table.cc

来自「nachos test nachos 有关实验」· CC 代码 · 共 86 行

#include "Table.h"

//#include <malloc.h>
//----------------------------------------------------------------------------------
     // create a table to hold at most 'size' entries.

Table::Table(int fixsize)
{
      size=fixsize;  
      now=0;    
      p=new TElement[size];
      lock = new LockSem("Table lock"); 
      tableFull = new ConditionSem("table full cond");
}

//-------------------------------------------------------------------------------------

Table::~Table()
{
      delete p;
      delete lock;
      delete tableFull;
}

//--------------------------------------------------------------------------------------
     // allocate a table slot for 'object'.
     // return the table index for the slot or -1 on error.

int
Table::Alloc(void *object)
{      int j;
       lock->Acquire();
          while (IsFull())
	           tableFull->Wait(lock);
          for(int i=0;i<size;i++){
                 if((p+i)->flag==0){
                    (p+i)->object=object;
                    (p+i)->flag=1;now++;j=i;break;}
                  }
       lock->Release();
       return j;
}

//----------------------------------------------------------------------------------------   
     // return the object from table index 'index' or NULL on error.
     // (assert index is in range).  Leave the table entry allocated
     // and the pointer in place.

void *
Table::Get(int index)
{               
      void *item=NULL;
if(index>=0&&index<size){
             lock->Acquire();
             item=(p+index)->object;
             lock->Release(); }
      return item;
}

//-------------------------------------------------------------------------------------------

     // free a table slot

void
Table::Release(int index)
{
  if(index>=0&&index<size){
    lock->Acquire();
       if((p+index)->flag==1){//delete ((int *)(p+index)->object);
                         (p+index)->object=NULL;
                         (p+index)->flag=0;now--;
                         tableFull->Signal(lock);}
    lock->Release();
                                }
   else return;
}
//-----------------------------------------------------------------------------------------------
  
bool
Table::IsFull()
{
 if(now==size)return true;
 else return false;
}