/*

 * Copyright © 2010 Codethink Limited

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This 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.

 *

 * This 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 this library; if not, see <http://www.gnu.org/licenses/>.

 *

 * Author: Ryan Lortie <desrt@desrt.ca>

 */

#include "gvdb-reader.h"

#include "gvdb-format.h"

#include <string.h>

struct _GvdbTable {

  GBytes *bytes;

  const gchar *data;

  gsize size;

  gboolean byteswapped;

  gboolean trusted;

  const guint32_le *bloom_words;

  guint32 n_bloom_words;

  guint bloom_shift;

  const guint32_le *hash_buckets;

  guint32 n_buckets;

  struct gvdb_hash_item *hash_items;

  guint32 n_hash_items;

};

static const gchar *

gvdb_table_item_get_key (GvdbTable                   *file,

                         const struct gvdb_hash_item *item,

                         gsize                       *size)

{

  guint32 start, end;

  start = guint32_from_le (item->key_start);

  *size = guint16_from_le (item->key_size);

  end = start + *size;

  if G_UNLIKELY (start > end || end > file->size)

    return NULL;

  return file->data + start;

}

static gconstpointer

gvdb_table_dereference (GvdbTable                 *file,

                        const struct gvdb_pointer *pointer,

                        gint                       alignment,

                        gsize                     *size)

{

  guint32 start, end;

  start = guint32_from_le (pointer->start);

  end = guint32_from_le (pointer->end);

  if G_UNLIKELY (start > end || end > file->size || start & (alignment - 1))

    return NULL;

  *size = end - start;

  return file->data + start;

}

static void

gvdb_table_setup_root (GvdbTable                 *file,

                       const struct gvdb_pointer *pointer)

{

  const struct gvdb_hash_header *header;

  guint32 n_bloom_words;

  guint32 n_buckets;

  gsize size;

  header = gvdb_table_dereference (file, pointer, 4, &size);

  if G_UNLIKELY (header == NULL || size < sizeof *header)

    return;

  size -= sizeof *header;

  n_bloom_words = guint32_from_le (header->n_bloom_words);

  n_buckets = guint32_from_le (header->n_buckets);

  n_bloom_words &= (1u << 27) - 1;

  if G_UNLIKELY (n_bloom_words * sizeof (guint32_le) > size)

    return;

  file->bloom_words = (gpointer) (header + 1);

  size -= n_bloom_words * sizeof (guint32_le);

  file->n_bloom_words = n_bloom_words;

  if G_UNLIKELY (n_buckets > G_MAXUINT / sizeof (guint32_le) ||

                 n_buckets * sizeof (guint32_le) > size)

    return;

  file->hash_buckets = file->bloom_words + file->n_bloom_words;

  size -= n_buckets * sizeof (guint32_le);

  file->n_buckets = n_buckets;

  if G_UNLIKELY (size % sizeof (struct gvdb_hash_item))

    return;

  file->hash_items = (gpointer) (file->hash_buckets + n_buckets);

  file->n_hash_items = size / sizeof (struct gvdb_hash_item);

}

/**

 * gvdb_table_new_from_bytes:

 * @bytes: the #GBytes with the data

 * @trusted: if the contents of @bytes are trusted

 * @error: %NULL, or a pointer to a %NULL #GError

 *

 * Creates a new #GvdbTable from the contents of @bytes.

 *

 * This call can fail if the header contained in @bytes is invalid or if @bytes

 * is empty; if so, %G_FILE_ERROR_INVAL will be returned.

 *

 * You should call gvdb_table_free() on the return result when you no

 * longer require it.

