public FsmValue Get(long pageIndex)
{
if (!_isInitialized)
{
Init();
}
IPage page = GetFsmPageByTargetPageIndex(pageIndex);
return(page == null
? FsmValue.Full :
PageFormatter.GetFsmValue(page, (int)pageIndex % _entryPerPage));
}
public void FsmPage()
{
int pageSize = 32768;
var dummyPageManager = new FileSystemPageManager(pageSize);
var p = new Page(dummyPageManager, 0, new byte[pageSize]);
var fsmh = new FreeSpaceMapPageHeader();
var r = new Random();
PageFormatter.InitPage(p, fsmh);
int fsmEntryCount = PageFormatter.GetFsmEntryCount(p);
// set all values to "full"
PageFormatter.SetAllFsmValues(p, FsmValue.Full);
// check if all values are actually "full"
for (int i = 0; i < fsmEntryCount; i++)
{
Assert.AreEqual(FsmValue.Full, PageFormatter.GetFsmValue(p, i));
}
var values = new FsmValue[fsmEntryCount];
// set and keep random values
for (int i = 0; i < fsmEntryCount; i++)
{
var value = (byte)r.Next((byte)FsmValue.Full + 1);
PageFormatter.SetFsmValue(p, i, (FsmValue)value);
values[i] = (FsmValue)value;
}
// compare it
for (int i = 0; i < fsmEntryCount; i++)
{
Assert.AreEqual(values[i], PageFormatter.GetFsmValue(p, i));
}
}
public long GetFreePageIndex(FsmValue value)
{
if (!_isInitialized)
{
Init();
}
// try to find in lucky pages
if (_luckyFsmPages.ContainsKey(value))
{
IPage page = _luckyFsmPages[value].Page;
var requestedFsmIndex = (int)(_luckyFsmPages[value].LastGoodIndex % _entryPerPage);
int matchingFsmIndex;
if (PageFormatter.GetFsmValue(page, requestedFsmIndex) == value)
{
matchingFsmIndex = requestedFsmIndex;
}
else
{
matchingFsmIndex = PageFormatter.GetIndexOfFirstMatchingFsmValue(page, value);
_luckyFsmPages[value].LastGoodIndex = matchingFsmIndex;
}
if (matchingFsmIndex == -1)
{
// page becomes unlucky
_luckyFsmPages.Remove(value);
}
else
{
return(PageFormatter.GetBasePageIndex(page) + matchingFsmIndex);
}
}
var currentPageIndex = _firstFsmPageIndex;
long index = 0;
if (_scanned.Contains(value))
{
return(-1);
}
while (true)
{
// sequential scan all fsm pages for specified fsm-value
var currentPage = _pageManager.FetchPage(currentPageIndex);
int matchingFsmIndex = PageFormatter.GetIndexOfFirstMatchingFsmValue(currentPage, value);
if (matchingFsmIndex == -1)
{
index += _entryPerPage;
var header = (FreeSpaceMapPageHeader)PageFormatter.GetPageHeader(currentPage);
if (header.NextPageIndex == -1)
{
_scanned.Add(value);
return(-1);
}
currentPageIndex = header.NextPageIndex;
}
else
{
// make found page lucky
_luckyFsmPages[value] = new LuckyPage {
Page = currentPage, LastGoodIndex = matchingFsmIndex + index
};
return(index + matchingFsmIndex);
}
}
}
