/* Cache handling for iconv modules.
   Copyright (C) 2001-2019 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 2001.

   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
   <http://www.gnu.org/licenses/>.  */

#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include <gconv_int.h>
#include <iconvconfig.h>
#include <not-cancel.h>

#include "../intl/hash-string.h"

static void *gconv_cache;
static size_t cache_size;
static int cache_malloced;


void *
__gconv_get_cache (void)
{
  return gconv_cache;
}


int
__gconv_load_cache (void)
{
  int fd;
  struct stat64 st;
  struct gconvcache_header *header;

  /* We cannot use the cache if the GCONV_PATH environment variable is
     set.  */
  __gconv_path_envvar = getenv ("GCONV_PATH");
  if (__gconv_path_envvar != NULL)
    return -1;

  /* See whether the cache file exists.  */
  fd = __open_nocancel (GCONV_MODULES_CACHE, O_RDONLY, 0);
  if (__builtin_expect (fd, 0) == -1)
    /* Not available.  */
    return -1;

  /* Get information about the file.  */
  if (__builtin_expect (__fxstat64 (_STAT_VER, fd, &st), 0) < 0
      /* We do not have to start looking at the file if it cannot contain
	 at least the cache header.  */
      || (size_t) st.st_size < sizeof (struct gconvcache_header))
    {
    close_and_exit:
      __close_nocancel_nostatus (fd);
      return -1;
    }

  /* Make the file content available.  */
  cache_size = st.st_size;
#ifdef _POSIX_MAPPED_FILES
  gconv_cache = __mmap (NULL, cache_size, PROT_READ, MAP_SHARED, fd, 0);
  if (__glibc_unlikely (gconv_cache == MAP_FAILED))
#endif
    {
      size_t already_read;

      gconv_cache = malloc (cache_size);
      if (gconv_cache == NULL)
	goto close_and_exit;

      already_read = 0;
      do
	{
	  ssize_t n = __read (fd, (char *) gconv_cache + already_read,
			      cache_size - already_read);
	  if (__builtin_expect (n, 0) == -1)
	    {
	      free (gconv_cache);
	      gconv_cache = NULL;
	      goto close_and_exit;
	    }

	  already_read += n;
	}
      while (already_read < cache_size);

      cache_malloced = 1;
    }

  /* We don't need the file descriptor anymore.  */
  __close_nocancel_nostatus (fd);

  /* Check the consistency.  */
  header = (struct gconvcache_header *) gconv_cache;
  if (__builtin_expect (header->magic, GCONVCACHE_MAGIC) != GCONVCACHE_MAGIC
      || __builtin_expect (header->string_offset >= cache_size, 0)
      || __builtin_expect (header->hash_offset >= cache_size, 0)
      || __builtin_expect (header->hash_size == 0, 0)
      || __builtin_expect ((header->hash_offset
			    + header->hash_size * sizeof (struct hash_entry))
			   > cache_size, 0)
      || __builtin_expect (header->module_offset >= cache_size, 0)
      || __builtin_expect (header->otherconv_offset > cache_size, 0))
    {
      if (cache_malloced)
	{
	  free (gconv_cache);
	  cache_malloced = 0;
	}
#ifdef _POSIX_MAPPED_FILES
      else
	__munmap (gconv_cache, cache_size);
#endif
      gconv_cache = NULL;

      return -1;
    }

  /* That worked.  */
  return 0;
}


static int
find_module_idx (const char *str, size_t *idxp)
{
  unsigned int idx;
  unsigned int hval;
  unsigned int hval2;
  const struct gconvcache_header *header;
  const char *strtab;
  const struct hash_entry *hashtab;
  unsigned int limit;

  header = (const struct gconvcache_header *) gconv_cache;
  strtab = (char *) gconv_cache + header->string_offset;
  hashtab = (struct hash_entry *) ((char *) gconv_cache
				   + header->hash_offset);

  hval = __hash_string (str);
  idx = hval % header->hash_size;
  hval2 = 1 + hval % (header->hash_size - 2);

  limit = cache_size - header->string_offset;
  while (hashtab[idx].string_offset != 0)
    if (hashtab[idx].string_offset < limit
	&& strcmp (str, strtab + hashtab[idx].string_offset) == 0)
      {
	*idxp = hashtab[idx].module_idx;
	return 0;
      }
    else
      if ((idx += hval2) >= header->hash_size)
	idx -= header->hash_size;

