/*
 * Program: Global Communicator II - band data converter
 * Programmer: Robert John Morton UK-YE572246C
 * Date:  Wed 30 Sep 2020

From the directory in which bandconv.c resides: 
to compile: gcc bandconv.c -o bandconv


INPUT FILE FORMAT

  Number of bands of this type
  |      Type of Band
  |      |
#29 Broadcast

  Starting frequency of graticule [kHz]
  |     Official starting frequency of band
  |     |    Extent of band
  |     |    |  Name of band [up to 20 characters]
  |     |    |  |
11600 11600 300 25-metres 1  


OUTPUT FILE FORMAT

IIIIBANDTYPE00000000000000000000  // band header
IIIIIIIIIIIIBANDNAME000000000000  // band data line  */


#include <stdio.h>   // input output to/from the console and keyboard
#include <stdlib.h>  // standard functions for the 'C' language

FILE *FI;    // open the input file for reading
FILE *FO;    // open the output file for writing
char S[33];  // to hold the string versions of numbers, names and types
int NB = 0,  // number of bands of the current type type
    c,       // for a character got from the input file
    GS,      // Graticule Start frequency
    BS,      // official Band Start frequency
    BE,      // official Band Extent
    R = 0;   // File pointer for that '.dat' output file

int getInt(FILE *F) {    // GET INT FROM A 4-BYTE TRAIN IN A FILE
  return fgetc(F) << 24  // shift first byte to left of int
       | fgetc(F) << 16  // shift second byte to 2nd from left
       | fgetc(F) << 8   // shift 3rd byte to 2nd from right
       | fgetc(F);       // leave 4th byte where it is at far right
}

void getStr() {  // GET A STRING FROM THE INPUT FILE
  int x = 0;
  while((c = fgetc(FI)) != '\0')
    S[x++] = c;
  S[x] = '\0';
}

void putInt(int x, FILE *F) {  // SAVE AN INT TO FILE AS A 4-BYTE TRAIN
  fputc((x >> 24) & 0xFF, F);  // Store the new number of records
  fputc((x >> 16) & 0xFF, F);  // as a 4 byte int in the first
  fputc((x >>  8) & 0xFF, F);  // 4 bytes of the records file.
  fputc(x & 0xFF, F);
}


/* GET AND SAVE THE NAME OF THE BAND OR THE BAND-TYPE. 'i' is the number of
   the start character of the name in the 32-byte output file record. */

void getName(int i) {
  fgetc(FI);           // pass over the space character
  while((c = fgetc(FI)) != '\n') {  // until a 'new line' character is en-
    fputc(c,FO);                    // transfer characters to the output
    i++;                            // file, counting them as you go
  }
  for(int j = i; j < 32; j++)  // Fill in the rest of the 32-byte record
    fputc('\0',FO);            // with null characters.
}


// GET & SAVE THE NUMBER OF BANDS OF THIS TYPE AND THE NAME OF THE BAND-TYPE
int getType() {
  S[0] = fgetc(FI);           // get the first digit
  S[1] = fgetc(FI);           // get the second digit
  S[2] = '\0';                // append a terminating null character
  NB = atoi(S);               // integer from string
  if(NB == 0) return -1;      // end of input file is marked by '#00'
  putInt(NB,FO);              // save integer as 4-byte train
  getName(4);                 // read-in and save the band name
  return 0;
}


// GET & SAVE THE DETAILS OF THE CURRENT BAND
void getBand() {
  S[0] = c;            // first digit already got from #-test
  S[1] = fgetc(FI);   
  S[2] = fgetc(FI);    // These 5 digits pertain to the
  S[3] = fgetc(FI);    // graticule start frequency
  S[4] = fgetc(FI);
  S[5] = '\0';         // append null terminator for atoi()
  putInt(atoi(S),FO);  // save integer as a 4-byte train
  fgetc(FI);           // pass over the space character
  S[0] = fgetc(FI);
  S[1] = fgetc(FI);    // Thes 5 digits pertain to the
  S[2] = fgetc(FI);    // official band-start frequency
  S[3] = fgetc(FI);
  S[4] = fgetc(FI);
  S[5] = '\0';         // append null terminator for atoi()
  putInt(atoi(S),FO);  // save integer as a 4-byte train
  fgetc(FI);           // pass over the space character
  S[0] = fgetc(FI);
  S[1] = fgetc(FI);    // These 3 digits pertain to the
  S[2] = fgetc(FI);    // extent of the official band.
  S[3] = '\0';         // append null terminator for atoi()
  putInt(atoi(S),FO);  // save integer as a 4-byte train
  getName(12);         // Read-in and save the band name,
}                      // which starts at character 12 in the output file.


void main() {
  FI = fopen("bands.txt","rb");   // open the input file for reading
  FO = fopen("bands.dat","wb");   // open the output file for writing
  while(!feof(FI)) {              // while not yet reached end of input file
    if((c = fgetc(FI)) == '#') {  // if line begins with a '#'
      if(getType() == -1)         // get number of bands & band type name
        break;                    // '#00' end of input file encountered
    } else                        // else it is a band data line
      getBand();                  // so get the band data
  }
  fclose(FI);  // Close both input and output files because the
  fclose(FO);  // creation of the '.dat' file is now complete.

  // READ BACK THE DATA FILE TO CHECK THAT IT HAS BEEN FORMED CORRECTLY
  FI = fopen("bands.dat","rb");
  FO = fopen("bandy.txt","w");

  for(int j = 0; j < 4; j++) {
    fseek(FI,R,SEEK_SET);
    NB = getInt(FI);
    getStr();
    fprintf(FO,"NumBands=%i TypeName=%s\n",NB,S);
    R += 32;
    for(int i = 0; i < NB; i++) {
      fseek(FI,R,SEEK_SET);
      GS = getInt(FI);
      BS = getInt(FI);
      BE = getInt(FI);
      getStr();
      fprintf(FO,"GS=%i BS=%i  BE=%i  %s\n",GS,BS,BE,S);
      R += 32;
    }
  }
  fclose(FI);
  fclose(FO);
}