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[thirdparty/glibc.git] / iconv / gconv_db.c

/* Provide access to the collection of available transformation modules.
   Copyright (C) 1997, 1998 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 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 <search.h>
#include <stdlib.h>
#include <string.h>
#include <bits/libc-lock.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.  */
size_t __gconv_nmodules;
struct gconv_module **__gconv_modules_db;

/* We modify global data.   */
__libc_lock_define_initialized (static, lock)


/* Function for searching alias.  */
int
__gconv_alias_compare (const void *p1, const void *p2)
{
  struct gconv_alias *s1 = (struct gconv_alias *) p1;
  struct gconv_alias *s2 = (struct gconv_alias *) p2;
  return __strcasecmp (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;
  struct gconv_module *code;
  struct derivation_step *last;
  struct derivation_step *next;
};

#define NEW_STEP(result, module, last_mod) \
  ({ struct derivation_step *newp = alloca (sizeof (struct derivation_step)); \
     newp->result_set = result;                                               \
     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)
{
  struct known_derivation *s1 = (struct known_derivation *) p1;
  struct known_derivation *s2 = (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 = memcpy (new_deriv + 1, fromset, fromset_len);
      new_deriv->to = memcpy ((char *) new_deriv->from + fromset_len,
                              toset, toset_len);

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

      __tsearch (new_deriv, &known_derivations, derivation_compare);
    }
  /* 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
internal_function
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].end_fct)
      (*deriv->steps[cnt].end_fct) (&deriv->steps[cnt]);

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


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;

      *nsteps = step_cnt;
      current = best;
      while (step_cnt-- > 0)
        {
          result[step_cnt].from_name = (step_cnt == 0
                                        ? __strdup (fromset)
                                        : current->last->result_set);
          result[step_cnt].to_name = (step_cnt + 1 == *nsteps
                                      ? __strdup (current->result_set)
                                      : result[step_cnt + 1].from_name);

          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].counter = 0;
              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;
            }
          else
            /* It's a builtin transformation.  */
            __gconv_get_builtin_trans (current->code->module_name,
                                       &result[step_cnt]);

          /* Call the init function.  */
          if (result[step_cnt].init_fct != NULL)
            (*result[step_cnt].init_fct) (&result[step_cnt]);

          current = current->last;
        }

      if (failed != 0)
        {
          /* Something went wrong while initializing the modules.  */
          while (++step_cnt < *nsteps)
            {
              if (result[step_cnt].end_fct != NULL)
                (*result[step_cnt].end_fct) (&result[step_cnt]);
              __gconv_release_shlib (result[step_cnt].shlib_handle);
            }
          free (result);
          *nsteps = 0;
          status = GCONV_NOCONV;
        }
      else
        {
          *handle = result;
          status = GCONV_OK;
        }
    }

  return status;
}


/* 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)
{
  __libc_lock_define_initialized (static, lock)
  struct derivation_step *first, *current, **lastp, *best = NULL;
  int best_cost = 0;
  int result;

  result = derivation_lookup (fromset_expand ?: fromset, toset_expand ?: toset,
                              handle, nsteps);
  if (result == GCONV_OK)
    return result;

  __libc_lock_lock (lock);

  /* There is a small chance that this derivation is meanwhile found.  This
     can happen if in `find_derivation' we look for this derivation, didn't
     find it but at the same time another thread looked for this derivation. */
  result = derivation_lookup (fromset_expand ?: fromset, toset_expand ?: toset,
                              handle, nsteps);
  if (result == GCONV_OK)
    return result;

