       builtin_alias[cnt].to,
	       strlen (builtin_alias[cnt].to) + 1);

  /* add the builtin transformations.  */
  for (cnt = 0; cnt < nbuiltin_trans; ++cnt)
    new_module (builtin_trans[cnt].from,
		strlen (builtin_trans[cnt].from) + 1,
		builtin_trans[cnt].to,
		strlen (builtin_trans[cnt].to) + 1,
		"", builtin_trans[cnt].module,
		strlen (builtin_trans[cnt].module) + 1,
		builtin_trans[cnt].cost, 0);
}


static int
name_compare (const void *p1, const void *p2)
{
  const struct name *n1 = (const struct name *) p1;
  const struct name *n2 = (const struct name *) p2;

  return strcmp (n1->name, n2->name);
}


static struct name *
new_name (const char *str, struct Strent *strent)
{
  struct name *newp = (struct name *) xmalloc (sizeof (struct name));

  newp->name = str;
  newp->strent = strent;
  newp->module_idx = -1;
  newp->hashval = hash_string (str);

  ++nnames;

  return newp;
}


static void
generate_name_list (void)
{
  size_t i;

  for (i = 0; i < nmodule_list; ++i)
    {
      struct module *runp;

      if (strcmp (module_list[i]->fromname, "INTERNAL") != 0)
	tsearch (new_name (module_list[i]->fromname,
			   module_list[i]->fromname_strent),
		 &names, name_compare);

      for (runp = module_list[i]; runp != NULL; runp = runp->next)
	if (strcmp (runp->toname, "INTERNAL") != 0)
	  tsearch (new_name (runp->toname, runp->toname_strent),
		   &names, name_compare);
    }
}


static int
name_to_module_idx (const char *name, int add)
{
  struct name **res;
  struct name fake_name = { .name = name };
  int idx;

  res = (struct name **) tfind (&fake_name, &names, name_compare);
  if (res == NULL)
    abort ();

  idx = (*res)->module_idx;
  if (idx == -1 && add)
    /* No module index assigned yet.  */
    idx = (*res)->module_idx = nname_info++;

  return idx;
}


static void
generate_name_info (void)
{
  size_t i;

  name_info = (struct name_info *) xcalloc (nmodule_list,
					    sizeof (struct name_info));

  for (i = 0; i < nmodule_list; ++i)
    {
      struct module *runp;

      for (runp = module_list[i]; runp != NULL; runp = runp->next)
	if (strcmp (runp->fromname, "INTERNAL") == 0)
	  {
	    int idx = name_to_module_idx (runp->toname, 1);
	    name_info[idx].from_internal = runp;
	    assert (name_info[idx].canonical_name == NULL
		    || strcmp (name_info[idx].canonical_name,
			       runp->toname) == 0);
	    name_info[idx].canonical_name = runp->toname;
	    name_info[idx].canonical_strent = runp->toname_strent;
	  }
	else if (strcmp (runp->toname, "INTERNAL") == 0)
	  {
	    int idx = name_to_module_idx (runp->fromname, 1);
	    name_info[idx].to_internal = runp;
	    assert (name_info[idx].canonical_name == NULL
		    || strcmp (name_info[idx].canonical_name,
			       runp->fromname) == 0);
	    name_info[idx].canonical_name = runp->fromname;
	    name_info[idx].canonical_strent = runp->fromname_strent;
	  }
	else
	  {
	    /* This is a transformation not to or from the INTERNAL
	       encoding.  */
	    int from_idx = name_to_module_idx (runp->fromname, 1);
	    int to_idx = name_to_module_idx (runp->toname, 1);
	    struct other_conv_list *newp;

	    newp = (struct other_conv_list *)
	      xmalloc (sizeof (struct other_conv_list));
	    newp->other_conv.module_idx = to_idx;
	    newp->other_conv.module = runp;
	    newp->other_conv.next = NULL; /* XXX Allow multiple module sequence */
	    newp->dest_idx = to_idx;
	    newp->next = name_info[from_idx].other_conv_list;
	    name_info[from_idx].other_conv_list = newp;
	    assert (name_info[from_idx].canonical_name == NULL
		    || strcmp (name_info[from_idx].canonical_name,
			       runp->fromname) == 0);
	    name_info[from_idx].canonical_name = runp->fromname;
	    name_info[from_idx].canonical_strent = runp->fromname_strent;

