private void WriteRecordToDisk(RecoveryRecord record, long?offset = null)
{
if (offset.HasValue)
{
Stream.Seek(offset.Value, SeekOrigin.Begin);
}
byte[] intBytes = BitConverter.GetBytes((int)record.RecordType);
Stream.Write(intBytes, 0, intBytes.Length);
byte[] longBytes = BitConverter.GetBytes(record.PageIndex);
switch (record.RecordType)
{
case RecoveryRecordType.Update:
Stream.Write(longBytes, 0, longBytes.Length); // page index
Stream.Write(BitConverter.GetBytes(_pageSize), 0, sizeof(int)); // page size
Stream.Write(record.PageContent, 0, record.PageContent.Length); // page content
break;
case RecoveryRecordType.Delete:
Stream.Write(longBytes, 0, longBytes.Length);
break;
case RecoveryRecordType.Final:
longBytes = BitConverter.GetBytes(_stream.Position + 8);
Stream.Write(longBytes, 0, longBytes.Length);
Stream.Flush();
break;
}
if (offset.HasValue)
{
Stream.Seek(0, SeekOrigin.End);
}
}
/// <summary>
/// Writes an information of the deleted page to the recovery file
/// </summary>
public void WriteDeletePageRecord(long pageIndex)
{
CheckDisposed();
CheckWriteEnabled();
EnsureFileExists(FileName);
if (!_deletedPages.Contains(pageIndex))
{
_deletedPages.Add(pageIndex);
if (_updatedPages.ContainsKey(pageIndex))
{
_updatedPages.Remove(pageIndex);
}
}
else
{
throw new PageMapException("Page is already removed");
}
var record = new RecoveryRecord
{
RecordType = RecoveryRecordType.Delete,
PageIndex = pageIndex,
};
WriteRecordToDisk(record);
}
/// <summary>
/// Writes an information of the updated page to the recovery file
/// </summary>
/// <param name="page">An updated page</param>
public void WriteUpdatePageRecord(IPage page)
{
CheckDisposed();
CheckWriteEnabled();
EnsureFileExists(FileName);
var record = new RecoveryRecord
{
RecordType = RecoveryRecordType.Update,
PageIndex = page.Index,
PageContent = page.ContentCopy
};
var updateRecord = new UpdateRecord {
Content = record.PageContent, Offset = Stream.Length
};
if (_updatedPages.ContainsKey(page.Index))
{
_updatedPages[page.Index] = updateRecord;
}
else
{
_updatedPages.Add(page.Index, new UpdateRecord {
Content = record.PageContent, Offset = Stream.Length
});
}
WriteRecordToDisk(record);
}