  /* ### TODO
     For now we use a simple algorithm with quadratic runtime behaviour.
     The task is to match the `toset' with any of the available rules,
     starting from FROMSET.  */
  if (fromset_expand != NULL)
    {
      first = NEW_STEP (fromset_expand, NULL, NULL);
      first->next = NEW_STEP (fromset, NULL, NULL);
      lastp = &first->next->next;
    }
  else
    {
      first = NEW_STEP (fromset, NULL, NULL);
      lastp = &first->next;
    }

  current = first;
  while (current != NULL)
    {
      /* 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.  */
      size_t cnt;

      for (cnt = 0; cnt < __gconv_nmodules; ++cnt)
        {
          const char *result_set = NULL;

          if (__gconv_modules_db[cnt]->from_pattern == NULL)
            {
              if (__strcasecmp (current->result_set,
                                __gconv_modules_db[cnt]->from_constpfx) == 0)
                {
                  if (strcmp (__gconv_modules_db[cnt]->to_string, "-") == 0)
                    result_set = toset_expand ?: toset;
                  else
                    result_set = __gconv_modules_db[cnt]->to_string;
                }
            }
          else
            /* We have a regular expression.  First see if the prefix
               matches.  */
            if (__strncasecmp (current->result_set,
                               __gconv_modules_db[cnt]->from_constpfx,
                               __gconv_modules_db[cnt]->from_constpfx_len)
                == 0)
              {
                /* First compile the regex if not already done.  */
                if (__gconv_modules_db[cnt]->from_regex == NULL)
                  {
                    regex_t *newp = (regex_t *) malloc (sizeof (regex_t));

                    if (regcomp (newp, __gconv_modules_db[cnt]->from_pattern,
                                 REG_EXTENDED | REG_ICASE) != 0)
                      {
                        /* Something is wrong.  Remember this.  */
                        free (newp);
                        __gconv_modules_db[cnt]->from_regex = (regex_t *) -1L;
                      }
                    else
                      __gconv_modules_db[cnt]->from_regex = newp;
                  }

                if (__gconv_modules_db[cnt]->from_regex != (regex_t *) -1L)
                  {
                    /* Try to match the from name.  */
                    regmatch_t match[4];

                    if (regexec (__gconv_modules_db[cnt]->from_regex,
                                 current->result_set, 4, match, 0) == 0
                        && match[0].rm_so == 0
                        && current->result_set[match[0].rm_eo] == '\0')
                      {
                        /* At least the whole <from> string is matched.
                           We must now match sed-like possible
                           subexpressions from the match to the
                           toset expression.  */
#define ENSURE_LEN(LEN) \
  if (wp + (LEN) >= constr + len - 1)                                         \
    {                                                                         \
      char *newp = alloca (len += 128);                                       \
      memcpy (newp, constr, wp - constr);                                     \
      wp = newp + (wp - constr);                                              \
      constr = newp;                                                          \
    }
                        size_t len = 128;
                        char *constr = alloca (len);
                        char *wp = constr;
                        const char *cp = __gconv_modules_db[cnt]->to_string;

                        while (*cp != '\0')
                          {
                            if (*cp != '\\')
                              {
                                ENSURE_LEN (1);
                                *wp++ = *cp++;
                              }
                            else if (cp[1] == '\0')
                              /* Backslash at end of string.  */
                              break;
                            else
                              {
                                ++cp;
                                if (*cp == '\\')
                                  {
                                    *wp++ = *cp++;
                                    ENSURE_LEN (1);
                                  }
                                else if (*cp < '1' || *cp > '3')
                                  break;
                                else
                                  {
                                    int idx = *cp - '0';
                                    if (match[idx].rm_so == -1)
                                      /* No match.  */
                                      break;

                                    ENSURE_LEN (match[idx].rm_eo
                                                - match[idx].rm_so);
                                    wp = __mempcpy (wp,
                                                    &current->result_set[match[idx].rm_so],
                                                    match[idx].rm_eo
                                                    - match[idx].rm_so);
                                    ++cp;
                                  }
                              }
                          }
                        if (*cp == '\0' && wp != constr)
                          {
                                /* Terminate the constructed string.  */
                            *wp = '\0';
                            result_set = constr;
                          }
                      }
                  }
              }