 *

 * Returns: a new #GvdbTable

 **/

GvdbTable *

gvdb_table_new_from_bytes (GBytes    *bytes,

                           gboolean   trusted,

                           GError   **error)

{

  const struct gvdb_header *header;

  GvdbTable *file;

  file = g_slice_new0 (GvdbTable);

  file->bytes = g_bytes_ref (bytes);

  file->data = g_bytes_get_data (bytes, &file->size);

  file->trusted = trusted;

  if (file->size < sizeof (struct gvdb_header))

    goto invalid;

  header = (gpointer) file->data;

  if (header->signature[0] == GVDB_SIGNATURE0 &&

      header->signature[1] == GVDB_SIGNATURE1 &&

      guint32_from_le (header->version) == 0)

    file->byteswapped = FALSE;

  else if (header->signature[0] == GVDB_SWAPPED_SIGNATURE0 &&

           header->signature[1] == GVDB_SWAPPED_SIGNATURE1 &&

           guint32_from_le (header->version) == 0)

    file->byteswapped = TRUE;

  else

    goto invalid;

  gvdb_table_setup_root (file, &header->root);

  return file;

invalid:

  g_set_error_literal (error, G_FILE_ERROR, G_FILE_ERROR_INVAL, "invalid gvdb header");

  g_bytes_unref (file->bytes);

  g_slice_free (GvdbTable, file);

  return NULL;

}

/**

 * gvdb_table_new:

 * @filename: a filename

 * @trusted: if the contents of @bytes are trusted

 * @error: %NULL, or a pointer to a %NULL #GError

 *

 * Creates a new #GvdbTable using the #GMappedFile for @filename as the

 * #GBytes.

 *

 * This function will fail if the file cannot be opened.

 * In that case, the #GError that is returned will be an error from

 * g_mapped_file_new().

 *

 * An empty or corrupt file will result in %G_FILE_ERROR_INVAL.

 *

 * Returns: a new #GvdbTable

 **/

GvdbTable *

gvdb_table_new (const gchar  *filename,

                gboolean      trusted,

                GError      **error)

{

  GMappedFile *mapped;

  GvdbTable *table;

  GBytes *bytes;

  mapped = g_mapped_file_new (filename, FALSE, error);

  if (!mapped)

    return NULL;

  bytes = g_mapped_file_get_bytes (mapped);

  table = gvdb_table_new_from_bytes (bytes, trusted, error);

  g_mapped_file_unref (mapped);

  g_bytes_unref (bytes);

  g_prefix_error (error, "%s: ", filename);

  return table;

}

static gboolean

gvdb_table_bloom_filter (GvdbTable *file,

                          guint32    hash_value)

{

  guint32 word, mask;

  if (file->n_bloom_words == 0)

    return TRUE;

  word = (hash_value / 32) % file->n_bloom_words;

  mask = 1 << (hash_value & 31);

  mask |= 1 << ((hash_value >> file->bloom_shift) & 31);

  return (guint32_from_le (file->bloom_words[word]) & mask) == mask;

}

static gboolean

gvdb_table_check_name (GvdbTable             *file,

                       struct gvdb_hash_item *item,

                       const gchar           *key,

                       guint                  key_length)

{

  const gchar *this_key;

  gsize this_size;

  guint32 parent;

  this_key = gvdb_table_item_get_key (file, item, &this_size);

  if G_UNLIKELY (this_key == NULL || this_size > key_length)

    return FALSE;

  key_length -= this_size;

  if G_UNLIKELY (memcmp (this_key, key + key_length, this_size) != 0)

    return FALSE;

  parent = guint32_from_le (item->parent);

  if (key_length == 0 && parent == 0xffffffffu)

    return TRUE;

  if G_LIKELY (parent < file->n_hash_items && this_size > 0)

    return gvdb_table_check_name (file,

                                   &file->hash_items[parent],

                                   key, key_length);

  return FALSE;

}

static const struct gvdb_hash_item *

gvdb_table_lookup (GvdbTable   *file,

                   const gchar *key,

                   gchar        type)

{

  guint32 hash_value = 5381;

  guint key_length;

  guint32 bucket;

  guint32 lastno;

  guint32 itemno;

  if G_UNLIKELY (file->n_buckets == 0 || file->n_hash_items == 0)

    return NULL;

  for (key_length = 0; key[key_length]; key_length++)

    hash_value = (hash_value * 33) + ((signed char *) key)[key_length];

  if (!gvdb_table_bloom_filter (file, hash_value))

    return NULL;

  bucket = hash_value % file->n_buckets;

  itemno = guint32_from_le (file->hash_buckets[bucket]);

  if (bucket == file->n_buckets - 1 ||

      (lastno = guint32_from_le(file->hash_buckets[bucket + 1])) > file->n_hash_items)

    lastno = file->n_hash_items;

  while G_LIKELY (itemno < lastno)

