wallet: extract ParseSendManyRecipients from z_sendmany

Second slice of the z_sendmany split. The ~60-line loop that parses and
validates the "outputs" array — rejecting unknown keys, bad addresses, memos
on taddrs, oversize memos and negative amounts, and sorting recipients into
taddr/zaddr lists while accumulating nTotalOut — is lifted verbatim into
ParseSendManyRecipients(outputs, branchId, taddrRecipients, zaddrRecipients,
nTotalOut).

Verbatim extract-method (the loop text was moved unchanged, not retyped); the
helper reads only outputs + branchId and writes the three by-reference outputs
the loop already produced, which the clean compile proves self-contained (a
reference to any other z_sendmany local would fail to link). Built clean;
verifychain=true.

Together with the SelectAnyZaddrSource slice, z_sendmany is now ~135 lines
shorter, with source-address resolution and recipient parsing separated out.
Remaining: note selection, Sietch padding, and tx assembly (later slices,
best validated against a synced node since z_sendmany's linkability guard
blocks the send path on a peerless node).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/wallet/rpcwallet.cpp

@@ -5189,6 +5189,77 @@ static std::string SelectAnyZaddrSource(const UniValue& outputs, const UniValue&
     throw JSONRPCError(RPC_INVALID_PARAMETER, "No single zaddr currently has enough funds to make that transaction, you may need to wait for confirmations.");
 }
 
+// Parse and validate the z_sendmany "outputs" array into taddr/zaddr recipient lists
+// (accumulating nTotalOut). Extracted verbatim from z_sendmany; throws JSONRPCError on
+// any malformed entry (unknown key, bad address, memo misuse/oversize, negative amount).
+static void ParseSendManyRecipients(const UniValue& outputs, uint32_t branchId,
+                                    std::vector<SendManyRecipient>& taddrRecipients,
+                                    std::vector<SendManyRecipient>& zaddrRecipients,
+                                    CAmount& nTotalOut)
+{
+    for (const UniValue& o : outputs.getValues()) {
+        if (!o.isObject())
+            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, expected object");
+
+        // sanity check, report error if unknown key-value pairs
+        for (const string& name_ : o.getKeys()) {
+            std::string s = name_;
+            if (s != "address" && s != "amount" && s!="memo") {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, string("Invalid parameter, unknown key: ")+s);
+            }
+        }
+
+        string address = find_value(o, "address").get_str();
+        bool isZaddr = false;
+        CTxDestination taddr = DecodeDestination(address);
+        if (!IsValidDestination(taddr)) {
+            auto res = DecodePaymentAddress(address);
+            if (IsValidPaymentAddress(res, branchId)) {
+                isZaddr = true;
+            } else {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, string("Invalid parameter, unknown address format: ")+address );
+            }
+        }// else if ( ASSETCHAINS_PRIVATE != 0 && hush_isnotaryvout((char *)address.c_str()) == 0 ) {
+        //    throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Extreme Privacy! You must send to a zaddr");
+        //}
+
+        UniValue memoValue = find_value(o, "memo");
+        string memo;
+        if (!memoValue.isNull()) {
+            memo = memoValue.get_str();
+            if (!isZaddr) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Memo cannot be used with a taddr.  It can only be used with a zaddr.");
+            } else if(memo.substr(0,5) == "utf8:") {
+                // Support a prefix "utf8:" which allows giving utf8 text instead of hex
+                auto str = memo.substr(5);
+                if (utf8::is_valid(str)) {
+                    memo = HexStr(str);
+                } else {
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid utf8 in memo");
+                }
+            } else if (!IsHex(memo)) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, expected memo data in hexadecimal format or to use 'utf8:' prefix.");
+            }
+            if (memo.length() > HUSH_MEMO_SIZE*2) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER,  strprintf("Invalid parameter, size of memo is larger than maximum allowed %d", HUSH_MEMO_SIZE ));
+            }
+        }
+
+        UniValue av = find_value(o, "amount");
+        CAmount nAmount = AmountFromValue( av );
+        if (nAmount < 0)
+            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, amount must be positive");
+
+        if (isZaddr) {
+            zaddrRecipients.push_back( SendManyRecipient(address, nAmount, memo) );
+        } else {
+            taddrRecipients.push_back( SendManyRecipient(address, nAmount, memo) );
+        }
+
+        nTotalOut += nAmount;
+    }
+}
+
 UniValue z_sendmany(const UniValue& params, bool fHelp, const CPubKey& mypk)
 {
     if (!EnsureWalletIsAvailable(fHelp))
@@ -5296,67 +5367,7 @@ UniValue z_sendmany(const UniValue& params, bool fHelp, const CPubKey& mypk)
         opret << OP_RETURN << ParseHex(opretValue.get_str().c_str());
     }
 
-    for (const UniValue& o : outputs.getValues()) {
+    ParseSendManyRecipients(outputs, branchId, taddrRecipients, zaddrRecipients, nTotalOut);
-        if (!o.isObject())
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, expected object");
-
-        // sanity check, report error if unknown key-value pairs
-        for (const string& name_ : o.getKeys()) {
-            std::string s = name_;
-            if (s != "address" && s != "amount" && s!="memo") {
-                throw JSONRPCError(RPC_INVALID_PARAMETER, string("Invalid parameter, unknown key: ")+s);
-            }
-        }
-
-        string address = find_value(o, "address").get_str();
-        bool isZaddr = false;
-        CTxDestination taddr = DecodeDestination(address);
-        if (!IsValidDestination(taddr)) {
-            auto res = DecodePaymentAddress(address);
-            if (IsValidPaymentAddress(res, branchId)) {
-                isZaddr = true;
-            } else {
-                throw JSONRPCError(RPC_INVALID_PARAMETER, string("Invalid parameter, unknown address format: ")+address );
-            }
-        }// else if ( ASSETCHAINS_PRIVATE != 0 && hush_isnotaryvout((char *)address.c_str()) == 0 ) {
-        //    throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Extreme Privacy! You must send to a zaddr");
-        //}
-
-        UniValue memoValue = find_value(o, "memo");
-        string memo;
-        if (!memoValue.isNull()) {
-            memo = memoValue.get_str();
-            if (!isZaddr) {
-                throw JSONRPCError(RPC_INVALID_PARAMETER, "Memo cannot be used with a taddr.  It can only be used with a zaddr.");
-            } else if(memo.substr(0,5) == "utf8:") {
-                // Support a prefix "utf8:" which allows giving utf8 text instead of hex
-                auto str = memo.substr(5);
-                if (utf8::is_valid(str)) {
-                    memo = HexStr(str);
-                } else {
-                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid utf8 in memo");
-                }
-            } else if (!IsHex(memo)) {
-                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, expected memo data in hexadecimal format or to use 'utf8:' prefix.");
-            }
-            if (memo.length() > HUSH_MEMO_SIZE*2) {
-                throw JSONRPCError(RPC_INVALID_PARAMETER,  strprintf("Invalid parameter, size of memo is larger than maximum allowed %d", HUSH_MEMO_SIZE ));
-            }
-        }
-
-        UniValue av = find_value(o, "amount");
-        CAmount nAmount = AmountFromValue( av );
-        if (nAmount < 0)
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, amount must be positive");
-
-        if (isZaddr) {
-            zaddrRecipients.push_back( SendManyRecipient(address, nAmount, memo) );
-        } else {
-            taddrRecipients.push_back( SendManyRecipient(address, nAmount, memo) );
-        }
-
-        nTotalOut += nAmount;
-    }
 
     std::vector<SaplingNoteEntry> saplingEntries;
     // find all unspent and unlocked notes in this zaddr