Clean up and modernize code:

This commit removes obsolete comments, dead or no longer useful
code, and workarounds for several issues that were present in older
compilers that we no longer support.

Specifically:

- It improves the transaction metadata handling class, simplifying
  its use and making it less error-prone.
- It reduces the footprint of the Serializer class by consolidating
  code and leveraging templates.
- It cleanups the ST* class hierarchy, removing dead code, improving
  and consolidating code to reduce complexity and code duplication.
- It shores up the handling of currency codes and the conversation
  between 160-bit currency codes and their string representation.
- It migrates beast::secure_erase to the ripple namespace and uses
  a call to OpenSSL_cleanse instead of the custom implementation.

src/ripple/ledger/TxMeta.h

@@ -29,13 +29,8 @@
 
 namespace ripple {
 
-// VFALCO Move to ripple/app/ledger/detail, rename to TxMeta
 class TxMeta
 {
-public:
-    using pointer = std::shared_ptr<TxMeta>;
-    using ref = const pointer&;
-
 private:
     struct CtorHelper
     {
@@ -49,32 +44,11 @@ private:
         CtorHelper);
 
 public:
-    TxMeta() : mLedger(0), mIndex(static_cast<std::uint32_t>(-1)), mResult(255)
-    {
-    }
-
-    TxMeta(uint256 const& txID, std::uint32_t ledger, std::uint32_t index)
-        : mTransactionID(txID)
-        , mLedger(ledger)
-        , mIndex(static_cast<std::uint32_t>(-1))
-        , mResult(255)
-    {
-    }
-
+    TxMeta(uint256 const& transactionID, std::uint32_t ledger);
     TxMeta(uint256 const& txID, std::uint32_t ledger, Blob const&);
     TxMeta(uint256 const& txID, std::uint32_t ledger, std::string const&);
     TxMeta(uint256 const& txID, std::uint32_t ledger, STObject const&);
 
-    void
-    init(uint256 const& transactionID, std::uint32_t ledger);
-    void
-    clear()
-    {
-        mNodes.clear();
-    }
-    void
-    swap(TxMeta&) noexcept;
-
     uint256 const&
     getTxID()
     {
@@ -101,16 +75,12 @@ public:
         return mIndex;
     }
 
-    bool
-    isNodeAffected(uint256 const&) const;
     void
     setAffectedNode(uint256 const&, SField const& type, std::uint16_t nodeType);
     STObject&
     getAffectedNode(SLE::ref node, SField const& type);  // create if needed
     STObject&
     getAffectedNode(uint256 const&);
-    const STObject&
-    peekAffectedNode(uint256 const&) const;
 
     /** Return a list of accounts affected by this transaction */
     boost::container::flat_set<AccountID>
@@ -151,9 +121,6 @@ public:
         return static_cast<bool>(mDelivered);
     }
 
-    static bool
-    thread(STObject& node, uint256 const& prevTxID, std::uint32_t prevLgrID);
-
 private:
     uint256 mTransactionID;
     std::uint32_t mLedger;

src/ripple/ledger/impl/ApplyStateTable.cpp

@@ -123,9 +123,7 @@ ApplyStateTable::apply(
     std::shared_ptr<Serializer> sMeta;
     if (!to.open())
     {
-        TxMeta meta;
-        // VFALCO Shouldn't TxMeta ctor do this?
-        meta.init(tx.getTransactionID(), to.seq());
+        TxMeta meta(tx.getTransactionID(), to.seq());
         if (deliver)
             meta.setDeliveredAmount(*deliver);
         Mods newMod;
@@ -526,12 +524,24 @@ ApplyStateTable::threadItem(TxMeta& meta, std::shared_ptr<SLE> const& sle)
 {
     key_type prevTxID;
     LedgerIndex prevLgrID;
+
     if (!sle->thread(meta.getTxID(), meta.getLgrSeq(), prevTxID, prevLgrID))
         return;
-    if (prevTxID.isZero())
-        return;
-    TxMeta::thread(
-        meta.getAffectedNode(sle, sfModifiedNode), prevTxID, prevLgrID);
+
+    if (!prevTxID.isZero())
+    {
+        auto& node = meta.getAffectedNode(sle, sfModifiedNode);
+
+        if (node.getFieldIndex(sfPreviousTxnID) == -1)
+        {
+            assert(node.getFieldIndex(sfPreviousTxnLgrSeq) == -1);
+            node.setFieldH256(sfPreviousTxnID, prevTxID);
+            node.setFieldU32(sfPreviousTxnLgrSeq, prevLgrID);
+        }
+
+        assert(node.getFieldH256(sfPreviousTxnID) == prevTxID);
+        assert(node.getFieldU32(sfPreviousTxnLgrSeq) == prevLgrID);
+    }
 }
 
