source: trunk/libs/newlib/src/newlib/libc/sys/linux/iconv/gconv_db.c @ 444

/* 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;
    }

  /* 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.  */
#ifdef HAVE_DD_LOCK
  __lock_release(lock);
#endif

      return __GCONV_NOCONV;
    }

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

  /* Release the lock.  */
#ifdef HAVE_DD_LOCK
  __lock_release(lock);
#endif


  /* 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.  */
#ifdef HAVE_DD_LOCK
  __lock_acquire(lock);
#endif


#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.  */
#ifdef HAVE_DD_LOCK
  __lock_release(lock);
#endif


  return result;
}


/* Free the modules mentioned.  */
static void
internal_function
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.  */
static void __attribute__ ((unused))
free_mem (void)
{
  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);
}

text_set_element (__libc_subfreeres, free_mem);