ex_apprec_rec.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: ex_apprec_rec.c,v 12.1 2005/06/16 20:22:06 bostic Exp $
 */

/*
 * This file is based on the template file ex_apprec_template.  Note that
 * because ex_apprec_mkdir, like most application-specific recovery functions,
 * does not make use of DB-private structures, it has actually been simplified
 * significantly.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>

#include <db.h>

#include "ex_apprec.h"

/*
 * ex_apprec_mkdir_recover --
 *      Recovery function for mkdir.
 *
 * PUBLIC: int ex_apprec_mkdir_recover
 * PUBLIC:   __P((DB_ENV *, DBT *, DB_LSN *, db_recops, void *));
 */
int
ex_apprec_mkdir_recover(dbenv, dbtp, lsnp, op, info)
        DB_ENV *dbenv;
        DBT *dbtp;
        DB_LSN *lsnp;
        db_recops op;
        void *info;
{
        ex_apprec_mkdir_args *argp;
        int ret;

        argp = NULL;

        /*
         * Shut up the compiler--"info" is used for the recovery functions
         * belonging to transaction meta-operations such as txn_create, and
         * need not concern us here either.
         */
        info = NULL;

        if ((ret = ex_apprec_mkdir_read(dbenv, dbtp->data, &argp)) != 0)
                goto out;

        switch (op) {
        case DB_TXN_ABORT:
        case DB_TXN_BACKWARD_ROLL:
                /*
                 * If we're aborting, we need to remove the directory if it
                 * exists.  We log the trailing zero in pathnames, so we can
                 * simply pass the data part of the DBT into rmdir as a string.
                 * (Note that we don't have any alignment guarantees, but for
                 * a char * this doesn't matter.)
                 *
                 * Ignore all errors other than ENOENT;  DB may attempt to undo
                 * or redo operations without knowing whether they have already
                 * been done or undone, so we should never assume in a recovery
                 * function that the task definitely needs doing or undoing.
                 */
                ret = rmdir(argp->dirname.data);
                if (ret != 0 && errno != ENOENT)
                        dbenv->err(dbenv, ret, "Error in abort of mkdir");
                else
                        ret = 0;
                break;
        case DB_TXN_FORWARD_ROLL:
                /*
                 * The forward direction is just the opposite;  here, we ignore
                 * EEXIST, because the directory may already exist.
                 */
                ret = mkdir(argp->dirname.data, 0755);
                if (ret != 0 && errno != EEXIST)
                        dbenv->err(dbenv,
                            ret, "Error in roll-forward of mkdir");
                else
                        ret = 0;
                break;
        default:
                /*
                 * We might want to handle DB_TXN_PRINT or DB_TXN_APPLY here,
                 * too, but we don't try to print the log records and aren't
                 * using replication, so there's no need to in this example.
                 */
                dbenv->errx(dbenv, "Unexpected operation type\n");
                return (EINVAL);
        }

        /*
         * The recovery function is responsible for returning the LSN of the
         * previous log record in this transaction, so that transaction aborts
         * can follow the chain backwards.
         *
         * (If we'd wanted the LSN of this record earlier, we could have
         * read it from lsnp, as well--but because we weren't working with
         * pages or other objects that store their LSN and base recovery
         * decisions on it, we didn't need to.)
         */
        *lsnp = argp->prev_lsn;

out:    if (argp != NULL)
                free(argp);
        return (ret);
}

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