private FileHeader m_fileHeader; //the only file header in the two files, it is located at page 0.
public memSegmentManager(DiskFile file)
{
m_cache = new CacheHashtable(m_cacheSize);
m_pageSize = 1 << m_pageBits;
m_diskFile = file;
m_bitmap = new PageBitmap();
m_fileHeader = new FileHeader();
if (file.Length < m_bitmap.Data.Length + m_pageSize * 2) //page 0 for fileheader, page 33 for segTree, page 44 for spacetree
{
//this helper file is a new one
for (int i = 0; i < (m_bitmap.Data.Length >> (m_pageBits + 3)); i++)
{
m_bitmap.Data[i] = 0xFF;
}
m_bitmap.SetPageTaken(m_bitmap.GetFirstFreePageID()); //one more page taken because of the fileheader
m_bitmap.Dirty = true;
m_fileHeader.SetInitializeNeeded();
}
else
{
byte[] header = file.SynRead(0, m_pageSize);
m_fileHeader.Deserialize(header);
file.SynRead(m_bitmap.Data, 0, m_pageSize, m_bitmap.Data.Length);
}
m_LRU = new BNode();
}
private FileHeader m_fileHeader; //the only file header in the two files, it is located at page 0.
public memSegmentManager(DiskFile file)
{
m_cache = new CacheHashtable(m_cacheSize);
m_pageSize = 1 << m_pageBits;
m_diskFile = file;
m_bitmap = new PageBitmap();
m_fileHeader = new FileHeader();
if (file.Length < m_bitmap.Data.Length + m_pageSize*2) //page 0 for fileheader, page 33 for segTree, page 44 for spacetree
{
//this helper file is a new one
for (int i=0; i<(m_bitmap.Data.Length >> (m_pageBits + 3)); i++)
m_bitmap.Data[i] = 0xFF;
m_bitmap.SetPageTaken(m_bitmap.GetFirstFreePageID()); //one more page taken because of the fileheader
m_bitmap.Dirty = true;
m_fileHeader.SetInitializeNeeded();
}
else
{
byte[] header = file.SynRead(0, m_pageSize);
m_fileHeader.Deserialize(header);
file.SynRead(m_bitmap.Data, 0, m_pageSize, m_bitmap.Data.Length);
}
m_LRU = new BNode();
}
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 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);
}
}
