//RwL 1-14-2008

//
// TraceOutputs.c
//     for 8000 Hz input daa

//This is the second of two programs derived from awk scripts of approximately 1 year
// ago. 
//
//The scheme is fairly straightforward.  In the program TraceStarts.c, which evolved
// from TraceStarts.txt, an awk script on the PC, a table of trace start times was
// generated based on a threshold detection scheme.  An exclusion window of about 3.8
// s attempted to allow recognizing of only real seismic traces and not noise
// bursts.
//
//The plan is to read a record from the Starts.dat file that was generated with
// the TraceStarts script.  This record will have the tape time for the start of the
// each trace.  The Track2_*_all2.dat file will then be read until the pointer
// position is found.  From the pointer position in the seismic data file, 8000 
// samples, 1 s, of data will be read and output.
//


//
// When this is compiled, you need to compile with large file support.  The
// following command seems to work.
//
// gcc -o TraceOutputs -D_FILE_OFFSET_BITS=64 TraceOutputs.c
//


#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>

int main()
{

FILE *fileIn, *fileOut, *fileStarts;
double startTime;			// the trace start time read from Starts.dat
double inTime;				// the input time from the seismic file
float inAmp;				// the input amplitude from the seismic file
int i, j=0;					// counters


	// Open the input and output files
	fileStarts = fopen("Starts.dat","r");		//Trace starts file
	fileIn = fopen("Track4_8_all2.dat","r");	//Seismic data file
	fileOut = fopen("T4-8kHz.dat","w");		//Trace otput file

//Using multiple files in awk is difficult.  Consquently, the following code may
// not match the original awk code very well.

	// Set up a do-while loop for reading in the trace start values
	do
		{
	 	 //Read a start time
		 fscanf (fileStarts, "%lf", &startTime);
			//Set up a loop to read until startTime is encoutered
			do
				{
				 fscanf (fileIn, "%lf %f", &inTime, &inAmp);
				} while (inTime < startTime);
			//We are now at the trace start time in the input seismic file
			//Read and output the next second of data (8000 samples)
			 for (i=1; i<=8000; ++i)
				{
				 fscanf (fileIn, "%lf %e", &inTime, &inAmp);
				 fprintf (fileOut, "%f\n", inAmp);
				}
				printf ("Trace: %d\n", ++j);

		} while (!feof(fileStarts));


	fclose (fileIn);
	fclose (fileOut);
	fclose (fileStarts);
	return 0;
 }  // end of main()