Allocate memory program

[Jenica]

I am trying to change this header file without changing the class so that it has 2048 locations, but 0-511 are for operating system and memory blocks less than 30 are from 512 to 1023 using best fit and bigger than 30 start at 1024 using worst fit. I am really kind of confused on how this works so if someone can at least give me some ideas about how to do this it would be great.

Thanks!!

struct process
{
  int id;
  char name[21];
  int start;
  int size;
  char state[6];
  char starttime[15];
  int cputime;
};


struct hole
{
  int start;
  int size;
};


class memman
{
  private:
    list<process> plist;
    list<hole> freelist;
  public:
    memman( int memsize = 2048 );
    bool allocate( int processid, int locations );
    bool free( int processid );
    void displayfree();
    void process_list();
};

memman::memman(int memsize)
{
  hole h;
  h.size = memsize - 512 - 1024; // changed, used to read h.size = memsize
  h.start = 512;                // changed, used to read h.start = 0
  freelist.push_front(h);
  h.size = memsize - 512 - 512;  //added this line
  h.start = 1024;               //added this line
  freelist.push_front(h);      //added this line
}

bool memman::allocate( int processid, int locations )
{
  int mystart,mysize,newsize, newstart;
  hole h;
  list<hole>::iterator p;
  process ptemp;
  ptemp.id = processid;
  p = freelist.begin();
  bool found = false;
      while ( p != freelist.end() && !found)
          if (locations <= (*p).size )
                found = true;
          else
                p++;

 if( found )
   {
     mystart = (*p).start;
     mysize = (*p).size;
     freelist.erase(p);
     newsize = mysize - locations;
     newstart = mystart + locations;
     if( newsize != 0 )
       {
         h.start = newstart;
         h.size = newsize;
         p = freelist.begin();

        // error corrected 6/19/03
        // while( p != freelist.end() && mysize > (*p).size )
         while( p != freelist.end() && newsize > (*p).size )
           p++;
         freelist.insert(p,h);
       }
     ptemp.start = mystart;
     ptemp.size = locations;
     plist.push_front(ptemp);
     return true;
    }
    else
      {
        cout << "Memory Allocation Is Not Possible" << endl;
        return false;
      }
}

bool memman::free( int processid )
{
  list<process>::iterator p;
  list<hole>::iterator q;
  p = plist.begin();
  bool found = false, found2;
  int mystart,mysize;
  while( p != plist.end() && !found )
    if( (*p).id == processid )
      found = true;
    else
      p++;
  if( found )
  {
    mystart=(*p).start;
    mysize=(*p).size;
    q = freelist.begin();
    found2 = false;
    while(q != freelist.end() && !found2 )

//  error corrected 6/19/03
//  if( mysize <= (*q).start )
      if( mysize <= (*q).size )
        found2 = true;
      else
        q++;
    hole h;
    h.start=mystart;
    h.size=mysize;
    freelist.insert(q,h);
    plist.erase(p);
  }
  else
   cout << "No process for " << processid << endl;
  return 1;
}

void memman::displayfree()
{
  list<hole>::iterator p;
  p = freelist.begin();
  cout << endl << "Free List:  " << endl;
  while( p != freelist.end() )
  {
     cout << (*p).start << setw(8) << (*p).size << endl;
     p++;
  }
}

void memman::process_list()
{
  list<process>::iterator p;
  p = plist.begin();
  cout << endl << "Process List:  " << endl;
  while( p != plist.end() )
  {
     cout << (*p).id << "     " << (*p).start << endl;
     p++;
  }
}