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gconv_db.c

/* Provide access to the collection of available transformation modules.
   Copyright (C) 1997-2003, 2004 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

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

#include <limits.h>
#include <search.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <bits/libc-lock.h>
#include <locale/localeinfo.h>

#include <dlfcn.h>
#include <gconv_int.h>


/* Simple data structure for alias mapping.  We have two names, `from'
   and `to'.  */
void *__gconv_alias_db;

/* Array with available modules.  */
struct gconv_module *__gconv_modules_db;

/* We modify global data.   */
__libc_lock_define_initialized (, __gconv_lock)


/* Provide access to module database.  */
struct gconv_module *
__gconv_get_modules_db (void)
{
  return __gconv_modules_db;
}

void *
__gconv_get_alias_db (void)
{
  return __gconv_alias_db;
}


/* Function for searching alias.  */
int
__gconv_alias_compare (const void *p1, const void *p2)
{
  const struct gconv_alias *s1 = (const struct gconv_alias *) p1;
  const struct gconv_alias *s2 = (const struct gconv_alias *) p2;
  return strcmp (s1->fromname, s2->fromname);
}


/* To search for a derivation we create a list of intermediate steps.
   Each element contains a pointer to the element which precedes it
   in the derivation order.  */
struct derivation_step
{
  const char *result_set;
  size_t result_set_len;
  int cost_lo;
  int cost_hi;
  struct gconv_module *code;
  struct derivation_step *last;
  struct derivation_step *next;
};

#define NEW_STEP(result, hi, lo, module, last_mod) \
  ({ struct derivation_step *newp = alloca (sizeof (struct derivation_step)); \
     newp->result_set = result;                                         \
     newp->result_set_len = strlen (result);                            \
     newp->cost_hi = hi;                                          \
     newp->cost_lo = lo;                                          \
     newp->code = module;                                         \
     newp->last = last_mod;                                       \
     newp->next = NULL;                                           \
     newp; })


/* If a specific transformation is used more than once we should not need
   to start looking for it again.  Instead cache each successful result.  */
struct known_derivation
{
  const char *from;
  const char *to;
  struct __gconv_step *steps;
  size_t nsteps;
};

/* Compare function for database of found derivations.  */
static int
derivation_compare (const void *p1, const void *p2)
{
  const struct known_derivation *s1 = (const struct known_derivation *) p1;
  const struct known_derivation *s2 = (const struct known_derivation *) p2;
  int result;

  result = strcmp (s1->from, s2->from);
  if (result == 0)
    result = strcmp (s1->to, s2->to);
  return result;
}

/* The search tree for known derivations.  */
static void *known_derivations;

/* Look up whether given transformation was already requested before.  */
static int
internal_function
derivation_lookup (const char *fromset, const char *toset,
               struct __gconv_step **handle, size_t *nsteps)
{
  struct known_derivation key = { fromset, toset, NULL, 0 };
  struct known_derivation **result;

  result = __tfind (&key, &known_derivations, derivation_compare);

  if (result == NULL)
    return __GCONV_NOCONV;

  *handle = (*result)->steps;
  *nsteps = (*result)->nsteps;

  /* Please note that we return GCONV_OK even if the last search for
     this transformation was unsuccessful.  */
  return __GCONV_OK;
}

/* Add new derivation to list of known ones.  */
static void
internal_function
add_derivation (const char *fromset, const char *toset,
            struct __gconv_step *handle, size_t nsteps)
{
  struct known_derivation *new_deriv;
  size_t fromset_len = strlen (fromset) + 1;
  size_t toset_len = strlen (toset) + 1;

  new_deriv = (struct known_derivation *)
    malloc (sizeof (struct known_derivation) + fromset_len + toset_len);
  if (new_deriv != NULL)
    {
      new_deriv->from = (char *) (new_deriv + 1);
      new_deriv->to = memcpy (__mempcpy (new_deriv + 1, fromset, fromset_len),
                        toset, toset_len);

      new_deriv->steps = handle;
      new_deriv->nsteps = nsteps;

      if (__tsearch (new_deriv, &known_derivations, derivation_compare)
        == NULL)
      /* There is some kind of memory allocation problem.  */
      free (new_deriv);
    }
  /* Please note that we don't complain if the allocation failed.  This
     is not tragically but in case we use the memory debugging facilities
     not all memory will be freed.  */
}

static void __libc_freeres_fn_section
free_derivation (void *p)
{
  struct known_derivation *deriv = (struct known_derivation *) p;
  size_t cnt;

  for (cnt = 0; cnt < deriv->nsteps; ++cnt)
    if (deriv->steps[cnt].__counter > 0
      && deriv->steps[cnt].__end_fct != NULL)
      DL_CALL_FCT (deriv->steps[cnt].__end_fct, (&deriv->steps[cnt]));