  /* Nothing found.  */
  return -1;
}


#ifndef STATIC_GCONV
static int
find_module (const char *directory, const char *filename,
	     struct __gconv_step *result)
{
  size_t dirlen = strlen (directory);
  size_t fnamelen = strlen (filename) + 1;
  char fullname[dirlen + fnamelen];
  int status = __GCONV_NOCONV;

  memcpy (__mempcpy (fullname, directory, dirlen), filename, fnamelen);

  result->__shlib_handle = __gconv_find_shlib (fullname);
  if (result->__shlib_handle != NULL)
    {
      status = __GCONV_OK;

      result->__modname = NULL;
      result->__fct = result->__shlib_handle->fct;
      result->__init_fct = result->__shlib_handle->init_fct;
      result->__end_fct = result->__shlib_handle->end_fct;

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

      /* Call the init function.  */
      __gconv_init_fct init_fct = result->__init_fct;
#ifdef PTR_DEMANGLE
      PTR_DEMANGLE (init_fct);
#endif
      if (init_fct != NULL)
	{
	  status = DL_CALL_FCT (init_fct, (result));

#ifdef PTR_MANGLE
	  PTR_MANGLE (result->__btowc_fct);
#endif
	}
    }

  return status;
}
#endif


int
__gconv_compare_alias_cache (const char *name1, const char *name2, int *result)
{
  size_t name1_idx;
  size_t name2_idx;

  if (gconv_cache == NULL)
    return -1;

  if (find_module_idx (name1, &name1_idx) != 0
      || find_module_idx (name2, &name2_idx) != 0)
    *result = strcmp (name1, name2);
  else
    *result = (int) (name1_idx - name2_idx);

  return 0;
}


int
__gconv_lookup_cache (const char *toset, const char *fromset,
		      struct __gconv_step **handle, size_t *nsteps, int flags)
{
  const struct gconvcache_header *header;
  const char *strtab;
  size_t fromidx;
  size_t toidx;
  const struct module_entry *modtab;
  const struct module_entry *from_module;
  const struct module_entry *to_module;
  struct __gconv_step *result;

  if (gconv_cache == NULL)
    /* We have no cache available.  */
    return __GCONV_NODB;

  header = (const struct gconvcache_header *) gconv_cache;
  strtab = (char *) gconv_cache + header->string_offset;
  modtab = (const struct module_entry *) ((char *) gconv_cache
					  + header->module_offset);

  if (find_module_idx (fromset, &fromidx) != 0
      || (header->module_offset + (fromidx + 1) * sizeof (struct module_entry)
	  > cache_size))
    return __GCONV_NOCONV;
  from_module = &modtab[fromidx];

  if (find_module_idx (toset, &toidx) != 0
      || (header->module_offset + (toidx + 1) * sizeof (struct module_entry)
	  > cache_size))
    return __GCONV_NOCONV;
  to_module = &modtab[toidx];

  /* Avoid copy-only transformations if the user requests.   */
  if (__builtin_expect (flags & GCONV_AVOID_NOCONV, 0) && fromidx == toidx)
    return __GCONV_NULCONV;

  /* If there are special conversions available examine them first.  */
  if (fromidx != 0 && toidx != 0
      && __builtin_expect (from_module->extra_offset, 0) != 0)
    {
      /* Search through the list to see whether there is a module
	 matching the destination character set.  */
      const struct extra_entry *extra;

      /* Note the -1.  This is due to the offset added in iconvconfig.
	 See there for more explanations.  */
      extra = (const struct extra_entry *) ((char *) gconv_cache
					    + header->otherconv_offset
					    + from_module->extra_offset - 1);
      while (extra->module_cnt != 0
	     && extra->module[extra->module_cnt - 1].outname_offset != toidx)
	extra = (const struct extra_entry *) ((char *) extra
					      + sizeof (struct extra_entry)
					      + (extra->module_cnt
						 * sizeof (struct extra_entry_module)));

      if (extra->module_cnt != 0)
	{
	  /* Use the extra module.  First determine how many steps.  */
	  char *fromname;
	  int idx;

	  *nsteps = extra->module_cnt;
	  *handle = result =
	    (struct __gconv_step *) malloc (extra->module_cnt
					    * sizeof (struct __gconv_step));
	  if (result == NULL)
	    return __GCONV_NOMEM;

	  fromname = (char *) strtab + from_module->canonname_offset;
	  idx = 0;
	  do
	    {
	      result[idx].__from_name = fromname;
	      fromname = result[idx].__to_name =
		(char *) strtab + modtab[extra->module[idx].outname_offset].canonname_offset;

