Add control functions to PcmStream

-move json parsing to Server class
-improve error handling with the new ErrorCode object

server/streamreader/control_error.cpp

@@ -0,0 +1,89 @@
+/***
+    This file is part of snapcast
+    Copyright (C) 2014-2021  Johannes Pohl
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "control_error.hpp"
+
+namespace snapcast::error::control
+{
+
+namespace detail
+{
+
+struct category : public std::error_category
+{
+public:
+    const char* name() const noexcept override;
+    std::string message(int value) const override;
+};
+
+
+const char* category::name() const noexcept
+{
+    return "control";
+}
+
+std::string category::message(int value) const
+{
+    switch (static_cast<ControlErrc>(value))
+    {
+        case ControlErrc::success:
+            return "Success";
+        case ControlErrc::can_not_control:
+            return "Stream can not be controlled";
+        case ControlErrc::can_go_previous_is_false:
+            return "Stream property can_go_previous is false";
+        case ControlErrc::can_play_is_false:
+            return "Stream property can_play is false";
+        case ControlErrc::can_pause_is_false:
+            return "Stream property can_pause is false";
+        case ControlErrc::can_seek_is_false:
+            return "Stream property can_seek is false";
+        case ControlErrc::can_control_is_false:
+            return "Stream property can_control is false";
+        case ControlErrc::parse_error:
+            return "Parse error";
+        case ControlErrc::invalid_request:
+            return "Invalid request";
+        case ControlErrc::method_not_found:
+            return "Method not found";
+        case ControlErrc::invalid_params:
+            return "Invalid params";
+        case ControlErrc::internal_error:
+            return "Internal error";
+        default:
+            return "Unknown";
+    }
+}
+
+} // namespace detail
+
+const std::error_category& category()
+{
+    // The category singleton
+    static detail::category instance;
+    return instance;
+}
+
+} // namespace snapcast::error::control
+
+std::error_code make_error_code(ControlErrc errc)
+{
+    // Create an error_code with the original mpg123 error value
+    // and the mpg123 error category.
+    return std::error_code(static_cast<int>(errc), snapcast::error::control::category());
+}