  /* Free the name strings.  */
  free ((char *) deriv->steps[0].__from_name);
  free ((char *) deriv->steps[deriv->nsteps - 1].__to_name);

  free ((struct __gconv_step *) deriv->steps);
  free (deriv);
}


/* Decrement the reference count for a single step in a steps array.  */
void
internal_function
__gconv_release_step (struct __gconv_step *step)
{
  if (--step->__counter == 0)
    {
      /* Call the destructor.  */
      if (step->__end_fct != NULL)
      DL_CALL_FCT (step->__end_fct, (step));

#ifndef STATIC_GCONV
      /* Skip builtin modules; they are not reference counted.  */
      if (step->__shlib_handle != NULL)
      {
        /* Release the loaded module.  */
        __gconv_release_shlib (step->__shlib_handle);
        step->__shlib_handle = NULL;
      }
#endif
    }
}

static int
internal_function
gen_steps (struct derivation_step *best, const char *toset,
         const char *fromset, struct __gconv_step **handle, size_t *nsteps)
{
  size_t step_cnt = 0;
  struct __gconv_step *result;
  struct derivation_step *current;
  int status = __GCONV_NOMEM;

  /* First determine number of steps.  */
  for (current = best; current->last != NULL; current = current->last)
    ++step_cnt;

  result = (struct __gconv_step *) malloc (sizeof (struct __gconv_step)
                                 * step_cnt);
  if (result != NULL)
    {
      int failed = 0;

      status = __GCONV_OK;
      *nsteps = step_cnt;
      current = best;
      while (step_cnt-- > 0)
      {
        result[step_cnt].__from_name = (step_cnt == 0
                                ? __strdup (fromset)
                                : (char *)current->last->result_set);
        result[step_cnt].__to_name = (step_cnt + 1 == *nsteps
                              ? __strdup (current->result_set)
                              : result[step_cnt + 1].__from_name);

        result[step_cnt].__counter = 1;
        result[step_cnt].__data = NULL;

#ifndef STATIC_GCONV
        if (current->code->module_name[0] == '/')
          {
            /* Load the module, return handle for it.  */
            struct __gconv_loaded_object *shlib_handle =
            __gconv_find_shlib (current->code->module_name);

            if (shlib_handle == NULL)
            {
              failed = 1;
              break;
            }

            result[step_cnt].__shlib_handle = shlib_handle;
            result[step_cnt].__modname = shlib_handle->name;
            result[step_cnt].__fct = shlib_handle->fct;
            result[step_cnt].__init_fct = shlib_handle->init_fct;
            result[step_cnt].__end_fct = shlib_handle->end_fct;

            /* These settings can be overridden by the init function.  */
            result[step_cnt].__btowc_fct = NULL;

            /* Call the init function.  */
            if (result[step_cnt].__init_fct != NULL)
            {
              status = DL_CALL_FCT (result[step_cnt].__init_fct,
                              (&result[step_cnt]));

              if (__builtin_expect (status, __GCONV_OK) != __GCONV_OK)
                {
                  failed = 1;
                  /* Make sure we unload this modules.  */
                  --step_cnt;
                  result[step_cnt].__end_fct = NULL;
                  break;
                }
            }
          }
        else
#endif
          /* It's a builtin transformation.  */
          __gconv_get_builtin_trans (current->code->module_name,
                               &result[step_cnt]);

        current = current->last;
      }

      if (__builtin_expect (failed, 0) != 0)
      {
        /* Something went wrong while initializing the modules.  */
        while (++step_cnt < *nsteps)
          __gconv_release_step (&result[step_cnt]);
        free (result);
        *nsteps = 0;
        *handle = NULL;
        if (status == __GCONV_OK)
          status = __GCONV_NOCONV;
      }
      else
      *handle = result;
    }
  else
    {
      *nsteps = 0;
      *handle = NULL;
    }

  return status;
}


#ifndef STATIC_GCONV
static int
internal_function
increment_counter (struct __gconv_step *steps, size_t nsteps)
{
  /* Increment the user counter.  */
  size_t cnt = nsteps;
  int result = __GCONV_OK;

  while (cnt-- > 0)
    {
      struct __gconv_step *step = &steps[cnt];

      if (step->__counter++ == 0)
      {
        /* Skip builtin modules.  */
        if (step->__modname != NULL)
          {
            /* Reopen a previously used module.  */
            step->__shlib_handle = __gconv_find_shlib (step->__modname);
            if (step->__shlib_handle == NULL)
            {
              /* Oops, this is the second time we use this module
                 (after unloading) and this time loading failed!?  */
              --step->__counter;
              while (++cnt < nsteps)
                __gconv_release_step (&steps[cnt]);
              result = __GCONV_NOCONV;
              break;
            }

