Add control functions to PcmStream

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

server/streamreader/control_error.hpp

@@ -0,0 +1,82 @@
+/***
+    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/>.
+***/
+
+#ifndef STREAMREADER_ERROR_HPP
+#define STREAMREADER_ERROR_HPP
+
+
+#include <system_error>
+
+
+// https://www.boost.org/doc/libs/develop/libs/outcome/doc/html/motivation/plug_error_code.html
+// https://akrzemi1.wordpress.com/examples/error_code-example/
+// https://breese.github.io/2017/05/12/customizing-error-codes.html
+// http://blog.think-async.com/2010/04/system-error-support-in-c0x-part-5.html
+
+
+enum class ControlErrc
+{
+    success = 0,
+
+    // Stream can not be controlled
+    can_not_control = 1,
+
+    // Stream property can_go_next is false
+    can_go_next_is_false = 2,
+    // Stream property can_go_previous is false
+    can_go_previous_is_false = 3,
+    // Stream property can_play is false
+    can_play_is_false = 4,
+    // Stream property can_pause is false
+    can_pause_is_false = 5,
+    // Stream property can_seek is false
+    can_seek_is_false = 6,
+    // Stream property can_control is false
+    can_control_is_false = 7,
+
+    // Invalid JSON was received by the server. An error occurred on the server while parsing the JSON text.
+    parse_error = -32700,
+    // The JSON sent is not a valid Request object.
+    invalid_request = -32600,
+    // The method does not exist / is not available.
+    method_not_found = -32601,
+    // Invalid method parameter(s).
+    invalid_params = -32602,
+    // Internal JSON-RPC error.
+    internal_error = -32603
+};
+
+namespace snapcast::error::control
+{
+const std::error_category& category();
+}
+
+
+
+namespace std
+{
+template <>
+struct is_error_code_enum<ControlErrc> : public std::true_type
+{
+};
+} // namespace std
+
+std::error_code make_error_code(ControlErrc);
+
+
+#endif