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

char *buffer;

char * testchar(char *in){
    char *nN;
    nN = (char*) malloc(256*sizeof(char));
    return (char*)nN;
}
/*   Generate the output file name based on in */

char * OPFileName (char *in){
    int index;

    char *nN;
    nN = (char*) malloc(256*sizeof(char));

    index=0;
    while (in[index]!='\0' && in[index]!='.'){
        nN[index]=in[index];
        index++;
    }
    nN[index]='\0';
    strcat(nN,".b\0");
   return  (char*)nN;
 }

/* Reads in 1 hex digit, skips all other characters, replaces eof with \0*/
 char readInput(FILE *fptr){
    char c;
    fscanf(fptr,"%c",&c);
    while (!feof(fptr)){
        if (isxdigit(c))
            return c;
        fscanf(fptr,"%c",&c);
    }
    return '\0';
 }

 /* Reads the text file looking for hex characters, once it reads byte width chars
    it converts the string to an int. and returns the result*/

 int buildInt(FILE *fptr, int size){
    char str[9]="\0";
    int loop=0;
    int num;
    unsigned char c;
    for(loop=0;loop<2*size;loop++){
        c=readInput(fptr);
        if (feof(fptr))
            break;
        str[loop]=c;
    }
    num = (int) strtol (str ,NULL,16);
    return num;
 }

int main()
{
    FILE* fptr, *outfptr;
    //char extension[] = "";
    //unsigned char c1,c2;
    //unsigned char outC;
    int outBits;
    int byteWidth=0;

    char *file_name;  // input file name
    char *file_nameOut; //out put file name

    file_name = (char*) malloc(256*sizeof(char));

    printf("\n\nFile name :\t");  // get input file and open it
    scanf("%s",file_name);
    fptr=fopen(file_name,"r");
    printf("\n Enter byte width: ");
    scanf("%i",&byteWidth);
    if (!fptr) {                 // exit if input file does not exist
        printf("\nERROR - File Note Found\n");
        return 1;
    }

    file_nameOut =  OPFileName(file_name);  //make o/p file name
    printf("%s  %s \n",file_name,file_nameOut);   //debugging code
    outfptr=fopen(file_nameOut,"wb");    //open o/p file

    while (!feof(fptr)){         // writes byte to o/p file
        outBits = buildInt(fptr,byteWidth);
        fwrite( &outBits, byteWidth, 1, outfptr ) ;
    }

    fclose(fptr);
    fclose(outfptr);
    return 0;
}