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// Copyright (c) 2009 Satoshi Nakamoto
// Distributed under the MIT/X11 software license, see the accompanying
// file license.txt or http://www.opensource.org/licenses/mit-license.php.
//
// Why base-58 instead of standard base-64 encoding?
// - Don't want 0OIl characters that look the same in some fonts and
// could be used to create visually identical looking account numbers.
// - A string with non-alphanumeric characters is not as easily accepted as an account number.
// - E-mail usually won't line-break if there's no punctuation to break at.
// - Doubleclicking selects the whole number as one word if it's all alphanumeric.
//
static const char* pszBase58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
inline 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
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 string
string str;
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.getulong();
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 string to big endian
reverse(str.begin(), str.end());
return str;
}
inline string EncodeBase58(const vector<unsigned char>& vch)
{
return EncodeBase58(&vch[0], &vch[0] + vch.size());
}
inline bool DecodeBase58(const char* psz, 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.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
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;
}
inline bool DecodeBase58(const string& str, vector<unsigned char>& vchRet)
{
return DecodeBase58(str.c_str(), vchRet);
}
inline string EncodeBase58Check(const vector<unsigned char>& vchIn)
{
// add 4-byte hash check to the end
vector<unsigned char> vch(vchIn);
uint256 hash = Hash(vch.begin(), vch.end());
vch.insert(vch.end(), (unsigned char*)&hash, (unsigned char*)&hash + 4);
return EncodeBase58(vch);
}
inline bool DecodeBase58Check(const char* psz, vector<unsigned char>& vchRet)
{
if (!DecodeBase58(psz, vchRet))
return false;
if (vchRet.size() < 4)
{
vchRet.clear();
return false;
}
uint256 hash = Hash(vchRet.begin(), vchRet.end()-4);
if (memcmp(&hash, &vchRet.end()[-4], 4) != 0)
{
vchRet.clear();
return false;
}
vchRet.resize(vchRet.size()-4);
return true;
}
inline bool DecodeBase58Check(const string& str, vector<unsigned char>& vchRet)
{
return DecodeBase58Check(str.c_str(), vchRet);
}
static const unsigned char ADDRESSVERSION = 0;
inline string Hash160ToAddress(uint160 hash160)
{
// add 1-byte version number to the front
vector<unsigned char> vch(1, ADDRESSVERSION);
vch.insert(vch.end(), UBEGIN(hash160), UEND(hash160));
return EncodeBase58Check(vch);
}
inline bool AddressToHash160(const char* psz, uint160& hash160Ret)
{
vector<unsigned char> vch;
if (!DecodeBase58Check(psz, vch))
return false;
if (vch.empty())
return false;
unsigned char nVersion = vch[0];
if (vch.size() != sizeof(hash160Ret) + 1)
return false;
memcpy(&hash160Ret, &vch[1], sizeof(hash160Ret));
return (nVersion <= ADDRESSVERSION);
}
inline bool AddressToHash160(const string& str, uint160& hash160Ret)
{
return AddressToHash160(str.c_str(), hash160Ret);
}
inline bool IsValidBitcoinAddress(const char* psz)
{
uint160 hash160;
return AddressToHash160(psz, hash160);
}
inline bool IsValidBitcoinAddress(const string& str)
{
return IsValidBitcoinAddress(str.c_str());
}
inline string PubKeyToAddress(const vector<unsigned char>& vchPubKey)
{
return Hash160ToAddress(Hash160(vchPubKey));
}
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