Bitcoin

src/base58.cpp

// Copyright (c) 2014-present 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 <base58.h>
#include <hash.h>
#include <uint256.h>
#include <util/strencodings.h>
#include <util/string.h>
#include <cassert>
#include <cstring>
#include <limits>
using util::ContainsNoNUL;
/** 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,
};
[[nodiscard]] static bool DecodeBase58(const char* psz, std::vector<unsigned char>& vch, int max_ret_len)
{
// Skip leading spaces.
while (*psz && IsSpace(*psz))
psz++;
// Skip and count leading '1's.
int zeroes = 0;
int length = 0;
while (*psz == '1') {
zeroes++;
if (zeroes > max_ret_len) return false;
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(std::size(mapBase58) == 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;
if (length + zeroes > max_ret_len) return false;
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);
// 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(std::span<const unsigned char> input)
{
// Skip & count leading zeroes.
int zeroes = 0;
int length = 0;
while (input.size() > 0 && input[0] == 0) {
input = input.subspan(1);
zeroes++;
}
// Allocate enough space in big-endian base58 representation.
int size = input.size() * 138 / 100 + 1; // log(256) / log(58), rounded up.
std::vector<unsigned char> b58(size);
// Process the bytes.
while (input.size() > 0) {
int carry = input[0];
int i = 0;
// Apply "b58 = b58 * 256 + ch".
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;
input = input.subspan(1);
}
// 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;
}
bool DecodeBase58(const std::string& str, std::vector<unsigned char>& vchRet, int max_ret_len)
{
if (!ContainsNoNUL(str)) {
return false;
}
return DecodeBase58(str.c_str(), vchRet, max_ret_len);
}
std::string EncodeBase58Check(std::span<const unsigned char> input)
{
// add 4-byte hash check to the end
std::vector<unsigned char> vch(input.begin(), input.end());
uint256 hash = Hash(vch);
vch.insert(vch.end(), hash.data(), hash.data() + 4);
return EncodeBase58(vch);
}
[[nodiscard]] static bool DecodeBase58Check(const char* psz, std::vector<unsigned char>& vchRet, int max_ret_len)
{
if (!DecodeBase58(psz, vchRet, max_ret_len > std::numeric_limits<int>::max() - 4 ? std::numeric_limits<int>::max() : max_ret_len + 4) ||
(vchRet.size() < 4)) {
vchRet.clear();
return false;
}
// re-calculate the checksum, ensure it matches the included 4-byte checksum
uint256 hash = Hash(std::span{vchRet}.first(vchRet.size() - 4));
if (memcmp(&hash, &vchRet[vchRet.size() - 4], 4) != 0) {
vchRet.clear();
return false;
}
vchRet.resize(vchRet.size() - 4);
return true;
}
bool DecodeBase58Check(const std::string& str, std::vector<unsigned char>& vchRet, int max_ret)
{
if (!ContainsNoNUL(str)) {
return false;
}
return DecodeBase58Check(str.c_str(), vchRet, max_ret);
}