public static List <DbItem> ReadFixedSizeItems(IPage page)
{
short[] itemLengths = ReadFixedSizeItemLengths(page);
var result = new List <DbItem>(itemLengths.Length);
short maxSize = DbItem.GetMaxSize(PageHeaderBase.GetSizeRange(page));
int offset = page.Content.Length - maxSize;
var content = page.Content;
int cnt = itemLengths.Length;
for (int i = 0; i < cnt; i++)
{
var il = itemLengths[i];
if (il != -1) // item is actualy present on page, read it
{
var itemBytes = new byte[Math.Max(il, (short)0)];
Buffer.BlockCopy(content, offset, itemBytes, 0, itemBytes.Length);
result.Add(new DbItem(itemBytes));
}
offset -= maxSize;
}
return(result);
}
public static bool HasFreeSpaceForFixedSizeItem(IPage page)
{
PageHeaderBase header = GetPageHeader(page);
if (header.SizeRange == SizeRange.NotApplicable ||
header.SizeRange == SizeRange.MultiPage)
{
return(false);
}
short fixedSizeItemMarkersLength = ReadFixedSizeItemMarkersLength(page);
short slotSize = DbItem.GetMaxSize(header.SizeRange);
int remainingSpace =
page.Length - // full page length
header.Length - // subtract header length
fixedSizeItemMarkersLength * OnPagePointerSize - OnPagePointerSize - // subtract item length markers array and its length
ReadFixedSizeItemsCount(page) * slotSize // subtract non-deleted items
- OnPagePointerSize; // subtruct new item length marker needed to add a new item
if (remainingSpace < slotSize)
{
return(false);
}
return(true);
}
public static short[] ReadFixedSizeItemLengths(IPage page)
{
SizeRange range = PageHeaderBase.GetSizeRange(page);
if (range == SizeRange.MultiPage || range == SizeRange.NotApplicable)
{
throw new PageFormatException("Page is not dedicated to fixed size items.");
}
short headerLength = PageHeaderBase.GetHeaderLength(page);
short itemSizesLength = BitConverter.ToInt16(page.Content, headerLength);
var result = new short[itemSizesLength];
int offset = headerLength + OnPagePointerSize;
var content = page.Content;
for (int i = 0; i < itemSizesLength; i++)
{
result[i] = BitConverter.ToInt16(content, offset);
offset += OnPagePointerSize;
}
return(result);
}
public static List <byte[]> ReadVariableSizeItems(IPage page)
{
PageType pageType = PageHeaderBase.GetPageType(page);
if (pageType != PageType.RadixTree)
{
throw new PageFormatException("Page is not dedicated to variable size items.");
}
short headerLength = BitConverter.ToInt16(page.Content, OnPageOffsets.HeaderLength);
var result = new List <byte[]>();
var lengthMarkers = ReadMarkers(page, headerLength);
int offset = 0;
foreach (var length in lengthMarkers)
{
offset += Math.Abs(length);
var bytes = new byte[length];
Buffer.BlockCopy(page.Content, page.Content.Length - offset, bytes, 0, length);
result.Add(bytes);
}
return(result);
}
public static void RewriteFixedSizeItem(IPage page, short itemIndex, DbItem item)
{
if (itemIndex < 0)
{
throw new ArgumentOutOfRangeException(nameof(itemIndex));
}
PageHeaderBase header = GetPageHeader(page);
if (header.SizeRange == SizeRange.MultiPage ||
header.SizeRange == SizeRange.NotApplicable)
{
throw new PageFormatException("Page is not dedicated to fixed size items.");
}
if (ReadFixedSizeItemMarkersLength(page) - 1 < itemIndex)
{
throw new PageFormatException("Unable to rewrite fixed size item. Index is too large.");
}
// write the item length marker
byte[] lengthBytes = BitConverter.GetBytes((short)item.RawData.Length);
lengthBytes.CopyTo(page.Content,
header.Length + // length of header
OnPagePointerSize + // length of length marker array
itemIndex * OnPagePointerSize // offset in length marker array
);
Buffer.BlockCopy(item.RawData,
0,
page.Content,
page.Length - DbItem.GetMaxSize(header.SizeRange) * (itemIndex + 1),
item.RawData.Length);
}
public static ushort GetFreeSpace(IPage page)
{
PageType pageType = PageHeaderBase.GetPageType(page);
if (pageType != PageType.RadixTree)
{
throw new PageFormatException("Page is not dedicated to variable size items.");
}
return(RadixTreeNodesPageHeader.ReadFreeSpace(page));
}
private static MultipageItemPageHeader GetMultipageItemPageHeader(IPage page)
{
PageHeaderBase result = GetPageHeader(page);
if (result.SizeRange != SizeRange.MultiPage)
{
throw new PageFormatException("Page is not dedicated to multipage items.");
}
