From fa9796de83b7a3ec401a4b502c246a55d79ef0c1 Mon Sep 17 00:00:00 2001
From: CryptoManiac <balthazar@yandex.ru>
Date: Thu, 10 Jul 2014 23:03:49 +0400
Subject: [PATCH] Relay OP_RETURN data TxOut as standard transaction type

---
 src/main.cpp   |   24 +++++++++++++++++++-----
 src/script.cpp |   20 ++++++++++++++++++--
 src/script.h   |    4 +++-
 3 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index 44444a7..d8fedf4 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -300,6 +300,8 @@ bool CTransaction::IsStandard() const
     if (nVersion > CTransaction::CURRENT_VERSION)
         return false;
 
+    unsigned int nDataOut = 0;
+    txnouttype whichType;
     BOOST_FOREACH(const CTxIn& txin, vin)
     {
         // Biggest 'standard' txin is a 3-signature 3-of-3 CHECKMULTISIG
@@ -314,14 +316,26 @@ bool CTransaction::IsStandard() const
         }
     }
     BOOST_FOREACH(const CTxOut& txout, vout) {
-        if (!::IsStandard(txout.scriptPubKey))
-            return false;
-        if (txout.nValue == 0)
-            return false;
-        if (fEnforceCanonical && !txout.scriptPubKey.HasCanonicalPushes()) {
+        if (!::IsStandard(txout.scriptPubKey, whichType)) {
             return false;
         }
+        if (whichType == TX_NULL_DATA)
+            nDataOut++;
+        else {
+            if (txout.nValue == 0) {
+                return false;
+            }
+            if (fEnforceCanonical && !txout.scriptPubKey.HasCanonicalPushes()) {
+                return false;
+            }
+        }
+    }
+
+    // only one OP_RETURN txout is permitted
+    if (nDataOut > 1) {
+        return false;
     }
+
     return true;
 }
 
diff --git a/src/script.cpp b/src/script.cpp
index 2bf2cbf..15733a7 100644
--- a/src/script.cpp
+++ b/src/script.cpp
@@ -102,6 +102,7 @@ const char* GetTxnOutputType(txnouttype t)
     case TX_PUBKEYHASH: return "pubkeyhash";
     case TX_SCRIPTHASH: return "scripthash";
     case TX_MULTISIG: return "multisig";
+    case TX_NULL_DATA: return "nulldata";
     }
     return NULL;
 }
@@ -1232,6 +1233,9 @@ bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, vector<vector<unsi
 
         // Sender provides N pubkeys, receivers provides M signatures
         mTemplates.insert(make_pair(TX_MULTISIG, CScript() << OP_SMALLINTEGER << OP_PUBKEYS << OP_SMALLINTEGER << OP_CHECKMULTISIG));
+
+        // Empty, provably prunable, data-carrying output
+        mTemplates.insert(make_pair(TX_NULL_DATA, CScript() << OP_RETURN << OP_SMALLDATA));
     }
 
     // Shortcut for pay-to-script-hash, which are more constrained than the other types:
@@ -1316,6 +1320,12 @@ bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, vector<vector<unsi
                 else
                     break;
             }
+            else if (opcode2 == OP_SMALLDATA)
+            {
+                // small pushdata, <= 80 bytes
+                if (vch1.size() > 80)
+                    break;
+            }
             else if (opcode1 != opcode2 || vch1 != vch2)
             {
                 // Others must match exactly
@@ -1378,6 +1388,7 @@ bool Solver(const CKeyStore& keystore, const CScript& scriptPubKey, uint256 hash
     switch (whichTypeRet)
     {
     case TX_NONSTANDARD:
+    case TX_NULL_DATA:
         return false;
     case TX_PUBKEY:
         keyID = CPubKey(vSolutions[0]).GetID();
@@ -1409,6 +1420,8 @@ int ScriptSigArgsExpected(txnouttype t, const std::vector<std::vector<unsigned c
     {
     case TX_NONSTANDARD:
         return -1;
+    case TX_NULL_DATA:
+        return 1;
     case TX_PUBKEY:
         return 1;
     case TX_PUBKEYHASH:
@@ -1423,10 +1436,9 @@ int ScriptSigArgsExpected(txnouttype t, const std::vector<std::vector<unsigned c
     return -1;
 }
 
-bool IsStandard(const CScript& scriptPubKey)
+bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType)
 {
     vector<valtype> vSolutions;
-    txnouttype whichType;
     if (!Solver(scriptPubKey, whichType, vSolutions))
         return false;
 
@@ -1485,6 +1497,7 @@ bool IsMine(const CKeyStore &keystore, const CScript& scriptPubKey)
     switch (whichType)
     {
     case TX_NONSTANDARD:
+    case TX_NULL_DATA:
         return false;
     case TX_PUBKEY:
         keyID = CPubKey(vSolutions[0]).GetID();
@@ -1583,6 +1596,8 @@ bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, vecto
     vector<valtype> vSolutions;
     if (!Solver(scriptPubKey, typeRet, vSolutions))
         return false;
+    if (typeRet == TX_NULL_DATA)
+        return true;
 
     if (typeRet == TX_MULTISIG)
     {
@@ -1772,6 +1787,7 @@ static CScript CombineSignatures(CScript scriptPubKey, const CTransaction& txTo,
     switch (txType)
     {
     case TX_NONSTANDARD:
+    case TX_NULL_DATA:
         // Don't know anything about this, assume bigger one is correct:
         if (sigs1.size() >= sigs2.size())
             return PushAll(sigs1);
diff --git a/src/script.h b/src/script.h
index 577e80c..8901981 100644
--- a/src/script.h
+++ b/src/script.h
@@ -36,6 +36,7 @@ enum txnouttype
     TX_PUBKEYHASH,
     TX_SCRIPTHASH,
     TX_MULTISIG,
+    TX_NULL_DATA,
 };
 
 class CNoDestination {
@@ -192,6 +193,7 @@ enum opcodetype
 
 
     // template matching params
+    OP_SMALLDATA = 0xf9,
     OP_SMALLINTEGER = 0xfa,
     OP_PUBKEYS = 0xfb,
     OP_PUBKEYHASH = 0xfd,
@@ -590,7 +592,7 @@ public:
 bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, const CTransaction& txTo, unsigned int nIn, int nHashType);
 bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet);
 int ScriptSigArgsExpected(txnouttype t, const std::vector<std::vector<unsigned char> >& vSolutions);
-bool IsStandard(const CScript& scriptPubKey);
+bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType);
 bool IsMine(const CKeyStore& keystore, const CScript& scriptPubKey);
 bool IsMine(const CKeyStore& keystore, const CTxDestination &dest);
 void ExtractAffectedKeys(const CKeyStore &keystore, const CScript& scriptPubKey, std::vector<CKeyID> &vKeys);
-- 
1.7.1