tasource of type @a datasource.
   *  Return a "token" in @a *token.   Return a hash of "token" in @a *hash.
   *  Leave @a token and @a hash untouched when the datasource is exhausted.
   */
  svn_error_t *(*datasource_get_next_token)(apr_uint32_t *hash, void **token,
                                            void *diff_baton,
                                            svn_diff_datasource_e datasource);

  /** A function for ordering the tokens, resembling 'strcmp' in functionality.
   * @a compare should contain the return value of the comparison:
   * If @a ltoken and @a rtoken are "equal", return 0.  If @a ltoken is
   * "less than" @a rtoken, return a number < 0.  If @a ltoken  is
   * "greater than" @a rtoken, return a number > 0.
   */
  svn_error_t *(*token_compare)(void *diff_baton,
                                void *ltoken,
                                void *rtoken,
                                int *compare);

  /** Free @a token from memory, the diff algorithm is done with it. */
  void (*token_discard)(void *diff_baton,
                        void *token);

  /** Free *all* tokens from memory, they're no longer needed. */
  void (*token_discard_all)(void *diff_baton);
} svn_diff_fns2_t;


/** Like #svn_diff_fns2_t except with datasource_open() instead of
 * datasources_open().
 *
 * @deprecated Provided for backward compatibility with the 1.6 API.
 */
typedef struct svn_diff_fns_t
{
  svn_error_t *(*datasource_open)(void *diff_baton,
                                  svn_diff_datasource_e datasource);

  svn_error_t *(*datasource_close)(void *diff_baton,
                                   svn_diff_datasource_e datasource);

  svn_error_t *(*datasource_get_next_token)(apr_uint32_t *hash, void **token,
                                            void *diff_baton,
                                            svn_diff_datasource_e datasource);

  svn_error_t *(*token_compare)(void *diff_baton,
                                void *ltoken,
                                void *rtoken,
                                int *compare);

  void (*token_discard)(void *diff_baton,
                        void *token);

  void (*token_discard_all)(void *diff_baton);
} svn_diff_fns_t;


/* The Main Events */

/** Given a vtable of @a diff_fns/@a diff_baton for reading datasources,
 * return a diff object in @a *diff that represents a difference between
 * an "original" and "modified" datasource.  Do all allocation in @a pool.
 *
 * @since New in 1.7.
 */
svn_error_t *
svn_diff_diff_2(svn_diff_t **diff,
                void *diff_baton,
                const svn_diff_fns2_t *diff_fns,
                apr_pool_t *pool);

/** Like svn_diff_diff_2() but using #svn_diff_fns_t instead of
 * #svn_diff_fns2_t.
 *
 * @deprecated Provided for backward compatibility with the 1.6 API.
 */
SVN_DEPRECATED
svn_error_t *
svn_diff_diff(svn_diff_t **diff,
              void *diff_baton,
              const svn_diff_fns_t *diff_fns,
              apr_pool_t *pool);

/** Given a vtable of @a diff_fns/@a diff_baton for reading datasources,
 * return a diff object in @a *diff that represents a difference between
 * three datasources: "original", "modified", and "latest".  Do all
 * allocation in @a pool.
 *
 * @since New in 1.7.
 */
svn_error_t *
svn_diff_diff3_2(svn_diff_t **diff,
                 void *diff_baton,
                 const svn_diff_fns2_t *diff_fns,
                 apr_pool_t *pool);

/** Like svn_diff_diff3_2() but using #svn_diff_fns_t instead of
 * #svn_diff_fns2_t.
 *
 * @deprecated Provided for backward compatibility with the 1.6 API.
 */
SVN_DEPRECATED
svn_error_t *
svn_diff_diff3(svn_diff_t **diff,
               void *diff_baton,
               const svn_diff_fns_t *diff_fns,
               apr_pool_t *pool);

/** Given a vtable of @a diff_fns/@a diff_baton for reading datasources,
 * return a diff object in @a *diff that represents a difference between
 * two datasources: "original" and "latest", adjusted to become a full
 * difference between "original", "modified" and "latest" using "ancestor".
 * Do all allocation in @a pool.
 *
 * @since New in 1.7.
 */
svn_error_t *
svn_diff_diff4_2(svn_diff_t **diff,
                 void *diff_baton,
                 const svn_diff_fns2_t *diff_fns,
                 apr_pool_t *pool);

/** Like svn_diff_diff4_2() but using #svn_diff_fns_t instead of
 * #svn_diff_fns2_t.
 *
 * @deprecated Provided for backward compatibility with the 1.6 API.
 */
SVN_DEPRECATED
svn_error_t *
svn_diff_diff4(svn_diff_t **diff,
               void *diff_baton,
               const svn_diff_fns_t *diff_fns,
               apr_pool_t *pool);