          if (result_set != NULL)
            {
              /* We managed to find a derivation.  First see whether
                 this is what we are looking for.  */
              if (__strcasecmp (result_set, toset) == 0
                  || (toset_expand != NULL
                      && __strcasecmp (result_set, toset_expand) == 0))
                {
                  /* Determine the costs.  If they are lower than the
                     previous solution (or this is the first solution)
                     remember this solution.  */
                  int cost = __gconv_modules_db[cnt]->cost;
                  struct derivation_step *runp = current;
                  while (runp->code != NULL)
                    {
                      cost += runp->code->cost;
                      runp = runp->last;
                    }
                  if (best == NULL || cost < best_cost)
                    {
                      best = NEW_STEP (result_set, __gconv_modules_db[cnt],
                                       current);
                      best_cost = cost;
                    }
                }
              else
                {
                  /* Append at the end if there is no entry with this name.  */
                  struct derivation_step *runp = first;

                  while (runp != NULL)
                    {
                      if (__strcasecmp (result_set, runp->result_set) == 0)
                        break;
                      runp = runp->next;
                    }

                  if (runp == NULL)
                    {
                      *lastp = NEW_STEP (result_set, __gconv_modules_db[cnt],
                                         current);
                      lastp = &(*lastp)->next;
                    }
                }
            }
        }

      /* Go on with the next entry.  */
      current = current->next;
    }

  if (best != NULL)
    /* We really found a way to do the transformation.  Now build a data
       structure describing the transformation steps.*/
    result = gen_steps (best, 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);

  __libc_lock_unlock (lock);

  return result;
}


int
internal_function
__gconv_find_transform (const char *toset, const char *fromset,
                        struct gconv_step **handle, size_t *nsteps)
{
  __libc_once_define (static, once);
  const char *fromset_expand = NULL;
  const char *toset_expand = NULL;
  int result;

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

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

  /* If we don't have a module database return with an error.  */
  if (__gconv_modules_db == NULL)
    return GCONV_NOCONV;

  /* See whether the names are aliases.  */
  if (__gconv_alias_db != NULL)
    {
      struct gconv_alias key;
      struct gconv_alias **found;

      key.fromname = fromset;
      found = __tfind (&key, &__gconv_alias_db, __gconv_alias_compare);
      fromset_expand = found != NULL ? (*found)->toname : NULL;

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

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

  /* Increment the user counter.  */
  if (result == GCONV_OK)
    {
      size_t cnt = *nsteps;
      struct gconv_step *steps = *handle;

      do
        if (steps[--cnt].counter++ == 0)
          {
            steps[--cnt].shlib_handle =
              __gconv_find_shlib (steps[--cnt].modname);
            if (steps[--cnt].shlib_handle == NULL)
              {
                /* Oops, this is the second time we use this module (after
                   unloading) and this time loading failed!?  */
                while (++cnt < *nsteps)
                  __gconv_release_shlib (steps[cnt].shlib_handle);
                result = GCONV_NOCONV;
                break;
              }
          }
      while (cnt > 0);
    }

  /* Release the lock.  */
  __libc_lock_unlock (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;

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

  while (nsteps-- > 0)
    if (steps[nsteps].shlib_handle != NULL
        && --steps[nsteps].counter == 0)
      {
        result = __gconv_release_shlib (steps[nsteps].shlib_handle);
        if (result != GCONV_OK)
          break;
        steps[nsteps].shlib_handle = NULL;
      }

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

  return result;
}


/* Free all resources if necessary.  */
static void __attribute__ ((unused))
free_mem (void)
{
  size_t cnt;

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

  for (cnt = 0; cnt < __gconv_nmodules; ++cnt)
    {
      if (__gconv_modules_db[cnt]->from_regex != NULL)
        regfree ((regex_t *) __gconv_modules_db[cnt]->from_regex);

      /* Modules which names do not start with a slash are builtin
         transformations and the memory is not allocated dynamically.  */
      if (__gconv_modules_db[cnt]->module_name[0] == '/')
        free (__gconv_modules_db[cnt]);
    }

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

text_set_element (__libc_subfreeres, free_mem);