/// <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;
}
private void ReadCurrentPage(StoragePage page, int itemCount)
{
for (int idx = 0; idx < (itemCount + 1); idx++)
{
if (ListHdr.HeaderRecordIdx == idx)
{
// skip over the header record
continue;
}
T item = (T)page.ReadRecord(idx);
this.itemList.Add(item);
}
}
private void ReadRecords(StoragePage page, TestData[] data)
{
foreach (TestData test in data)
{
try
{
string result = (string)page.ReadRecord(test.recordIdx);
Assert.AreEqual(test.data, result,
"Read record did not match. Test Data = [{0}]", test.ToString());
}
catch (Exception e)
{
Assert.AreEqual(test.exception, e.GetType().Name,
"Unexpected exception. Test Data = [{0}]", test.ToString());
}
}
}
