DB-MANAGER HEADER FILE
----------------------

#ifndef _DB_H
#define _DB_H

#include <string.h>
#include <stdlib.h>

#include "page.h"


// Each database is basically a UNIX file and consists of several relations
// (viewed as heapfiles and their indexes) within it.

// Class definition for DB which manages a database.


  // This is the maximum length of the name of a "file" within a database.
const int MAX_NAME = 50;
  

enum dbErrCodes {
    DB_FULL,
    DUPLICATE_ENTRY,
    UNIX_ERROR,
    BAD_PAGE_NO,
    FILE_IO_ERROR,
    FILE_NOT_FOUND,
    FILE_NAME_TOO_LONG,
    NEG_RUN_SIZE,
};

// oooooooooooooooooooooooooooooooooooooo

class DB {

  public:
    // Constructors
    // Create a database with the specified number of pages where the page
    // size is the default page size.
    DB( const char* name, unsigned num_pages, Status& status );

    // Open the database with the given name.
    DB( const char* name, Status& status );

    // Destructor: closes the database
   ~DB();

    // Destroy the database, removing the file that stores it. 
    Status db_destroy();

    // Read the contents of the specified page into the given memory area.
    Status read_page(PageId pageno, Page* pageptr);

    // Write the contents of the specified page.
    Status write_page(PageId pageno, Page* pageptr);

    // Allocate a set of pages where the run size is taken to be 1 by default.
    // Gives back the page number of the first page of the allocated run.
    Status allocate_page(PageId& start_page_num, int run_size = 1);

    // Deallocate a set of pages starting at the specified page number and
    // a run size can be specified.
    Status deallocate_page(PageId start_page_num, int run_size = 1);


    // oooooooooooooooooooooooooooooooooooooo

    // Adds a file entry to the header page(s).
    Status add_file_entry(const char* fname, PageId start_page_num);

    // Delete the entry corresponding to a file from the header page(s).
    Status delete_file_entry(const char* fname);

    // Get the entry corresponding to the given file.
    Status get_file_entry(const char* name, PageId& start_pg);

    // Functions to return some characteristics of the database.
    const char* db_name() const;
    int db_num_pages() const;
    int db_page_size() const;

    // Print out the space map of the database.
    // The space map is a bitmap showing which
    // pages of the db are currently allocated.
    Status dump_space_map();
};

// oooooooooooooooooooooooooooooooooooooo

#endif    // _DB_H