/// <summary>
/// Deserializes a compressed data object from the given file stream.
/// </summary>
/// <param name="inputStream">input file stream</param>
/// <returns>object with a compressed byte[] and corresponding index</returns>
public static IndexedDataObject Deserialize(FileStream inputStream)
{
IFormatter formatter = new BinaryFormatter();
IndexedDataObject compressedDataObject = (IndexedDataObject)formatter.Deserialize(inputStream);
return(compressedDataObject);
}
/// <summary>
/// Compresses data inside the input indexedDataObject.
/// </summary>
/// <param name="dataObjectForCompression">input data object with byte[] and corresponding index</param>
/// <returns>data object with compressed byte[] and corresponding index</returns>
protected override IndexedDataObject ProcessData(IndexedDataObject dataObjectForCompression)
{
byte[] processedBlock = Compression.Compress(dataObjectForCompression.DataBlock);
dataObjectForCompression.DataBlock = processedBlock;
IndexedDataObject compressedDataObject = dataObjectForCompression;
return(compressedDataObject);
}
/// <summary>
/// Reads (deserializes) indexed data objects wth compressed byte arrays from an input file and inserts them to the queue.
/// </summary>
/// <param name="inputFileStream">input file</param>
protected override void ReadFromFileAndEnqueue(FileStream inputFileStream)
{
while (inputFileStream.Position != inputFileStream.Length)
{
IndexedDataObject compressedDataObject = Deserialization.Deserialize(inputFileStream);
EnqueueObject(compressedDataObject); // put the data block into the queue
}
}
/// <summary>
/// puts the indexed data object into a queue
/// </summary>
/// <param name="data"></param>
protected void EnqueueObject(IndexedDataObject data)
{
lock (lockQueue)
{
while (queue.Count >= Settings.maxQueueSize)
{
Monitor.Wait(lockQueue);
}
queue.Enqueue(data);
if (queue.Count == 1)
{
// wake up any blocked dequeue, i.e. the consumer threads
Monitor.PulseAll(lockQueue);
}
}
}
/// <summary>
/// Reads data blocks (as byte[]) from an input file, assigns a unique number to each block (so that compressed data can later be saved to a file in the correct order)
/// and inserts a new indexed data object (containing the input data block and the block number) to the queue.
/// </summary>
/// <param name="inputFileStream">input file</param>
protected override void ReadFromFileAndEnqueue(FileStream inputFileStream)
{
byte[] block = new byte[Settings.blockSize];
int bytesRead;
uint i = 1;
while ((bytesRead = (inputFileStream).Read(block, 0, Settings.blockSize)) > 0) // read "blockSize" of bytes to a "block" (byte[])
{
if (bytesRead < block.Length)
{
byte[] block2 = new byte[bytesRead];
Array.Copy(block, block2, bytesRead);
block = block2;
}
IndexedDataObject indexedDataObject = new IndexedDataObject(block, i);
EnqueueObject(indexedDataObject); // put the data block into the queue
block = new byte[Settings.blockSize];
i++;
}
}
/// <summary>
/// Writes compressed data from the given data object to a file (using object serialization).
/// </summary>
/// <param name="outputDataObject">data object to be written (serialized) into the output file</param>
/// <param name="outputFileStream">output file</param>
protected override void WriteToFile(IndexedDataObject outputDataObject, FileStream outputFileStream)
{
Serialization.Serialize(outputDataObject, outputFileStream);
}
/// <summary>
/// Writes decompressed data from the given indexed data object to the output file (in correct order based on the data objects's index number) as byte[].
/// </summary>
/// <param name="outputDataObject">data object with byte[] to be written into the output file</param>
/// <param name="outputFileStream">output file</param>
protected override void WriteToFile(IndexedDataObject outputDataObject, FileStream outputFileStream)
{
outputFileStream.Write(outputDataObject.DataBlock, 0, outputDataObject.DataBlock.Length);
}
/// <summary>
/// Serializes a compressed data object to the given file stream.
