/// <summary>
/// insert this segment into cache, kick out other if needed
/// </summary>
/// <param name="seg"></param>
/// <precondition>seg is a new page brought in memory</precondition>
/// <postcondition>seg is insert into the cache, and the front of the LRU list, kick out one page if needed.</postcondition>
internal void _put_in_cache(Segment seg)
{
//if the cache is full, kick least recently used one out
if (m_cache.Count > m_cacheLimit)
{
//pick least recently used one
Segment victim = m_LRU.Prev;
Debug.Assert(victim != m_LRU);
if (victim.Dirty)
{
_write_back(victim);
}
victim.BreakLinks();
bool t = m_cache.Delete(victim.SegmentID); //removed this one out of the cache
Debug.Assert(t);
}
if (m_cache.Insert(seg) == false)
{
throw new OOD.Exception.ProgramLogicError(
this,
"Trying to insert an existing key into CacheHashtable");
}
seg.BuildLinks(m_LRU, m_LRU.Next); //move it the front of the LRU list
}
/// <summary>
/// insert this segment into cache, kick out other if needed
/// </summary>
/// <param name="seg"></param>
/// <precondition>seg is a new page brought in memory</precondition>
/// <postcondition>seg is insert into the cache, and the front of the LRU list, kick out one page if needed.</postcondition>
internal void _put_in_cache(Segment seg)
{
//if the cache is full, kick least recently used one out
if (m_cache.Count > m_cacheLimit)
{
//pick least recently used one
Segment victim = m_LRU.Prev;
Debug.Assert(victim != m_LRU);
if (victim.Dirty)
{
//write it out to the disk
byte[] content = victim.Serialize();
Debug.Assert(content.Length <= m_pageSize);
m_diskFile.SynWrite(content, 0, victim.SegmentID * m_pageSize, content.Length);
}
victim.BreakLinks();
bool t = m_cache.Delete(victim.SegmentID); //removed this one out of the cache
Debug.Assert(t);
}
if (m_cache.Insert(seg) == false)
{
throw new OOD.Exception.ProgramLogicError(
this,
"Trying to insert a existing key into CacheHashtable.");
}
seg.BuildLinks(m_LRU, m_LRU.Next); //move it the front of the LRU list
}
public override Segment GetSegment(uint segId, Segment segFactory, object helper)
{
Debug.Assert(segId >= (m_bitmap.Data.Length >> m_pageBits));
Debug.Assert(m_bitmap.PageFree(segId) == false);
if (m_cache.Exists(segId))
{
//requested page is in the cache
Segment seg = m_cache.Retrive(segId);
//update recently used page list, move this one to the front of the list, most recently used.
seg.BreakLinks();
seg.BuildLinks(m_LRU, m_LRU.Next);
return(seg);
}
else
{
//the requested page is not in the cache, read it from disk
byte[] content = m_diskFile.SynRead(segId * m_pageSize, m_pageSize);
Segment seg = segFactory.Deserialize(segId, helper, content);
_put_in_cache(seg);
return(seg);
}
}
public override void FreeSegment(Segment seg)
{
m_bitmap.SetPageFree(seg.SegmentID);
//remove that one from cache
m_cache.Delete(seg.SegmentID);
//remove it from the LRU list also
seg.BreakLinks();
}
public override Segment GetSegment(uint segId, Segment segFactory, object helper)
{
Segment result = null;
//check if this segment is already in cache
if (m_cache.Exists(segId))
{
result = m_cache.Retrive(segId);
//update the least recently used list
result.BreakLinks();
result.BuildLinks(m_LRU, m_LRU.Next);
return(result);
}
else
{
//if not, read that from disk
uint offset = 0;
int length = 0;
if (m_segTree.GetAddr(segId, ref offset, ref length))
{
// put this segment into cache
byte[] content = m_diskFile.SynRead(offset, length);
result = segFactory.Deserialize(segId, helper, content);
_put_in_cache(result);
}
else
{
throw new OOD.Exception.ProgramLogicError(
this,
"Trying to access a non-existing segment.");
}
return(result);
}
}
public override void FreeSegment(Segment seg)
{
//remove it from cache
this.m_cache.Delete(seg.SegmentID);
//remove it from LRU list
seg.BreakLinks();
uint offset = 0;
int length = -1;
if (m_segTree.GetAddr(seg.SegmentID, ref offset, ref length))
{
Debug.Assert(length != -1);
//this segment's addressing info is in the system.
//put this segment into the free tree
m_spaceTree.SetSegmentFree(offset, length);
//remove its addressing information from segTree
m_segTree.DeleteSegment(seg.SegmentID);
}
//if this segment is never written back to disk, just delete it from memory is enough
}
public override void FreeSegment(Segment seg)
{
//remove it from cache
this.m_cache.Delete(seg.SegmentID);
//remove it from LRU list
seg.BreakLinks();
uint offset = 0;
int length = -1;
if (m_segTree.GetAddr(seg.SegmentID, ref offset, ref length))
{
Debug.Assert(length != -1);
//this segment's addressing info is in the system.
//put this segment into the free tree
m_spaceTree.SetSegmentFree(offset, length);
//remove its addressing information from segTree
m_segTree.DeleteSegment(seg.SegmentID);
}
//if this segment is never written back to disk, just delete it from memory is enough
}
public override void FreeSegment(Segment seg)
{
m_bitmap.SetPageFree(seg.SegmentID);
//remove that one from cache
m_cache.Delete(seg.SegmentID);
//remove it from the LRU list also
seg.BreakLinks();
}