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/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
/**
* \file rec_tail.h
*
* Qpid asynchronous store plugin library
*
* File containing code for class mrg::journal::rec_tail (record tail), used to
* finalize a persistent record. The presence of a valid tail at the expected
* position in the journal file indicates that the record write was completed.
*
* \author Kim van der Riet
*/
#ifndef QPID_LEGACYSTORE_JRNL_REC_TAIL_H
#define QPID_LEGACYSTORE_JRNL_REC_TAIL_H
#include <cstddef>
#include "qpid/legacystore/jrnl/jcfg.h"
namespace mrg
{
namespace journal
{
#pragma pack(1)
/**
* \brief Struct for data common to the tail of all records. The magic number
* used here is the binary inverse (1's complement) of the magic used in the
* record header; this minimizes possible confusion with other headers that may
* be present during recovery. The tail is used with all records that have either
* XIDs or data - ie any size-variable content. Currently the only records that
* do NOT use the tail are non-transactional dequeues and filler records.
*
* Record header info in binary format (12 bytes):
* <pre>
* 0 7
* +---+---+---+---+---+---+---+---+
* | ~(magic) | rid |
* +---+---+---+---+---+---+---+---+
* | rid (con't) |
* +---+---+---+---+
* </pre>
*/
struct rec_tail
{
u_int32_t _xmagic; ///< Binary inverse (1's complement) of hdr magic number
u_int64_t _rid; ///< ID (rotating 64-bit counter)
/**
* \brief Default constructor, which sets all values to 0.
*/
inline rec_tail(): _xmagic(0xffffffff), _rid(0) {}
/**
* \brief Convenience constructor which initializes values during construction from
* existing enq_hdr instance.
*/
inline rec_tail(const rec_hdr& h): _xmagic(~h._magic), _rid(h._rid) {}
/**
* \brief Convenience constructor which initializes values during construction.
*/
inline rec_tail(const u_int32_t xmagic, const u_int64_t rid): _xmagic(xmagic), _rid(rid) {}
/**
* \brief Returns the size of the header in bytes.
*/
inline static std::size_t size() { return sizeof(rec_tail); }
};
#pragma pack()
} // namespace journal
} // namespace mrg
#endif // ifndef QPID_LEGACYSTORE_JRNL_REC_TAIL_H
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