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241 lines
7.5 KiB
241 lines
7.5 KiB
//
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// Created by 马也驰 on 2024/12/9.
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//
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#ifndef LEVELDB_SLOTPAGE_H
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#define LEVELDB_SLOTPAGE_H
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#include <cassert>
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#include <cstdint>
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#include <cstdlib>
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#include <vector>
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#include <iostream>
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#include <fstream>
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#include <mutex>
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#define BITMAP_SIZE 8192
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#define BITS_PER_BYTE 8
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#define POSMASK(off) (0x01 << (BITS_PER_BYTE-(off)-1))
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#define SETBIT(byte, off) (*(byte) |= POSMASK(off))
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#define RESETBIT(byte, off) (*(byte) &= (0xff ^ POSMASK(off)))
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#define HASFREESLOT(byte) ((byte) != ~0x0)
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struct slot_content {
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uint32_t vlog_num;
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uint32_t value_offset;
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slot_content(uint32_t vn, uint32_t vo) {
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vlog_num = vn;
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value_offset = vo;
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}
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};
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class SlotCache {
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// slot number -> slot content
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#define BLOCK_NUM 16
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#define BLOCK_SIZE 4096
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#define SLOT_PER_BLOCK (BLOCK_SIZE/sizeof(slot_content))
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#define SLOT_OFFSET_IN_BLOCK(slot_num) ((slot_num)%SLOT_PER_BLOCK)
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public:
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SlotCache() {
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for (auto i = 0; i < BLOCK_NUM; i++) {
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block_cache[i] = static_cast<struct slot_content*>(malloc(BLOCK_SIZE));
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access_time[i] = 0;
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info[i] = block_info();
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}
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}
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void get_slot(std::string &slotpage_fname, size_t slot_num, struct slot_content *sc) {
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auto block_num = slotnum_hash2_blocknum(slot_num);
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auto blockcache_num = block_num % BLOCK_NUM;
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mtx.lock();
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if (info[blockcache_num].slotpage_fname != slotpage_fname) { // cache miss
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write_back_block(blockcache_num);
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read_in_block(blockcache_num, slotpage_fname, block_num);
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}
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read_slot(sc, blockcache_num, SLOT_OFFSET_IN_BLOCK(slot_num));
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access_time[blockcache_num]++;
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mtx.unlock();
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}
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void set_slot(std::string &slotpage_fname, size_t slot_num, struct slot_content *sc) {
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auto block_num = slotnum_hash2_blocknum(slot_num);
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auto blockcache_num = block_num % BLOCK_NUM;
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mtx.lock();
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if (info[blockcache_num].slotpage_fname != slotpage_fname) {
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write_back_block(blockcache_num);
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read_in_block(blockcache_num, slotpage_fname, block_num);
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}
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set_slot(sc, blockcache_num, SLOT_OFFSET_IN_BLOCK(slot_num));
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access_time[blockcache_num]++;
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info[blockcache_num].is_dirty = true;
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mtx.unlock();
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}
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private:
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struct block_info {
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std::string slotpage_fname;
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size_t block_num;
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bool is_dirty;
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block_info() {}
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block_info(std::string &slotpage_fname, size_t block_num, bool is_dirty=false) {
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this->slotpage_fname = slotpage_fname;
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this->block_num = block_num;
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this->is_dirty = is_dirty;
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}
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};
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private:
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inline static size_t slotnum_hash2_blocknum(size_t slot_num) {
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return slot_num * sizeof(slot_content) / BLOCK_SIZE;
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}
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void write_back_block(size_t blockcache_num) {
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auto &fname = info[blockcache_num].slotpage_fname;
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auto write_pos = info[blockcache_num].block_num * BLOCK_SIZE;
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auto slotpage_handler = std::fstream(fname, std::ios::in | std::ios::out);
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slotpage_handler.seekp(write_pos);
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slotpage_handler.write(
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reinterpret_cast<const char*>(block_cache[blockcache_num]), BLOCK_SIZE);
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}
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void read_in_block(size_t blockcache_num, std::string &slotpage_fname, size_t block_num) {
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auto slotpage_handler = std::fstream(slotpage_fname, std::ios::in | std::ios::out);
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slotpage_handler.seekp(block_num*BLOCK_SIZE);
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slotpage_handler.read(reinterpret_cast<char*>(block_cache[blockcache_num]), BLOCK_SIZE);
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access_time[blockcache_num] = 0;
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info[blockcache_num] = block_info(slotpage_fname, block_num);
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}
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inline void read_slot(struct slot_content *sc, size_t blockcache_num, size_t slot_num_offset) {
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auto src = &block_cache[blockcache_num][slot_num_offset];
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memcpy(sc, src, sizeof(slot_content));
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}
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inline void set_slot(struct slot_content *sc, size_t blockcache_num, size_t slot_num_offset) {
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auto src = &block_cache[blockcache_num][slot_num_offset];
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memcpy(src, sc, sizeof(slot_content));
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}
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private:
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std::mutex mtx;
