generic_page.h

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/*
 * (c) Copyright 2011-2013, Hewlett-Packard Development Company, LP
 */

#ifndef __GENERIC_PAGE_H
#define __GENERIC_PAGE_H

#include <boost/static_assert.hpp>

#include "basics.h"
#include "lsn.h"
#include "w_defines.h"

class generic_page_header {
public:
    static const size_t page_sz = SM_PAGESIZE;

    mutable uint32_t checksum;     // +4 -> 4

    PageID pid;          // +4 -> 8

    lsn_t lsn;          // +8 -> 16

    StoreID store;        // +4 -> 20

    uint16_t tag;          // +2 -> 22

protected:
    friend class fixable_page_h;   // for access to page_flags&t_to_be_deleted

    uint16_t page_flags;   //  +2 -> 24

    uint64_t reserved;     //  +8 -> 32

public:
    uint32_t calculate_checksum() const;

public:
    friend std::ostream& operator<<(std::ostream&, generic_page_header&);
};
// verify compiler tightly packed all of generic_page_header's fields:
BOOST_STATIC_ASSERT(sizeof(generic_page_header) == 32);


enum page_tag_t {
    t_bad_p = 0,        
    t_alloc_p = 1,        
    t_stnode_p = 2,        
    t_btree_p = 5,        
};

enum page_flag_t {
    // Flags used by fixable pages:
    t_to_be_deleted = 0x01,     
};

class generic_page : public generic_page_header {
private:
    char subclass_specific[page_sz - sizeof(generic_page_header)];
};

BOOST_STATIC_ASSERT(sizeof(generic_page) == generic_page_header::page_sz);

class generic_page_h {
public:
    generic_page_h(generic_page* s) : _pp(s) {}

    virtual ~generic_page_h() {}

    generic_page* get_generic_page() const {
        return _pp;
    }

    PageID pid() const {
        return _pp->pid;
    }

    StoreID store() const {
        return _pp->store;
    }

    page_tag_t tag() const {
        return (page_tag_t)_pp->tag;
    }

    const lsn_t& lsn() const {
        return _pp->lsn;
    }

protected:
    generic_page_h(generic_page* s, const PageID& pid, page_tag_t tag,
                   StoreID store)
            : _pp(s) {
        ::memset(_pp, 0, sizeof(*_pp));
        _pp->pid = pid;
        _pp->store = store;
        _pp->tag = tag;
    }

    generic_page* _pp;
};

#endif // __GENERIC_PAGE_H