	    ++nextra_modules;
	  }
    }

  /* Now add the module index information for all the aliases.  */
  for (i = 0; i < nalias_list; ++i)
    {
      struct name fake_name = { .name = alias_list[i]->toname };
      struct name **tonamep;

      tonamep = (struct name **) tfind (&fake_name, &names, name_compare);
      if (tonamep != NULL)
	{
	  struct name *newp = new_name (alias_list[i]->fromname,
					alias_list[i]->froment);
	  newp->module_idx = (*tonamep)->module_idx;
	  tsearch (newp, &names, name_compare);
	}
    }
}


static int
is_prime (unsigned long int candidate)
{
  /* No even number and none less than 10 will be passed here.  */
  unsigned long int divn = 3;
  unsigned long int sq = divn * divn;

  while (sq < candidate && candidate % divn != 0)
    {
      ++divn;
      sq += 4 * divn;
      ++divn;
    }

  return candidate % divn != 0;
}


static uint32_t
next_prime (uint32_t seed)
{
  /* Make it definitely odd.  */
  seed |= 1;

  while (!is_prime (seed))
    seed += 2;

  return seed;
}


/* Format of the output file.

   Offset   Length       Description
   0000     4            Magic header bytes
   0004     4            Offset of string table (stoff)
   0008     4            Offset of name hashing table (hoff)
   000C     4            Hashing table size (hsize)
   0010     4            Offset of module table (moff)
   0014     4            Offset of other conversion module table (ooff)

   stoff    ???          String table

   hoff     8*hsize      Array of tuples
                            string table offset
                            module index

   moff     ???          Array of tuples
                            canonical name offset
                            from-internal module dir name offset
                            from-internal module name off
                            to-internal module dir name offset
                            to-internal module name offset
                            offset into other conversion table

   ooff     ???          Sequence of words
                            name offset
                            one or more of tuple
                              canonical name offset
                              module dir name offset
                              module name offset
                            (following last entry canocical name offset is 0)
*/
static int
write_output (void)
{
  int fd;
  char *string_table;
  size_t string_table_size;
  struct gconvcache_header header;
  struct hash_entry *hash_table;
  size_t hash_size;
  struct module_entry *module_table;
  char *extra_table;
  char *cur_extra_table;
  size_t n;
  int idx;
  struct iovec iov[6];
  static const gidx_t null_word;
  size_t total;

  /* Function to insert the names.  */
  void name_insert (const void *nodep, VISIT value, int level)
    {
      struct name *name;
      unsigned int idx;
      unsigned int hval2;

      if (value != leaf && value != postorder)
	return;

      name = *(struct name **) nodep;
      idx = name->hashval % hash_size;
      hval2 = 1 + name->hashval % (hash_size - 2);

      while (hash_table[idx].string_offset != 0)
	if ((idx += hval2) >= hash_size)
	  idx -= hash_size;

      hash_table[idx].string_offset = strtaboffset (name->strent);

      assert (name->module_idx != -1);
      hash_table[idx].module_idx = name->module_idx;
    }

  /* Open the output file.  */
  fd = open (GCONV_MODULES_CACHE, O_TRUNC | O_CREAT | O_RDWR, 0644);
  if (fd == -1)
    return 1;

  /* Create the string table.  */
  string_table = strtabfinalize (strtab, &string_table_size);

  /* Create the hashing table.  We know how many strings we have.
     Creating a perfect hash table is not reasonable here.  Therefore
     we use open hashing and a table size which is the next prime 40%
     larger than the number of strings.  */
  hash_size = next_prime (nnames * 1.4);
  hash_table = (struct hash_entry *) xcalloc (hash_size,
					      sizeof (struct hash_entry));
  /* Fill the hash table.  */
  twalk (names, name_insert);

  /* Create the section for the module list.  */
  module_table = (struct module_entry *) xcalloc (sizeof (struct module_entry),
						  nname_info);

  /* Allocate memory for the non-INTERNAL conversions.  The allocated
     memory can be more than is actually needed.  */
  extra_table = (char *) xcalloc (sizeof (struct extra_entry)
				  + sizeof (gidx_t)
				  + sizeof (struct extra_entry_module),
				  nextra_modules);
  cur_extra_table = extra_table;

