Miscellaneous cleanups:

* Limit HashPrefix construction and disallow assignment

* Give KnownFormats deleted copy members so that derived
  classes will give the right answers if queried with the
  std::is_copy_constructible/assignable traits.

* Replace SharedSingleton with a local static in
  LedgerFormats::getInstance() to be consistent with
  similar code in other places.  This also allows the
  LedgerFormats default constructor to be marked private
  so that the compiler enforces the design that
  LedgerFormats is a singleton type.

* Change return types of LedgerFormats::getInstance() and
  TxFormats::getInstance() from pointer to non-const to
  reference to const so as follow more established design
  guidelines for singletons.  This prevents pointers being
  mistaken for heap-allocated objects, and the const
  ensures the singleton isn't mutable.

* Change RippleAddress to inherit privately from
  CBase58Data instead of publicly.  This lets the compiler
  enforce that there are no unintended conversions from
  RippleAddress to CBase58Data.  This change allows us
  to remove a comment warning about unwanted conversions.

src/ripple/app/misc/SerializedLedger.cpp

@@ -46,7 +46,7 @@ SerializedLedgerEntry::SerializedLedgerEntry (
 
 void SerializedLedgerEntry::setSLEType ()
 {
-    mFormat = LedgerFormats::getInstance()->findByType (
+    mFormat = LedgerFormats::getInstance().findByType (
         static_cast <LedgerEntryType> (getFieldU16 (sfLedgerEntryType)));
 
     if (mFormat == nullptr)
@@ -65,7 +65,7 @@ void SerializedLedgerEntry::setSLEType ()
 SerializedLedgerEntry::SerializedLedgerEntry (LedgerEntryType type, uint256 const& index) :
     STObject (sfLedgerEntry), mIndex (index), mType (type), mMutable (true)
 {
-    mFormat = LedgerFormats::getInstance()->findByType (type);
+    mFormat = LedgerFormats::getInstance().findByType (type);
 
     if (mFormat == nullptr)
         throw std::runtime_error ("invalid ledger entry type");

src/ripple/app/misc/SerializedTransaction.cpp

@@ -29,7 +29,7 @@ SerializedTransaction::SerializedTransaction (TxType type)
     , mSigGood (false)
     , mSigBad (false)
 {
-    mFormat = TxFormats::getInstance()->findByType (type);
+    mFormat = TxFormats::getInstance().findByType (type);
 
     if (mFormat == nullptr)
     {
@@ -48,7 +48,7 @@ SerializedTransaction::SerializedTransaction (STObject const& object)
 {
     mType = static_cast <TxType> (getFieldU16 (sfTransactionType));
 
-    mFormat = TxFormats::getInstance()->findByType (mType);
+    mFormat = TxFormats::getInstance().findByType (mType);
 
     if (!mFormat)
     {
@@ -76,7 +76,7 @@ SerializedTransaction::SerializedTransaction (SerializerIterator& sit) : STObjec
     set (sit);
     mType = static_cast<TxType> (getFieldU16 (sfTransactionType));
 
-    mFormat = TxFormats::getInstance()->findByType (mType);
+    mFormat = TxFormats::getInstance().findByType (mType);
 
     if (!mFormat)
     {

src/ripple/data/protocol/HashPrefix.h

@@ -42,7 +42,6 @@ class HashPrefix
 private:
     std::uint32_t m_prefix;
 
-public:
     HashPrefix (char a, char b, char c)
         : m_prefix (0)
     {
@@ -52,6 +51,10 @@ public:
         m_prefix = m_prefix << 8;
     }
 
+public:
+    HashPrefix(HashPrefix const&) = delete;
+    HashPrefix& operator=(HashPrefix const&) = delete;
+
     /** Returns the hash prefix associated with this object */
     operator std::uint32_t () const
     {

src/ripple/data/protocol/KnownFormats.h

@@ -182,6 +182,9 @@ protected:
     virtual void addCommonFields (Item& item) = 0;
 
 private:
+    KnownFormats(KnownFormats const&) = delete;
+    KnownFormats& operator=(KnownFormats const&) = delete;
+
     std::vector <std::unique_ptr <Item>> m_formats;
     NameMap m_names;
     TypeMap m_types;

src/ripple/data/protocol/LedgerFormats.cpp

@@ -119,9 +119,11 @@ void LedgerFormats::addCommonFields (Item& item)
         ;
 }
 
-LedgerFormats* LedgerFormats::getInstance ()
+LedgerFormats const&
+LedgerFormats::getInstance ()
 {
-    return beast::SharedSingleton <LedgerFormats>::getInstance ();
+    static LedgerFormats instance;
+    return instance;
 }
 
 } // ripple

src/ripple/data/protocol/LedgerFormats.h

@@ -131,10 +131,11 @@ enum LedgerSpecificFlags
 */
 class LedgerFormats : public KnownFormats <LedgerEntryType>
 {
-public:
+private:
     LedgerFormats ();
 
-    static LedgerFormats* getInstance ();
+public:
+    static LedgerFormats const& getInstance ();
 
 private:
     void addCommonFields (Item& item);

src/ripple/data/protocol/RippleAddress.h

@@ -38,9 +38,8 @@ namespace ripple {
 // Used to hold addresses and parse and produce human formats.
 //
 // XXX This needs to be reworked to store data in uint160 and uint256.
-// Conversion to CBase58Data should only happen as needed.
 