 std::shared_ptr<SLE>

src/ripple/ledger/impl/TxMeta.cpp

@@ -26,8 +26,6 @@
 
 namespace ripple {
 
-// VFALCO TODO rename class to TransactionMeta
-
 template <class T>
 TxMeta::TxMeta(
     uint256 const& txid,
@@ -78,16 +76,14 @@ TxMeta::TxMeta(
 {
 }
 
-bool
-TxMeta::isNodeAffected(uint256 const& node) const
+TxMeta::TxMeta(uint256 const& transactionID, std::uint32_t ledger)
+    : mTransactionID(transactionID)
+    , mLedger(ledger)
+    , mIndex(static_cast<std::uint32_t>(-1))
+    , mResult(255)
+    , mNodes(sfAffectedNodes)
 {
-    for (auto const& n : mNodes)
-    {
-        if (n.getFieldH256(sfLedgerIndex) == node)
-            return true;
-    }
-
-    return false;
+    mNodes.reserve(32);
 }
 
 void
@@ -205,57 +201,6 @@ TxMeta::getAffectedNode(uint256 const& node)
     return *(mNodes.begin());  // Silence compiler warning.
 }
 
-const STObject&
-TxMeta::peekAffectedNode(uint256 const& node) const
-{
-    for (auto const& n : mNodes)
-    {
-        if (n.getFieldH256(sfLedgerIndex) == node)
-            return n;
-    }
-
-    Throw<std::runtime_error>("Affected node not found");
-    return *(mNodes.begin());  // Silence compiler warning.
-}
-
-void
-TxMeta::init(uint256 const& id, std::uint32_t ledger)
-{
-    mTransactionID = id;
-    mLedger = ledger;
-    mNodes = STArray(sfAffectedNodes, 32);
-    mDelivered = boost::optional<STAmount>();
-}
-
-void
-TxMeta::swap(TxMeta& s) noexcept
-{
-    assert((mTransactionID == s.mTransactionID) && (mLedger == s.mLedger));
-    mNodes.swap(s.mNodes);
-}
-
-bool
-TxMeta::thread(STObject& node, uint256 const& prevTxID, std::uint32_t prevLgrID)
-{
-    if (node.getFieldIndex(sfPreviousTxnID) == -1)
-    {
-        assert(node.getFieldIndex(sfPreviousTxnLgrSeq) == -1);
-        node.setFieldH256(sfPreviousTxnID, prevTxID);
-        node.setFieldU32(sfPreviousTxnLgrSeq, prevLgrID);
-        return true;
-    }
-
-    assert(node.getFieldH256(sfPreviousTxnID) == prevTxID);
-    assert(node.getFieldU32(sfPreviousTxnLgrSeq) == prevLgrID);
-    return false;
-}
-
-static bool
-compare(const STObject& o1, const STObject& o2)
-{
-    return o1.getFieldH256(sfLedgerIndex) < o2.getFieldH256(sfLedgerIndex);
-}
-
 STObject
 TxMeta::getAsObject() const
 {
@@ -276,7 +221,9 @@ TxMeta::addRaw(Serializer& s, TER result, std::uint32_t index)
     mIndex = index;
     assert((mResult == 0) || ((mResult > 100) && (mResult <= 255)));
 
-    mNodes.sort(compare);
+    mNodes.sort([](STObject const& o1, STObject const& o2) {
+        return o1.getFieldH256(sfLedgerIndex) < o2.getFieldH256(sfLedgerIndex);
+    });
 
     getAsObject().add(s);
 }

src/ripple/ledger/impl/View.cpp

@@ -44,9 +44,9 @@ addRaw(LedgerInfo const& info, Serializer& s)
 {
     s.add32(info.seq);
     s.add64(info.drops.drops());
-    s.add256(info.parentHash);
-    s.add256(info.txHash);
-    s.add256(info.accountHash);
+    s.addBitString(info.parentHash);
+    s.addBitString(info.txHash);
+    s.addBitString(info.accountHash);
     s.add32(info.parentCloseTime.time_since_epoch().count());
     s.add32(info.closeTime.time_since_epoch().count());
     s.add8(info.closeTimeResolution.count());