            /* The function addresses defined by the module may
             have changed.  */
            step->__fct = step->__shlib_handle->fct;
            step->__init_fct = step->__shlib_handle->init_fct;
            step->__end_fct = step->__shlib_handle->end_fct;

            /* These settings can be overridden by the init function.  */
            step->__btowc_fct = NULL;
          }

        /* Call the init function.  */
        if (step->__init_fct != NULL)
          DL_CALL_FCT (step->__init_fct, (step));
      }
    }
  return result;
}
#endif


/* The main function: find a possible derivation from the `fromset' (either
   the given name or the alias) to the `toset' (again with alias).  */
static int
internal_function
find_derivation (const char *toset, const char *toset_expand,
             const char *fromset, const char *fromset_expand,
             struct __gconv_step **handle, size_t *nsteps)
{
  struct derivation_step *first, *current, **lastp, *solution = NULL;
  int best_cost_hi = INT_MAX;
  int best_cost_lo = INT_MAX;
  int result;

  /* Look whether an earlier call to `find_derivation' has already
     computed a possible derivation.  If so, return it immediately.  */
  result = derivation_lookup (fromset_expand ?: fromset, toset_expand ?: toset,
                        handle, nsteps);
  if (result == __GCONV_OK)
    {
#ifndef STATIC_GCONV
      result = increment_counter (*handle, *nsteps);
#endif
      return result;
    }

  /* The task is to find a sequence of transformations, backed by the
     existing modules - whether builtin or dynamically loadable -,
     starting at `fromset' (or `fromset_expand') and ending at `toset'
     (or `toset_expand'), and with minimal cost.

     For computer scientists, this is a shortest path search in the
     graph where the nodes are all possible charsets and the edges are
     the transformations listed in __gconv_modules_db.

     For now we use a simple algorithm with quadratic runtime behaviour.
     A breadth-first search, starting at `fromset' and `fromset_expand'.
     The list starting at `first' contains all nodes that have been
     visited up to now, in the order in which they have been visited --
     excluding the goal nodes `toset' and `toset_expand' which get
     managed in the list starting at `solution'.
     `current' walks through the list starting at `first' and looks
     which nodes are reachable from the current node, adding them to
     the end of the list [`first' or `solution' respectively] (if
     they are visited the first time) or updating them in place (if
     they have have already been visited).
     In each node of either list, cost_lo and cost_hi contain the
     minimum cost over any paths found up to now, starting at `fromset'
     or `fromset_expand', ending at that node.  best_cost_lo and
     best_cost_hi represent the minimum over the elements of the
     `solution' list.  */

  if (fromset_expand != NULL)
    {
      first = NEW_STEP (fromset_expand, 0, 0, NULL, NULL);
      first->next = NEW_STEP (fromset, 0, 0, NULL, NULL);
      lastp = &first->next->next;
    }
  else
    {
      first = NEW_STEP (fromset, 0, 0, NULL, NULL);
      lastp = &first->next;
    }

  for (current = first; current != NULL; current = current->next)
    {
      /* Now match all the available module specifications against the
         current charset name.  If any of them matches check whether
         we already have a derivation for this charset.  If yes, use the
         one with the lower costs.  Otherwise add the new charset at the
         end.

       The module database is organized in a tree form which allows
       searching for prefixes.  So we search for the first entry with a
       matching prefix and any other matching entry can be found from
       this place.  */
      struct gconv_module *node;

      /* Maybe it is not necessary anymore to look for a solution for
       this entry since the cost is already as high (or higher) as
       the cost for the best solution so far.  */
      if (current->cost_hi > best_cost_hi
        || (current->cost_hi == best_cost_hi
            && current->cost_lo >= best_cost_lo))
      continue;

      node = __gconv_modules_db;
      while (node != NULL)
      {
        int cmpres = strcmp (current->result_set, node->from_string);
        if (cmpres == 0)
          {
            /* Walk through the list of modules with this prefix and
             try to match the name.  */
            struct gconv_module *runp;

            /* Check all the modules with this prefix.  */
            runp = node;
            do
            {
              const char *result_set = (strcmp (runp->to_string, "-") == 0
                                  ? (toset_expand ?: toset)
                                  : runp->to_string);
              int cost_hi = runp->cost_hi + current->cost_hi;
              int cost_lo = runp->cost_lo + current->cost_lo;
              struct derivation_step *step;

