diskmgr.h

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/*
 * SwatDB
 *
 * @authors: See Contributors.doc for code contributors
 *
 * Copyright (c) 2020 Swarthmore College Computer Science Department
 * Swarthmore PA, Professors Tia Newhall, Ameet Soni
 */

#pragma once

#include<iostream>
#include<string>
#include <fstream>
#include <vector>
#include <unordered_set>
#include <unordered_map>
#include <mutex>

#include "swatdb_types.h"

class Catalog;
class Page;

class DiskManager {

  public:

    DiskManager(Catalog *catalog);

    ~DiskManager();

    void createFile(FileId file_id);

    void removeFile(FileId file_id);

    PageId allocatePage(FileId file_id);

    void deallocatePage(PageId page_id);

    void readPage(PageId page_id, Page* page);

    void writePage(PageId page_id, Page* page);

    bool isValidPage(PageId page_id);

    void printFile(FileId file_id);

    std::uint32_t getCapacity(FileId file_id);

    std::uint32_t getSize(FileId file_id);

  private:

    // this needs a comment describing this expression!
    static const std::uint32_t DISK_HEADER_SIZE =
      ((((MAX_PAGE_NUM/8)+1+(sizeof(std::uint32_t)*2))/PAGE_SIZE)+1)*PAGE_SIZE;

    static const std::uint32_t DISK_HEADER_BITMAP_SIZE =
        DISK_HEADER_SIZE - (sizeof(std::uint32_t)*2);

    struct SerializedFileHeader{
      std::uint32_t size;
      std::uint32_t capacity;
      char bitmap[DISK_HEADER_BITMAP_SIZE];
    };

    struct DiskFileInfo{

      std::fstream file;

      std::uint32_t capacity;

      std::unordered_set<PageNum> unused_pages;

      std::mutex file_mtx;
    };

    std::unordered_map <FileId, DiskFileInfo*> file_map;

    Catalog* catalog;

    std::mutex file_map_mtx;

    char temp_page[PAGE_SIZE];

    void _getDiskFileInfo(FileId file_id, DiskFileInfo**
      disk_file_info);

    void _flushDiskFileInfo(FileId file_id);

    void _serializeFileHeader(SerializedFileHeader* file_header,
      DiskFileInfo* disk_file_info);

    void _deserializeFileHeader(SerializedFileHeader* file_header,
      DiskFileInfo* disk_file_info);

};