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glibc/iconv/gconv_db.c

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/* Provide access to the collection of available transformation modules.
Copyright (C) 1997-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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, see
<https://www.gnu.org/licenses/>. */
#include <assert.h>
#include <limits.h>
#include <search.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <libc-lock.h>
#include <locale/localeinfo.h>
#include <dlfcn.h>
#include <gconv_int.h>
#include <pointer_guard.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
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
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
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].__shlib_handle != NULL)
{
__gconv_end_fct end_fct = deriv->steps[cnt].__end_fct;
PTR_DEMANGLE (end_fct);
if (end_fct != NULL)
DL_CALL_FCT (end_fct, (&deriv->steps[cnt]));
}
/* Free the name strings. */
if (deriv->steps != NULL)
{
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
__gconv_release_step (struct __gconv_step *step)
{
/* Skip builtin modules; they are not reference counted. */
if (step->__shlib_handle != NULL && --step->__counter == 0)
{
/* Call the destructor. */
__gconv_end_fct end_fct = step->__end_fct;
PTR_DEMANGLE (end_fct);
if (end_fct != NULL)
DL_CALL_FCT (end_fct, (step));
#ifndef STATIC_GCONV
/* Release the loaded module. */
__gconv_release_shlib (step->__shlib_handle);
step->__shlib_handle = NULL;
#endif
}
else if (step->__shlib_handle == NULL)
/* Builtin modules should not have end functions. */
assert (step->__end_fct == NULL);
}
static int
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;
char *from_name = NULL;
char *to_name = NULL;
/* 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)
{
if (step_cnt == 0)
{
result[step_cnt].__from_name = from_name = __strdup (fromset);
if (from_name == NULL)
{
failed = 1;
break;
}
}
else
result[step_cnt].__from_name = (char *)current->last->result_set;
if (step_cnt + 1 == *nsteps)
{
result[step_cnt].__to_name = to_name
= __strdup (current->result_set);
if (to_name == NULL)
{
failed = 1;
break;
}
}
else
result[step_cnt].__to_name = 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. */
__gconv_init_fct init_fct = result[step_cnt].__init_fct;
PTR_DEMANGLE (init_fct);
if (init_fct != NULL)
{
status = DL_CALL_FCT (init_fct, (&result[step_cnt]));
if (__builtin_expect (status, __GCONV_OK) != __GCONV_OK)
{
failed = 1;
/* Do not call the end function because the init
function has failed. */
result[step_cnt].__end_fct = NULL;
PTR_MANGLE (result[step_cnt].__end_fct);
/* Make sure we unload this module. */
--step_cnt;
break;
}
}
PTR_MANGLE (result[step_cnt].__btowc_fct);
}
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);
free (from_name);
free (to_name);
*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
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. */
__gconv_init_fct init_fct = step->__init_fct;
PTR_DEMANGLE (init_fct);
if (init_fct != NULL)
DL_CALL_FCT (init_fct, (step));
PTR_MANGLE (step->__btowc_fct);
}
}
}
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
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;
}
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
__gconv_compare_alias (const char *name1, const char *name2)
{
int result;
/* Ensure that the configuration data is read. */
__gconv_load_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
__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. */
__gconv_load_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_NULCONV;
}
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
__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
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. */
void
__gconv_db_freemem (void)
{
/* 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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