  /* Fill in the module information.  */
  for (n = 0; n < nname_info; ++n)
    {
      module_table[n].canonname_offset =
	strtaboffset (name_info[n].canonical_strent);

      if (name_info[n].from_internal == NULL)
	{
	  module_table[n].fromdir_offset = 0;
	  module_table[n].fromname_offset = 0;
	}
      else
	{
	  module_table[n].fromdir_offset =
	    strtaboffset (name_info[n].from_internal->directory_strent);
	  module_table[n].fromname_offset =
	    strtaboffset (name_info[n].from_internal->filename_strent);
	}

      if (name_info[n].to_internal == NULL)
	{
	  module_table[n].todir_offset = 0;
	  module_table[n].toname_offset = 0;
	}
      else
	{
	  module_table[n].todir_offset =
	    strtaboffset (name_info[n].to_internal->directory_strent);
	  module_table[n].toname_offset =
	    strtaboffset (name_info[n].to_internal->filename_strent);
	}

      if (name_info[n].other_conv_list != NULL)
	{
	  struct other_conv_list *other = name_info[n].other_conv_list;

	  /* Store the reference.  We add 1 to distinguish the entry
	     at offset zero from the case where no extra modules are
	     available.  The file reader has to account for the
	     offset.  */
	  module_table[n].extra_offset = 1 + cur_extra_table - extra_table;

	  do
	    {
	      struct other_conv *runp;
	      struct extra_entry *extra;

	      /* Allocate new entry.  */
	      extra = (struct extra_entry *) cur_extra_table;
	      cur_extra_table += sizeof (struct extra_entry);
	      extra->module_cnt = 0;

	      runp = &other->other_conv;
	      do
		{
		  cur_extra_table += sizeof (struct extra_entry_module);
		  extra->module[extra->module_cnt].outname_offset =
		    runp->next == NULL
		    ? other->dest_idx : runp->next->module_idx;
		  extra->module[extra->module_cnt].dir_offset =
		    strtaboffset (runp->module->directory_strent);
		  extra->module[extra->module_cnt].name_offset =
		    strtaboffset (runp->module->filename_strent);
		  ++extra->module_cnt;

		  runp = runp->next;
		}
	      while (runp != NULL);

	      other = other->next;
	    }
	  while (other != NULL);

	  /* Final module_cnt is zero.  */
	  *((gidx_t *) cur_extra_table) = 0;
	  cur_extra_table += sizeof (gidx_t);
	}
    }

  header.magic = GCONVCACHE_MAGIC;

  iov[0].iov_base = &header;
  iov[0].iov_len = sizeof (struct gconvcache_header);
  total = iov[0].iov_len;

  header.string_offset = total;
  iov[1].iov_base = string_table;
  iov[1].iov_len = string_table_size;
  total += iov[1].iov_len;

  idx = 2;
  if ((string_table_size & (sizeof (gidx_t) - 1)) != 0)
    {
      iov[2].iov_base = (void *) &null_word;
      iov[2].iov_len = (sizeof (gidx_t)
			- (string_table_size & (sizeof (gidx_t) - 1)));
      total += iov[2].iov_len;
      ++idx;
    }

  header.hash_offset = total;
  header.hash_size = hash_size;
  iov[idx].iov_base = hash_table;
  iov[idx].iov_len = hash_size * sizeof (struct hash_entry);
  total += iov[idx].iov_len;
  ++idx;

  header.module_offset = total;
  iov[idx].iov_base = module_table;
  iov[idx].iov_len = nname_info * sizeof (struct module_entry);
  total += iov[idx].iov_len;
  ++idx;

  assert (cur_extra_table - extra_table
	  <= ((sizeof (struct extra_entry) + sizeof (gidx_t)
	       + sizeof (struct extra_entry_module))
	      * nextra_modules));
  header.otherconv_offset = total;
  iov[idx].iov_base = extra_table;
  iov[idx].iov_len = cur_extra_table - extra_table;
  total += iov[idx].iov_len;
  ++idx;

  if (TEMP_FAILURE_RETRY (writev (fd, iov, idx)) != total)
    {
      int save_errno = errno;
      close (fd);
      unlink (GCONV_MODULES_CACHE);
      error (EXIT_FAILURE, save_errno, gettext ("cannot write output file"));
    }

  close (fd);

  return 0;
}