ulong IPageStore.GetFirstIndexPage(ushort objectType)
{
if (objectType == 0)
{
return(_freePageHead.PageNumber);
}
ulong pageNumber;
lock (_indexPages)
{
if (!_indexPages.TryGetValue(objectType, out pageNumber))
{
pageNumber = AllocatePageNumber();
_indexPages[objectType] = pageNumber;
var indexPageData = new byte[_indexHead.Data.Length];
var offset = 0U;
foreach (var kvp in _indexPages)
{
if (offset + 9 > indexPageData.Length)
{
throw new FileLayerException("The page size of " + indexPageData.Length +
" is too small to accomodate all of the different object types in the file set");
}
BitConverter.GetBytes(kvp.Key).CopyTo(indexPageData, offset);
BitConverter.GetBytes(kvp.Value).CopyTo(indexPageData, offset + 2);
offset += 10;
}
_pageCache.Update(null, new[]
{
new PageUpdate
{
PageNumber = _indexHead.PageNumber,
Data = indexPageData
}
});
}
}
return(pageNumber);
}
public PageStore(IPageCache pageCache, IStartupLog startUpLog)
{
_pageCache = pageCache;
_startUpLog = startUpLog;
_indexPages = new Dictionary <ushort, ulong>();
// The index master page is always page 0
// This page contains the starting page numbers for other indexes
_indexHead = _pageCache.Get(null, 0, CacheHints.None);
if (_indexHead == null)
{
startUpLog.WriteLine("Creating a new page store in a set of empty data files from " + _pageCache);
_indexHead = _pageCache.NewPage(0);
}
else
{
startUpLog.WriteLine("Opening a page store on " + _pageCache);
var offset = 0;
ushort objectType;
ulong startPage;
do
{
objectType = BitConverter.ToUInt16(_indexHead.Data, offset);
startPage = BitConverter.ToUInt64(_indexHead.Data, offset + 2);
if (objectType > 0)
{
startUpLog.WriteLine("- the index for type " + objectType + " objects starts at page " + startPage);
_indexPages[objectType] = startPage;
}
else
{
break;
}
offset += 10;
} while (offset < _indexHead.Data.Length);
}
// The free page map is always page 1
// This is the first in a chain of pages used to manage
// unused space in the file set
_freePageHead = _pageCache.Get(null, 1, CacheHints.None);
if (_freePageHead == null)
{
startUpLog.WriteLine("Initializing a new free page map in this page store");
_freePageHead = _pageCache.NewPage(1);
_highestPageNumber = 1;
_pageCache.Update(null, new[]
{
new PageUpdate
{
PageNumber = _freePageHead.PageNumber,
Data = BitConverter.GetBytes((ulong)_highestPageNumber)
}
});
}
else
{
_highestPageNumber = (long)BitConverter.ToUInt64(_freePageHead.Data, 0);
startUpLog.WriteLine("This page store contains " + _highestPageNumber + " pages");
}
}