              /* We managed to find a derivation.  First see whether
                 we have reached one of the goal nodes.  */
              if (strcmp (result_set, toset) == 0
                  || (toset_expand != NULL
                    && strcmp (result_set, toset_expand) == 0))
                {
                  /* Append to the `solution' list if there
                   is no entry with this name.  */
                  for (step = solution; step != NULL; step = step->next)
                  if (strcmp (result_set, step->result_set) == 0)
                    break;

                  if (step == NULL)
                  {
                    step = NEW_STEP (result_set,
                                 cost_hi, cost_lo,
                                 runp, current);
                    step->next = solution;
                    solution = step;
                  }
                  else if (step->cost_hi > cost_hi
                         || (step->cost_hi == cost_hi
                           && step->cost_lo > cost_lo))
                  {
                    /* A better path was found for the node,
                       on the `solution' list.  */
                    step->code = runp;
                    step->last = current;
                    step->cost_hi = cost_hi;
                    step->cost_lo = cost_lo;
                  }

                  /* Update best_cost accordingly.  */
                  if (cost_hi < best_cost_hi
                    || (cost_hi == best_cost_hi
                        && cost_lo < best_cost_lo))
                  {
                    best_cost_hi = cost_hi;
                    best_cost_lo = cost_lo;
                  }
                }
              else if (cost_hi < best_cost_hi
                     || (cost_hi == best_cost_hi
                         && cost_lo < best_cost_lo))
                {
                  /* Append at the end of the `first' list if there
                   is no entry with this name.  */
                  for (step = first; step != NULL; step = step->next)
                  if (strcmp (result_set, step->result_set) == 0)
                    break;

                  if (step == NULL)
                  {
                    *lastp = NEW_STEP (result_set,
                                   cost_hi, cost_lo,
                                   runp, current);
                    lastp = &(*lastp)->next;
                  }
                  else if (step->cost_hi > cost_hi
                         || (step->cost_hi == cost_hi
                           && step->cost_lo > cost_lo))
                  {
                    /* A better path was found for the node,
                       on the `first' list.  */
                    step->code = runp;
                    step->last = current;

                    /* Update the cost for all steps.  */
                    for (step = first; step != NULL;
                         step = step->next)
                      /* But don't update the start nodes.  */
                      if (step->code != NULL)
                        {
                        struct derivation_step *back;
                        int hi, lo;

                        hi = step->code->cost_hi;
                        lo = step->code->cost_lo;

                        for (back = step->last; back->code != NULL;
                             back = back->last)
                          {
                            hi += back->code->cost_hi;
                            lo += back->code->cost_lo;
                          }

                        step->cost_hi = hi;
                        step->cost_lo = lo;
                        }

                    /* Likewise for the nodes on the solution list.
                       Also update best_cost accordingly.  */
                    for (step = solution; step != NULL;
                         step = step->next)
                      {
                        step->cost_hi = (step->code->cost_hi
                                     + step->last->cost_hi);
                        step->cost_lo = (step->code->cost_lo
                                     + step->last->cost_lo);

                        if (step->cost_hi < best_cost_hi
                          || (step->cost_hi == best_cost_hi
                              && step->cost_lo < best_cost_lo))
                        {
                          best_cost_hi = step->cost_hi;
                          best_cost_lo = step->cost_lo;
                        }
                      }
                  }
                }

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

            break;
          }
        else if (cmpres < 0)
          node = node->left;
        else
          node = node->right;
      }
    }

  if (solution != NULL)
    {
      /* We really found a way to do the transformation.  */

      /* Choose the best solution.  This is easy because we know that
       the solution list has at most length 2 (one for every possible
       goal node).  */
      if (solution->next != NULL)
      {
        struct derivation_step *solution2 = solution->next;

        if (solution2->cost_hi < solution->cost_hi
            || (solution2->cost_hi == solution->cost_hi
              && solution2->cost_lo < solution->cost_lo))
          solution = solution2;
      }

      /* Now build a data structure describing the transformation steps.  */
      result = gen_steps (solution, toset_expand ?: toset,
                    fromset_expand ?: fromset, handle, nsteps);
    }
  else
    {
      /* We haven't found a transformation.  Clear the result values.  */
      *handle = NULL;
      *nsteps = 0;
    }

  /* Add result in any case to list of known derivations.  */
  add_derivation (fromset_expand ?: fromset, toset_expand ?: toset,
              *handle, *nsteps);

  return result;
}


/* Control of initialization.  */
__libc_once_define (static, once);


static const char *
do_lookup_alias (const char *name)
{
  struct gconv_alias key;
  struct gconv_alias **found;

  key.fromname = (char *) name;
  found = __tfind (&key, &__gconv_alias_db, __gconv_alias_compare);
  return found != NULL ? (*found)->toname : NULL;
}


int
internal_function
__gconv_compare_alias (const char *name1, const char *name2)
{
  int result;

