Base58.cpp

/*
 * This file is part of the VanitySearch distribution (https://github.com/JeanLucPons/VanitySearch).
 * Copyright (c) 2019 Jean Luc PONS.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3.
 *
 * This program 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

#include "Base58.h"

#include <algorithm>
#include <string.h>

/** All alphanumeric characters except for "0", "I", "O", and "l" */
static const char* pszBase58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";

bool DecodeBase58(const char* psz, std::vector<unsigned char>& vch)
{
    // Skip leading spaces.
    while (*psz && isspace(*psz))
        psz++;
    // Skip and count leading '1's.
    int zeroes = 0;
    int length = 0;
    while (*psz == '1') {
        zeroes++;
        psz++;
    }
    // Allocate enough space in big-endian base256 representation.
    int size = (int)strlen(psz) * 733 /1000 + 1; // log(58) / log(256), rounded up.
    std::vector<unsigned char> b256(size);
    // Process the characters.
    while (*psz && !isspace(*psz)) {
        // Decode base58 character
        const char* ch = strchr(pszBase58, *psz);
        if (ch == nullptr)
            return false;
        // Apply "b256 = b256 * 58 + ch".
        int carry = (int)(ch - pszBase58);
        int i = 0;
        for (std::vector<unsigned char>::reverse_iterator it = b256.rbegin(); (carry != 0 || i < length) && (it != b256.rend()); ++it, ++i) {
            carry += 58 * (*it);
            *it = carry % 256;
            carry /= 256;
        }
        length = i;
        psz++;
    }
    // Skip trailing spaces.
    while (isspace(*psz))
        psz++;
    if (*psz != 0)
        return false;
    // Skip leading zeroes in b256.
    std::vector<unsigned char>::iterator it = b256.begin() + (size - length);
    while (it != b256.end() && *it == 0)
        it++;
    // Copy result into output vector.
    vch.reserve(zeroes + (b256.end() - it));
    vch.assign(zeroes, 0x00);
    while (it != b256.end())
        vch.push_back(*(it++));
    return true;
}

std::string EncodeBase58(const unsigned char* pbegin, const unsigned char* pend) {

  std::string ret;
  unsigned char digits[256];
  
  // Skip leading zeroes.
  while (pbegin != pend && *pbegin == 0) {
    ret.push_back('1');
    pbegin++;
  }
  int length = (int)(pend - pbegin);

  int digitslen = 1;
  digits[0]=0;
  for(int i = 0; i < length; i++) {
    uint32_t carry = pbegin[i];
    for(int j = 0; j < digitslen; j++) {
      carry += (uint32_t)(digits[j]) << 8;
      digits[j] = (unsigned char)(carry % 58);
      carry /= 58;
    }
    while(carry > 0) {
      digits[digitslen++] = (unsigned char)(carry % 58);
      carry /= 58;
    }
  }

  // reverse
  for(int i = 0; i < digitslen; i++)
    ret.push_back(pszBase58[digits[digitslen - 1 - i]]);

  return ret;

}

std::string EncodeBase58(const std::vector<unsigned char>& vch)
{
    return EncodeBase58(vch.data(), vch.data() + vch.size());
}

bool DecodeBase58(const std::string& str, std::vector<unsigned char>& vchRet)
{
    return DecodeBase58(str.c_str(), vchRet);
}