    {

      struct gvdb_hash_item *item = &file->hash_items[itemno];

      if (hash_value == guint32_from_le (item->hash_value))

        if G_LIKELY (gvdb_table_check_name (file, item, key, key_length))

          if G_LIKELY (item->type == type)

            return item;

      itemno++;

    }

  return NULL;

}

static gboolean

gvdb_table_list_from_item (GvdbTable                    *table,

                           const struct gvdb_hash_item  *item,

                           const guint32_le            **list,

                           guint                        *length)

{

  gsize size;

  *list = gvdb_table_dereference (table, &item->value.pointer, 4, &size);

  if G_LIKELY (*list == NULL || size % 4)

    return FALSE;

  *length = size / 4;

  return TRUE;

}

/**

 * gvdb_table_get_names:

 * @table: a #GvdbTable

 * @length: (out) (optional): the number of items returned, or %NULL

 *

 * Gets a list of all names contained in @table.

 *

 * No call to gvdb_table_get_table(), gvdb_table_list() or

 * gvdb_table_get_value() will succeed unless it is for one of the

 * names returned by this function.

 *

 * Note that some names that are returned may still fail for all of the

 * above calls in the case of the corrupted file.  Note also that the

 * returned strings may not be utf8.

 *

 * Returns: (array length=length): a %NULL-terminated list of strings, of length @length

 **/

gchar **

gvdb_table_get_names (GvdbTable *table,

                      gsize     *length)

{

  gchar **names;

  guint n_names;

  guint filled;

  guint total;

  guint i;

  /* We generally proceed by iterating over the list of items in the

   * hash table (in order of appearance) recording them into an array.

   *

   * Each item has a parent item (except root items).  The parent item

   * forms part of the name of the item.  We could go fetching the

   * parent item chain at the point that we encounter each item but then

   * we would need to implement some sort of recursion along with checks

   * for self-referential items.

   *

   * Instead, we do a number of passes.  Each pass will build up one

   * level of names (starting from the root).  We continue to do passes

   * until no more items are left.  The first pass will only add root

   * items and each further pass will only add items whose direct parent

   * is an item added in the immediately previous pass.  It's also

   * possible that items get filled if they follow their parent within a

   * particular pass.

   *

   * At most we will have a number of passes equal to the depth of the

   * tree.  Self-referential items will never be filled in (since their

   * parent will have never been filled in).  We continue until we have

   * a pass that fills in no additional items.

   *

   * This takes an O(n) algorithm and turns it into O(n*m) where m is

   * the depth of the tree, but typically the tree won't be very

   * deep and the constant factor of this algorithm is lower (and the

   * complexity of coding it, as well).

   */

  n_names = table->n_hash_items;

  names = g_new0 (gchar *, n_names + 1);

  /* 'names' starts out all-NULL.  On each pass we record the number

   * of items changed from NULL to non-NULL in 'filled' so we know if we

   * should repeat the loop.  'total' counts the total number of items

   * filled.  If 'total' ends up equal to 'n_names' then we know that

   * 'names' has been completely filled.

   */

  total = 0;

  do

    {

      /* Loop until we have filled no more entries */

      filled = 0;

      for (i = 0; i < n_names; i++)

        {

          const struct gvdb_hash_item *item = &table->hash_items[i];

          const gchar *name;

          gsize name_length;

          guint32 parent;

          /* already got it on a previous pass */

          if (names[i] != NULL)

            continue;

          parent = guint32_from_le (item->parent);

          if (parent == 0xffffffffu)

            {

              /* it's a root item */

              name = gvdb_table_item_get_key (table, item, &name_length);

              if (name != NULL)

                {

                  names[i] = g_strndup (name, name_length);

                  filled++;

                }

            }

          else if (parent < n_names && names[parent] != NULL)

            {

              /* It's a non-root item whose parent was filled in already.

               *

               * Calculate the name of this item by combining it with

               * its parent name.