/// </summary>
/// <param name="compressedDataObject">object with a compressed byte[] and corresponding index</param>
/// <param name="outputStream">output file stream</param>
public static void Serialize(IndexedDataObject compressedDataObject, FileStream outputStream)
{
IFormatter formatter = new BinaryFormatter();
formatter.Serialize(outputStream, compressedDataObject);
}
/// <summary>
/// Takes data objects from a queue, processes them (compression/decompression) and writes them to the output file.
/// </summary>
/// <param name="outputFileStreamObject">output file stream</param>
public void ConsumeData(object outputFileStreamObject) //takes data from a queue
{
try
{
FileStream outputFileStream = (FileStream)outputFileStreamObject;
while (true) // keeps the consumer thread running
{
IndexedDataObject dataElementFromQueue = null;
lock (lockQueue)
{
if (queue.Count > 0) // queue not empty
{
dataElementFromQueue = queue.Dequeue();
Monitor.PulseAll(lockQueue); // data removed from a queue => wake up the producer to put more data into the queue
if (dataElementFromQueue == null) // null object in queue means end of file reached, nothing more to read
{
ProducerConsumer.lastBlockRead = true; // last block in the queue (there are no more bytes to read from the input file)
return; // Producer ended, all objects from the queue have been already processed => this thread ends
}
}
else
{
if (ProducerConsumer.lastBlockRead)
{
return; // Producer ended, all objects from the queue have been already processed (or are processed by other threads) => this thread ends
}
Monitor.Wait(lockQueue);
}
}
// data object was read from the queue => we can release the lock and enable access to the queue again to the producer or other consumer threads
if (dataElementFromQueue != null)
{
IndexedDataObject processedData = ProcessData(dataElementFromQueue);
lock (lockOutputFile)
{
// thread waits for previous data blocks to be written to the file before it can write its own data block to the file
while ((processedData.Index - 1) != ProducerConsumer.GetProcessedBlocksCount())
{
Monitor.Wait(lockOutputFile);
}
WriteToFile(processedData, outputFileStream);
ProducerConsumer.IncrementProcessedBlocksCount();
Monitor.PulseAll(lockOutputFile);
}
}
}
}
catch (DirectoryNotFoundException)
{
ErrorsChecker.SetError(new DirectoryNotFoundException("Error message: The output directory you're looking for doesn't exist."));
}
catch (DriveNotFoundException)
{
ErrorsChecker.SetError(new DriveNotFoundException("Error message: The output drive you're looking for doesn't exist."));
}
catch (PathTooLongException)
{
ErrorsChecker.SetError(new PathTooLongException("Error message: The output path is longer or fully qualified file name is longer than the system-defined maximum length."));
}
catch (UnauthorizedAccessException)
{
ErrorsChecker.SetError(new UnauthorizedAccessException("Error message: Access to the output directory was denied."));
}
catch (OutOfMemoryException)
{
ErrorsChecker.SetError(new OutOfMemoryException("Error message: There is not enough memory to continue the execution of the program."));
}
catch (Exception e)
{
Console.WriteLine(e.Message);
ErrorsChecker.SetError(new Exception("Error message: An error occured during the execution of the program."));
}
}
/// <summary> /// Writes the processed data into the output file. /// </summary> /// <param name="outputDataObject">data object to be written in the output file</param> /// <param name="outputFileStream">output file</param> protected abstract void WriteToFile(IndexedDataObject outputDataObject, FileStream outputFileStream);
/// <summary> /// Retrieves an indexed data object from the queue nad processes it (compresses or decompresses the data). /// </summary> /// <param name="indexedDataObject"></param> /// <returns>data object with compressed or decompressed byte[] and corresponding index</returns> protected abstract IndexedDataObject ProcessData(IndexedDataObject indexedDataObject);
