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Annotation of parser3/src/lib/sdbm/sdbm_lock.c, revision 1.1

1.1     ! paf         1: /* ====================================================================
        !             2:  * The Apache Software License, Version 1.1
        !             3:  *
        !             4:  * Copyright (c) 2000-2002 The Apache Software Foundation.  All rights
        !             5:  * reserved.
        !             6:  *
        !             7:  * Redistribution and use in source and binary forms, with or without
        !             8:  * modification, are permitted provided that the following conditions
        !             9:  * are met:
        !            10:  *
        !            11:  * 1. Redistributions of source code must retain the above copyright
        !            12:  *    notice, this list of conditions and the following disclaimer.
        !            13:  *
        !            14:  * 2. Redistributions in binary form must reproduce the above copyright
        !            15:  *    notice, this list of conditions and the following disclaimer in
        !            16:  *    the documentation and/or other materials provided with the
        !            17:  *    distribution.
        !            18:  *
        !            19:  * 3. The end-user documentation included with the redistribution,
        !            20:  *    if any, must include the following acknowledgment:
        !            21:  *       "This product includes software developed by the
        !            22:  *        Apache Software Foundation (http://www.apache.org/)."
        !            23:  *    Alternately, this acknowledgment may appear in the software itself,
        !            24:  *    if and wherever such third-party acknowledgments normally appear.
        !            25:  *
        !            26:  * 4. The names "Apache" and "Apache Software Foundation" must
        !            27:  *    not be used to endorse or promote products derived from this
        !            28:  *    software without prior written permission. For written
        !            29:  *    permission, please contact apache@apache.org.
        !            30:  *
        !            31:  * 5. Products derived from this software may not be called "Apache",
        !            32:  *    nor may "Apache" appear in their name, without prior written
        !            33:  *    permission of the Apache Software Foundation.
        !            34:  *
        !            35:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
        !            36:  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
        !            37:  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
        !            38:  * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
        !            39:  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
        !            40:  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
        !            41:  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
        !            42:  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
        !            43:  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
        !            44:  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
        !            45:  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            46:  * SUCH DAMAGE.
        !            47:  * ====================================================================
        !            48:  *
        !            49:  * This software consists of voluntary contributions made by many
        !            50:  * individuals on behalf of the Apache Software Foundation.  For more
        !            51:  * information on the Apache Software Foundation, please see
        !            52:  * <http://www.apache.org/>.
        !            53:  */
        !            54: 
        !            55: #include "apr_file_info.h"
        !            56: #include "apr_file_io.h"
        !            57: #include "apr_sdbm.h"
        !            58: 
        !            59: #include "sdbm_private.h"
        !            60: #include "sdbm_tune.h"
        !            61: 
        !            62: /* NOTE: this function blocks until it acquires the lock */
        !            63: APU_DECLARE(apr_status_t) apr_sdbm_lock(apr_sdbm_t *db, int type)
        !            64: {
        !            65:     apr_status_t status;
        !            66: 
        !            67:     if (!(type == APR_FLOCK_SHARED || type == APR_FLOCK_EXCLUSIVE))
        !            68:         return APR_EINVAL;
        !            69: 
        !            70:     if (db->flags & SDBM_EXCLUSIVE_LOCK) {
        !            71:         ++db->lckcnt;
        !            72:         return APR_SUCCESS;
        !            73:     }
        !            74:     else if (db->flags & SDBM_SHARED_LOCK) {
        !            75:         /*
        !            76:          * Cannot promote a shared lock to an exlusive lock
        !            77:          * in a cross-platform compatibile manner.
        !            78:          */
        !            79:         if (type == APR_FLOCK_EXCLUSIVE)
        !            80:             return APR_EINVAL;
        !            81:         ++db->lckcnt;
        !            82:         return APR_SUCCESS;
        !            83:     }
        !            84:     /*
        !            85:      * zero size: either a fresh database, or one with a single,
        !            86:      * unsplit data page: dirpage is all zeros.
        !            87:      */
        !            88:     if ((status = apr_file_lock(db->dirf, type)) == APR_SUCCESS) 
        !            89:     {
        !            90:         apr_finfo_t finfo;
        !            91:         if ((status = apr_file_info_get(&finfo, APR_FINFO_SIZE, db->dirf))
        !            92:                 != APR_SUCCESS) {
        !            93:             (void) apr_file_unlock(db->dirf);
        !            94:             return status;
        !            95:         }
        !            96: 
        !            97:         SDBM_INVALIDATE_CACHE(db, finfo);
        !            98: 
        !            99:         ++db->lckcnt;
        !           100:         if (type == APR_FLOCK_SHARED)
        !           101:             db->flags |= SDBM_SHARED_LOCK;
        !           102:         else if (type == APR_FLOCK_EXCLUSIVE)
        !           103:             db->flags |= SDBM_EXCLUSIVE_LOCK;
        !           104:     }
        !           105:     return status;
        !           106: }
        !           107: 
        !           108: APU_DECLARE(apr_status_t) apr_sdbm_unlock(apr_sdbm_t *db)
        !           109: {
        !           110:     if (!(db->flags & (SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK)))
        !           111:         return APR_EINVAL;
        !           112:     if (--db->lckcnt > 0)
        !           113:         return APR_SUCCESS;
        !           114:     db->flags &= ~(SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK);
        !           115:     return apr_file_unlock(db->dirf);
        !           116: }