bool Base58::decode (const char* psz, Blob& vchRet, Alphabet const& alphabet)
{
CAutoBN_CTX pctx;
vchRet.clear ();
CBigNum bn58 = 58;
CBigNum bn = 0;
CBigNum bnChar;
while (isspace (*psz))
psz++;
// Convert big endian string to bignum
for (const char* p = psz; *p; p++)
{
// VFALCO TODO Make this use the inverse table!
// Or better yet ditch this and call raw_decode
//
const char* p1 = strchr (alphabet.chars(), *p);
if (p1 == nullptr)
{
while (isspace (*p))
p++;
if (*p != '\0')
return false;
break;
}
bnChar.setuint (p1 - alphabet.chars());
if (!BN_mul (&bn, &bn, &bn58, pctx))
throw bignum_error ("DecodeBase58 : BN_mul failed");
bn += bnChar;
}
// Get bignum as little endian data
Blob vchTmp = bn.getvch ();
// Trim off sign byte if present
if (vchTmp.size () >= 2 && vchTmp.end ()[-1] == 0 && vchTmp.end ()[-2] >= 0x80)
vchTmp.erase (vchTmp.end () - 1);
// Restore leading zeros
int nLeadingZeros = 0;
for (const char* p = psz; *p == alphabet.chars()[0]; p++)
nLeadingZeros++;
vchRet.assign (nLeadingZeros + vchTmp.size (), 0);
// Convert little endian data to big endian
std::reverse_copy (vchTmp.begin (), vchTmp.end (), vchRet.end () - vchTmp.size ());
return true;
}
// Decode a base58-encoded string psz into byte vector vchRet
// returns true if decoding is successful
bool DecodeBase58(const char* psz, std::vector<unsigned char>& vchRet)
{
CAutoBN_CTX pctx;
vchRet.clear();
CBigNum bn58 = 58;
CBigNum bn = 0;
CBigNum bnChar;
while (isspace(*psz))
psz++;
// Convert big endian string to bignum
for (const char* p = psz; *p; p++)
{
const char* p1 = strchr(pszBase58, *p);
if (p1 == NULL)
{
while (isspace(*p))
p++;
if (*p != '\0')
return false;
break;
}
bnChar.setuint32((uint32_t)(p1 - pszBase58));
if (!BN_mul(&bn, &bn, &bn58, pctx))
throw bignum_error("DecodeBase58 : BN_mul failed");
bn += bnChar;
}
// Get bignum as little endian data
std::vector<unsigned char> vchTmp = bn.getvch();
// Trim off sign byte if present
if (vchTmp.size() >= 2 && vchTmp.end()[-1] == 0 && vchTmp.end()[-2] >= 0x80)
vchTmp.erase(vchTmp.end()-1);
// Restore leading zeros
int nLeadingZeros = 0;
for (const char* p = psz; *p == pszBase58[0]; p++)
nLeadingZeros++;
vchRet.assign(nLeadingZeros + vchTmp.size(), 0);
// Convert little endian data to big endian
reverse_copy(vchTmp.begin(), vchTmp.end(), vchRet.end() - vchTmp.size());
return true;
}
// Encode a byte sequence as a base58-encoded string
std::string EncodeBase58(const unsigned char* pbegin, const unsigned char* pend)
{
CAutoBN_CTX pctx;
CBigNum bn58 = 58;
CBigNum bn0 = 0;
// Convert big endian data to little endian
// Extra zero at the end make sure bignum will interpret as a positive number
std::vector<unsigned char> vchTmp(pend-pbegin+1, 0);
reverse_copy(pbegin, pend, vchTmp.begin());
// Convert little endian data to bignum
CBigNum bn;
bn.setvch(vchTmp);
// Convert bignum to std::string
std::string str;
// Expected size increase from base58 conversion is approximately 137%
// use 138% to be safe
str.reserve((pend - pbegin) * 138 / 100 + 1);
CBigNum dv;
CBigNum rem;
while (bn > bn0)
{
if (!BN_div(&dv, &rem, &bn, &bn58, pctx))
throw bignum_error("EncodeBase58 : BN_div failed");
bn = dv;
