public static int WriteMultipageItemBlock(IPage page, DbItem item, long offset)
{
if (offset < 0 || offset >= item.RawData.LongLength)
{
throw new ArgumentOutOfRangeException(nameof(offset));
}
MultipageItemPageHeader header = GetMultipageItemPageHeader(page);
if (item.GetAllocationType(page.Length) == AllocationType.SinglePage)
{
throw new PageFormatException("Unable to add item block on page. Item allocation type is single page.");
}
int last = Math.Min(page.Length - header.Length, (int)(item.RawData.LongLength - offset)) - 1;
int contentOffset = header.Length;
if (offset == 0)
{
// we should write the length of the object
var lengthBytes = BitConverter.GetBytes(item.RawData.LongLength);
lengthBytes.CopyTo(page.Content, header.Length);
last -= 8;
contentOffset += 8;
}
for (long i = 0; i <= last; i++)
{
page.Content[i + contentOffset] = item.RawData[i + offset];
}
return(last + 1);
}
public static DbItemReference AddFixedSizeItem(IPage page, DbItem item, out bool hasRemainingSpace)
{
var header = (FixedSizeItemsPageHeader)GetPageHeader(page);
if (header.SizeRange == SizeRange.MultiPage ||
header.SizeRange == SizeRange.NotApplicable)
{
throw new PageFormatException("Page is not dedicated to fixed size items.");
}
if (item.GetAllocationType(page.Length) == AllocationType.MultiPage)
{
throw new PageFormatException("Unable to add item on page. Item is too large.");
}
if (header.SizeRange != item.SizeRange)
{
throw new PageFormatException("Unable to add item on page. Mismatch size ranges.");
}
hasRemainingSpace = false;
byte[] lengthBytes;
if (header.EmptySlotCount > 0)
{
// find an empty slot for a new item
var slotIndex = GetFirstFixedSizeItemEmptySlotIndex(page, header.Length);
if (slotIndex == -1)
{
throw new DataTankerException($"Page is corrupt: empty slot counter is {header.EmptySlotCount}, but there is no empty slot found");
}
// write the item length marker
lengthBytes = BitConverter.GetBytes((short)item.RawData.Length);
lengthBytes.CopyTo(page.Content,
header.Length + // length of header
OnPagePointerSize + // length of length marker array
slotIndex * OnPagePointerSize // offset in length marker array
);
Buffer.BlockCopy(item.RawData,
0,
page.Content,
page.Length - DbItem.GetMaxSize(header.SizeRange) * (slotIndex + 1),
item.RawData.Length);
if (header.EmptySlotCount > 1)
{
hasRemainingSpace = true;
}
// decrease empty slot count
BitConverter.GetBytes((short)(header.EmptySlotCount - 1)).CopyTo(page.Content, OnPageOffsets.FixedSizeItem.EmptySlotCount);
return(new DbItemReference(page.Index, slotIndex));
}
// there are no empty slots on this page
// check the page have the enough space to allocate a new slot
var newSlotCount = GetNewSlotCount(page, header);
if (newSlotCount == 0)
{
throw new PageFormatException("The page have no space to add an item.");
}
var itemLengthsLength = BitConverter.ToInt16(page.Content, header.Length);
// write the length marker
lengthBytes = BitConverter.GetBytes((short)item.RawData.Length);
lengthBytes.CopyTo(page.Content,
header.Length + // length of header
OnPagePointerSize + // length of length marker array
itemLengthsLength * OnPagePointerSize // skip to the end of length marker array
);
// write the increased length of length marker array
byte[] lengthLengthMarkers = BitConverter.GetBytes((short)(itemLengthsLength + 1));
lengthLengthMarkers.CopyTo(page.Content, header.Length);
// write the item body
Buffer.BlockCopy(item.RawData,
0,
page.Content,
page.Length - DbItem.GetMaxSize(header.SizeRange) * (itemLengthsLength + 1),
item.RawData.Length);
if (newSlotCount > 1)
{
hasRemainingSpace = true;
}
return(new DbItemReference(page.Index, itemLengthsLength));
}
