File.h

#ifndef FILE_H
#define FILE_H

#include "TwoWayList.h"
#include "Record.h"
#include "Schema.h"
#include "Comparison.h"
#include "ComparisonEngine.h"

class Record;

using namespace std;

class Page {
private:
    TwoWayList<Record> *myRecs;

    int numRecs;
    int curSizeInBytes;

public:
    // constructor
    Page();

    virtual ~Page();

    // this takes a page and writes its binary representation to bits
    void ToBinary(char *bits);

    // this takes a binary representation of a page and gets the
    // records from it
    void FromBinary(char *bits);

    // the deletes the first record from a page and returns it; returns
    // a zero if there were no records on the page
    int GetFirst(Record *firstOne);

    // this appends the record to the end of a page.  The return value
    // is a one on success and a aero if there is no more space
    // note that the record is consumed so it will have no value after
    int Append(Record *addMe);

    // empty it out
    void EmptyItOut();

};


class File {
private:

    int myFilDes;
    off_t curLength;

public:

    File();

    ~File();

    // returns the current length of the file, in pages
    off_t GetLength();

    // opens the given file; the first parameter tells whether or not to
    // create the file.  If the parameter is zero, a new file is created
    // the file; if notNew is zero, then the file is created and any other
    // file located at that location is erased.  Otherwise, the file is
    // simply opened
    int Open(int length, char *fName);

    // allows someone to explicitly get a specified page from the file
    void GetPage(Page *putItHere, off_t whichPage);

    // allows someone to explicitly write a specified page to the file
    // if the write is past the end of the file, all of the new pages that
    // are before the page to be written are zeroed out
    void AddPage(Page *addMe, off_t whichPage);

    // closes the file and returns the file length (in number of pages)
    int Close();

};


#endif