Beispiel #1
0
        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);
            }
        }
Beispiel #2
0
        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);
            }
        }