/*
   * (C) Copyright 2016
   * Olliver Schinagl <oliver@schinagl.nl>
   *
   * SPDX-License-Identifier:	GPL-2.0+
   */
  
  #include <ctype.h>

  #include <stdbool.h>

  #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <u-boot/crc.h>
  
  #define ARP_HLEN 6 /* Length of hardware address */
  #define ARP_HLEN_ASCII (ARP_HLEN * 2) + (ARP_HLEN - 1) /* with separators */
  #define ARP_HLEN_LAZY (ARP_HLEN * 2) /* separatorless hardware address length */
  
  uint8_t nibble_to_hex(const char *nibble, bool lo)
  {
  	return (strtol(nibble, NULL, 16) << (lo ? 0 : 4)) & (lo ? 0x0f : 0xf0);
  }
  
  int process_mac(const char *mac_address)
  {
  	uint8_t ethaddr[ARP_HLEN + 1] = { 0x00 };
  	uint_fast8_t i = 0;
  
  	while (*mac_address != '\0') {
  		char nibble[2] = { 0x00, '
  ' }; /* for strtol */
  
  		nibble[0] = *mac_address++;
  		if (isxdigit(nibble[0])) {
  			if (isupper(nibble[0]))
  				nibble[0] = tolower(nibble[0]);
  			ethaddr[i >> 1] |= nibble_to_hex(nibble, (i % 2) != 0);
  			i++;
  		}
  	}
  
  	for (i = 0; i < ARP_HLEN; i++)
  		printf("%.2x", ethaddr[i]);
  	printf("%.2x
  ", crc8(0, ethaddr, ARP_HLEN));
  
  	return 0;
  }
  
  void print_usage(char *cmdname)
  {
  	printf("Usage: %s <mac_address>
  ", cmdname);
  	puts("<mac_address> may be with or without separators.");
  	puts("Valid seperators are ':' and '-'.");
  	puts("<mac_address> digits are in base 16.
  ");
  }
  
  int main(int argc, char *argv[])
  {
  	if (argc < 2) {
  		print_usage(argv[0]);
  		return 1;
  	}
  
  	if (!((strlen(argv[1]) == ARP_HLEN_ASCII) || (strlen(argv[1]) == ARP_HLEN_LAZY))) {
  		puts("The MAC address is not valid.
  ");
  		print_usage(argv[0]);
  		return 1;
  	}
  
  	if (process_mac(argv[1])) {
  		puts("Failed to calculate the MAC's checksum.");
  		return 1;
  	}
  
  	return 0;
  }