root/debug/hex2bin.c

DEFINITIONS

1. getbin
2. main

///////////////////////////////////////////////////////////////////////////////
//
/// \file       hex2bin.c
/// \brief      Converts hexadecimal input strings to binary
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "sysdefs.h"
#include <stdio.h>
#include <ctype.h>


static int
getbin(int x)
{
        if (x >= '0' && x <= '9')
                return x - '0';

        if (x >= 'A' && x <= 'F')
                return x - 'A' + 10;

        return x - 'a' + 10;
}


int
main(void)
{
        while (true) {
                int byte = getchar();
                if (byte == EOF)
                        return 0;
                if (!isxdigit(byte))
                        continue;

                const int digit = getchar();
                if (digit == EOF || !isxdigit(digit)) {
                        fprintf(stderr, "Invalid input\n");
                        return 1;
                }

                byte = (getbin(byte) << 4) | getbin(digit);
                if (putchar(byte) == EOF) {
                        perror(NULL);
                        return 1;
                }
        }
}