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Add OP_DETERMINISTICRANDOM

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This commit is contained in:
Steven Roose 2019-01-08 13:47:26 +00:00
parent 5a18be3769
commit 358a1bb494
5 changed files with 59 additions and 4 deletions
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55
src/script/interpreter.cpp
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@ -1071,6 +1071,61 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript&
}
break;
case OP_DETERMINISTICRANDOM:
{
if (stack.size() < 3)
return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
valtype vchSeed = stacktop(-3);
CScriptNum bnMin(stacktop(-2), fRequireMinimal);
CScriptNum bnMax(stacktop(-1), fRequireMinimal);
if (bnMin > bnMax)
return set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR);
if (bnMin == bnMax) {
popstack(stack);
popstack(stack);
popstack(stack);
stack.push_back(bnMin.getvch());
break;
}
// The range of the random source must be a multiple of the modulus
// to give every possible output value an equal possibility
uint64_t nMax = (bnMax-bnMin).getint();
uint64_t nRange = (std::numeric_limits<uint64_t>::max() / nMax) * nMax;
uint64_t nRand;
valtype vchHash(32, 0);
uint64_t nCounter = 0;
int nHashIndex = 3;
CSHA256 hasher;
hasher.Write(vchSeed.data(), vchSeed.size());
do {
if (nHashIndex >= 3) {
//TODO this isn't endian safe
CSHA256(hasher).Write((const unsigned char*)&nCounter, sizeof(nCounter)).Finalize(vchHash.data());
nHashIndex = 0;
nCounter++;
}
nRand = 0;
for (size_t i=0; i<8; ++i)
nRand |= ((uint64_t)vchHash[(nHashIndex*8) + i]) << (8*i);
nHashIndex++;
} while (nRand > nRange);
CScriptNum result(nRand % nMax);
result += bnMin.getint();
popstack(stack);
popstack(stack);
popstack(stack);
stack.push_back(result.getvch());
}
break;
default:
return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
}