z_embedstring and z_readstring

src/rpcclient.cpp

@@ -34,6 +34,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "getnetworkhashps", 1 },
     { "sendtoaddress", 1 },
     { "sendtoaddress", 4 },
+    { "z_embedstring", 1 },
     { "settxfee", 0 },
     { "getreceivedbyaddress", 1 },
     { "getreceivedbyaccount", 1 },
@@ -73,6 +74,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "getblockheader", 1 },
     { "gettransaction", 1 },
     { "getrawtransaction", 1 },
+    { "z_readstring", 0 },
     { "createrawtransaction", 0 },
     { "createrawtransaction", 1 },
     { "signrawtransaction", 1 },

src/rpcrawtransaction.cpp

@@ -282,6 +282,73 @@ UniValue getrawtransaction(const UniValue& params, bool fHelp)
     return result;
 }
 
+UniValue z_readstring(const UniValue& params, bool fHelp)
+{
+    if (fHelp || params.size() != 1)
+        throw runtime_error(
+            "z_readstring \"txid\"\n"
+            "\nNOTE: By default this function only works sometimes. This is when the tx is in the mempool\n"
+            "or there is an unspent output in the utxo for this transaction. To make it always work,\n"
+            "you need to maintain a transaction index, using the -txindex command line option.\n"
+            "\nReturn the string embedded into the transaction with z_embedstring (as a json object).\n"
+
+            "\nArguments:\n"
+            "1. \"txid\"      (string, required) The transaction id\n"
+
+
+            "\nResult:\n"
+            "\"embedded-string\"                  (string) The embedded string.\n"
+
+            "\nExamples:\n"
+            + HelpExampleCli("z_readstring", "\"mytxid\"")
+        );
+
+    LOCK(cs_main);
+
+    uint256 hash = ParseHashV(params[0], "parameter 1");
+
+    CTransaction tx;
+    uint256 hashBlock;
+    if (!GetTransaction(hash, tx, hashBlock, true))
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "No information available about transaction");
+
+    UniValue bad_txn = JSONRPCError(RPC_INVALID_PARAMETER, "It doesn't look like this transaction was created with z_embedstring.");
+
+    if (tx.vout.size() < 1 || tx.vjoinsplit.size() > 0) {
+        throw bad_txn;
+    }
+
+    // Find the first script beginning with OP_RETURN.
+    for (size_t i = 0; i < tx.vout.size(); i++) {
+        CScript script = tx.vout[i].scriptPubKey;
+        opcodetype opcode;
+        std::vector<unsigned char> vch;
+        CScript::const_iterator pc = script.begin();
+
+        if (!script.GetOp(pc, opcode, vch)) {
+            throw bad_txn;
+        }
+        if (opcode == OP_RETURN) {
+            // Next should come the embedded string.
+            if (!script.GetOp(pc, opcode, vch)) {
+                throw bad_txn;
+            }
+            if (opcode < 0 || opcode > OP_PUSHDATA4) {
+                throw bad_txn;
+            }
+
+            // Make sure there there's nothing else after the embedded string.
+            if (pc < script.end()) {
+                throw bad_txn;
+            }
+            return std::string(vch.begin(), vch.end());
+        }
+    }
+
+    // Didn't find an OP_RETURN.
+    throw bad_txn;
+}
+
 UniValue gettxoutproof(const UniValue& params, bool fHelp)
 {
     if (fHelp || (params.size() != 1 && params.size() != 2))

src/rpcserver.cpp

@@ -316,6 +316,7 @@ static const CRPCCommand vRPCCommands[] =
     { "rawtransactions",    "decoderawtransaction",   &decoderawtransaction,   true  },
     { "rawtransactions",    "decodescript",           &decodescript,           true  },
     { "rawtransactions",    "getrawtransaction",      &getrawtransaction,      true  },
+    { "rawtransactions",    "z_readstring",           &z_readstring,           true  },
     { "rawtransactions",    "sendrawtransaction",     &sendrawtransaction,     false },
     { "rawtransactions",    "signrawtransaction",     &signrawtransaction,     false }, /* uses wallet if enabled */
 #ifdef ENABLE_WALLET
@@ -373,6 +374,7 @@ static const CRPCCommand vRPCCommands[] =
     { "wallet",             "sendfrom",               &sendfrom,               false },
     { "wallet",             "sendmany",               &sendmany,               false },
     { "wallet",             "sendtoaddress",          &sendtoaddress,          false },
+    { "wallet",             "z_embedstring",          &z_embedstring,          false },
     { "wallet",             "setaccount",             &setaccount,             true  },
     { "wallet",             "settxfee",               &settxfee,               true  },
     { "wallet",             "signmessage",            &signmessage,            true  },

