/// <summary>
/// Gets DbItem instance by reference.
/// </summary>
/// <param name="reference">Reference to the requested db item</param>
/// <returns></returns>
public DbItem Get(DbItemReference reference)
{
if (!_pageManager.PageExists(reference.PageIndex))
{
return(null);
}
IPage page = _pageManager.FetchPage(reference.PageIndex);
var header = PageFormatter.GetPageHeader(page);
if (header.SizeRange == SizeRange.MultiPage)
{
var length = PageFormatter.ReadMultipageItemLength(page);
var content = new byte[length];
long offset = 0;
while (page != null)
{
var readBytes = PageFormatter.ReadMultipageItemBlock(page, Math.Min(_pageManager.PageSize, (int)(length - offset)));
readBytes.CopyTo(content, offset);
offset += readBytes.Length;
var nextPageIndex = ((MultipageItemPageHeader)header).NextPageIndex;
if (nextPageIndex != -1)
{
page = _pageManager.FetchPage(nextPageIndex);
header = PageFormatter.GetPageHeader(page);
}
else
{
page = null;
}
}
return(new DbItem(content));
}
return(PageFormatter.IsFixedSizeItemAllocated(page, reference.ItemIndex)
? PageFormatter.ReadFixedSizeItem(page, reference.ItemIndex)
: null);
}
/// <summary>
/// Gets the db item length (in bytes).
/// </summary>
/// <param name="reference">Reference to the requested db item</param>
/// <returns>The length of requested db item</returns>
public long GetLength(DbItemReference reference)
{
if (!_pageManager.PageExists(reference.PageIndex))
{
return(0);
}
IPage page = _pageManager.FetchPage(reference.PageIndex);
var header = PageFormatter.GetPageHeader(page);
if (header.SizeRange == SizeRange.MultiPage)
{
return(PageFormatter.ReadMultipageItemLength(page));
}
return(PageFormatter.IsFixedSizeItemAllocated(page, reference.ItemIndex)
? PageFormatter.ReadFixedSizeItemLength(page, reference.ItemIndex)
: 0);
}
private byte[] GetFixedSizeItemSegment(IPage page, DbItemReference reference, long startIndex, long endIndex)
{
if (!PageFormatter.IsFixedSizeItemAllocated(page, reference.ItemIndex))
{
return new byte[] { }
}
;
var item = PageFormatter.ReadFixedSizeItem(page, reference.ItemIndex);
if (item.RawData.Length >= endIndex)
{
throw new ArgumentOutOfRangeException(nameof(endIndex));
}
var length = endIndex - startIndex + 1;
var result = new byte[length];
Array.Copy(item.RawData, startIndex, result, 0, length);
return(result);
}
