path: root/src/libkeccak/hex.c

/**
 * libkeccak – Keccak-family hashing library
 * 
 * Copyright © 2014, 2015  Mattias Andrée (maandree@member.fsf.org)
 * 
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "hex.h"

#include <string.h>



/**
 * Convert a binary hashsum to lower case hexadecimal representation
 * 
 * @param  output   Output array, should have an allocation size of at least `2 * n + 1`
 * @param  hashsum  The hashsum to convert
 * @param  n        The size of `hashsum`
 */
void libkeccak_behex_lower(char* restrict output, const char* restrict hashsum, size_t n)
{
  output[2 * n] = '\0';
  while (n--)
    {
      output[2 * n + 0] = "0123456789abcdef"[(hashsum[n] >> 4) & 15];
      output[2 * n + 1] = "0123456789abcdef"[(hashsum[n] >> 0) & 15];
    }
}


/**
 * Convert a binary hashsum to upper case hexadecimal representation
 * 
 * @param  output   Output array, should have an allocation size of at least `2 * n + 1`
 * @param  hashsum  The hashsum to convert
 * @param  n        The size of `hashsum`
 */
void libkeccak_behex_upper(char* restrict output, const char* restrict hashsum, size_t n)
{
  output[2 * n] = '\0';
  while (n--)
    {
      output[2 * n + 0] = "0123456789ABCDEF"[(hashsum[n] >> 4) & 15];
      output[2 * n + 1] = "0123456789ABCDEF"[(hashsum[n] >> 0) & 15];
    }
}


/**
 * Convert a hexadecimal hashsum (both lower case, upper
 * case and mixed is supported) to binary representation
 * 
 * @param  output   Output array, should have an allocation size of at least `strlen(hashsum) / 2`
 * @param  hashsum  The hashsum to convert
 */
void libkeccak_unhex(char* restrict output, const char* restrict hashsum)
{
  size_t n = strlen(hashsum) / 2;
  while (n--)
    {
      char a = hashsum[2 * n + 0];
      char b = hashsum[2 * n + 1];
      
      a = (char)((a & 15) + (a > '9' ? 9 : 0));
      b = (char)((b & 15) + (b > '9' ? 9 : 0));
      
      output[n] = (char)((a << 4) | b);
    }
}