Persist changes to settings

Persist changes made to settings, if any, such that those changes can be
restored upon a reboot.

Use Cereal for serialization of the settings' properties. Since the
settings code is generated based on a system specific settings policy,
generate the serialization code as well such that only relevant settings
are serialized.

Resolves openbmc/openbmc#1764.

Change-Id: Id8bd84a9455cf4348b22f255d038b050d004eb7c
Signed-off-by: Deepak Kodihalli <dkodihal@in.ibm.com>

4 files changed, 146 insertions, 23 deletions

diff --git a/Makefile.am b/Makefile.am
index 65f95cb..55ea2d6 100755
--- a/Makefile.am
+++ b/Makefile.am
@@ -30,4 +30,5 @@ phosphor_settings_manager_CXXFLAGS = \
 
 phosphor_settings_manager_LDADD = \
 	$(PHOSPHOR_DBUS_INTERFACES_LIBS) \
-	$(SDBUSPLUS_LIBS)
+	$(SDBUSPLUS_LIBS) \
+	-lstdc++fs
diff --git a/configure.ac b/configure.ac
index 3ee9c6b..083d623 100644
--- a/configure.ac
+++ b/configure.ac
@@ -32,5 +32,12 @@ AS_IF([test "x$SETTINGS_YAML" == "x"], [SETTINGS_YAML="settings_example.yaml"])
 SETTINGSGEN="$PYTHON $srcdir/settings.py -i $SETTINGS_YAML"
 AC_SUBST(SETTINGSGEN)
 
+AC_ARG_VAR(SETTINGS_PERSIST_PATH, \
+    [Path of directory housing persisted settings.])
+AS_IF([test "x$SETTINGS_PERSIST_PATH" == "x"], \
+    [SETTINGS_PERSIST_PATH="/var/lib/phosphor-settings-manager/settings"])
+AC_DEFINE_UNQUOTED([SETTINGS_PERSIST_PATH], ["$SETTINGS_PERSIST_PATH"], \
+    [Path of directory housing persisted settings])
+
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT
diff --git a/settings_main.cpp b/settings_main.cpp
index 0d775e2..fbb9a0d 100644
--- a/settings_main.cpp
+++ b/settings_main.cpp
@@ -11,11 +11,10 @@ int main(int argc, char *argv[])
     // the object namespace and are not under a (settings) root. Hence register
     // "/" as the path.
     sdbusplus::server::manager::manager objManager(bus, "/");
+    bus.request_name(SETTINGS_BUSNAME);
 
     phosphor::settings::Manager mgr(bus);
 
-    bus.request_name(SETTINGS_BUSNAME);
-
     while(true)
     {
         bus.process_discard();
diff --git a/settings_manager.mako.hpp b/settings_manager.mako.hpp
index acdf66d..6a4f1bf 100644
--- a/settings_manager.mako.hpp
+++ b/settings_manager.mako.hpp
@@ -1,17 +1,23 @@
 ## This file is a template.  The comment below is emitted
 ## into the rendered file; feel free to edit this file.
 // WARNING: Generated header. Do not edit!
-
 <%
+from collections import defaultdict
 objects = list(settingsDict.viewkeys())
-ns_list = []
-includes = []
+sdbusplus_namespaces = []
+sdbusplus_includes = []
+interfaces = []
+props = defaultdict(list)
 
-def get_setting_type(setting_intf):
+def get_setting_sdbusplus_type(setting_intf):
     setting = "sdbusplus::" + setting_intf.replace('.', '::')
     i = setting.rfind('::')
     setting = setting[:i] + '::server::' + setting[i+2:]
     return setting
+
+def get_setting_type(setting_intf):
+    setting = setting_intf.replace('.', '::')
+    return setting
 %>\
 #pragma once
 
@@ -20,30 +26,130 @@ def get_setting_type(setting_intf):
     include = settingsDict[object]['Interface']
     include = include.replace('.', '/')
     include = include + "/server.hpp"
-    includes.append(include)
+    sdbusplus_includes.append(include)
 %>\
 % endfor
-% for i in set(includes):
+#include <cereal/archives/json.hpp>
+#include <fstream>
+#include <utility>
+#include <experimental/filesystem>
+#include "config.h"
+
+% for i in set(sdbusplus_includes):
 #include "${i}"
 % endfor
 
