/// <summary>
///
/// </summary>
/// <param name="page"></param>
/// <param name="virtualIndex"></param>
/// <returns></returns>
public uint VirtualAddrToPhysical(MemoryPage page, uint virtualIndex)
{
if (page.isValid == false)
{
int i = 0;
for (; i < freePhysicalPages.Length; i++)
{
if (freePhysicalPages[i] == true)
{
// Found a free physical page!
freePhysicalPages[i] = false;
break;
}
}
// If we have reach the end of the freePhysicalPages
// without finding a free page - we are out of physical memory, therefore
// we PageFault and start looking for victim pages to swap out
if (i == freePhysicalPages.Length)
{
MemoryPage currentVictim = null;
foreach (MemoryPage possibleVictim in _pageTable)
{
if (!page.Equals(possibleVictim) && possibleVictim.isValid == true)
{
if (currentVictim == null)
{
currentVictim = possibleVictim;
}
// If this is the least accessed Memory Page we've found so far
if (possibleVictim.lastAccessed < currentVictim.lastAccessed)
{
currentVictim = possibleVictim;
}
}
}
// Did we find no victims? That's a HUGE problem, and shouldn't ever happen
Debug.Assert(currentVictim != null);
SwapOut(currentVictim);
// Take the physical address of this page
page.addrPhysical = currentVictim.addrPhysical;
SwapIn(page);
}
else // no page fault
{
// Map this page to free physical page "i"
page.addrPhysical = (uint)(i * CPU.pageSize);
SwapIn(page);
}
}
// Adjust the physical address with pageOffset from a page boundary
uint pageOffset = virtualIndex % CPU.pageSize;
uint physicalIndex = page.addrPhysical + pageOffset;
return(physicalIndex);
}
