apr_sdbm.h

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00001 /* Licensed to the Apache Software Foundation (ASF) under one or more
00002  * contributor license agreements.  See the NOTICE file distributed with
00003  * this work for additional information regarding copyright ownership.
00004  * The ASF licenses this file to You under the Apache License, Version 2.0
00005  * (the "License"); you may not use this file except in compliance with
00006  * the License.  You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 /*
00018  * sdbm - ndbm work-alike hashed database library
00019  * based on Per-Ake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
00020  * author: oz@nexus.yorku.ca
00021  * status: ex-public domain
00022  */
00023 
00024 #ifndef APR_SDBM_H
00025 #define APR_SDBM_H
00026 
00027 #include "apu.h"
00028 #include "apr_errno.h"
00029 #include "apr_file_io.h"   /* for apr_fileperms_t */
00030 
00031 /** 
00032  * @file apr_sdbm.h
00033  * @brief apr-util SDBM library
00034  */
00035 /**
00036  * @defgroup APR_Util_DBM_SDBM SDBM library
00037  * @ingroup APR_Util_DBM
00038  * @{
00039  */
00040 
00041 /**
00042  * Structure for referencing an sdbm
00043  */
00044 typedef struct apr_sdbm_t apr_sdbm_t;
00045 
00046 /**
00047  * Structure for referencing the datum record within an sdbm
00048  */
00049 typedef struct {
00050     /** pointer to the data stored/retrieved */
00051     char *dptr;
00052     /** size of data */
00053     int dsize;
00054 } apr_sdbm_datum_t;
00055 
00056 /* The extensions used for the database files */
00057 /** SDBM Directory file extension */
00058 #define APR_SDBM_DIRFEXT        ".dir"
00059 /** SDBM page file extension */
00060 #define APR_SDBM_PAGFEXT        ".pag"
00061 
00062 /* flags to sdbm_store */
00063 #define APR_SDBM_INSERT     0   /**< Insert */
00064 #define APR_SDBM_REPLACE    1   /**< Replace */
00065 #define APR_SDBM_INSERTDUP  2   /**< Insert with duplicates */
00066 
00067 /**
00068  * Open an sdbm database by file name
00069  * @param db The newly opened database
00070  * @param name The sdbm file to open
00071  * @param mode The flag values (APR_READ and APR_BINARY flags are implicit)
00072  * <PRE>
00073  *           APR_WRITE          open for read-write access
00074  *           APR_CREATE         create the sdbm if it does not exist
00075  *           APR_TRUNCATE       empty the contents of the sdbm
00076  *           APR_EXCL           fail for APR_CREATE if the file exists
00077  *           APR_DELONCLOSE     delete the sdbm when closed
00078  *           APR_SHARELOCK      support locking across process/machines
00079  * </PRE>
00080  * @param perms Permissions to apply to if created
00081  * @param p The pool to use when creating the sdbm
00082  * @remark The sdbm name is not a true file name, as sdbm appends suffixes 
00083  * for seperate data and index files.
00084  */
00085 APU_DECLARE(apr_status_t) apr_sdbm_open(apr_sdbm_t **db, const char *name, 
00086                                         apr_int32_t mode, 
00087                                         apr_fileperms_t perms, apr_pool_t *p);
00088 
00089 /**
00090  * Close an sdbm file previously opened by apr_sdbm_open
00091  * @param db The database to close
00092  */
00093 APU_DECLARE(apr_status_t) apr_sdbm_close(apr_sdbm_t *db);
00094 
00095 /**
00096  * Lock an sdbm database for concurency of multiple operations
00097  * @param db The database to lock
00098  * @param type The lock type
00099  * <PRE>
00100  *           APR_FLOCK_SHARED
00101  *           APR_FLOCK_EXCLUSIVE
00102  * </PRE>
00103  * @remark Calls to apr_sdbm_lock may be nested.  All apr_sdbm functions
00104  * perform implicit locking.  Since an APR_FLOCK_SHARED lock cannot be 
00105  * portably promoted to an APR_FLOCK_EXCLUSIVE lock, apr_sdbm_store and 
00106  * apr_sdbm_delete calls will fail if an APR_FLOCK_SHARED lock is held.
00107  * The apr_sdbm_lock call requires the database to be opened with the
00108  * APR_SHARELOCK mode value.
00109  */
00110 APU_DECLARE(apr_status_t) apr_sdbm_lock(apr_sdbm_t *db, int type);
00111 
00112 /**
00113  * Release an sdbm lock previously aquired by apr_sdbm_lock
00114  * @param db The database to unlock
00115  */
00116 APU_DECLARE(apr_status_t) apr_sdbm_unlock(apr_sdbm_t *db);
00117 
00118 /**
00119  * Fetch an sdbm record value by key
00120  * @param db The database 
00121  * @param value The value datum retrieved for this record
00122  * @param key The key datum to find this record
00123  */
00124 APU_DECLARE(apr_status_t) apr_sdbm_fetch(apr_sdbm_t *db, 
00125                                          apr_sdbm_datum_t *value, 
00126                                          apr_sdbm_datum_t key);
00127 
00128 /**
00129  * Store an sdbm record value by key
00130  * @param db The database 
00131  * @param key The key datum to store this record by
00132  * @param value The value datum to store in this record
00133  * @param opt The method used to store the record
00134  * <PRE>
00135  *           APR_SDBM_INSERT     return an error if the record exists
00136  *           APR_SDBM_REPLACE    overwrite any existing record for key
00137  * </PRE>
00138  */
00139 APU_DECLARE(apr_status_t) apr_sdbm_store(apr_sdbm_t *db, apr_sdbm_datum_t key,
00140                                          apr_sdbm_datum_t value, int opt);
00141 
00142 /**
00143  * Delete an sdbm record value by key
00144  * @param db The database 
00145  * @param key The key datum of the record to delete
00146  * @remark It is not an error to delete a non-existent record.
00147  */
00148 APU_DECLARE(apr_status_t) apr_sdbm_delete(apr_sdbm_t *db, 
00149                                           const apr_sdbm_datum_t key);
00150 
00151 /**
00152  * Retrieve the first record key from a dbm
00153  * @param db The database 
00154  * @param key The key datum of the first record
00155  * @remark The keys returned are not ordered.  To traverse the list of keys
00156  * for an sdbm opened with APR_SHARELOCK, the caller must use apr_sdbm_lock
00157  * prior to retrieving the first record, and hold the lock until after the
00158  * last call to apr_sdbm_nextkey.
00159  */
00160 APU_DECLARE(apr_status_t) apr_sdbm_firstkey(apr_sdbm_t *db, apr_sdbm_datum_t *key);
00161 
00162 /**
00163  * Retrieve the next record key from an sdbm
00164  * @param db The database 
00165  * @param key The key datum of the next record
00166  */
00167 APU_DECLARE(apr_status_t) apr_sdbm_nextkey(apr_sdbm_t *db, apr_sdbm_datum_t *key);
00168 
00169 /**
00170  * Returns true if the sdbm database opened for read-only access
00171  * @param db The database to test
00172  */
00173 APU_DECLARE(int) apr_sdbm_rdonly(apr_sdbm_t *db);
00174 /** @} */
00175 #endif /* APR_SDBM_H */

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