Refactor View classes:

The View hierarchy of classes is reorganized to include new
classes with member functions moved and renamed, to solve
defects in the original design:

OpenView accumulates raw state and tx changes and
can be applied to the base. ApplyView accumulates changes
for a single transaction, including metadata, and can be
applied to an OpenView. The Sandbox allows changes with
the option to apply or throw them out. The PaymentSandbox
provides a sandbox with account credit deferral.

Call sites are changed to use the class appropriate for
the task.

src/ripple/ledger/impl/OpenView.cpp

@@ -0,0 +1,253 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2012, 2013 Ripple Labs Inc.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include <BeastConfig.h>
+#include <ripple/ledger/OpenView.h>
+#include <ripple/basics/contract.h>
+
+namespace ripple {
+
+open_ledger_t const open_ledger {};
+
+//------------------------------------------------------------------------------
+
+class OpenView::txs_iter_impl
+    : public txs_type::iter_base
+{
+private:
+    bool metadata_;
+    txs_map::const_iterator iter_;
+
+public:
+    explicit
+    txs_iter_impl (bool metadata,
+            txs_map::const_iterator iter)
+        : metadata_(metadata)
+        , iter_(iter)
+    {
+    }
+
+    std::unique_ptr<base_type>
+    copy() const override
+    {
+        return std::make_unique<
+            txs_iter_impl>(
+                metadata_, iter_);
+    }
+
+    bool
+    equal (base_type const& impl) const override
+    {
+        auto const& other = dynamic_cast<
+            txs_iter_impl const&>(impl);
+        return iter_ == other.iter_;
+    }
+
+    void
+    increment() override
+    {
+        ++iter_;
+    }
+
+    value_type
+    dereference() const override
+    {
+        value_type result;
+        {
+            SerialIter sit(
+                iter_->second.first->slice());
+            result.first = std::make_shared<
+                STTx const>(sit);
+        }
+        if (metadata_)
+        {
+            SerialIter sit(
+                iter_->second.second->slice());
+            result.second = std::make_shared<
+                STObject const>(sit, sfMetadata);
+        }
+        return result;
+    }
+};
+
+//------------------------------------------------------------------------------
+
+OpenView::OpenView (open_ledger_t,
+    ReadView const* base,
+        std::shared_ptr<void const> hold)
+    : info_ (base->info())
+    , base_ (base)
+    , hold_ (std::move(hold))
+{
+    info_.open = true;
+    info_.seq = base_->info().seq + 1;
+    info_.parentCloseTime = base_->info().closeTime;
+}
+
+OpenView::OpenView (ReadView const* base,
+        std::shared_ptr<void const> hold)
+    : info_ (base->info())
+    , base_ (base)
+    , hold_ (std::move(hold))
+{
+}
+
+std::size_t
+OpenView::txCount() const
+{
+    return txs_.size();
+}
+
+void
+OpenView::apply (TxsRawView& to) const
+{
+    items_.apply(to);
+    for (auto const& item : txs_)
+        to.rawTxInsert (item.first,
+            item.second.first,
+                item.second.second);
+}
+
+//---
+
+LedgerInfo const&
+OpenView::info() const
+{
+    return info_;
+}
+
+Fees const&
+OpenView::fees() const
+{
+    return base_->fees();
+}
+
+bool
+OpenView::exists (Keylet const& k) const
+{
+    return items_.exists(*base_, k);
+}
+
+auto
+OpenView::succ (key_type const& key,
+    boost::optional<key_type> last) const ->
+        boost::optional<key_type>
+{
+    return items_.succ(*base_, key, last);
+}
+
+std::shared_ptr<SLE const>
+OpenView::read (Keylet const& k) const
+{
+    return items_.read(*base_, k);
+}
+
+auto
+OpenView::txsBegin() const ->
+    std::unique_ptr<txs_type::iter_base>
+{
+    return std::make_unique<
+        txs_iter_impl>(
+            closed(), txs_.cbegin());
+}
+
+auto
+OpenView::txsEnd() const ->
+    std::unique_ptr<txs_type::iter_base>
+{
+    return std::make_unique<
+        txs_iter_impl>(
+            closed(), txs_.cend());
+}
+
+bool
+OpenView::txExists (key_type const& key) const
+{
+    return txs_.find(key) != txs_.end();
+}
+
+auto
+OpenView::txRead (key_type const& key) const ->
+    tx_type
+{
+    auto const iter = txs_.find(key);
+    if (iter == txs_.end())
+        return base_->txRead(key);
+    auto const& item = iter->second;
+    auto stx = std::make_shared<STTx const
+        >(SerialIter{ item.first->slice() });
+    decltype(tx_type::second) sto;
+    if (item.second)
+        sto = std::make_shared<STObject const>(
+                SerialIter{ item.second->slice() },
+                    sfMetadata);
+    else
+        sto = nullptr;
+    return { std::move(stx), std::move(sto) };
+}
+
+//---
+
+void
+OpenView::rawErase(
+    std::shared_ptr<SLE> const& sle)
+{
+    items_.erase(sle);
+}
+
+void
+OpenView::rawInsert(
+    std::shared_ptr<SLE> const& sle)
+{
+    items_.insert(sle);
+}
+
+void
+OpenView::rawReplace(
+    std::shared_ptr<SLE> const& sle)
+{
+    items_.replace(sle);
+}
+
+void
+OpenView::rawDestroyXRP(
+    std::uint64_t feeDrops)
+{
+    items_.destroyXRP(feeDrops);
+    // VFALCO Deduct from info_.totalDrops ?
+    //        What about child views?
+}
+
+//---
+
+void
+OpenView::rawTxInsert (key_type const& key,
+    std::shared_ptr<Serializer const>
+        const& txn, std::shared_ptr<
+            Serializer const>
+                const& metaData)
+{
+    auto const result = txs_.emplace (key,
+        std::make_pair(txn, metaData));
+    if (! result.second)
+        LogicError("rawTxInsert: duplicate TX id" +
+            to_string(key));
+}
+
+} // ripple