public override int Read(byte[] buffer, int offset, int count)
{
if (count <= 0)
return 0;
uint bytesRead = 0U;
var bytesRemaining = (uint) count;
var addr = _ram.VirtualAddressCalculator.New((uint) (_pageSet.Offset + Position));
if (_page == null || _page.PageNumber != addr.PageNumber)
_page = _pageSet.Pages.Single(x => x.PageNumber == addr.PageNumber);
MemoryStream current = _ram.GetStream(_page);
current.Seek(addr.Offset, SeekOrigin.Begin);
uint remaining = _page.Size - addr.Offset;
while (bytesRemaining > 0)
{
var read = (uint) current.Read(buffer, offset, (int) Math.Min(remaining, bytesRemaining));
bytesRemaining -= read;
bytesRead += read;
offset += (int) read;
Position += read;
_page = _pageSet.Next(_page);
if (_page == null)
break;
current = _ram.GetStream(_page);
remaining = _page.Size;
}
return (int) bytesRead;
}
public void Append(Page page)
{
if (page == null)
throw new ArgumentNullException(nameof(page));
if (_page == null)
_page = page;
_pages.Add(page);
}
public PageStream(Ram ram, PageInfo pageSet)
{
if (ram == null)
throw new ArgumentNullException(nameof(ram));
if (pageSet == null)
throw new ArgumentNullException(nameof(pageSet));
_ram = ram;
_pageSet = pageSet;
_page = pageSet.Pages.FirstOrDefault();
}
public VirtualAddress ToVirtualAddress(Page page)
{
return VirtualAddressCalculator.New(0, (int) page.PageNumber);
}
public MemoryStream GetStream(Page page)
{
return GetStream(page.FrameNumber);
}
public void Free(Page page)
{
var frameList = _pageTable[page.FrameNumber];
var frameIndex = frameList.FindIndex(x => x.PageNumber == page.PageNumber);
if (frameIndex == -1)
return;
if (frameIndex == 0)
{
var frame = frameList[0];
frame.PageNumber = 0;
frame.ProcessId = 0;
}
else
{
frameList.RemoveAt(frameIndex);
}
}
public override void Write(byte[] buffer, int offset, int count)
{
if (count <= 0)
return;
var addr = _ram.VirtualAddressCalculator.New((uint) (_pageSet.Offset + Position));
if (_page == null || _page.PageNumber != addr.PageNumber)
{
_page = _pageSet.Find(addr.PageNumber);
}
MemoryStream current = _ram.GetStream(_page);
current.Seek(addr.Offset, SeekOrigin.Begin);
uint remaining = _page.Size - addr.Offset;
while (offset < count)
{
long write = Math.Min(remaining, count - offset);
current.Write(buffer, offset, (int) write);
offset += (int) write;
Position += write;
_page = _pageSet.Next(_page);
if (_page == null)
break;
current = _ram.GetStream(_page);
remaining = _page.Size;
}
if ( offset == count )
{
return;
}
throw new InvalidOperationException("Attempt to write past stream boundary");
}
public Page Next(Page page)
{
var pageIndex = _pages.IndexOf(page) + 1;
return pageIndex == _pages.Count ? null : _pages[pageIndex];
}