Add policy::Table class

This class holds the error log policy data defined by
IBM's service people.  The raw data is stored in a JSON
file on the BMC, and loaded into the class on construction.

The policy data is a map of error messages (i.e.  the
xyz.openbmc_project.Foo.Error.Bar strings) to a list of
policy details structures.

Each details structure has:
* a search modifier - used to find the specific details
  entry for a specific error log message.
* a message - a customer facing description of the error
* an event ID - an ID defined by IBM that can be used to
                locate information about the error online.

An example of an entry of the JSON data it consumes is:
  {
    "dtls":[
      {
        "CEID":"ID 1",
        "mod":"mod 1",
        "msg":"Error 1"
      },
      {
        "CEID":"ID 2",
        "mod":"mod 2",
        "msg":"Error 2 "
      }
    ],
    "err":"xyz.openbmc_project.Error.Test1"
  }

A future commit will add the ability to find an entry.

Change-Id: I9869c15799914acf9cbc9d91ff714edb6e2512ef
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/policy_table.hpp b/policy_table.hpp
new file mode 100644
index 0000000..b6fade3
--- /dev/null
+++ b/policy_table.hpp
@@ -0,0 +1,90 @@
+#pragma once
+
+#include <map>
+#include <vector>
+#include "config.h"
+
+namespace ibm
+{
+namespace logging
+{
+namespace policy
+{
+
+
+/**
+ *  The details of a policy table entry:
+ *  - search modifier
+ *  - error message
+ *  - common error event ID
+ */
+struct Details
+{
+    std::string modifier;
+    std::string msg;
+    std::string ceid;
+};
+
+using DetailsList = std::vector<Details>;
+using PolicyMap = std::map<std::string, DetailsList>;
+
+/**
+ * @class Table
+ *
+ * This class wraps the error policy table data, and provides the
+ * ability to find a policy table entry based on the error and a
+ * search modifier.  This data contains additional information
+ * about error logs and may be system specific.
+ */
+class Table
+{
+    public:
+
+        Table() = delete;
+        ~Table() = default;
+        Table(const Table&) = default;
+        Table& operator=(const Table&) = default;
+        Table(Table&&) = default;
+        Table& operator=(Table&&) = default;
+
+        /**
+         * Constructor
+         *
+         * @param[in] jsonFile - the path to the policy JSON.
+         */
+        explicit Table(const std::string& jsonFile);
+
+        /**
+         * Says if the JSON has been loaded successfully.
+         *
+         * @return bool
+         */
+        inline bool isLoaded() const
+        {
+            return loaded;
+        }
+
+    private:
+
+        /**
+         * Loads the JSON data into the PolicyMap map
+         *
+         * @param[in] jsonFile - the path to the .json file
+         */
+        void load(const std::string& jsonFile);
+
+        /**
+         * Reflects if the JSON was successfully loaded or not.
+         */
+        bool loaded = false;
+
+        /**
+         * The policy table
+         */
+        PolicyMap policies;
+};
+
+
+}
+}
+}