Exemple #1
0
        /// <summary>
        /// Reads a list of items from persistent storage. The list is written as a chain of pages,
        /// where the current page stores a pointer to the page storing the next range of items.
        /// The items can be any "serializable" C# type.
        /// </summary>
        /// <param name="stream">data file to read from</param>
        /// <param name="pageIdx">index of the page storing the head of the list</param>
        /// <param name="list">list of items read</param>
        /// <param name="pages">list of physical pages we read from</param>
        public void ReadList(FileStreamWrapper stream, int pageIdx, out List <T> list, out List <int> pages)
        {
            // read pages one by one
            while (ListHdr.EOLPageIndex != pageIdx)
            {
                // read the page data
                StoragePage page     = new StoragePage();
                int         readPage = page.ReadPageData(stream, pageIdx);
                if (readPage != pageIdx)
                {
                    throw new InvalidListException();
                }

                // read the header
                ListHdr header = (ListHdr)page.ReadRecord(ListHdr.HeaderRecordIdx);
                if (null == header)
                {
                    throw new InvalidListException();
                }

                // process the page
                this.ReadCurrentPage(page, header.PageEntriesCount);

                // update the page index
                this.pageList.Add(pageIdx);
                pageIdx = header.NextPageIndex;
            }

            // set the output variables
            list  = this.itemList;
            pages = this.pageList;
        }
Exemple #2
0
        private void CreateNewPage(int count, StoragePageManager freeSpaceMgr)
        {
            // create a new header object
            ListHdr header = new ListHdr()
            {
                NextPageIndex     = ListHdr.EOLPageIndex,
                TotalEntriesCount = count,
                PageEntriesCount  = 0,
                PageWriteIndex    = freeSpaceMgr.GetFreePage()
            };

            this.pageHeaderList.Push(header);

            // create the page - and write a placeholder record for the header
            StoragePage page = new StoragePage();

            page.AddRecord(header);
            this.pageList.Push(page);
        }
Exemple #3
0
        private int WriteTopPage(FileStreamWrapper stream, int lastPageAddress)
        {
            // update the header
            ListHdr header = this.pageHeaderList.Pop();

            header.NextPageIndex = lastPageAddress;

            // update the page
            StoragePage page = this.pageList.Pop();

            page.WriteRecord(ListHdr.HeaderRecordIdx, header);

            // get the page to write to
            int pageIdx = header.PageWriteIndex;

            // write the page
            pageIdx = page.WritePageData(stream, pageIdx);
            this.pageIdxList.Insert(0, pageIdx);

            return(pageIdx);
        }