subversion/libsvn_fs/dbt.h

/* dbt.h --- interface to DBT-frobbing functions
 *
 * ====================================================================
 * Copyright (c) 2000-2002 CollabNet.  All rights reserved.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution.  The terms
 * are also available at http://subversion.tigris.org/license-1.html.
 * If newer versions of this license are posted there, you may use a
 * newer version instead, at your option.
 *
 * This software consists of voluntary contributions made by many
 * individuals.  For exact contribution history, see the revision
 * history and logs, available at http://subversion.tigris.org/.
 * ====================================================================
 */

#ifndef SVN_LIBSVN_FS_DBT_H
#define SVN_LIBSVN_FS_DBT_H

#include <apr_pools.h>

#include "svn_fs.h"
#include "db.h"
#include "skel.h"

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */


/* Set all fields of DBT to zero.  Return DBT.  */
DBT *svn_fs__clear_dbt (DBT *dbt);


/* Set DBT to retrieve no data.  This is useful when you're just
   probing the table to see if an entry exists, or to find a key, but
   don't care what the value is.  Return DBT.  */
DBT *svn_fs__nodata_dbt (DBT *dbt);


/* Set DBT to refer to the SIZE bytes at DATA.  Return DBT.  */
DBT *svn_fs__set_dbt (DBT *dbt, void *data, u_int32_t size);


/* Prepare DBT to hold data returned from Berkeley DB.  Return DBT.

   Clear all its fields to zero, but set the DB_DBT_MALLOC flag,
   requesting that Berkeley DB place the returned data in a freshly
   malloc'd block.  If the database operation succeeds, the caller
   then owns the data block, and is responsible for making sure it
   gets freed.  

   You can use this with svn_fs__track_dbt:

       svn_fs__result_dbt (&foo);
       ... some Berkeley DB operation that puts data in foo ...
       svn_fs__track_dbt (&foo, pool);

   This arrangement is:
   - thread-safe --- the returned data is allocated via malloc, and
     won't be overwritten if some other thread performs an operation
     on the same table.  See the explanation of ``Retrieved key/data
     permanence'' in the section of the Berkeley DB manual on the DBT
     type.
   - pool-friendly --- the data returned by Berkeley DB is now guaranteed
     to be freed when POOL is cleared.  */
DBT *svn_fs__result_dbt (DBT *dbt);

/* Arrange for POOL to `track' DBT's data: when POOL is cleared,
   DBT->data will be freed, using `free'.  If DBT->data is zero,
   do nothing.

   This is meant for use with svn_fs__result_dbt; see the explanation
   there.  */
DBT *svn_fs__track_dbt (DBT *dbt, apr_pool_t *pool);


/* Prepare DBT for use as a key into a RECNO table.  This call makes
   DBT refer to the db_recno_t pointed to by RECNO as its buffer; the
   record number you assign to *RECNO will be the table key.  */
DBT *svn_fs__recno_dbt (DBT *dbt, db_recno_t *recno);


/* Compare two DBT values in byte-by-byte lexicographic order.  */
int svn_fs__compare_dbt (const DBT *a, const DBT *b);


/* Set DBT to the unparsed form of ID; allocate memory from POOL.
   Return DBT.  */
DBT *svn_fs__id_to_dbt (DBT *dbt, const svn_fs_id_t *id, apr_pool_t *pool);


/* Set DBT to the unparsed form of SKEL; allocate memory from POOL.
   Return DBT.  */
DBT *svn_fs__skel_to_dbt (DBT *dbt, skel_t *skel, apr_pool_t *pool);


/* Set DBT to the text of the null-terminated string STR.  DBT will
   refer to STR's storage.  Return DBT.  */
DBT *svn_fs__str_to_dbt (DBT *dbt, char *str);


#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif /* SVN_LIBSVN_FS_DBT_H */


/* 
 * local variables:
 * eval: (load-file "../../tools/dev/svn-dev.el")
 * end:
 */