Add ExtractAffectedKeys to script

This function finds all keys affected by a particular output script,
supporting everything ExtractDestinations supports (pay-to-pubkey,
pay-to-pubkeyhash, multisig) and recurses into subscripts (P2SH).

src/script.cpp

@@ -1474,6 +1474,42 @@ bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, vecto
     return true;
 }
 
+class CAffectedKeysVisitor : public boost::static_visitor<void> {
+private:
+    const CKeyStore &keystore;
+    std::vector<CKeyID> &vKeys;
+
+public:
+    CAffectedKeysVisitor(const CKeyStore &keystoreIn, std::vector<CKeyID> &vKeysIn) : keystore(keystoreIn), vKeys(vKeysIn) {}
+
+    void Process(const CScript &script) {
+        txnouttype type;
+        std::vector<CTxDestination> vDest;
+        int nRequired;
+        if (ExtractDestinations(script, type, vDest, nRequired)) {
+            BOOST_FOREACH(const CTxDestination &dest, vDest)
+                boost::apply_visitor(*this, dest);
+        }
+    }
+
+    void operator()(const CKeyID &keyId) {
+        if (keystore.HaveKey(keyId))
+            vKeys.push_back(keyId);
+    }
+
+    void operator()(const CScriptID &scriptId) {
+        CScript script;
+        if (keystore.GetCScript(scriptId, script))
+            Process(script);
+    }
+
+    void operator()(const CNoDestination &none) {}
+};
+
+void ExtractAffectedKeys(const CKeyStore &keystore, const CScript& scriptPubKey, std::vector<CKeyID> &vKeys) {
+    CAffectedKeysVisitor(keystore, vKeys).Process(scriptPubKey);
+}
+
 bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CTransaction& txTo, unsigned int nIn,
                   unsigned int flags, int nHashType)
 {

src/script.h

@@ -674,6 +674,7 @@ int ScriptSigArgsExpected(txnouttype t, const std::vector<std::vector<unsigned c
 bool IsStandard(const CScript& scriptPubKey);
 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);
 bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet);
 bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<CTxDestination>& addressRet, int& nRequiredRet);
 bool SignSignature(const CKeyStore& keystore, const CScript& fromPubKey, CTransaction& txTo, unsigned int nIn, int nHashType=SIGHASH_ALL);