regulators: Create exception_utils namespace

This namespace contains utility functions for handling exceptions.

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: Ie945c7882cdede398af56dcd2d2c3c9c70320e92
diff --git a/phosphor-regulators/src/exception_utils.cpp b/phosphor-regulators/src/exception_utils.cpp
new file mode 100644
index 0000000..dc7f9b7
--- /dev/null
+++ b/phosphor-regulators/src/exception_utils.cpp
@@ -0,0 +1,62 @@
+/**
+ * Copyright © 2020 IBM Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "exception_utils.hpp"
+
+namespace phosphor::power::regulators::exception_utils
+{
+
+std::vector<std::string> getMessages(const std::exception& e)
+{
+    std::vector<std::string> messages{};
+    internal::getMessages(e, messages);
+    return messages;
+}
+
+void log(const std::exception& e)
+{
+    std::vector<std::string> messages = getMessages(e);
+    for (const std::string& message : messages)
+    {
+        journal::logErr(message);
+    }
+}
+
+namespace internal
+{
+
+void getMessages(const std::exception& e, std::vector<std::string>& messages)
+{
+    // If this exception is nested, get messages from inner exception(s)
+    try
+    {
+        std::rethrow_if_nested(e);
+    }
+    catch (const std::exception& inner)
+    {
+        getMessages(inner, messages);
+    }
+    catch (...)
+    {
+    }
+
+    // Append error message from this exception
+    messages.emplace_back(e.what());
+}
+
+} // namespace internal
+
+} // namespace phosphor::power::regulators::exception_utils
diff --git a/phosphor-regulators/src/exception_utils.hpp b/phosphor-regulators/src/exception_utils.hpp
new file mode 100644
index 0000000..825b155
--- /dev/null
+++ b/phosphor-regulators/src/exception_utils.hpp
@@ -0,0 +1,77 @@
+/**
+ * Copyright © 2020 IBM Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include "journal.hpp"
+
+#include <exception>
+#include <string>
+#include <vector>
+
+/**
+ * @namespace exception_utils
+ *
+ * Contains utility functions for handling exceptions.
+ */
+namespace phosphor::power::regulators::exception_utils
+{
+
+/**
+ * Gets the error messages from the specified exception and any nested inner
+ * exceptions.
+ *
+ * If the exception contains nested inner exceptions, the messages in the
+ * returned vector will be ordered from innermost exception to outermost
+ * exception.
+ *
+ * @param e exception
+ * @return error messages from exceptions
+ */
+std::vector<std::string> getMessages(const std::exception& e);
+
+/**
+ * Logs the specified exception to the systemd journal.
+ *
+ * Gets the error messages from the specified exception and any nested inner
+ * exceptions.
+ *
+ * Logs each error message to the journal with a priority value of 'ERR'.
+ *
+ * @param e exception
+ */
+void log(const std::exception& e);
+
+/*
+ * Internal implementation details
+ */
+namespace internal
+{
+
+/**
+ * Gets the error messages from the specified exception and any nested inner
+ * exceptions.
+ *
+ * Stores the error messages in the specified vector, from innermost exception
+ * to outermost exception.
+ *
+ * @param e exception
+ * @param messages vector where error messages will be stored
+ */
+void getMessages(const std::exception& e, std::vector<std::string>& messages);
+
+} // namespace internal
+
+} // namespace phosphor::power::regulators::exception_utils
diff --git a/phosphor-regulators/src/meson.build b/phosphor-regulators/src/meson.build
index aa8921c..d8616f6 100644
--- a/phosphor-regulators/src/meson.build
+++ b/phosphor-regulators/src/meson.build
@@ -7,6 +7,7 @@
     'chassis.cpp',
     'config_file_parser.cpp',
     'device.cpp',
+    'exception_utils.cpp',
     'id_map.cpp',
     'pmbus_utils.cpp',
     'system.cpp',