wallet: Add GetClosestWalletFeature function

Given a version number, get the closest supported WalletFeature
for a version number.

Author: achow101

src/wallet/walletutil.cpp

@@ -75,3 +75,16 @@ bool IsFeatureSupported(int wallet_version, int feature_version)
 {
     return wallet_version >= feature_version;
 }
+
+WalletFeature GetClosestWalletFeature(int version)
+{
+    if (version >= FEATURE_LATEST) return FEATURE_LATEST;
+    if (version >= FEATURE_PRE_SPLIT_KEYPOOL) return FEATURE_PRE_SPLIT_KEYPOOL;
+    if (version >= FEATURE_NO_DEFAULT_KEY) return FEATURE_NO_DEFAULT_KEY;
+    if (version >= FEATURE_HD_SPLIT) return FEATURE_HD_SPLIT;
+    if (version >= FEATURE_HD) return FEATURE_HD;
+    if (version >= FEATURE_COMPRPUBKEY) return FEATURE_COMPRPUBKEY;
+    if (version >= FEATURE_WALLETCRYPT) return FEATURE_WALLETCRYPT;
+    if (version >= FEATURE_BASE) return FEATURE_BASE;
+    return static_cast<WalletFeature>(0);
+}

src/wallet/walletutil.h

@@ -30,6 +30,7 @@ enum WalletFeature
 };
 
 bool IsFeatureSupported(int wallet_version, int feature_version);
+WalletFeature GetClosestWalletFeature(int version);
 
 enum WalletFlags : uint64_t {
     // wallet flags in the upper section (> 1 << 31) will lead to not opening the wallet if flag is unknown