C code to convert RadioAstron RDF to Mark 5B

rdf25b.c

#include <math.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include <stdio.h>
#include <sys/types.h>
#define _FILE_OFFSET_BITS 64
//much of this  taken from from Ari Mujunen vsib code
static unsigned char bytetable[256];
unsigned char crcdata[6];
unsigned int crcc () ;
int main(int argc, char *argv[])
{
    char filenamein[256],filenameout[256];
    unsigned char hh[256],ddin[10000]; //space for rdf header and data blocks
    char data_type[5],data_date[18],terminal[3];
    char source [11],format_set[11],format_name[7];
    FILE *file1, *file2;
    int iret,iw,iyear,idoy,ihh,imm,iss,iy,ic,im,ix1,ix2,ix3,mjd,short_mjd;
    int secday_start,secmjd,fracsec, frame_per_sec, framepersec;
    unsigned char j1, j2, j3, s1, s2, s3, s4, s5,y1;
    unsigned short nframe, crc;
    u_int32_t mk5bheader[4];
// Mark5b Sync word is constant. Blank user bits
    mk5bheader[0] = 0xABADDEED; mk5bheader[1] = 0xF00F0000;
    mk5bheader[2] = 0x0; mk5bheader[3] = 0x0;
    filenamein[0]=filenameout[0]=0;
    if(argc < 2) { printf("NEED readastr filein  fileout \n"); return 0; }
    if (argc > 1) sscanf(argv[1], "%255s", filenamein);
    if (argc > 2) sscanf(argv[2], "%255s", filenameout);
    if ((file1 = fopen(filenamein, "r")) == NULL) return 0;
    if ((file2 = fopen(filenameout, "w")) == NULL) return 0;
    iret=fread(hh, sizeof(hh), 1, file1); //========Read RDF header
    strncpy(data_type,&hh[0],5);
    strncpy(data_date,&hh[6],18);
    strncpy(terminal,&hh[24],3);
    strncpy(source,&hh[35],11);
    strncpy(format_set,&hh[46],11);
    hh[63]='\0'; strncpy(format_name,&hh[57],7);
    printf("%s:%s:%s:%s:%s:%s\n",data_type,data_date,terminal,source,format_set,format_name);
    data_date[8]=' '; data_date[11]=' '; data_date[14]=' ';
    sscanf(data_date,"%4d %3d %2d %2d %2d",&iyear,&idoy,&ihh,&imm,&iss);
    y1=iyear-2000; //years since 2000
    im = 10; iy = iyear-1; //MJD make
    ic = iy/100; iy = iy-ic*100;
    ix1 = 146097*ic/4; ix2 = 1461*iy/4; ix3 = (153*im+2)/5;
    mjd=ix1+ix2+ix3+idoy-678882;
    ic=mjd/1000; short_mjd=mjd-ic*1000;
    secday_start=ihh*3600+imm*60+iss;
    j1 = (short_mjd%1000/100); j2 = ((short_mjd%100)/10); j3 = (short_mjd%10); //digits of mjd
    if(strcmp(format_name,"32IDAS") == 0){ frame_per_sec=3200; } else {frame_per_sec=1600;}
    printf("framepersec=%d \n",frame_per_sec);
    nframe=0; secmjd=secday_start;
    while(iret !=0){ //====================loop reading 10kbyte blocks until data finished
      iret=fread(ddin, sizeof(ddin), 1, file1);
      s1 = (secmjd/10000)&0xF; s2 = ((secmjd%10000)/1000)&0xF; s3 = ((secmjd%1000)/100)&0xF;
      s4 = ((secmjd%100)/10)&0xF; s5 = (secmjd%10)&0xF;
      mk5bheader[1]= y1<<28 | 0x0ead <<16 | nframe; //year put according to mk5 memo 58
      mk5bheader[2]  = j1<<28 | j2<<24 | j3<<20 |
      s1<<16 | s2<<12 | s3<<8 | s4<<4 | s5;
      crcdata[0] = j1<<4|j2; crcdata[1] = j3<<4|s1;
      crcdata[2] = s2<<4|s3; crcdata[3] = s4<<4|s5;
      fracsec = (nframe/(double)frame_per_sec)*10000; //MJD sec fraction
      s1 = fracsec/1000;     s2 = (fracsec%1000)/100;
      s3 = (fracsec%100)/10; s4 = fracsec%10;
      mk5bheader[3] = s1<<28 | s2<<24 | s3<<20 | s4<<16;
/// CRC according to mk5 memo 58, CRC and frac seconds only needed for Mk5A+ compatibility
      crcdata[4] = s1<<4|s2; crcdata[5] = s3<<4|s4;
      crc = crcc(crcdata, 48, 040003, 16);
      crc = ((crc >> 1) & 0x55555555) | ((crc & 0x55555555) << 1); //reverse bit order
      crc = ((crc >> 2) & 0x33333333) | ((crc & 0x33333333) << 2);
      crc = ((crc >> 4) & 0x0F0F0F0F) | ((crc & 0x0F0F0F0F) << 4);
      crc = ((crc >> 8) & 0x00FF00FF) | ((crc & 0x00FF00FF) << 8);
      mk5bheader[3]=mk5bheader[3] | crc;
      iw=fwrite(mk5bheader,sizeof(mk5bheader),1,file2); //========write header
      iw=fwrite(ddin,sizeof(ddin),1,file2); //========write data block
      nframe++;
      if(nframe >=frame_per_sec){
        nframe=0; secmjd++;   //assume scan never goes over midnight
      }
    } //===========================================================
}
// crc subroutine - converts input into a 16 bit CRC code
unsigned int crcc (unsigned char *idata, int len, int mask, int cycl) {
  unsigned int istate = 0;
  int idbit;
  int q, ich, icb;
  for (idbit = 1; idbit <= len; idbit++) {
    q = istate & 1;
    ich = (idbit - 1) / 8;
    icb = 7 - (idbit - 1) % 8;
    if ((((idata[ich] >> icb) & 1) ^ q)  ==  0)
      istate &= -2;
    else {
      istate ^=  mask;
      istate |= 1;
    }
    istate = (istate >> 1) | (istate & 1) << (cycl -1);
  }
  return (istate);
}