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

#ifndef STATIC_GCONV
	      if (strtab[extra->module[idx].dir_offset] != '\0')
		{
		  /* Load the module, return handle for it.  */
		  int res;

		  res = find_module (strtab + extra->module[idx].dir_offset,
				     strtab + extra->module[idx].name_offset,
				     &result[idx]);
		  if (__builtin_expect (res, __GCONV_OK) != __GCONV_OK)
		    {
		      /* Something went wrong.  */
		      free (result);
		      goto try_internal;
		    }
		}
	      else
#endif
		/* It's a builtin transformation.  */
		__gconv_get_builtin_trans (strtab
					   + extra->module[idx].name_offset,
					   &result[idx]);

	    }
	  while (++idx < extra->module_cnt);

	  return __GCONV_OK;
	}
    }

 try_internal:
  /* See whether we can convert via the INTERNAL charset.  */
  if ((fromidx != 0 && __builtin_expect (from_module->fromname_offset, 1) == 0)
      || (toidx != 0 && __builtin_expect (to_module->toname_offset, 1) == 0)
      || (fromidx == 0 && toidx == 0))
    /* Not possible.  Nothing we can do.  */
    return __GCONV_NOCONV;

  /* We will use up to two modules.  Always allocate room for two.  */
  result = (struct __gconv_step *) malloc (2 * sizeof (struct __gconv_step));
  if (result == NULL)
    return __GCONV_NOMEM;

  *handle = result;
  *nsteps = 0;

  /* Generate data structure for conversion to INTERNAL.  */
  if (fromidx != 0)
    {
      result[0].__from_name = (char *) strtab + from_module->canonname_offset;
      result[0].__to_name = (char *) "INTERNAL";

      result[0].__counter = 1;
      result[0].__data = NULL;

#ifndef STATIC_GCONV
      if (strtab[from_module->todir_offset] != '\0')
	{
	  /* Load the module, return handle for it.  */
	  int res = find_module (strtab + from_module->todir_offset,
				 strtab + from_module->toname_offset,
				 &result[0]);
	  if (__builtin_expect (res, __GCONV_OK) != __GCONV_OK)
	    {
	      /* Something went wrong.  */
	      free (result);
	      return res;
	    }
	}
      else
#endif
	/* It's a builtin transformation.  */
	__gconv_get_builtin_trans (strtab + from_module->toname_offset,
				   &result[0]);

      ++*nsteps;
    }

  /* Generate data structure for conversion from INTERNAL.  */
  if (toidx != 0)
    {
      int idx = *nsteps;

      result[idx].__from_name = (char *) "INTERNAL";
      result[idx].__to_name = (char *) strtab + to_module->canonname_offset;

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

#ifndef STATIC_GCONV
      if (strtab[to_module->fromdir_offset] != '\0')
	{
	  /* Load the module, return handle for it.  */
	  int res = find_module (strtab + to_module->fromdir_offset,
				 strtab + to_module->fromname_offset,
				 &result[idx]);
	  if (__builtin_expect (res, __GCONV_OK) != __GCONV_OK)
	    {
	      /* Something went wrong.  */
	      if (idx != 0)
		__gconv_release_step (&result[0]);
	      free (result);
	      return res;
	    }
	}
      else
#endif
	/* It's a builtin transformation.  */
	__gconv_get_builtin_trans (strtab + to_module->fromname_offset,
				   &result[idx]);

      ++*nsteps;
    }

  return __GCONV_OK;
}


/* Free memory allocated for the transformation record.  */
void
__gconv_release_cache (struct __gconv_step *steps, size_t nsteps)
{
  /* The only thing we have to deallocate is the record with the
     steps.  But do not do this if the reference counter is still
     positive.  This can happen if the steps array was cloned by
     __wcsmbs_clone_conv.  (The array elements have separate __counter
     fields, but they are only out of sync temporarily.)  */
  if (gconv_cache != NULL && steps->__counter == 0)
    free (steps);
}


/* Free all resources if necessary.  */
libc_freeres_fn (free_mem)
{
  if (cache_malloced)
    free (gconv_cache);
#ifdef _POSIX_MAPPED_FILES
  else if (gconv_cache != NULL)
    __munmap (gconv_cache, cache_size);
#endif
}