/// <summary>
/// Reads a single trace header from the file
/// </summary>
/// <param name="traceIndex">The trace index as it appears in squence in the file</param>
/// <returns>The segy trace header</returns>
public SegyTraceHeader ReadTraceHeader(long traceIndex)
{
CodeContract.Requires(traceIndex < (long)TraceCount, "Trace index to read must be less than the number of traces in the file.");
CodeContract.Requires(traceIndex >= 0, "Trace index must be greater than or equal to 0");
var isLilEndian = IsLittleEndian;
_stream.Seek(0, SeekOrigin.Begin);
var textFileHeadersCount = FileTextualHeaders.Length;
var binaryHeader = FileBinaryHeader;
var dataStartIndex = TextHeaderBytesCount + BinaryHeaderBytesCount + TextHeaderBytesCount * (textFileHeadersCount - 1);
var sampleFormat = (FormatCode)binaryHeader.DataSampleFormatCode;
var sampleSz = SizeFrom(sampleFormat);
var initStreamPosition = dataStartIndex +
traceIndex * (TraceHeaderBytesCount + sampleSz * binaryHeader.SamplesPerTraceOfFile);
// as per rev 1, all data values are assumed big endian
CodeContract.Assume(initStreamPosition <= _stream.Length, "initial trace index exceeds file length.");
_stream.Seek(initStreamPosition, SeekOrigin.Begin);
var traceHeaderByteArr = _reader.ReadBytes(TraceHeaderBytesCount);
return(SegyTraceHeader.From(traceHeaderByteArr, isLilEndian));
}
/// <summary>
/// Reads a single trace from the file.
/// </summary>
/// <param name="traceIndex">The trace index as it appears in squence in the file</param>
/// <returns>The segy trace</returns>
public SegyTrace ReadTrace(long traceIndex)
{
CodeContract.Requires(traceIndex < TraceCount, "Trace index to read must be less than the number of traces in the file.");
CodeContract.Requires(traceIndex >= 0, "Trace index must be greater than or equal to 0");
var islilEndian = IsLittleEndian;
_stream.Seek(0, SeekOrigin.Begin);
var textFileHeadersCount = FileTextualHeaders.Length;
var binaryHeader = FileBinaryHeader;
var dataStartIndex = TextHeaderBytesCount + BinaryHeaderBytesCount + TextHeaderBytesCount * (textFileHeadersCount - 1);
var sampleFormat = (FormatCode)binaryHeader.DataSampleFormatCode;
int sampleSz = SizeFrom(sampleFormat);
// as per rev 1, all data values are assumed big endian
var ns = binaryHeader.SamplesPerTraceOfFile;
var initStreamPosition = dataStartIndex + (240 + ns * sampleSz) * traceIndex;
CodeContract.Assume(initStreamPosition <= _stream.Length, "initial trace index exceeds file length.");
_stream.Seek(initStreamPosition, SeekOrigin.Begin);
var traceHeaderByteArr = _reader.ReadBytes(TraceHeaderBytesCount);
var trHeader = SegyTraceHeader.From(traceHeaderByteArr, islilEndian);
var traceDataBytesSz = trHeader.SampleCount * sampleSz;
var traceDataBytes = _reader.ReadBytes(traceDataBytesSz);
var traceData = GetData(traceDataBytes, sampleFormat, trHeader.SampleCount);
var seismicTrace = new SegyTrace {
ComponentAxis = 0, Data = traceData, Header = trHeader
};
return(seismicTrace);
}
/// <summary>
/// Ctor
/// </summary>
/// <param name="traceHeader">The trace header to use for this trace</param>
/// <param name="data">Trace data for this trace</param>
/// <param name="componentAxis">The cartesian coordinate direction in which this trace exists</param>
public SegyTrace(SegyTraceHeader traceHeader, float[] data, int componentAxis = 0)
{
Header = traceHeader;
Data = data;
ComponentAxis = componentAxis;
CodeContract.Assume(data.Length <= ushort.MaxValue, "The length of the data array for this trace must not exceed ushort.MaxValue due to type definitions of the sample count property in the trace header.");
Header.SampleCount = (ushort)data.Length;
}
/// <summary>
/// Reads a set of segy traceheaders in the file within a defined range
/// <remarks>
/// if startTrace and endTrace are default for this method, all traces in the file will be read</remarks>
/// </summary>
/// <param name="progress">A progress handler</param>
/// <param name="ct">A cancellation token</param>
/// <param name="startTrace">The 0 based starting trace index to read</param>
/// <param name="endTrace">The 0 based ending trace index to read</param>
/// <returns>A collection of segy trace headers</returns>
public IEnumerable <SegyTraceHeader> ReadTraceHeaders(IProgress <int> progress = null, CancellationToken ct = default(CancellationToken), long startTrace = 0, long nTraces = Int64.MaxValue)
{
var lastTraceToReadIndex = startTrace + nTraces;
if (lastTraceToReadIndex > TraceCount)
{
lastTraceToReadIndex = TraceCount;
}
if (lastTraceToReadIndex != Int64.MaxValue)
{
CodeContract.Requires(lastTraceToReadIndex <= TraceCount, "Ending trace index must be less than the number of traces in the file.");
}
CodeContract.Requires(startTrace >= 0, "Cannot read a negative number of traces.");
CodeContract.Requires(startTrace >= 0, "Starting trace index must be greater than 0.");
var islilEndian = IsLittleEndian;
var dataStartIndex = 3600 + (3200 * (FileTextualHeaders.Length - 1));
var sampleFormat = (FormatCode)FileBinaryHeader.DataSampleFormatCode;
int sampleSz = SizeFrom(sampleFormat);
// as per rev 1, all data values are assumed big endian
//BigList<SgyTraceHeader> trHdrs;
BigArray <SegyTraceHeader> trHArr;
if (nTraces == long.MaxValue)
{
trHArr = new BigArray <SegyTraceHeader>(TraceCount - startTrace);
}
else
{
trHArr = new BigArray <SegyTraceHeader>(nTraces);
}
var streamLen = _stream.Length;
var streamPos = dataStartIndex + startTrace * (240 + sampleSz * FileBinaryHeader.SamplesPerTraceOfFile);
CodeContract.Assume(streamPos <= _stream.Length, "initial trace index exceeds file length.");
_stream.Seek(streamPos, SeekOrigin.Begin);
int ns = FileBinaryHeader.SamplesPerTraceOfFile; // Assume that the binary header has num samples per trace. dont trust trace headers
var traceDataBytesSz = ns * sampleSz;
int progPercent = 0;
for (long i = startTrace; (i < lastTraceToReadIndex) && (streamPos < streamLen); i++)
{
var traceHeaderByteArr = _reader.ReadBytes(TraceHeaderBytesCount);
var trHdr = SegyTraceHeader.From(traceHeaderByteArr, islilEndian);
trHArr[i - startTrace] = trHdr;
_stream.Seek(traceDataBytesSz, SeekOrigin.Current);
streamPos += 240 + traceDataBytesSz;
if (ct.IsCancellationRequested)
{
break;
}
if (progress == null)
{
continue;
}
var percent = (int)(100 * (double)_stream.Position / _stream.Length);
if (progPercent == percent)
{
continue;
}
progress.Report(percent);
progPercent = percent;
}
return(trHArr);
}
/// <summary>
/// Ctor
/// </summary>
public SegyTrace()
{
Header = new SegyTraceHeader();
}
