bool Base58::raw_decode (char const* first, char const* last, void* dest,
std::size_t size, bool checked, Alphabet const& alphabet)
{
CAutoBN_CTX pctx;
CBigNum bn58 = 58;
CBigNum bn = 0;
CBigNum bnChar;
// Convert big endian string to bignum
for (char const* p = first; p != last; ++p)
{
int i (alphabet.from_char (*p));
if (i == -1)
return false;
bnChar.setuint ((unsigned int) i);
int const success (BN_mul (&bn, &bn, &bn58, pctx));
assert (success);
(void) success;
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);
char* const out (static_cast <char*> (dest));
// Count leading zeros
int nLeadingZeros = 0;
for (char const* p = first; p!=last && *p==alphabet[0]; p++)
nLeadingZeros++;
// Verify that the size is correct
if (vchTmp.size() + nLeadingZeros != size)
return false;
// Fill the leading zeros
memset (out, 0, nLeadingZeros);
// Copy little endian data to big endian
std::reverse_copy (vchTmp.begin (), vchTmp.end (),
out + nLeadingZeros);
if (checked)
{
char hash4 [4];
fourbyte_hash256 (hash4, out, size - 4);
if (memcmp (hash4, out + size - 4, 4) != 0)
return false;
}
return true;
}
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;
}