Add [features] section to .cfg:

This non-production config section allows features to be enabled
by listing their text descriptions, one line each, in the config
section titled "features".

NOTE: Feature names with leading or trailing whitespace, or
      containing an equals sign ('=') are not supported.

Builds/VisualStudio2013/RippleD.vcxproj

@@ -2751,6 +2751,8 @@
     </ClInclude>
     <ClInclude Include="..\..\src\ripple\protocol\ErrorCodes.h">
     </ClInclude>
+    <ClInclude Include="..\..\src\ripple\protocol\Feature.h">
+    </ClInclude>
     <ClInclude Include="..\..\src\ripple\protocol\HashPrefix.h">
     </ClInclude>
     <ClCompile Include="..\..\src\ripple\protocol\impl\AccountID.cpp">
@@ -2773,6 +2775,10 @@
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='debug|x64'">True</ExcludedFromBuild>
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='release|x64'">True</ExcludedFromBuild>
     </ClCompile>
+    <ClCompile Include="..\..\src\ripple\protocol\impl\Feature.cpp">
+      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='debug|x64'">True</ExcludedFromBuild>
+      <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='release|x64'">True</ExcludedFromBuild>
+    </ClCompile>
     <ClCompile Include="..\..\src\ripple\protocol\impl\HashPrefix.cpp">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='debug|x64'">True</ExcludedFromBuild>
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='release|x64'">True</ExcludedFromBuild>
@@ -2945,6 +2951,8 @@
     </ClInclude>
     <ClInclude Include="..\..\src\ripple\protocol\SOTemplate.h">
     </ClInclude>
+    <ClInclude Include="..\..\src\ripple\protocol\st.h">
+    </ClInclude>
     <ClInclude Include="..\..\src\ripple\protocol\STAccount.h">
     </ClInclude>
     <ClInclude Include="..\..\src\ripple\protocol\STAmount.h">

Builds/VisualStudio2013/RippleD.vcxproj.filters

@@ -3471,6 +3471,9 @@
     <ClInclude Include="..\..\src\ripple\protocol\ErrorCodes.h">
       <Filter>ripple\protocol</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\src\ripple\protocol\Feature.h">
+      <Filter>ripple\protocol</Filter>
+    </ClInclude>
     <ClInclude Include="..\..\src\ripple\protocol\HashPrefix.h">
       <Filter>ripple\protocol</Filter>
     </ClInclude>
@@ -3489,6 +3492,9 @@
     <ClCompile Include="..\..\src\ripple\protocol\impl\ErrorCodes.cpp">
       <Filter>ripple\protocol\impl</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\src\ripple\protocol\impl\Feature.cpp">
+      <Filter>ripple\protocol\impl</Filter>
+    </ClCompile>
     <ClCompile Include="..\..\src\ripple\protocol\impl\HashPrefix.cpp">
       <Filter>ripple\protocol\impl</Filter>
     </ClCompile>
@@ -3651,6 +3657,9 @@
     <ClInclude Include="..\..\src\ripple\protocol\SOTemplate.h">
       <Filter>ripple\protocol</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\src\ripple\protocol\st.h">
+      <Filter>ripple\protocol</Filter>
+    </ClInclude>
     <ClInclude Include="..\..\src\ripple\protocol\STAccount.h">
       <Filter>ripple\protocol</Filter>
     </ClInclude>

src/ripple/app/tx/impl/Transactor.h

@@ -29,23 +29,25 @@ namespace ripple {
 struct PreflightContext
 {
 public:
-    explicit PreflightContext(STTx const& tx_,
-        Rules const& rules_, ApplyFlags flags_,
-            SigVerify verify_,
-                beast::Journal j_ = {})
-        : tx(tx_)
-        , rules(rules_)
-        , flags(flags_)
-        , verify(verify_)
-        , j(j_)
-    {
-    }
-
     STTx const& tx;
     Rules const& rules;
     ApplyFlags flags;
     SigVerify verify;
+    Config const& config;
     beast::Journal j;
+
+    PreflightContext(STTx const& tx_,
+        Rules const& rules_, ApplyFlags flags_,
+            SigVerify verify_, Config const& config_,
+                beast::Journal j_)
+        : tx(tx_)
+        , rules(rules_)
+        , flags(flags_)
+        , verify(verify_)
+        , config(config_)
+        , j(j_)
+    {
+    }
 };
 
 class Transactor

src/ripple/app/tx/impl/apply.cpp

@@ -86,8 +86,8 @@ preflight (Rules const& rules, STTx const& tx,
 {
     try
     {
-        PreflightContext pfctx(
+        PreflightContext pfctx(tx,
-            tx, rules, flags, verify, j);
+            rules, flags, verify, config, j);
         return invoke_preflight(pfctx);
     }
     catch (std::exception const& e)

src/ripple/core/Config.h

@@ -21,6 +21,7 @@
 #define RIPPLE_CORE_CONFIG_H_INCLUDED
 
 #include <ripple/basics/BasicConfig.h>
+#include <ripple/basics/base_uint.h>
 #include <ripple/protocol/SystemParameters.h>
 #include <ripple/protocol/RippleAddress.h>
 #include <ripple/json/json_value.h>
@@ -36,6 +37,7 @@
 #include <map>
 #include <string>
 #include <type_traits>
+#include <unordered_set>
 #include <vector>
 
 namespace ripple {
@@ -53,6 +55,8 @@ countSectionEntries (IniFileSections& secSource, std::string const& strSection);
 IniFileSections::mapped_type*
 getIniFileSection (IniFileSections& secSource, std::string const& strSection);
 
