/// <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;
}
public void SP_TestReadWritePage()
{
string dataFile = "SP_TestData1.tpdb";
if (File.Exists(dataFile))
{
File.Delete(dataFile);
}
TestData[] pageData =
{
new TestData {
data = "Record_0", recordIdx = 0
},
new TestData {
data = "Record_1", recordIdx = 1
},
new TestData {
data = "Record_2", recordIdx = 2
}
};
int pageIndex = int.MinValue;
// write the page
using (FileStreamWrapper dataFileStream = FileStreamWrapper.CreateObject(dataFile))
{
// populate the page with some data
StoragePage page = new StoragePage();
AddRecords(page, pageData);
// write the file to disk
pageIndex = page.WritePageData(dataFileStream, -1);
}
// read the page
using (FileStreamWrapper dataFileStream = FileStreamWrapper.CreateObject(dataFile))
{
// read page from file
StoragePage page = new StoragePage();
page.ReadPageData(dataFileStream, pageIndex);
// validate the page data
ReadRecords(page, pageData);
}
}
