/// <summary>
/// Request a segment with size of length.
/// </summary>
/// <param name="length"></param>
/// <returns>True if succeed, otherwise false.</returns>
/// <preCondition></preCondition>
/// <PostCondition>A free segment will offset as the starting place and length as size
/// is cleared from this free space tree.</PostCondition>
public bool RequireSegment(int length, ref uint offset)
{
//do the sequential search
OOD.Imp.Storage.BTree.BTEnumerator enumerator = m_tree.GetEnumerator();
KOffset finding = null;
// while (enumerator.MoveNext())
// {
// KOffset temp = (KOffset)enumerator.Current;
// if (temp != null && temp.Length.Num >= length)
// {
// finding = temp;
// break;
// }
// }
if (finding == null)
{
//no free space find in the b-tree, create a new segment after the file end
offset = (uint)m_dbFile.Length;
m_dbFile.SetLength(offset + length);
}
else
{
//find new space in the tree
offset = finding.Offset;
int len = finding.Length.Num;
if (m_tree.Delete(finding) == false)
{
throw new OOD.Exception.ProgramLogicError(
this,
"Delete free space failed.");
}
if (finding.Length.Num > length)
{
//put the left back
finding.Offset = (uint)(offset + length);
finding.Length.Num = len - length;
if (m_tree.Insert(finding) == false)
{
throw new OOD.Exception.ProgramLogicError(
this,
"Insert free space failed.");
}
}
}
return(true);
}
public IKey Deserialize(byte[] bytes, int offset, int count)
{
KOffset result = new KOffset();
result.m_offset = OOD.Utility.Bytes.Unpack4U(bytes, offset);
DLength dFactory = new DLength();
if (count > 4)
{
result.m_length = (DLength)dFactory.Deserialize(bytes, offset + 4, count - 4);
}
return(result);
}
/* Needed operations:
* 1. Given an offset and length, set that range to be free space.
* 2. Given an length, return the pair (offset, length) can be used.
* that range will be removed from free space tree before this
* operation returns.
*/
/// <summary>
/// Set the segment in the databse file to be free.
/// </summary>
/// <param name="offset"></param>
/// <param name="length"></param>
public void SetSegmentFree(uint offset, int length)
{
if (offset + length != m_dbFile.Length)
{
uint nextSeg = (uint)(offset + length);
KOffset target = new KOffset(nextSeg);
KOffset finding = (KOffset)m_tree.Search(target);
if (finding == null)
{
//combine to next segment is not possible, just go ahead to insert this one
target.Offset = offset;
target.Length = new DLength(length);
if (m_tree.Insert(target) == false)
{
throw new OOD.Exception.ProgramLogicError(
this,
"Insert into free space b-tree failed.");
}
}
else
{
//combine these two free segment into a big one
length += finding.Length.Num;
target.Length = new DLength(length);
target.Offset = offset;
if (m_tree.Delete(finding) == false || m_tree.Insert(target) == false)
{
throw new OOD.Exception.ProgramLogicError(
this,
"Delete free space failed.");
}
}
}
else
{
//this is the last segment in the database file, just remove it from the file
m_dbFile.SetLength(offset);
}
}
/* Needed operations:
* 1. Given an offset and length, set that range to be free space.
* 2. Given an length, return the pair (offset, length) can be used.
* that range will be removed from free space tree before this
* operation returns.
*/
/// <summary>
/// Set the segment in the databse file to be free.
/// </summary>
/// <param name="offset"></param>
/// <param name="length"></param>
public void SetSegmentFree(uint offset, int length)
{
if (offset + length != m_dbFile.Length)
{
uint nextSeg = (uint)(offset + length);
KOffset target = new KOffset(nextSeg);
KOffset finding = (KOffset)m_tree.Search(target);
if (finding == null)
{
//combine to next segment is not possible, just go ahead to insert this one
target.Offset = offset;
target.Length = new DLength(length);
if (m_tree.Insert(target) == false)
throw new OOD.Exception.ProgramLogicError(
this,
"Insert into free space b-tree failed.");
}
else
{
//combine these two free segment into a big one
length += finding.Length.Num;
target.Length = new DLength(length);
target.Offset = offset;
if (m_tree.Delete(finding) == false || m_tree.Insert(target) == false)
throw new OOD.Exception.ProgramLogicError(
this,
"Delete free space failed.");
}
}
else
{
//this is the last segment in the database file, just remove it from the file
m_dbFile.SetLength(offset);
}
}
public IKey Deserialize(byte[] bytes, int offset, int count)
{
KOffset result = new KOffset();
result.m_offset = OOD.Utility.Bytes.Unpack4U(bytes, offset);
DLength dFactory = new DLength();
if (count > 4)
{
result.m_length = (DLength)dFactory.Deserialize(bytes, offset + 4, count - 4);
}
return result;
}
public int CompareTo(IKey B)
{
KOffset bb = (KOffset)B;
return((int)(this.m_offset - bb.m_offset));
}