+class Rules;
+
 //------------------------------------------------------------------------------
 
 enum SizedItemName
@@ -257,6 +261,8 @@ public:
     boost::optional<boost::asio::ip::address_v4> rpc_ip;
     boost::optional<std::uint16_t> rpc_port;
 
+    std::unordered_set<uint256, beast::uhash<>> features;
+
 public:
     Config ();
 

src/ripple/core/impl/Config.cpp

@@ -22,6 +22,7 @@
 #include <ripple/core/ConfigSections.h>
 #include <ripple/basics/Log.h>
 #include <ripple/json/json_reader.h>
+#include <ripple/protocol/Feature.h>
 #include <ripple/protocol/SystemParameters.h>
 #include <ripple/net/HTTPClient.h>
 #include <beast/http/URL.h>
@@ -553,6 +554,12 @@ void Config::loadFromString (std::string const& fileContents)
 
     if (getSingleSection (secConfig, SECTION_DEBUG_LOGFILE, strTemp))
         DEBUG_LOGFILE       = strTemp;
+
+    {
+        auto const part = section("features");
+        for(auto const& s : part.values())
+            features.insert(feature(s));
+    }
 }
 
 int Config::getSize (SizedItemName item) const

src/ripple/ledger/ReadView.h

@@ -26,10 +26,12 @@
 #include <ripple/protocol/Protocol.h>
 #include <ripple/protocol/STLedgerEntry.h>
 #include <ripple/protocol/STTx.h>
+#include <beast/hash/uhash.h>
 #include <boost/optional.hpp>
 #include <cassert>
 #include <cstdint>
 #include <memory>
+#include <unordered_set>
 
 namespace ripple {
 
@@ -137,7 +139,9 @@ public:
 
     /** Returns `true` if a feature is enabled. */
     bool
-    enabled (uint256 const& feature) const;
+    enabled (uint256 const& id,
+        std::unordered_set<uint256,
+            beast::uhash<>> const& presets) const;
 
     /** Returns `true` if these rules don't match the ledger. */
     bool

src/ripple/ledger/impl/ReadView.cpp

@@ -86,11 +86,15 @@ Rules::Rules (DigestAwareReadView const& ledger)
 }
 
 bool
-Rules::enabled (uint256 const& feature) const
+Rules::enabled (uint256 const& id,
+    std::unordered_set<uint256,
+        beast::uhash<>> const& presets) const
 {
+    if (presets.count(id) > 0)
+        return true;
     if (! impl_)
         return false;
-    return impl_->enabled(feature);
+    return impl_->enabled(id);
 }
 
 bool

src/ripple/protocol/Feature.h

@@ -0,0 +1,39 @@
+//------------------------------------------------------------------------------
+/*
+    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.
+*/
+//==============================================================================
+
+#ifndef RIPPLE_PROTOCOL_FEATURE_H_INCLUDED
+#define RIPPLE_PROTOCOL_FEATURE_H_INCLUDED
+
+#include <ripple/basics/base_uint.h>
+#include <string>
+
+namespace ripple {
+
+/** Convert feature description to feature id. */
+/** @{ */
+uint256
+feature (std::string const& name);
+
+uint256
+feature (const char* name);
+/** @} */
+
+} // ripple
+
+#endif

src/ripple/protocol/impl/Feature.cpp

@@ -0,0 +1,48 @@
+//------------------------------------------------------------------------------
+/*
+    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/protocol/digest.h>
+#include <ripple/protocol/Feature.h>
+#include <cstring>
+
+namespace ripple {
+
+static
+uint256
+feature (char const* s, std::size_t n)
+{
+    sha512_half_hasher h;
+    h(s, n);
+    return static_cast<uint256>(h);
+}
+
+uint256
+feature (std::string const& name)
+{
+    return feature(name.c_str(), name.size());
+}
+
+uint256
+feature (const char* name)
+{
+    return feature(name, std::strlen(name));
+}
+
+} // ripple

src/ripple/unity/protocol.cpp

@@ -24,6 +24,7 @@
 #include <ripple/protocol/impl/ByteOrder.cpp>
 #include <ripple/protocol/impl/digest.cpp>
 #include <ripple/protocol/impl/ErrorCodes.cpp>
+#include <ripple/protocol/impl/Feature.cpp>
 #include <ripple/protocol/impl/HashPrefix.cpp>
 #include <ripple/protocol/impl/Indexes.cpp>
 #include <ripple/protocol/impl/Keylet.cpp>