From 2fd88093002ed7b54590166105ee9affed15cd03 Mon Sep 17 00:00:00 2001
From: Marko Bencun <marko.bencun@monetas.net>
Date: Sun, 23 Jul 2017 23:32:57 +0200
Subject: [PATCH] keystore GetKeys(): return result instead of writing to
 reference

Issue: #10905

By returning the result, a few useless lines can be removed.

Return-value-optimization means there should be no copy.

zcash: cherry picked from commit 5cb3da04b8882ca975b4e3d6c089c64bbaf67d0d
zcash: https://github.com/bitcoin/bitcoin/pull/10916
---
 src/keystore.h        | 18 +++++++-----------
 src/wallet/crypter.h  | 19 ++++++++-----------
 src/wallet/wallet.cpp |  5 +----
 3 files changed, 16 insertions(+), 26 deletions(-)

diff --git a/src/keystore.h b/src/keystore.h
index 69baf26e8..8246461aa 100644
--- a/src/keystore.h
+++ b/src/keystore.h
@@ -38,7 +38,7 @@ public:
     //! Check whether a key corresponding to a given address is present in the store.
     virtual bool HaveKey(const CKeyID &address) const =0;
     virtual bool GetKey(const CKeyID &address, CKey& keyOut) const =0;
-    virtual void GetKeys(std::set<CKeyID> &setAddress) const =0;
+    virtual std::set<CKeyID> GetKeys() const =0;
     virtual bool GetPubKey(const CKeyID &address, CPubKey& vchPubKeyOut) const =0;
 
     //! Support for BIP 0013 : see https://github.com/bitcoin/bips/blob/master/bip-0013.mediawiki
@@ -148,18 +148,14 @@ public:
         }
         return result;
     }
-    void GetKeys(std::set<CKeyID> &setAddress) const
+    std::set<CKeyID> GetKeys() const
     {
-        setAddress.clear();
-        {
-            LOCK(cs_KeyStore);
-            KeyMap::const_iterator mi = mapKeys.begin();
-            while (mi != mapKeys.end())
-            {
-                setAddress.insert((*mi).first);
-                mi++;
-            }
+        std::set<CKeyID> set_address;
+        LOCK(cs_KeyStore);
+        for (const auto& mi : mapKeys) {
+            set_address.insert(mi.first);
         }
+        return set_address;
     }
     bool GetKey(const CKeyID &address, CKey &keyOut) const
     {
diff --git a/src/wallet/crypter.h b/src/wallet/crypter.h
index 7b291cf04..e03cb287c 100644
--- a/src/wallet/crypter.h
+++ b/src/wallet/crypter.h
@@ -20,13 +20,13 @@ const unsigned int WALLET_CRYPTO_IV_SIZE = 16;
 /**
  * Private key encryption is done based on a CMasterKey,
  * which holds a salt and random encryption key.
- * 
+ *
  * CMasterKeys are encrypted using AES-256-CBC using a key
  * derived using derivation method nDerivationMethod
  * (0 == EVP_sha512()) and derivation iterations nDeriveIterations.
  * vchOtherDerivationParameters is provided for alternative algorithms
  * which may require more parameters (such as scrypt).
- * 
+ *
  * Wallet Private Keys are then encrypted using AES-256-CBC
  * with the double-sha256 of the public key as the IV, and the
  * master key's key as the encryption key (see keystore.[ch]).
@@ -186,21 +186,18 @@ public:
     }
     bool GetKey(const CKeyID &address, CKey& keyOut) const;
     bool GetPubKey(const CKeyID &address, CPubKey& vchPubKeyOut) const;
-    void GetKeys(std::set<CKeyID> &setAddress) const
+    std::set<CKeyID> GetKeys() const
     {
         LOCK(cs_KeyStore);
         if (!fUseCrypto)
         {
-            CBasicKeyStore::GetKeys(setAddress);
-            return;
+            return CBasicKeyStore::GetKeys();
         }
-        setAddress.clear();
-        CryptedKeyMap::const_iterator mi = mapCryptedKeys.begin();
-        while (mi != mapCryptedKeys.end())
-        {
-            setAddress.insert((*mi).first);
-            mi++;
+        std::set<CKeyID> set_address;
+        for (const auto& mi : mapCryptedKeys) {
+            set_address.insert(mi.first);
         }
+        return set_address;
     }
     virtual bool AddCryptedSproutSpendingKey(
         const libzcash::SproutPaymentAddress &address,
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index b8a141b1c..4a39156e2 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -4591,13 +4591,10 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64_t> &mapKeyBirth) const {
     // map in which we'll infer heights of other keys
     CBlockIndex *pindexMax = chainActive[std::max(0, chainActive.Height() - 144)]; // the tip can be reorganised; use a 144-block safety margin
     std::map<CKeyID, CBlockIndex*> mapKeyFirstBlock;
-    std::set<CKeyID> setKeys;
-    GetKeys(setKeys);
-    for (const CKeyID &keyid : setKeys) {
+    for (const CKeyID &keyid : GetKeys()) {
         if (mapKeyBirth.count(keyid) == 0)
             mapKeyFirstBlock[keyid] = pindexMax;
     }
-    setKeys.clear();
 
     // if there are no such keys, we're done
     if (mapKeyFirstBlock.empty())