Add OP_DETERMINISTICRANDOM

Author: stevenroose

src/script/interpreter.cpp

@@ -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);
             }

src/script/script.cpp

@@ -126,6 +126,7 @@ const char* GetOpName(opcodetype opcode)
     case OP_CHECKSIGVERIFY         : return "OP_CHECKSIGVERIFY";
     case OP_CHECKMULTISIG          : return "OP_CHECKMULTISIG";
     case OP_CHECKMULTISIGVERIFY    : return "OP_CHECKMULTISIGVERIFY";
+    case OP_DETERMINISTICRANDOM    : return "OP_DETERMINISTICRANDOM";
 
     // expansion
     case OP_NOP1                   : return "OP_NOP1";

src/script/script.h

@@ -173,6 +173,7 @@ enum opcodetype
     OP_CHECKSIGVERIFY = 0xad,
     OP_CHECKMULTISIG = 0xae,
     OP_CHECKMULTISIGVERIFY = 0xaf,
+    OP_DETERMINISTICRANDOM = 0xc0,
 
     // expansion
     OP_NOP1 = 0xb0,
@@ -192,7 +193,7 @@ enum opcodetype
 };
 
 // Maximum value that an opcode can be
-static const unsigned int MAX_OPCODE = OP_NOP10;
+static const unsigned int MAX_OPCODE = OP_DETERMINISTICRANDOM;
 
 const char* GetOpName(opcodetype opcode);
 

src/test/data/script_tests.json

@@ -258,7 +258,6 @@
 ["0", "IF 0xbd ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
 ["0", "IF 0xbe ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
 ["0", "IF 0xbf ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
-["0", "IF 0xc0 ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
 ["0", "IF 0xc1 ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
 ["0", "IF 0xc2 ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
 ["0", "IF 0xc3 ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
@@ -894,7 +893,6 @@
 ["1", "IF 0xbd ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
 ["1", "IF 0xbe ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
 ["1", "IF 0xbf ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
-["1", "IF 0xc0 ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
 ["1", "IF 0xc1 ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
 ["1", "IF 0xc2 ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
 ["1", "IF 0xc3 ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],

src/test/script_tests.cpp

@@ -1474,7 +1474,7 @@ BOOST_AUTO_TEST_CASE(script_HasValidOps)
     BOOST_CHECK(script.HasValidOps());
     script = ScriptFromHex("ff88ac"); // Script with OP_INVALIDOPCODE explicit
     BOOST_CHECK(!script.HasValidOps());
-    script = ScriptFromHex("88acc0"); // Script with undefined opcode
+    script = ScriptFromHex("88acc1"); // Script with undefined opcode: one higher then MAX_OPCODE
     BOOST_CHECK(!script.HasValidOps());
 }