path: root/src/util/container_meta_data.c

/*
     This file is part of GNUnet.
     Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009, 2010 GNUnet e.V.

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet 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
     Affero General Public License for more details.
    
     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
 * @file util/container_meta_data.c
 * @brief Storing of meta data
 * @author Christian Grothoff
 */

#include "platform.h"
#include "gnunet_util_lib.h"
#if HAVE_EXTRACTOR_H
#include <extractor.h>
#endif
#include <zlib.h>

#define LOG(kind,...) GNUNET_log_from (kind, "util-container-meta-data", __VA_ARGS__)



/**
 * Try to compress the given block of data using libz.  Only returns
 * the compressed block if compression worked and the new block is
 * actually smaller.  Decompress using #GNUNET_decompress().
 *
 * @param data block to compress; if compression
 *        resulted in a smaller block, the first
 *        bytes of data are updated to the compressed
 *        data
 * @param old_size number of bytes in data
 * @param[out] result set to the compressed data, if compression worked
 * @param[out] new_size set to size of result, if compression worked
 * @return #GNUNET_YES if compression reduce the size,
 *         #GNUNET_NO if compression did not help
 */
int
GNUNET_try_compression (const char *data,
                        size_t old_size,
                        char **result,
                        size_t *new_size)
{
  char *tmp;
  uLongf dlen;

  *result = NULL;
  *new_size = 0;
#ifdef compressBound
  dlen = compressBound (old_size);
#else
  dlen = old_size + (old_size / 100) + 20;
  /* documentation says 100.1% oldSize + 12 bytes, but we
   * should be able to overshoot by more to be safe */
#endif
  tmp = GNUNET_malloc (dlen);
  if (Z_OK ==
      compress2 ((Bytef *) tmp,
                 &dlen,
                 (const Bytef *) data,
                 old_size, 9))
  {
    if (dlen < old_size)
    {
      *result = tmp;
      *new_size = dlen;
      return GNUNET_YES;
    }
  }
  GNUNET_free (tmp);
  return GNUNET_NO;
}


/**
 * Decompress input, return the decompressed data as output.  Dual to
 * #GNUNET_try_compression(). Caller must set @a output_size to the
 * number of bytes that were originally compressed.
 *
 * @param input compressed data
 * @param input_size number of bytes in input
 * @param output_size expected size of the output
 * @return NULL on error, buffer of @a output_size decompressed bytes otherwise
 */
char *
GNUNET_decompress (const char *input,
                   size_t input_size,
                   size_t output_size)
{
  char *output;
  uLongf olen;

  olen = output_size;
  output = GNUNET_malloc (olen);
  if (Z_OK ==
      uncompress ((Bytef *) output,
                  &olen,
                  (const Bytef *) input,
                  input_size))
    return output;
  GNUNET_free (output);
  return NULL;
}


/**
 * Meta data item.
 */
struct MetaItem
{
  /**
   * This is a doubly linked list.
   */
  struct MetaItem *next;

  /**
   * This is a doubly linked list.
   */
  struct MetaItem *prev;

  /**
   * Name of the extracting plugin.
   */
  char *plugin_name;

  /**
   * Mime-type of data.
   */
  char *mime_type;

  /**
   * The actual meta data.
   */
  char *data;

  /**
   * Number of bytes in 'data'.
   */
  size_t data_size;

  /**
   * Type of the meta data.
   */
  enum EXTRACTOR_MetaType type;

  /**
   * Format of the meta data.
   */
  enum EXTRACTOR_MetaFormat format;

};

/**
 * Meta data to associate with a file, directory or namespace.
 */
struct GNUNET_CONTAINER_MetaData
{
  /**
   * Head of linked list of the meta data items.
   */
  struct MetaItem *items_head;

  /**
   * Tail of linked list of the meta data items.
   */
  struct MetaItem *items_tail;

  /**
   * Complete serialized and compressed buffer of the items.
   * NULL if we have not computed that buffer yet.
   */
  char *sbuf;

  /**
   * Number of bytes in 'sbuf'. 0 if the buffer is stale.
   */
  size_t sbuf_size;

  /**
   * Number of items in the linked list.
   */
  unsigned int item_count;

};


/**
 * Create a fresh struct CONTAINER_MetaData token.
 *
 * @return empty meta-data container
 *