sensorhandler: use entity-map from json if filled

Step 4 of the transition from YAML to JSON will return the data from the
JSON file if present and valid, otherwise it'll fallback and return the
default example YAML present in the repository.

Tested: This was not tested.
Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I33c773fc53660a9eb5e27a8c8c3e231c64fe079d

3 files changed, 57 insertions, 5 deletions

diff --git a/entity_map_json.cpp b/entity_map_json.cpp
index 96ef61c..c0b836c 100644
--- a/entity_map_json.cpp
+++ b/entity_map_json.cpp
@@ -3,6 +3,7 @@
 #include <exception>
 #include <fstream>
 #include <ipmid/types.hpp>
+#include <memory>
 #include <nlohmann/json.hpp>
 #include <string>
 #include <utility>
@@ -14,9 +15,34 @@ namespace sensor
 
 extern const EntityInfoMap entities;
 
-const EntityInfoMap& getIpmiEntityRecords()
+EntityInfoMapContainer* EntityInfoMapContainer::getContainer()
 {
-    return entities;
+    static std::unique_ptr<EntityInfoMapContainer> instance;
+
+    if (!instance)
+    {
+        /* TODO: With multi-threading this would all need to be locked so
+         * the first thread to hit it would set it up.
+         */
+        EntityInfoMap builtEntityMap = buildEntityMapFromFile();
+        if (!builtEntityMap.empty())
+        {
+            instance = std::unique_ptr<EntityInfoMapContainer>(
+                new EntityInfoMapContainer(builtEntityMap));
+        }
+        else
+        {
+            instance = std::unique_ptr<EntityInfoMapContainer>(
+                new EntityInfoMapContainer(entities));
+        }
+    }
+
+    return instance.get();
+}
+
+const EntityInfoMap& EntityInfoMapContainer::getIpmiEntityRecords()
+{
+    return entityRecords;
 }
 
 EntityInfoMap buildEntityMapFromFile()
diff --git a/entity_map_json.hpp b/entity_map_json.hpp
index 54884ee..3ab4ff2 100644
--- a/entity_map_json.hpp
+++ b/entity_map_json.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <ipmid/types.hpp>
+#include <memory>
 #include <nlohmann/json.hpp>
 
 namespace ipmi
@@ -33,5 +34,24 @@ EntityInfoMap buildEntityMapFromFile();
  */
 EntityInfoMap buildJsonEntityMap(const nlohmann::json& data);
 
+/**
+ * @brief Owner of the EntityInfoMap.
+ */
+class EntityInfoMapContainer
+{
+  public:
+    /** Get ahold of the owner. */
+    static EntityInfoMapContainer* getContainer();
+    /** Get ahold of the records. */
+    const EntityInfoMap& getIpmiEntityRecords();
+
+  private:
+    EntityInfoMapContainer(const EntityInfoMap& entityRecords) :
+        entityRecords(entityRecords)
+    {
+    }
+    EntityInfoMap entityRecords;
+};
+
 } // namespace sensor
 } // namespace ipmi
diff --git a/sensorhandler.cpp b/sensorhandler.cpp
index b5e2f2f..bda7fda 100644
--- a/sensorhandler.cpp
+++ b/sensorhandler.cpp
@@ -602,7 +602,9 @@ ipmi::RspType<uint8_t, // respcount
     if (count.value_or(0) == getSdrCount)
     {
         // Get SDR count. This returns the total number of SDRs in the device.
-        const auto& entityRecords = ipmi::sensor::getIpmiEntityRecords();
+        const auto& entityRecords =
+            ipmi::sensor::EntityInfoMapContainer::getContainer()
+                ->getIpmiEntityRecords();
         sdrCount =
             ipmi::sensor::sensors.size() + frus.size() + entityRecords.size();
     }
@@ -771,7 +773,9 @@ ipmi_ret_t ipmi_fru_get_sdr(ipmi_request_t request, ipmi_response_t response,
     {
         // we have reached till end of fru, so assign the next record id to
         // 512(Max fru ID = 511) + Entity Record ID(may start with 0).
-        const auto& entityRecords = ipmi::sensor::getIpmiEntityRecords();
+        const auto& entityRecords =
+            ipmi::sensor::EntityInfoMapContainer::getContainer()
+                ->getIpmiEntityRecords();
         auto next_record_id =
             (entityRecords.size())
                 ? entityRecords.begin()->first + ENTITY_RECORD_ID_START
@@ -810,7 +814,9 @@ ipmi_ret_t ipmi_entity_get_sdr(ipmi_request_t request, ipmi_response_t response,
     get_sdr::SensorDataEntityRecord record{};
     auto dataLength = 0;
 
-    const auto& entityRecords = ipmi::sensor::getIpmiEntityRecords();
+    const auto& entityRecords =
+        ipmi::sensor::EntityInfoMapContainer::getContainer()
+            ->getIpmiEntityRecords();
     auto entity = entityRecords.begin();
     uint8_t entityRecordID;
     auto recordID = get_sdr::request::get_record_id(req);