log_entry.hxx

/************************************************************************
Modifications Copyright 2017-2019 eBay Inc.
Author/Developer(s): Jung-Sang Ahn

Original Copyright:
See URL: https://github.com/datatechnology/cornerstone

Licensed 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

    https://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.
**************************************************************************/

#ifndef _LOG_ENTRY_HXX_
#define _LOG_ENTRY_HXX_

#include "basic_types.hxx"
#include "buffer.hxx"
#include "log_val_type.hxx"
#include "ptr.hxx"
#include <cstdint>

#ifdef _NO_EXCEPTION
#include <cassert>
#endif
#include <stdexcept>

namespace nuraft {

class log_entry {
public:
    log_entry(ulong term,
              const ptr<buffer>& buff,
              log_val_type value_type = log_val_type::app_log,
              uint64_t log_timestamp = 0,
              bool has_crc32 = false,
              uint32_t crc32 = 0,
              bool compute_crc = true);

    __nocopy__(log_entry);

public:
    ulong get_term() const {
        return term_;
    }

    void set_term(ulong term) {
        term_ = term;
    }

    log_val_type get_val_type() const {
        return value_type_;
    }

    bool is_buf_null() const {
        return (buff_.get()) ? false : true;
    }

    buffer& get_buf() const {
        // We accept nil buffer, but in that case,
        // the get_buf() shouldn't be called, throw runtime exception
        // instead of having segment fault (AV on Windows)
        if (!buff_) {
#ifndef _NO_EXCEPTION
            throw std::runtime_error("get_buf cannot be called for a log_entry "
                                     "with nil buffer");
#else
            assert(0);
#endif
        }

        return *buff_;
    }

    ptr<buffer> get_buf_ptr() const {
        return buff_;
    }

    void change_buf(const ptr<buffer>& buff);

    uint64_t get_timestamp() const {
        return timestamp_us_;
    }

    void set_timestamp(uint64_t t) {
        timestamp_us_ = t;
    }

    bool has_crc32() const {
        return has_crc32_;
    }

    uint32_t get_crc32() const {
        return crc32_;
    }

    void set_crc32(uint32_t crc) {
        crc32_ = crc;
    }

    ptr<buffer> serialize() {
        buff_->pos(0);
        ptr<buffer> buf = buffer::alloc( sizeof(ulong) +
                                         sizeof(char) +
                                         buff_->size() );
        buf->put(term_);
        buf->put( (static_cast<byte>(value_type_)) );
        buf->put(*buff_);
        buf->pos(0);
        return buf;
    }

    static ptr<log_entry> deserialize(buffer& buf) {
        ulong term = buf.get_ulong();
        log_val_type t = static_cast<log_val_type>(buf.get_byte());
        ptr<buffer> data = buffer::copy(buf);
        return cs_new<log_entry>(term, data, t);
    }

    static ulong term_in_buffer(buffer& buf) {
        ulong term = buf.get_ulong();
        buf.pos(0); // reset the position
        return term;
    }

private:
    /**
     * The term number when this log entry was generated.
     */
    ulong term_;

    /**
     * Type of this log entry.
     */
    log_val_type value_type_;

    /**
     * Actual data that this log entry carries.
     */
    ptr<buffer> buff_;

    /**
     * The timestamp (since epoch) when this log entry was generated
     * in microseconds. Used only when `replicate_log_timestamp_` in
     * `asio_service_options` is set.
     */
    uint64_t timestamp_us_;

    /**
     * CRC32 checksum of this log entry.
     * Used only when `crc_on_payload` in `asio_service_options` is set.
     */
    bool has_crc32_;
    uint32_t crc32_;
};

}

#endif //_LOG_ENTRY_HXX_