return((MultipageItemPageHeader)result);
}
private static FreeSpaceMapPageHeader GetFsmPageHeader(IPage page)
{
PageHeaderBase result = GetPageHeader(page);
if (result.SizeRange != SizeRange.MultiPage ||
result.PageType != PageType.FreeSpaceMap)
{
throw new PageFormatException("Page is not dedicated to free-space-map.");
}
return((FreeSpaceMapPageHeader)result);
}
public static void FormatVariableSizeItemsPage(IPage page, PageHeaderBase header, List <byte[]> items)
{
header.WriteToPage(page);
short itemsLength = items.Aggregate <byte[], short>(0, (current, item) => (short)(current + (short)(item.Length)));
int remainingSpace =
page.Length - // full page length
header.Length - // subtract header length
itemsLength - // subtract items length
items.Count * OnPagePointerSize + OnPagePointerSize; // subtract markers array and its length
if (remainingSpace < 0)
{
throw new ArgumentException("Page have no space to add specified items", nameof(items));
}
var content = page.Content;
int contentLength = page.Length;
int cnt = items.Count;
int headerLength = header.Length;
short offset = 0;
for (int index = 0; index < cnt; index++)
{
var item = items[index];
byte[] bytes;
if (item != null)
{
bytes = BitConverter.GetBytes((short)item.Length);
offset += (short)item.Length;
// write the body of item
Buffer.BlockCopy(item, 0, content, contentLength - offset, item.Length);
}
else
{
bytes = zeroBytesShort;
}
// write the length marker
Buffer.BlockCopy(bytes, 0, content, headerLength + OnPagePointerSize * (index + 1), sizeof(short));
}
// write the length of length marker array
byte[] lengthLengthMarkers = BitConverter.GetBytes((short)cnt);
lengthLengthMarkers.CopyTo(content, headerLength);
WriteFreeSpace(page, (ushort)remainingSpace);
}
public static void InitPage(IPage page, PageHeaderBase header)
{
if (header.Length > page.Length)
{
throw new PageFormatException("Unable to format page. Too large header.");
}
// fill whole page with zero
Array.Clear(page.Content, 0, page.Length);
header.WriteToPage(page);
}
public static short ReadItemMarkersLength(IPage page)
{
PageType pageType = PageHeaderBase.GetPageType(page);
if (pageType != PageType.RadixTree)
{
throw new PageFormatException("Page is not dedicated to variable size items.");
}
short headerLength = BitConverter.ToInt16(page.Content, OnPageOffsets.HeaderLength);
return(BitConverter.ToInt16(page.Content, headerLength));
}
public static short ReadFixedSizeItemMarkersLength(IPage page)
{
SizeRange sc = PageHeaderBase.GetSizeRange(page);
if (sc == SizeRange.MultiPage || sc == SizeRange.NotApplicable)
{
throw new PageFormatException("Page is not dedicated to fixed size items.");
}
short headerLength = BitConverter.ToInt16(page.Content, OnPageOffsets.HeaderLength);
return(BitConverter.ToInt16(page.Content, headerLength));
}
private static int GetNewSlotCount(IPage page, PageHeaderBase header)
{
short fixedSizeItemMarkersLength = BitConverter.ToInt16(page.Content, FixedSizeItemsPageHeader.FixedSizeItemsHeaderLength);
short slotSize = DbItem.GetMaxSize(header.SizeRange);
int remainingSpace =
page.Length - // full page length
header.Length - // subtract header length
fixedSizeItemMarkersLength * OnPagePointerSize - OnPagePointerSize - // subtract item length markers array and its length
fixedSizeItemMarkersLength * slotSize; // subtract items
return(remainingSpace / (slotSize + OnPagePointerSize));
}
public static void DeleteFixedSizeItems(IPage page)
{
PageHeaderBase header = GetPageHeader(page);
if (header.SizeRange == SizeRange.MultiPage ||
header.SizeRange == SizeRange.NotApplicable)
{
throw new PageFormatException("Page is not dedicated to fixed size items.");
}
// set length of item markers to zero
zeroBytesShort.CopyTo(page.Content, header.Length);
// set empty slot count to zero
zeroBytesShort.CopyTo(page.Content, OnPageOffsets.FixedSizeItem.EmptySlotCount);
}
public static void FormatFixedSizeItemsPage(IPage page, PageHeaderBase header, DbItem[] items)
{
var sizeRange = header.SizeRange;
if (items.Any())
{
if (items.Any(item => item.SizeRange != sizeRange))
{
throw new ArgumentException("Size ranges should be equal", nameof(items));
}
}
header.WriteToPage(page);
int remainingSpace =
page.Length - // full page length
