private byte[] GetLargeItemSegment(PageHeaderBase header, IPage page, long startIndex, long endIndex) { if (PageFormatter.ReadMultipageItemLength(page) <= endIndex) { throw new ArgumentOutOfRangeException(nameof(endIndex)); } var length = endIndex - startIndex + 1; var result = new byte[length]; long sourceOffset = 0; long destOffset = 0; // navigate through large item while (true) { var readBytes = PageFormatter.ReadMultipageItemBlock(page, Math.Min(_pageManager.PageSize, (int)(endIndex + 1 - sourceOffset))); sourceOffset += readBytes.Length; if (sourceOffset > startIndex) { var ssi = sourceOffset - startIndex - 1 < readBytes.Length ? startIndex + readBytes.Length - sourceOffset : 0; var l = readBytes.Length - Math.Max(0, sourceOffset - endIndex - 1) - ssi; Array.Copy(readBytes, ssi, result, destOffset, l); destOffset += l; if (sourceOffset >= endIndex) { return(result); } } var nextPageIndex = ((MultipageItemPageHeader)header).NextPageIndex; if (nextPageIndex != -1) { page = _pageManager.FetchPage(nextPageIndex); header = PageFormatter.GetPageHeader(page); } } }
/// <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); }