  /* Ensure that the configuration data is read.  */
  __libc_once (once, __gconv_read_conf);

  if (__gconv_compare_alias_cache (name1, name2, &result) != 0)
    result = strcmp (do_lookup_alias (name1) ?: name1,
                 do_lookup_alias (name2) ?: name2);

  return result;
}


int
internal_function
__gconv_find_transform (const char *toset, const char *fromset,
                  struct __gconv_step **handle, size_t *nsteps,
                  int flags)
{
  const char *fromset_expand;
  const char *toset_expand;
  int result;

  /* Ensure that the configuration data is read.  */
  __libc_once (once, __gconv_read_conf);

  /* Acquire the lock.  */
  __libc_lock_lock (__gconv_lock);

  result = __gconv_lookup_cache (toset, fromset, handle, nsteps, flags);
  if (result != __GCONV_NODB)
    {
      /* We have a cache and could resolve the request, successful or not.  */
      __libc_lock_unlock (__gconv_lock);
      return result;
    }

  /* If we don't have a module database return with an error.  */
  if (__gconv_modules_db == NULL)
    {
      __libc_lock_unlock (__gconv_lock);
      return __GCONV_NOCONV;
    }

  /* See whether the names are aliases.  */
  fromset_expand = do_lookup_alias (fromset);
  toset_expand = do_lookup_alias (toset);

  if (__builtin_expect (flags & GCONV_AVOID_NOCONV, 0)
      /* We are not supposed to create a pseudo transformation (means
       copying) when the input and output character set are the same.  */
      && (strcmp (toset, fromset) == 0
        || (toset_expand != NULL && strcmp (toset_expand, fromset) == 0)
        || (fromset_expand != NULL
            && (strcmp (toset, fromset_expand) == 0
              || (toset_expand != NULL
                  && strcmp (toset_expand, fromset_expand) == 0)))))
    {
      /* Both character sets are the same.  */
      __libc_lock_unlock (__gconv_lock);
      return __GCONV_NOCONV;
    }

  result = find_derivation (toset, toset_expand, fromset, fromset_expand,
                      handle, nsteps);

  /* Release the lock.  */
  __libc_lock_unlock (__gconv_lock);

  /* The following code is necessary since `find_derivation' will return
     GCONV_OK even when no derivation was found but the same request
     was processed before.  I.e., negative results will also be cached.  */
  return (result == __GCONV_OK
        ? (*handle == NULL ? __GCONV_NOCONV : __GCONV_OK)
        : result);
}


/* Release the entries of the modules list.  */
int
internal_function
__gconv_close_transform (struct __gconv_step *steps, size_t nsteps)
{
  int result = __GCONV_OK;
  size_t cnt;

  /* Acquire the lock.  */
  __libc_lock_lock (__gconv_lock);

#ifndef STATIC_GCONV
  cnt = nsteps;
  while (cnt-- > 0)
    __gconv_release_step (&steps[cnt]);
#endif

  /* If we use the cache we free a bit more since we don't keep any
     transformation records around, they are cheap enough to
     recreate.  */
  __gconv_release_cache (steps, nsteps);

  /* Release the lock.  */
  __libc_lock_unlock (__gconv_lock);

  return result;
}


/* Free the modules mentioned.  */
static void
internal_function __libc_freeres_fn_section
free_modules_db (struct gconv_module *node)
{
  if (node->left != NULL)
    free_modules_db (node->left);
  if (node->right != NULL)
    free_modules_db (node->right);
  do
    {
      struct gconv_module *act = node;
      node = node->same;
      if (act->module_name[0] == '/')
      free (act);
    }
  while (node != NULL);
}


/* Free all resources if necessary.  */
libc_freeres_fn (free_mem)
{
  /* First free locale memory.  This needs to be done before freeing derivations,
     as ctype cleanup functions dereference steps arrays which we free below.  */
  _nl_locale_subfreeres ();

  /* finddomain.c has similar problem.  */
  extern void _nl_finddomain_subfreeres (void) attribute_hidden;
  _nl_finddomain_subfreeres ();

  if (__gconv_alias_db != NULL)
    __tdestroy (__gconv_alias_db, free);

  if (__gconv_modules_db != NULL)
    free_modules_db (__gconv_modules_db);

  if (known_derivations != NULL)
    __tdestroy (known_derivations, free_derivation);
}

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