private DbItemReference AllocateMultiPage(DbItem item)
{
long bytesWritten = 0;
long startPageIndex = -1;
DbItemReference result = null;
IPage page = null;
IPage previousPage = null;
while (bytesWritten < item.RawData.LongLength)
{
page = _pageManager.CreatePage();
if (startPageIndex == -1)
{
startPageIndex = page.Index;
result = new DbItemReference(page.Index, 0);
}
var header = new MultipageItemPageHeader
{
StartPageIndex = startPageIndex,
PreviousPageIndex = previousPage?.Index ?? -1,
NextPageIndex = -1,
SizeRange = SizeRange.MultiPage
};
PageFormatter.InitPage(page, header);
bytesWritten += PageFormatter.WriteMultipageItemBlock(page, item, bytesWritten);
if (previousPage != null)
{
header = (MultipageItemPageHeader)PageFormatter.GetPageHeader(previousPage);
header.NextPageIndex = page.Index;
header.WriteToPage(previousPage);
_pageManager.UpdatePage(previousPage);
}
previousPage = page;
}
if (page != null)
{
_pageManager.UpdatePage(page);
}
return(result);
}
private DbItemReference AllocateSinglePage(DbItem item)
{
DbItemReference result;
IPage page;
var fsmValue = EnumHelper.FsmValueFromSizeRange(item.SizeRange);
var index = _fsm.GetFreePageIndex(fsmValue);
bool spaceRemains;
if (index != -1)
{
// place object to existing page
page = _pageManager.FetchPage(index);
result = PageFormatter.AddFixedSizeItem(page, item, out spaceRemains);
if (!spaceRemains)
{
_fsm.Set(index, FsmValue.Full);
}
}
else
{
// allocate on a new page
page = _pageManager.CreatePage();
var header = new FixedSizeItemsPageHeader {
SizeRange = item.SizeRange
};
PageFormatter.InitPage(page, header);
result = PageFormatter.AddFixedSizeItem(page, item, out spaceRemains);
_fsm.Set(result.PageIndex, spaceRemains ? fsmValue : FsmValue.Full);
}
_pageManager.UpdatePage(page);
return(result);
}
/// <summary>
/// Reallocates already allocated db item with specified content and produces reference to it.
/// </summary>
/// <param name="reference">Reference to already allocated item</param>
/// <param name="newContent">Content of item to reallocate</param>
/// <returns>Reference to the reallocated item</returns>
public DbItemReference Reallocate(DbItemReference reference, byte[] newContent)
{
var item = new DbItem(newContent);
if (item.GetAllocationType(_pageManager.PageSize) == AllocationType.SinglePage)
{
IPage page = _pageManager.FetchPage(reference.PageIndex);
if (PageFormatter.GetPageHeader(page).SizeRange == item.SizeRange)
{
PageFormatter.RewriteFixedSizeItem(page, reference.ItemIndex, item);
_pageManager.UpdatePage(page);
return(reference);
}
Free(reference);
return(AllocateSinglePage(item));
}
Free(reference);
return(AllocateMultiPage(item));
}