               */

              name = gvdb_table_item_get_key (table, item, &name_length);

              if (name != NULL)

                {

                  const gchar *parent_name = names[parent];

                  gsize parent_length;

                  gchar *fullname;

                  parent_length = strlen (parent_name);

                  fullname = g_malloc (parent_length + name_length + 1);

                  memcpy (fullname, parent_name, parent_length);

                  memcpy (fullname + parent_length, name, name_length);

                  fullname[parent_length + name_length] = '\0';

                  names[i] = fullname;

                  filled++;

                }

            }

        }

      total += filled;

    }

  while (filled && total < n_names);

  /* If the table was corrupted then 'names' may have holes in it.

   * Collapse those.

   */

  if G_UNLIKELY (total != n_names)

    {

      GPtrArray *fixed_names;

      fixed_names = g_ptr_array_sized_new (n_names + 1  /* NULL terminator */);

      for (i = 0; i < n_names; i++)

        if (names[i] != NULL)

          g_ptr_array_add (fixed_names, names[i]);

      g_free (names);

      n_names = fixed_names->len;

      g_ptr_array_add (fixed_names, NULL);

      names = (gchar **) g_ptr_array_free (fixed_names, FALSE);

    }

  if (length)

    {

      G_STATIC_ASSERT (sizeof (*length) >= sizeof (n_names));

      *length = n_names;

    }

  return names;

}

/**

 * gvdb_table_list:

 * @file: a #GvdbTable

 * @key: a string

 *

 * List all of the keys that appear below @key.  The nesting of keys

 * within the hash file is defined by the program that created the hash

 * file.  One thing is constant: each item in the returned array can be

 * concatenated to @key to obtain the full name of that key.

 *

 * It is not possible to tell from this function if a given key is

 * itself a path, a value, or another hash table; you are expected to

 * know this for yourself.

 *

 * You should call g_strfreev() on the return result when you no longer

 * require it.

 *

 * Returns: a %NULL-terminated string array

 **/

gchar **

gvdb_table_list (GvdbTable   *file,

                 const gchar *key)

{

  const struct gvdb_hash_item *item;

  const guint32_le *list;

  gchar **strv;

  guint length;

  guint i;

  if ((item = gvdb_table_lookup (file, key, 'L')) == NULL)

    return NULL;

  if (!gvdb_table_list_from_item (file, item, &list, &length))

    return NULL;

  strv = g_new (gchar *, length + 1);

  for (i = 0; i < length; i++)

    {

      guint32 itemno = guint32_from_le (list[i]);

      if (itemno < file->n_hash_items)

        {

          const struct gvdb_hash_item *child_item;

          const gchar *string;

          gsize strsize;

          child_item = file->hash_items + itemno;

          string = gvdb_table_item_get_key (file, child_item, &strsize);

          if (string != NULL)

            strv[i] = g_strndup (string, strsize);

          else

            strv[i] = g_malloc0 (1);

        }

      else

        strv[i] = g_malloc0 (1);

    }

  strv[i] = NULL;

  return strv;

}

/**

 * gvdb_table_n_children:

 * @file: a #GvdbTable

 * @key: a string

 *

 * Returns the number of keys that appear below @key.

 *

 * Returns: the number of keys below @key

 */

guint

gvdb_table_n_children (GvdbTable  *file,

                       const char *key)

{

  const struct gvdb_hash_item *item;

  const guint32_le *list;

  guint length;

  if ((item = gvdb_table_lookup (file, key, 'L')) == NULL)

    return 0;

  if (!gvdb_table_list_from_item (file, item, &list, &length))

    return 0;

  return length;

}

/**

 * gvdb_table_has_value:

 * @file: a #GvdbTable

 * @key: a string

 *

 * Checks for a value named @key in @file.

 *

 * Note: this function does not consider non-value nodes (other hash

 * tables, for example).