 % for object in objects:
 <%
-    ns = get_setting_type(settingsDict[object]['Interface'])
+    ns = get_setting_sdbusplus_type(settingsDict[object]['Interface'])
     i = ns.rfind('::')
     ns = ns[:i]
-    ns_list.append(ns)
+    sdbusplus_namespaces.append(ns)
 %>\
 % endfor
-% for n in set(ns_list):
-using namespace ${n};
-% endfor
 
 namespace phosphor
 {
 namespace settings
 {
 
+namespace fs = std::experimental::filesystem;
+
+% for n in set(sdbusplus_namespaces):
+using namespace ${n};
+% endfor
+
+% for object in objects:
+<%
+    intf = settingsDict[object]['Interface']
+    interfaces.append(intf)
+    if intf not in props:
+        for property, value in settingsDict[object]['Defaults'].items():
+            props[intf].append(property)
+%>\
+% endfor
+% for intf in set(interfaces):
+<%
+    ns = intf.split(".")
+    sdbusplus_type = get_setting_sdbusplus_type(intf)
+%>\
+% for n in ns:
+namespace ${n}
+{
+% endfor
+
+using Base = ${sdbusplus_type};
+<% parent = "sdbusplus::server::object::object" + "<" + sdbusplus_type + ">" %>\
+using Parent = ${parent};
+
+class Impl : public Parent
+{
+    public:
+        Impl(sdbusplus::bus::bus& bus, const char* path):
+            Parent(bus, path, true),
+            path(path)
+        {
+        }
+        virtual ~Impl() = default;
+
+% for arg in props[intf]:
+<% t = arg[:1].lower() + arg[1:] %>\
+        decltype(std::declval<Base>().${t}()) ${t}(decltype(std::declval<Base>().${t}()) value) override
+        {
+            auto result = Base::${t}();
+            if (value != result)
+            {
+                fs::path p(SETTINGS_PERSIST_PATH);
+                p /= path;
+                fs::create_directories(p.parent_path());
+                std::ofstream os(p.c_str(), std::ios::binary);
+                cereal::JSONOutputArchive oarchive(os);
+                result = Base::${t}(value);
+                oarchive(*this);
+            }
+            return result;
+        }
+        using Base::${t};
+
+    private:
+        fs::path path;
+% endfor
+};
+
+template<class Archive>
+void save(Archive& a,
+          const Impl& setting)
+{
+<%
+    args = ["setting." + p[:1].lower() + p[1:] + "()" for p in props[intf]]
+    args = ','.join(args)
+%>\
+    a(${args});
+}
+
+template<class Archive>
+void load(Archive& a,
+          Impl& setting)
+{
+% for arg in props[intf]:
+<% t = "setting." + arg[:1].lower() + arg[1:] + "()" %>\
+    decltype(${t}) ${arg}{};
+% endfor
+<%
+    args = ','.join(props[intf])
+%>\
+    a(${args});
+% for arg in props[intf]:
+<% t = "setting." + arg[:1].lower() + arg[1:] + "(" + arg + ")" %>\
+    ${t};
+% endfor
+}
+
+% for n in reversed(ns):
+} // namespace ${n}
+% endfor
+% endfor
+
 /** @class Manager
  *
  *  @brief Compose settings objects and put them on the bus.
@@ -63,10 +169,11 @@ class Manager
          */
         Manager(sdbusplus::bus::bus& bus)
         {
+            fs::path path{};
             settings =
                 std::make_tuple(
 % for index, object in enumerate(objects):
-<% type = get_setting_type(settingsDict[object]['Interface']) %>\
+<% type = get_setting_type(settingsDict[object]['Interface']) + "::Impl" %>\
                     std::make_unique<${type}>(
                         bus,
   % if index < len(settingsDict) - 1:
@@ -77,13 +184,22 @@ class Manager
 % endfor
 
 % for index, object in enumerate(objects):
-  % if 'Defaults' in settingsDict[object].viewkeys():
-    % for property, value in settingsDict[object]['Defaults'].items():
-            std::get<${index}>(settings)->
-                setPropertyByName("${property}", ${value});
-    % endfor
-  % endif
-            bus.emit_object_added("${object}");
+  % for property, value in settingsDict[object]['Defaults'].items():
+<% p = property[:1].lower() + property[1:] %>\
+            path = fs::path(SETTINGS_PERSIST_PATH) / "${object}";
+            if (fs::exists(path))
+            {
+                std::ifstream is(path.c_str(), std::ios::in);
+                cereal::JSONInputArchive iarchive(is);
+                iarchive(*std::get<${index}>(settings));
+            }
+            else
+            {
+                std::get<${index}>(settings)->
+                    ${get_setting_sdbusplus_type(settingsDict[object]['Interface'])}::${p}(${value});
+            }
+  % endfor
+            std::get<${index}>(settings)->emit_object_added();
 
 % endfor
         }
@@ -92,7 +208,7 @@ class Manager
         /* @brief Composition of settings objects. */
         std::tuple<
 % for index, object in enumerate(objects):
-<% type = get_setting_type(settingsDict[object]['Interface']) %>\
+<% type = get_setting_type(settingsDict[object]['Interface']) + "::Impl" %>\
   % if index < len(settingsDict) - 1:
             std::unique_ptr<${type}>,
   % else: