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Annotation of parser3/src/lib/sdbm/sdbm_lock.c, revision 1.3

1.3     ! moko        1: /* Copyright 2000-2005 The Apache Software Foundation or its licensors, as
        !             2:  * applicable.
1.1       paf         3:  *
1.3     ! moko        4:  * Licensed under the Apache License, Version 2.0 (the "License");
        !             5:  * you may not use this file except in compliance with the License.
        !             6:  * You may obtain a copy of the License at
        !             7:  *
        !             8:  *     http://www.apache.org/licenses/LICENSE-2.0
        !             9:  *
        !            10:  * Unless required by applicable law or agreed to in writing, software
        !            11:  * distributed under the License is distributed on an "AS IS" BASIS,
        !            12:  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
        !            13:  * See the License for the specific language governing permissions and
        !            14:  * limitations under the License.
1.1       paf        15:  */
                     16: 
1.2       moko       17: #include "pa_file_info.h"
                     18: #include "pa_file_io.h"
                     19: #include "pa_sdbm.h"
1.1       paf        20: 
                     21: #include "sdbm_private.h"
                     22: #include "sdbm_tune.h"
                     23: 
                     24: /* NOTE: this function blocks until it acquires the lock */
1.2       moko       25: pa_status_t pa_sdbm_lock(pa_sdbm_t *db, int type)
1.1       paf        26: {
1.2       moko       27:     pa_status_t status;
1.1       paf        28: 
1.2       moko       29:     if (!(type == PA_FLOCK_SHARED || type == PA_FLOCK_EXCLUSIVE))
                     30:         return PA_EINVAL;
1.1       paf        31: 
                     32:     if (db->flags & SDBM_EXCLUSIVE_LOCK) {
                     33:         ++db->lckcnt;
1.2       moko       34:         return PA_SUCCESS;
1.1       paf        35:     }
                     36:     else if (db->flags & SDBM_SHARED_LOCK) {
                     37:         /*
                     38:          * Cannot promote a shared lock to an exlusive lock
                     39:          * in a cross-platform compatibile manner.
                     40:          */
1.2       moko       41:         if (type == PA_FLOCK_EXCLUSIVE)
                     42:             return PA_EINVAL;
1.1       paf        43:         ++db->lckcnt;
1.2       moko       44:         return PA_SUCCESS;
1.1       paf        45:     }
                     46:     /*
                     47:      * zero size: either a fresh database, or one with a single,
                     48:      * unsplit data page: dirpage is all zeros.
                     49:      */
1.2       moko       50:     if ((status = pa_file_lock(db->dirf, type)) == PA_SUCCESS) 
1.1       paf        51:     {
1.2       moko       52:         pa_finfo_t finfo;
                     53:         if ((status = pa_file_info_get(&finfo, PA_FINFO_SIZE, db->dirf))
                     54:                 != PA_SUCCESS) {
                     55:             (void) pa_file_unlock(db->dirf);
1.1       paf        56:             return status;
                     57:         }
                     58: 
                     59:         SDBM_INVALIDATE_CACHE(db, finfo);
                     60: 
                     61:         ++db->lckcnt;
1.2       moko       62:         if (type == PA_FLOCK_SHARED)
1.1       paf        63:             db->flags |= SDBM_SHARED_LOCK;
1.2       moko       64:         else if (type == PA_FLOCK_EXCLUSIVE)
1.1       paf        65:             db->flags |= SDBM_EXCLUSIVE_LOCK;
                     66:     }
                     67:     return status;
                     68: }
                     69: 
1.2       moko       70: pa_status_t pa_sdbm_unlock(pa_sdbm_t *db)
1.1       paf        71: {
                     72:     if (!(db->flags & (SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK)))
1.2       moko       73:         return PA_EINVAL;
1.1       paf        74:     if (--db->lckcnt > 0)
1.2       moko       75:         return PA_SUCCESS;
1.1       paf        76:     db->flags &= ~(SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK);
1.2       moko       77:     return pa_file_unlock(db->dirf);
1.1       paf        78: }