 *

 * Returns: %TRUE if @key is in the table

 **/

gboolean

gvdb_table_has_value (GvdbTable    *file,

                      const gchar  *key)

{

  static const struct gvdb_hash_item *item;

  gsize size;

  item = gvdb_table_lookup (file, key, 'v');

  if (item == NULL)

    return FALSE;

  return gvdb_table_dereference (file, &item->value.pointer, 8, &size) != NULL;

}

static GVariant *

gvdb_table_value_from_item (GvdbTable                   *table,

                            const struct gvdb_hash_item *item)

{

  GVariant *variant, *value;

  gconstpointer data;

  GBytes *bytes;

  gsize size;

  data = gvdb_table_dereference (table, &item->value.pointer, 8, &size);

  if G_UNLIKELY (data == NULL)

    return NULL;

  bytes = g_bytes_new_from_bytes (table->bytes, ((gchar *) data) - table->data, size);

  variant = g_variant_new_from_bytes (G_VARIANT_TYPE_VARIANT, bytes, table->trusted);

  value = g_variant_get_variant (variant);

  g_variant_unref (variant);

  g_bytes_unref (bytes);

  return value;

}

/**

 * gvdb_table_get_value:

 * @file: a #GvdbTable

 * @key: a string

 *

 * Looks up a value named @key in @file.

 *

 * If the value is not found then %NULL is returned.  Otherwise, a new

 * #GVariant instance is returned.  The #GVariant does not depend on the

 * continued existence of @file.

 *

 * You should call g_variant_unref() on the return result when you no

 * longer require it.

 *

 * Returns: (transfer full) (nullable): a #GVariant, or %NULL

 **/

GVariant *

gvdb_table_get_value (GvdbTable    *file,

                      const gchar  *key)

{

  const struct gvdb_hash_item *item;

  GVariant *value;

  if ((item = gvdb_table_lookup (file, key, 'v')) == NULL)

    return NULL;

  value = gvdb_table_value_from_item (file, item);

  if (value && file->byteswapped)

    {

      GVariant *tmp;

      tmp = g_variant_byteswap (value);

      g_variant_unref (value);

      value = tmp;

    }

  return value;

}

/**

 * gvdb_table_get_raw_value:

 * @table: a #GvdbTable

 * @key: a string

 *

 * Looks up a value named @key in @file.

 *

 * This call is equivalent to gvdb_table_get_value() except that it

 * never byteswaps the value.

 *

 * Returns: (transfer full) (nullable): a #GVariant, or %NULL

 **/

GVariant *

gvdb_table_get_raw_value (GvdbTable   *table,

                          const gchar *key)

{

  const struct gvdb_hash_item *item;

  if ((item = gvdb_table_lookup (table, key, 'v')) == NULL)

    return NULL;

  return gvdb_table_value_from_item (table, item);

}

/**

 * gvdb_table_get_table:

 * @file: a #GvdbTable

 * @key: a string

 *

 * Looks up the hash table named @key in @file.

 *

 * The toplevel hash table in a #GvdbTable can contain reference to

 * child hash tables (and those can contain further references...).

 *

 * If @key is not found in @file then %NULL is returned.  Otherwise, a

 * new #GvdbTable is returned, referring to the child hashtable as

 * contained in the file.  This newly-created #GvdbTable does not depend

 * on the continued existence of @file.

 *

 * You should call gvdb_table_free() on the return result when you no

 * longer require it.

 *

 * Returns: a new #GvdbTable, or %NULL

 **/

GvdbTable *

gvdb_table_get_table (GvdbTable   *file,

                      const gchar *key)

{

  const struct gvdb_hash_item *item;

  GvdbTable *new;

  item = gvdb_table_lookup (file, key, 'H');

  if (item == NULL)

    return NULL;

  new = g_slice_new0 (GvdbTable);

  new->bytes = g_bytes_ref (file->bytes);

  new->byteswapped = file->byteswapped;

  new->trusted = file->trusted;

  new->data = file->data;

  new->size = file->size;

  gvdb_table_setup_root (new, &item->value.pointer);

  return new;

}

/**

 * gvdb_table_free:

 * @file: a #GvdbTable

 *

 * Frees @file.

 **/

void

gvdb_table_free (GvdbTable *file)

{

  g_bytes_unref (file->bytes);

  g_slice_free (GvdbTable, file);

}

/**

 * gvdb_table_is_valid:

 * @table: a #GvdbTable

 *

 * Checks if the table is still valid.

 *

 * An on-disk GVDB can be marked as invalid.  This happens when the file

 * has been replaced.  The appropriate action is typically to reopen the

 * file.

 *

 * Returns: %TRUE if @table is still valid

 **/

gboolean

gvdb_table_is_valid (GvdbTable *table)

{

  return !!*table->data;

}