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struct slot_content *block_cache[BLOCK_NUM];
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size_t access_time[BLOCK_NUM];
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struct block_info info[BLOCK_NUM];
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};
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class BitMap {
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// in memory bitmap
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public:
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BitMap() {
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char *bitmap = static_cast<char*>(malloc(BITMAP_SIZE*sizeof(char)));
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bitmaps_.push_back(bitmap);
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size = BITMAP_SIZE;
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first_empty_slot = 0;
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}
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void dealloc_slot(size_t slot_num) {
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mtx.lock();
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const size_t byte = slot2byte(slot_num);
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const size_t off = slot2offset(slot_num);
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char *target_byte = get_bitmap_byte(byte);
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assert(*target_byte & POSMASK(off));
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RESETBIT(target_byte, off);
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// set_bitmap_byte(byte, target_byte);
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first_empty_slot = first_empty_slot < slot_num ? first_empty_slot:slot_num;
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mtx.unlock();
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}
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size_t alloc_slot() {
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mtx.lock();
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size_t target_slot = first_empty_slot;
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char *start_byte = get_bitmap_byte(slot2byte(first_empty_slot));
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const size_t off = slot2offset(first_empty_slot);
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SETBIT(start_byte, off);
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if (HASFREESLOT(*start_byte)) {
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auto bit_off = find_first_free_slot_inbyte(*start_byte);
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first_empty_slot += bit_off - off;
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} else {
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size_t i;
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for (i = slot2byte(first_empty_slot)+1; i < size; i++) {
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char *byte = get_bitmap_byte(i);
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if (HASFREESLOT(*byte)) {
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auto bit_off = find_first_free_slot_inbyte(*byte);
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first_empty_slot = byte2slot(i) + bit_off;
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}
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}
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// scale the bitmap
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if (i >= size) {
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alloc_new_bitmap();
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char *byte = get_bitmap_byte(i);
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SETBIT(byte, 0);
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first_empty_slot = byte2slot(i) + 1;
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}
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}
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mtx.unlock();
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return target_slot;
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}
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private:
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static inline size_t slot2byte(size_t slot_num) { return slot_num / BITS_PER_BYTE; }
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static inline size_t byte2slot(uint8_t byte_num) { return byte_num * BITS_PER_BYTE; }
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static inline size_t slot2offset(size_t slot_num) { return slot_num % BITS_PER_BYTE; }
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inline char *get_bitmap_byte(size_t byte_num) {
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char *bitmap = bitmaps_.at(byte_num / BITMAP_SIZE);
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return &bitmap[byte_num % BITMAP_SIZE];
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}
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// inline void set_bitmap_byte(size_t byte_num, char byte) {
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// char *bitmap = bitmaps_.at(byte_num / BITMAP_SIZE);
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// bitmap[byte_num % BITMAP_SIZE] = byte;
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// }
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static inline size_t find_first_free_slot_inbyte(uint8_t byte) {
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uint32_t rbyte = __builtin_bswap32((uint32_t)byte) >> 24; // 使用 32 位变量
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return BITS_PER_BYTE - __builtin_ctz(~rbyte) - 1; // 使用 GCC 内建函数找到最低位 1 的位置
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}
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void alloc_new_bitmap() {
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char *bitmap = static_cast<char*>(malloc(BITMAP_SIZE*sizeof(char)));
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bitmaps_.push_back(bitmap);
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size += BITMAP_SIZE;
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}
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private:
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std::vector<char *> bitmaps_;
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size_t size;
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size_t first_empty_slot;
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std::mutex mtx;
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};
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// read and write slot in disk
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// first version with no cache
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class SlotPage {
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public:
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SlotPage(std::string &dbname) {
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slotpage_fname = slotpage_handler_name(dbname);
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bitmap = new BitMap();
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}
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public:
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void get_slot(size_t slot_num, struct slot_content *sc) {
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slotcache->get_slot(slotpage_fname, slot_num, sc);
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}
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void set_slot(size_t slot_num, struct slot_content *sc) {
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slotcache->set_slot(slotpage_fname, slot_num, sc);
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}
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size_t alloc_slot() { return bitmap->alloc_slot(); }
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void dealloc_slot(size_t slot_num) { bitmap->dealloc_slot(slot_num); }
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private:
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static std::string slotpage_handler_name(std::string &dbname) {
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return "./" + dbname + "_slotpage";
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}
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inline static size_t slotpage_pos(size_t slot_num) {
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return slot_num * sizeof(slot_content);
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}
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private:
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std::string slotpage_fname;
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BitMap *bitmap;
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static SlotCache *slotcache;
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};
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SlotCache *SlotPage::slotcache = new SlotCache();
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#endif // LEVELDB_SLOTPAGE_H
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