-class RippleAddress : public CBase58Data
+class RippleAddress : private CBase58Data
 {
 private:
     typedef enum
@@ -229,10 +228,66 @@ public:
 
     static RippleAddress createSeedRandom ();
     static RippleAddress createSeedGeneric (std::string const& strText);
+
+    std::string ToString () const
+        {return static_cast<CBase58Data const&>(*this).ToString();}
+
+    template <class Hasher>
+    friend
+    void
+    hash_append(Hasher& hasher, RippleAddress const& value)
+    {
+        using beast::hash_append;
+        hash_append(hasher, static_cast<CBase58Data const&>(value));
+    }
+
+    friend
+    bool
+    operator==(RippleAddress const& lhs, RippleAddress const& rhs)
+    {
+        return static_cast<CBase58Data const&>(lhs) ==
+               static_cast<CBase58Data const&>(rhs);
+    }
+
+    friend
+    bool
+    operator <(RippleAddress const& lhs, RippleAddress const& rhs)
+    {
+        return static_cast<CBase58Data const&>(lhs) <
+               static_cast<CBase58Data const&>(rhs);
+    }
 };
 
 //------------------------------------------------------------------------------
 
+inline
+bool
+operator!=(RippleAddress const& lhs, RippleAddress const& rhs)
+{
+    return !(lhs == rhs);
+}
+
+inline
+bool
+operator >(RippleAddress const& lhs, RippleAddress const& rhs)
+{
+    return rhs < lhs;
+}
+
+inline
+bool
+operator<=(RippleAddress const& lhs, RippleAddress const& rhs)
+{
+    return !(rhs < lhs);
+}
+
+inline
+bool
+operator>=(RippleAddress const& lhs, RippleAddress const& rhs)
+{
+    return !(lhs < rhs);
+}
+
 /** RipplePublicKey */
 template <>
 struct RipplePublicKeyTraits::assign <RippleAddress>

src/ripple/data/protocol/STInteger.cpp

@@ -85,7 +85,7 @@ std::string STUInt16::getText () const
 {
     if (getFName () == sfLedgerEntryType)
     {
-        auto item = LedgerFormats::getInstance ()->findByType (
+        auto item = LedgerFormats::getInstance ().findByType (
             static_cast <LedgerEntryType> (value_));
 
         if (item != nullptr)
@@ -95,7 +95,7 @@ std::string STUInt16::getText () const
     if (getFName () == sfTransactionType)
     {
         TxFormats::Item const* const item =
-            TxFormats::getInstance()->findByType (static_cast <TxType> (value_));
+            TxFormats::getInstance().findByType (static_cast <TxType> (value_));
 
         if (item != nullptr)
             return item->getName ();
@@ -110,7 +110,7 @@ Json::Value STUInt16::getJson (int) const
     if (getFName () == sfLedgerEntryType)
     {
         LedgerFormats::Item const* const item =
-            LedgerFormats::getInstance ()->findByType (static_cast <LedgerEntryType> (value_));
+            LedgerFormats::getInstance ().findByType (static_cast <LedgerEntryType> (value_));
 
         if (item != nullptr)
             return item->getName ();
@@ -119,7 +119,7 @@ Json::Value STUInt16::getJson (int) const
     if (getFName () == sfTransactionType)
     {
         TxFormats::Item const* const item =
-            TxFormats::getInstance()->findByType (static_cast <TxType> (value_));
+            TxFormats::getInstance().findByType (static_cast <TxType> (value_));
 
         if (item != nullptr)
             return item->getName ();

src/ripple/data/protocol/STParsedJSON.cpp

@@ -204,7 +204,7 @@ bool STParsedJSON::parse (std::string const& json_name,
                     {
                         if (field == sfTransactionType)
                         {
-                            TxType const txType (TxFormats::getInstance()->
+                            TxType const txType (TxFormats::getInstance().
                                 findTypeByName (strValue));
 
                             data.push_back (new STUInt16 (field,
@@ -215,7 +215,7 @@ bool STParsedJSON::parse (std::string const& json_name,
                         }
                         else if (field == sfLedgerEntryType)
                         {
-                            LedgerEntryType const type (LedgerFormats::getInstance()->
+                            LedgerEntryType const type (LedgerFormats::getInstance().
                                 findTypeByName (strValue));
 
                             data.push_back (new STUInt16 (field,

src/ripple/data/protocol/TxFormats.cpp

@@ -102,11 +102,11 @@ void TxFormats::addCommonFields (Item& item)
         ;
 }
 
-TxFormats* TxFormats::getInstance ()
+TxFormats const&
+TxFormats::getInstance ()
 {
     static TxFormats instance;
-    //return SharedSingleton <TxFormats>::getInstance ();
+    return instance;
-    return &instance;
 }
 
 } // ripple

src/ripple/data/protocol/TxFormats.h

@@ -64,7 +64,7 @@ public:
     */
     TxFormats ();
 
-    static TxFormats* getInstance ();
+    static TxFormats const& getInstance ();
 };
 
 } // ripple