/// <summary>
/// Creates a new <see cref="CommonFrameHeader"/> from given <paramref name="buffer"/>.
/// </summary>
/// <param name="buffer">Buffer that contains data to parse.</param>
/// <param name="startIndex">Start index into buffer where valid data begins.</param>
public CommonFrameHeader(byte[] buffer, int startIndex)
{
// Validate SEL Fast Message data image
if (buffer[startIndex] != Common.HeaderByte1 || buffer[startIndex + 1] != Common.HeaderByte2)
{
throw new InvalidOperationException($"Bad data stream, expected header bytes 0xA546 as first bytes in SEL Fast Message frame, got 0x{buffer[startIndex].ToString("X").PadLeft(2, '0')}{buffer[startIndex + 1].ToString("X").PadLeft(2, '0')}");
}
ushort sampleCount;
uint secondOfCentury;
NtpTimeTag timetag;
// Parse relevant common header values
m_frameSize = (FrameSize)buffer[startIndex + 2];
m_idCode = BigEndian.ToUInt32(buffer, startIndex + 12);
sampleCount = BigEndian.ToUInt16(buffer, startIndex + 18);
secondOfCentury = BigEndian.ToUInt32(buffer, startIndex + 20);
// We use an NTP time tag since SEL Fast Message SOC also starts at 1/1/1900
timetag = new NtpTimeTag(secondOfCentury, 0);
// Data frames have subsecond time information, so we add this fraction of time to current seconds value
timetag = new NtpTimeTag(timetag.Value + sampleCount * 50.0M / 1000.0M);
// Cache timestamp value
m_timestamp = timetag.ToDateTime().Ticks;
}
/// <summary>
/// Creates a new <see cref="CommonFrameHeader"/> from given <paramref name="buffer"/>.
/// </summary>
/// <param name="buffer">Buffer that contains data to parse.</param>
/// <param name="startIndex">Start index into buffer where valid data begins.</param>
public CommonFrameHeader(byte[] buffer, int startIndex)
{
uint secondOfCentury = BigEndian.ToUInt32(buffer, startIndex);
m_sampleCount = BigEndian.ToUInt16(buffer, startIndex + 4);
// We go ahead and pre-grab cell's status flags so we can determine framelength - we
// leave startindex at 6 so that cell will be able to parse flags as needed - note
// this increases needed common frame header size by 2 (i.e., BinaryLength + 2)
m_statusFlags = BigEndian.ToUInt16(buffer, startIndex + FixedLength);
// NTP timestamps based on NtpTimeTag class are designed to work for dates between
// 1968-01-20 and 2104-02-26 based on recommended bit interpretation in RFC-2030.
NtpTimeTag timetag = new NtpTimeTag(secondOfCentury, 0);
// Cache timestamp value
m_timestamp = timetag.ToDateTime().Ticks;
}
/// <summary>
/// Creates a new <see cref="CommonFrameHeader"/> from given <paramref name="buffer"/>.
/// </summary>
/// <param name="configurationFrame">IEEE 1344 <see cref="ConfigurationFrame"/> if already parsed.</param>
/// <param name="buffer">Buffer that contains data to parse.</param>
/// <param name="startIndex">Start index into buffer where valid data begins.</param>
public CommonFrameHeader(ConfigurationFrame configurationFrame, byte[] buffer, int startIndex)
{
uint secondOfCentury = BigEndian.ToUInt32(buffer, startIndex);
m_sampleCount = BigEndian.ToUInt16(buffer, startIndex + 4);
// We go ahead and pre-grab cell's status flags so we can determine framelength - we
// leave startindex at 6 so that cell will be able to parse flags as needed - note
// this increases needed common frame header size by 2 (i.e., BinaryLength + 2)
m_statusFlags = BigEndian.ToUInt16(buffer, startIndex + FixedLength);
// NTP timestamps based on NtpTimeTag class are designed to work for dates between
// 1968-01-20 and 2104-02-26 based on recommended bit interpretation in RFC-2030.
NtpTimeTag timetag = new NtpTimeTag(secondOfCentury, 0);
// Data frames have subsecond time information, so we add this fraction of time to current seconds value
if (TypeID == IEEE1344.FrameType.DataFrame && configurationFrame != null)
{
timetag.Value += SampleCount / Math.Truncate((double)Common.MaximumSampleCount / (double)configurationFrame.Period) / (double)configurationFrame.FrameRate;
}
// Cache timestamp value
m_timestamp = timetag.ToDateTime().Ticks;
}