public DbPartialWriter(IDataContext dataContext, FileContent content, int partSize = 1024)
{
_dataContext = dataContext;
_content = content;
_partSize = partSize;
_currentPart = _dataContext.Set <FileContentPart>()
.AsNoTracking()
.Where(x => x.ContentId == _content.Id)
.OrderByDescending(x => x.Order)
.FirstOrDefault();
if (_currentPart == null)
{
_currentPart = new FileContentPart()
{
Content = _content,
Data = new FileContentPartData()
{
Bytes = new byte[_partSize]
},
PositionInFile = 0,
Order = 0,
Length = 0,
};
_dataContext.Set <FileContentPart>().Add(_currentPart);
}
_currentPartPosition = (int)(_content.CurrentSize - _currentPart.PositionInFile);
}
/// <summary>
/// Получает <see cref="DbDataReader"/> для указанной части
/// </summary>
protected virtual DbDataReader GetReaderForPart(FileContentPart part)
{
var connection = Context.Database.GetDbConnection();
var command = connection.CreateCommand();
command.CommandText = @"SELECT Data FROM ""FileContentParts"" WHERE ""Id""=@id";
var id = command.CreateParameter();
id.ParameterName = "@id";
id.DbType = DbType.Guid;
id.Value = part.Id;
command.Parameters.Add(id);
var closedConnection = !connection.State.HasFlag(ConnectionState.Open);
if (closedConnection)
{
connection.Open();
}
try
{
var parameters =
CommandBehavior.SequentialAccess |
CommandBehavior.SingleResult |
CommandBehavior.SingleRow;
if (closedConnection)
{
parameters |= CommandBehavior.CloseConnection;
}
var reader = command.ExecuteReader(parameters);
if (!reader.Read())
{
return(null);
}
closedConnection = false;
return(reader);
}
finally
{
if (closedConnection)
{
connection.Close();
}
}
}
public void Seek(long streamOffset)
{
_currentPart = _dataContext.Set <FileContentPart>()
.AsNoTracking()
.FirstOrDefault(
x => x.ContentId == _content.Id &&
x.PositionInFile <= streamOffset &&
streamOffset < x.PositionInFile + x.Length);
if (_currentPart == null)
{
throw new InvalidOperationException();
}
_currentPartPosition = (int)(streamOffset - _currentPart.PositionInFile);
}
public bool Next()
{
if (_content.CurrentSize == _content.MaxSize)
{
return(false);
}
var newPart = new FileContentPart()
{
Content = _content,
Data = new FileContentPartData()
{
Bytes = new byte[_partSize]
},
PositionInFile = _currentPart.PositionInFile + _currentPart.Length + 1,
Order = _currentPart.Order + 1,
Length = 0
};
_dataContext.Set <FileContentPart>().Add(newPart);
return(true);
}
/// <summary>
/// Делает текущей частью указанный <see cref="FileContentPart"/>
/// </summary>
private void SetCurrentPart(FileContentPart part)
{
mCurrentPart = part;
CreateReaderForCurrentPart();
}
public void Dispose()
{
_dataContext = null;
_content = null;
_currentPart = null;
}