alloc_page.h

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

#ifndef __ALLOC_PAGE_H
#define __ALLOC_PAGE_H

#include "generic_page.h"
#include "sm_base.h"
#include "w_defines.h"

typedef uint32_t extent_id_t;

class alloc_page : public generic_page_header {
public:

    // First half of page (4KB) is the bitmap

    static constexpr int bitmapsize = sizeof(generic_page) / 2;

    static constexpr int bits_held = bitmapsize * 8;

    uint8_t bitmap[bitmapsize];

    // Fill second half of the page with char array (unused part). This is
    // currently 4KB, whereas the bitmap occupies the remaining 4KB.
    // This reserved space of 4KB is kept here just for future uses; it is
    // currently not used.
    char _fill[sizeof(generic_page) / 2 - sizeof(generic_page_header)];

    uint32_t byte_place(uint32_t index) {
        return index >> 3;
    }

    uint32_t bit_place(uint32_t index) {
        return index & 0x7;
    }

    uint32_t bit_mask(uint32_t index) {
        return 1 << bit_place(index);
    }

    bool get_bit(uint32_t index) {
        return (bitmap[byte_place(index)] & bit_mask(index)) != 0;
    }

    void unset_bit(uint32_t index) {
        bitmap[byte_place(index)] &= ~bit_mask(index);
    }

    void set_bit(uint32_t index) {
        bitmap[byte_place(index)] |= bit_mask(index);
    }

    uint32_t get_last_set_bit();

    void set_bits(uint32_t from, uint32_t to);

    void format_empty();

    // Used to generate page_img_format log records
    char* unused_part(size_t& length) {
        auto first_unset_byte = byte_place(get_last_set_bit()) + 1;
        char* pos = reinterpret_cast<char*>(&bitmap[first_unset_byte]);
        length = sizeof(alloc_page) - (pos - reinterpret_cast<char*>(this));
        w_assert1(length >= sizeof(_fill));
        return pos;
    }
};

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

#endif // __ALLOC_PAGE_H