src/rpcserver.h

@@ -209,6 +209,7 @@ extern UniValue setaccount(const UniValue& params, bool fHelp);
 extern UniValue getaccount(const UniValue& params, bool fHelp);
 extern UniValue getaddressesbyaccount(const UniValue& params, bool fHelp);
 extern UniValue sendtoaddress(const UniValue& params, bool fHelp);
+extern UniValue z_embedstring(const UniValue& params, bool fHelp);
 extern UniValue signmessage(const UniValue& params, bool fHelp);
 extern UniValue verifymessage(const UniValue& params, bool fHelp);
 extern UniValue getreceivedbyaddress(const UniValue& params, bool fHelp);
@@ -247,6 +248,7 @@ extern UniValue zc_raw_receive(const UniValue& params, bool fHelp);
 extern UniValue zc_sample_joinsplit(const UniValue& params, bool fHelp);
 
 extern UniValue getrawtransaction(const UniValue& params, bool fHelp); // in rcprawtransaction.cpp
+extern UniValue z_readstring(const UniValue& params, bool fHelp); // in rcprawtransaction.cpp
 extern UniValue listunspent(const UniValue& params, bool fHelp);
 extern UniValue lockunspent(const UniValue& params, bool fHelp);
 extern UniValue listlockunspent(const UniValue& params, bool fHelp);

src/wallet/rpcwallet.cpp

@@ -366,7 +366,7 @@ UniValue getaddressesbyaccount(const UniValue& params, bool fHelp)
     return ret;
 }
 
-static void SendMoney(const CTxDestination &address, CAmount nValue, bool fSubtractFeeFromAmount, CWalletTx& wtxNew)
+static void SendMoney(const CScript &scriptPubKey, CAmount nValue, bool fSubtractFeeFromAmount, CWalletTx& wtxNew)
 {
     CAmount curBalance = pwalletMain->GetBalance();
 
@@ -377,8 +377,9 @@ static void SendMoney(const CTxDestination &address, CAmount nValue, bool fSubtr
     if (nValue > curBalance)
         throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Insufficient funds");
 
+    // TODO: no longer needed?
     // Parse Hush address
-    CScript scriptPubKey = GetScriptForDestination(address);
+    //CScript scriptPubKey = GetScriptForDestination(address);
 
     // Create and send the transaction
     CReserveKey reservekey(pwalletMain);
@@ -450,7 +451,48 @@ UniValue sendtoaddress(const UniValue& params, bool fHelp)
 
     EnsureWalletIsUnlocked();
 
-    SendMoney(address.Get(), nAmount, fSubtractFeeFromAmount, wtx);
+    SendMoney(GetScriptForDestination(address.Get()), nAmount, fSubtractFeeFromAmount, wtx);
+
+    return wtx.GetHash().GetHex();
+}
+
+UniValue z_embedstring(const UniValue& params, bool fHelp)
+{
+    if (!EnsureWalletIsAvailable(fHelp))
+        return NullUniValue;
+
+    if (fHelp || params.size() != 2)
+        throw runtime_error(
+            "z_embedstring \"string-to-embed\" amount\n"
+            "\nEmbed a string into the blockchain (requires paying a fee).\n"
+            + HelpRequiringPassphrase() +
+            "\nArguments:\n"
+            "1. \"string-to-embed\"  (string, required) The string to embed into the blockchain.\n"
+            "2. \"amount\"      (numeric, required) The amount in zcash to burn (not including fee). eg 0.0001\n"
+            "\nResult:\n"
+            "\"transactionid\"  (string) The transaction id.\n"
+            "\nExamples:\n"
+            + HelpExampleCli("z_embedstring", "\"Hello, world!")
+        );
+
+    LOCK2(cs_main, pwalletMain->cs_wallet);
+
+    // String to embed
+    std::string string_to_embed = params[0].get_str();
+    std::vector<unsigned char> bytes_to_embed(string_to_embed.begin(), string_to_embed.end());
+
+    // TODO: Are zero-valued TXOUTs disallowed by consensus, or can we safely
+    // remove the 'amount' from this RPC and always have zero-value TXOUT?
+    CAmount nAmount = AmountFromValue(params[1]);
+    //if (nAmount <= 0)
+    //    throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount for send");
+    // Daira says they are supported, -- Duke
+
+    EnsureWalletIsUnlocked();
+
+    CWalletTx wtx;
+    CScript opreturn;
+    SendMoney(CScript() << OP_RETURN << bytes_to_embed, nAmount, false, wtx);
 
     return wtx.GetHash().GetHex();
 }
@@ -928,7 +970,7 @@ UniValue sendfrom(const UniValue& params, bool fHelp)
     if (nAmount > nBalance)
         throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Account has insufficient funds");
 
-    SendMoney(address.Get(), nAmount, false, wtx);
+    SendMoney(GetScriptForDestination(address.Get()), nAmount, false, wtx);
 
     return wtx.GetHash().GetHex();
 }