/// <summary>
/// Write the packet to the stream
/// </summary>
protected override void OnWrite(Stream stream)
{
//this will automatically figure out its length...
BinarySerializer.SerializeValue(stream, m_Timestamp);
BinarySerializer.SerializeValue(stream, m_ClockDrift);
byte[] rawData = m_SessionHeader.RawData();
stream.Write(rawData, 0, rawData.Length);
}
/// <summary>
/// Initialize the GLF writer for storing information about the current live session
/// </summary>
/// <param name="file">The file stream to write the session file into (should be empty)</param>
/// <param name="sessionSummary"></param>
/// <param name="fileSequence"></param>
/// <param name="fileStartTime">Used during initial collection to indicate the real time this file became the active file.</param>
/// <param name="majorVersion">Major version of the serialization protocol</param>
/// <param name="minorVersion">Minor version of the serialization protocol</param>
/// <remarks>The file header is configured with a copy of the session summary, assuming that we're about to make a copy of the
/// session. For live data collection the caller should supply the file start time to reflect the true time period
/// covered by this file. </remarks>
public GLFWriter(Stream file, SessionSummary sessionSummary, int fileSequence, DateTimeOffset?fileStartTime, int majorVersion, int minorVersion)
{
//for use to use the stream, it has to support
if (file.CanSeek == false)
{
throw new ArgumentException("Provided stream can't be used because it doesn't support seeking", nameof(file));
}
m_SessionSummary = sessionSummary;
m_OutputStream = file;
// This logic will store GZip compressed files for protocol version 2 and beyond
if (majorVersion > 1)
{
//we are explicitly *NOT* using the system GZipStream because it doesn't support flush.
m_PacketStream = new GZipStream(m_OutputStream, CompressionMode.Compress, CompressionLevel.Default, true)
{
FlushMode = FlushType.Sync
};
}
else
{
m_PacketStream = new MemoryStream(BufferSize + MaxExpectedPacketSize);
}
m_PacketWriter = new PacketWriter(m_PacketStream, majorVersion, minorVersion);
//initialize the stream with the file header and session header
m_FileHeader = new FileHeader(majorVersion, minorVersion);
m_SessionHeader = new SessionHeader(sessionSummary);
//There are two variants of the GLF format: One for a whole session, one for a session fragment.
if (fileStartTime.HasValue)
{
m_SessionHeader.FileId = Guid.NewGuid();
m_SessionHeader.FileSequence = fileSequence;
m_SessionHeader.FileStartDateTime = fileStartTime.Value;
m_SessionHeader.FileEndDateTime = m_SessionHeader.EndDateTime;
//by default, this is the last file - it won't be if we open another.
m_SessionHeader.IsLastFile = true;
}
//we need to know how big the session header will be (it's variable sized) before we can figure out the data offset.
byte[] sessionHeader = m_SessionHeader.RawData();
//where are we going to start our data block?
m_FileHeader.DataOffset = FileHeader.HeaderSize + sessionHeader.Length;
byte[] header = m_FileHeader.RawData();
m_OutputStream.Position = 0; //move to the start of the stream, we rely on this.
m_OutputStream.Write(header, 0, FileHeader.HeaderSize);
m_OutputStream.Write(sessionHeader, 0, sessionHeader.Length);
m_OutputStream.Flush();
m_OutputStream.Position = m_FileHeader.DataOffset; //so we are sure we start writing our data at the correct spot.
// When we added GZip compression to streams we noticed that we were sometimes
// losing a lot of data that went unflushed while programmers were testing in
// Visual Studio. To address this, we have the GZip stream flush to disk much
// more aggressively when we detect that the debugger is attached.
#if !DEBUG // We only want this behavior for release builds, not for our own debug builds
// we might prefer the writing to be the more typical optimized behavior.
AutoFlush = Debugger.IsAttached;
#endif
}