flatline.c

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/** @file flatline.c ad-hoc test file looking for an error condition.
 * test files for flatline condition
 * input files are channelized shorts
 */


#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>


#define NFLATS 32
#define MAXBUF 0x10000

unsigned short last_value;
int repeat_count;


int error_count;
short* buffer;
const char* fname;

void find_flatline(int fd)
{
#define FLATFMT "FLATLINE %s %5d 0x%04x %6s at %d\n"
#define HEXIBLE(v) ((v)&0x0000ffff)
        int totread = 0;
        int nread;
        int nflats;

        for( ; (nread = read(fd, buffer, MAXBUF)) > 0; totread += nread){
                int ibuf;

                for (ibuf = 0, nread /= 2; ibuf != nread; ++ibuf){
                        switch(last_value){
                        case 0xdead:
                        case 0xbeef:
                                nflats = 2; break;
                        default:
                                nflats = NFLATS;
                        }
                        if (buffer[ibuf] == last_value){
                                if (++repeat_count == nflats){
                                        fprintf(stderr, FLATFMT,
                                                fname,
                                                last_value, 
                                                HEXIBLE(last_value),
                                                "starts",
                                                totread + ibuf - nflats);
                                }
                        }else{
                                if (repeat_count >= nflats){
                                        fprintf(stderr, FLATFMT,
                                                fname,
                                                last_value, 
                                                HEXIBLE(last_value),
                                                "ends",
                                                totread + ibuf);
                                }
                                last_value = buffer[ibuf];
                                repeat_count = 0;
                        }
                }
        }
}

int main(int argc, const char* argv[])
{
        int iarg;

        buffer = malloc(MAXBUF);

        if (argc <= 1){
                fname = "stdin";
                find_flatline(0);
        }else{
                for (iarg = 1; iarg < argc; ++iarg){
                        int fd = open(fname = argv[iarg], O_RDONLY);

                        if (fd < 0){
                                perror("failed to open file");
                                exit(errno);
                        }else{
                                find_flatline(fd);
                        }
                }
        }

        exit(error_count != 0);
}