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/* Provide access to the collection of available transformation modules.

   Copyright (C) 1997,98,99,2000,2001 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 <dirent.h>

#include <dlfcn.h>

#include <gconv_int.h>

#include <gconv_charset.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.   */

__LOCK_INIT(static, lock);

/* 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)

    {

      char *tmp;

      new_deriv->from = (char *) (new_deriv + 1);

      tmp = memcpy (new_deriv + 1, fromset, fromset_len);

      tmp += fromset_len;

      new_deriv->to = memcpy (tmp,

                              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

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)

      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)

        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;

              /* Call the init function.  */

              if (result[step_cnt].__init_fct != NULL)

                {

                  status = 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;

            }

          if (step->__init_fct != NULL)

            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.  */

#ifdef HAVE_DD_LOCK

  __lock_acquire(lock);

#endif

  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.  */

#ifdef HAVE_DD_LOCK

      __lock_release(lock);

#endif

      return result;

    }

  /* If we don't have a module database return with an error.  */

  if (__gconv_modules_db == NULL)

    {

#ifdef HAVE_DD_LOCK

  __lock_release(lock);

#endif

      return __GCONV_NOCONV;

    }