base58.cpp

// Copyright (c) 2014-2018 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <vector>
#include <string>
#include <cctype>
#include <iostream>

#include <assert.h>
#include <string.h>
#include <stdint.h>
#include <stdio.h>

/** All alphanumeric characters except for "0", "I", "O", and "l" */
static const char *pszBase58 =
    "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
static const int8_t mapBase58[256] = {
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0,  1,  2,  3,  4,  5,  6,  7,
    8,  -1, -1, -1, -1, -1, -1, -1, 9,  10, 11, 12, 13, 14, 15, 16, -1, 17, 18,
    19, 20, 21, -1, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, -1, -1, -1, -1,
    -1, -1, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, -1, 44, 45, 46, 47, 48,
    49, 50, 51, 52, 53, 54, 55, 56, 57, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1,
};

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 = strlen(psz) * 733 / 1000 + 1; // log(58) / log(256), rounded up.
    std::vector<unsigned char> b256(size);
    // Process the characters.
    static_assert(
        sizeof(mapBase58) / sizeof(mapBase58[0]) == 256,
        "mapBase58.size() should be 256"); // guarantee not out of range
    while (*psz && !isspace(*psz)) {
        // Decode base58 character
        int carry = mapBase58[(uint8_t)*psz];
        if (carry == -1) // Invalid b58 character
            return false;
        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;
        }
        assert(carry == 0);
        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) {
    // Skip & count leading zeroes.
    int zeroes = 0;
    int length = 0;
    while (pbegin != pend && *pbegin == 0) {
        pbegin++;
        zeroes++;
    }
    // Allocate enough space in big-endian base58 representation.
    int size =
        (pend - pbegin) * 138 / 100 + 1; // log(256) / log(58), rounded up.
    std::vector<unsigned char> b58(size);
    // Process the bytes.
    while (pbegin != pend) {
        int carry = *pbegin;
        int i = 0;
        // Apply "b58 = b58 * 256 + ch".
        int m = size - 1;
        for (std::vector<unsigned char>::reverse_iterator it = b58.rbegin();
             (carry != 0 || i < length) && (it != b58.rend()); it++, i++) {
            carry += 256 * (*it);
            *it = carry % 58;
            carry /= 58;
        }
        assert(carry == 0);
        length = i;
        pbegin++;
    }
    // Skip leading zeroes in base58 result.
    std::vector<unsigned char>::iterator it = b58.begin() + (size - length);
    while (it != b58.end() && *it == 0)
        it++;
    // Translate the result into a string.
    std::string str;
    str.reserve(zeroes + (b58.end() - it));
    str.assign(zeroes, '1');
    while (it != b58.end()) {
        str += pszBase58[*(it++)];
    }
    return str;
}

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);
}

int main() {
    std::string hash = "2noDGfzjJERhDvQ3kifCdX6QiL5XBMX6y3A44D5cH8twybYN9g";
    std::vector<unsigned char> res;
    std::string bin;

    DecodeBase58(hash.c_str(), res);

    for (auto c : res) {
        bin += c;
    }

    std::cout << std::endl;

    std::cout << res.size() << std::endl;
    std::cout << bin << std::endl;

    auto b58 = EncodeBase58(&*res.cbegin(), &*res.cend());
    std::cout << b58 << ", " << b58.size() << std::endl;

    return 0;
}