unsigned int c = rem.getuint32();
str += pszBase58[c];
}
// Leading zeroes encoded as base58 zeros
for (const unsigned char* p = pbegin; p < pend && *p == 0; p++)
str += pszBase58[0];
// Convert little endian std::string to big endian
reverse(str.begin(), str.end());
return str;
}
std::string Base58::raw_encode (
unsigned char const* begin, unsigned char const* end,
Alphabet const& alphabet, bool withCheck)
{
CAutoBN_CTX pctx;
CBigNum bn58 = 58;
CBigNum bn0 = 0;
// Convert little endian data to bignum
CBigNum bn (begin, end);
std::size_t const size (std::distance (begin, end));
// Convert bignum to std::string
std::string str;
// Expected size increase from base58 conversion is approximately 137%
// use 138% to be safe
str.reserve (size * 138 / 100 + 1);
CBigNum dv;
CBigNum rem;
while (bn > bn0)
{
if (!BN_div (&dv, &rem, &bn, &bn58, pctx))
throw bignum_error ("EncodeBase58 : BN_div failed");
bn = dv;
unsigned int c = rem.getuint ();
str += alphabet [c];
}
for (const unsigned char* p = end-2; p >= begin && *p == 0; p--)
str += alphabet [0];
// Convert little endian std::string to big endian
reverse (str.begin (), str.end ());
return str;
}
bool DecodeBase58(const char* psz, std::vector<unsigned char>& vchRet) {
CAutoBN_CTX pctx;
vchRet.clear();
CBigNum bn58 = 58;
CBigNum bn = 0;
CBigNum bnChar;
// Skip leading spaces.
while (*psz && isspace(*psz))
psz++;
// Skip and count leading '1's.
int zeroes = 0;
while (*psz == '1') {
zeroes++;
psz++;
}
// Convert big endian string to bignum
for (const char* p = psz; *p; p++)
{
const char* p1 = strchr(pszBase58, *p);
if (p1 == NULL)
{
while (isspace(*p))
p++;
if (*p != '\0')
return false;
break;
}
bnChar.setulong(p1 - pszBase58);
if (!BN_mul(&bn, &bn, &bn58, pctx))
throw bignum_error("DecodeBase58 : BN_mul failed");
bn += bnChar;
}
// Get bignum as little endian data
std::vector<unsigned char> vchTmp = bn.getvch();
// Trim off sign byte if present
if (vchTmp.size() >= 2 && vchTmp.end()[-1] == 0 && vchTmp.end()[-2] >= 0x80)
vchTmp.erase(vchTmp.end()-1);
// Restore leading zeros
int nLeadingZeros = 0;
for (const char* p = psz; *p == pszBase58[0]; p++)
nLeadingZeros++;
vchRet.assign(nLeadingZeros + vchTmp.size(), 0);
// Convert little endian data to big endian
reverse_copy(vchTmp.begin(), vchTmp.end(), vchRet.end() - vchTmp.size());
return true;
// Allocate enough space in big-endian base256 representation.
std::vector<unsigned char> b256(strlen(psz) * 733 / 1000 + 1); // log(58) / log(256), rounded up.
// Process the characters.
while (*psz && !isspace(*psz)) {
// Decode base58 character
const char *ch = strchr(pszBase58, *psz);
if (ch == NULL)
return false;
// Apply "b256 = b256 * 58 + ch".
int carry = ch - pszBase58;
for (std::vector<unsigned char>::reverse_iterator it = b256.rbegin(); it != b256.rend(); it++) {
carry += 58 * (*it);
*it = carry % 256;
carry /= 256;
}
assert(carry == 0);
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();
while (it != b256.end() && *it == 0)
it++;
// Copy result into output vector.
vchRet.reserve(zeroes + (b256.end() - it));
vchRet.assign(zeroes, 0x00);
while (it != b256.end())
vchRet.push_back(*(it++));
return true;
}