header.Length - // subtract header length
items.Length * OnPagePointerSize - OnPagePointerSize; // subtract item length markers array and its length
if (remainingSpace < 0)
{
throw new ArgumentException("Page have no space to add specified items", nameof(items));
}
var maxSize = DbItem.GetMaxSize(sizeRange);
var content = page.Content;
int contentLength = page.Length;
int cnt = items.Length;
int headerLength = header.Length;
for (int index = 0; index < cnt; index++)
{
var rawData = items[index].RawData;
// write the length marker
Buffer.BlockCopy(BitConverter.GetBytes((short)rawData.Length), 0, content, headerLength + OnPagePointerSize * (index + 1), sizeof(short));
// write the body of item
Buffer.BlockCopy(rawData, 0, content, contentLength - maxSize * (index + 1), rawData.Length);
}
// write the length of length marker array
byte[] lengthLengthMarkers = BitConverter.GetBytes((short)cnt);
lengthLengthMarkers.CopyTo(content, headerLength);
}
public static DbItem ReadFixedSizeItem(IPage page, short itemIndex)
{
short itemLength = ReadFixedSizeItemLength(page, itemIndex);
if (itemLength == -1)
{
throw new PageFormatException("Item has been deleted.");
}
var itemBytes = new byte[itemLength];
short slotSize = DbItem.GetMaxSize(PageHeaderBase.GetSizeRange(page));
int offset = page.Content.Length - slotSize * (itemIndex + 1);
for (int j = 0; j < itemBytes.Length; j++)
{
itemBytes[j] = page.Content[j + offset];
}
return(new DbItem(itemBytes));
}
public static bool IsFixedSizeItemAllocated(IPage page, short itemIndex)
{
SizeRange sc = PageHeaderBase.GetSizeRange(page);
if (sc == SizeRange.MultiPage || sc == SizeRange.NotApplicable)
{
throw new PageFormatException("Page is not dedicated to fixed size items.");
}
short headerLength = BitConverter.ToInt16(page.Content, OnPageOffsets.HeaderLength);
short itemSizesLength = BitConverter.ToInt16(page.Content, headerLength);
if (itemIndex >= itemSizesLength)
{
return(false);
}
int offset = headerLength + OnPagePointerSize + itemIndex * OnPagePointerSize;
return(BitConverter.ToInt16(page.Content, offset) != -1);
}
public static short ReadFixedSizeItemLength(IPage page, short itemIndex)
{
SizeRange range = PageHeaderBase.GetSizeRange(page);
if (range == SizeRange.MultiPage || range == SizeRange.NotApplicable)
{
throw new PageFormatException("Page is not dedicated to fixed size items.");
}
short headerLength = BitConverter.ToInt16(page.Content, OnPageOffsets.HeaderLength);
short itemSizesLength = BitConverter.ToInt16(page.Content, headerLength);
if (itemIndex >= itemSizesLength)
{
throw new ArgumentOutOfRangeException(nameof(itemIndex));
}
int offset = headerLength + OnPagePointerSize + itemIndex * OnPagePointerSize;
return(BitConverter.ToInt16(page.Content, offset));
}
public static byte[] ReadVariableSizeItem(IPage page, short itemIndex)
{
PageType pageType = PageHeaderBase.GetPageType(page);
if (pageType != PageType.RadixTree)
{
throw new PageFormatException("Page is not dedicated to variable size items.");
}
short headerLength = BitConverter.ToInt16(page.Content, OnPageOffsets.HeaderLength);
var lengthMarkers = ReadMarkers(page, headerLength);
if (itemIndex >= lengthMarkers.Length)
{
throw new PageFormatException("Wrong item index.");
}
int offset = 0;
int length = 0;
for (int i = 0; i <= itemIndex; i++)
{
length = lengthMarkers[i];
offset += Math.Abs(length);
}
if (length <= 0)
{
throw new PageFormatException("Item has been deleted.");
}
var result = new byte[length];
Buffer.BlockCopy(page.Content, page.Content.Length - offset, result, 0, length);
return(result);
}
public static PageHeaderBase GetPageHeader(IPage page)
{
PageHeaderBase ph;
PageType pt = PageHeaderBase.GetPageType(page);
switch (pt)
{
case PageType.FreeSpaceMap:
ph = new FreeSpaceMapPageHeader();
ph.Read(page);
return(ph);
case PageType.Heading:
ph = new HeadingPageHeader();
ph.Read(page);
return(ph);
case PageType.MultipageItem:
ph = new MultipageItemPageHeader();
ph.Read(page);
return(ph);
case PageType.FixedSizeItem:
ph = new FixedSizeItemsPageHeader();
ph.Read(page);
return(ph);
case PageType.BPlusTree:
ph = new BPlusTreeNodePageHeader();
ph.Read(page);
return(ph);
case PageType.RadixTree:
ph = new RadixTreeNodesPageHeader();
ph.Read(page);
return(ph);
}
return(null);
}