Add type wsrep::xid

Create type `wsrep::xid`, and change all signatures that take
`std::string xid` to take `wsrep::xid xid`.

include/wsrep/client_state.hpp

@@ -41,6 +41,7 @@
 #include "lock.hpp"
 #include "buffer.hpp"
 #include "thread.hpp"
+#include "xid.hpp"
 
 namespace wsrep
 {
@@ -533,7 +534,7 @@ namespace wsrep
          *
          * @param xid transaction id
          */
-        void assign_xid(const std::string& xid)
+        void assign_xid(const wsrep::xid& xid)
         {
             transaction_.assign_xid(xid);
         }
@@ -544,7 +545,7 @@ namespace wsrep
          * The purpose of this method is to restore transaction state
          * during recovery of a prepared XA transaction.
          */
-        int restore_xid(std::string& xid)
+        int restore_xid(const wsrep::xid& xid)
         {
             return transaction_.restore_to_prepared_state(xid);
         }
@@ -562,7 +563,7 @@ namespace wsrep
          * @return Zero on success, non-zero on error. In case of error
          *         the client_state's current_error is set
          */
-        int commit_by_xid(const std::string& xid)
+        int commit_by_xid(const wsrep::xid& xid)
         {
             return transaction_.commit_or_rollback_by_xid(xid, true);
         }
@@ -580,7 +581,7 @@ namespace wsrep
          * @return Zero on success, non-zero on error. In case of error
          *         the client_state's current_error is set
          */
-        int rollback_by_xid(const std::string& xid)
+        int rollback_by_xid(const wsrep::xid& xid)
         {
             return transaction_.commit_or_rollback_by_xid(xid, false);
         }

include/wsrep/high_priority_service.hpp

@@ -24,6 +24,7 @@
 #ifndef WSREP_HIGH_PRIORITY_SERVICE_HPP
 #define WSREP_HIGH_PRIORITY_SERVICE_HPP
 
+#include "xid.hpp"
 #include "server_state.hpp"
 
 namespace wsrep
@@ -97,7 +98,7 @@ namespace wsrep
             const wsrep::ws_handle& ws_handle,
             const wsrep::ws_meta& ws_meta,
             const wsrep::const_buffer& data,
-            const std::string& xid) = 0;
+            const wsrep::xid& xid) = 0;
 
         /**
          * Remove fragments belonging to streaming transaction.

include/wsrep/server_state.hpp

@@ -90,6 +90,7 @@
 #include "logger.hpp"
 #include "provider.hpp"
 #include "compiler.hpp"
+#include "xid.hpp"
 
 #include <vector>
 #include <string>
@@ -268,7 +269,7 @@ namespace wsrep
          * Find a streaming applier matching xid
          */
         wsrep::high_priority_service* find_streaming_applier(
-            const std::string& xid) const;
+            const wsrep::xid& xid) const;
 
         /**
          * Load WSRep provider.

include/wsrep/storage_service.hpp

@@ -32,6 +32,7 @@
 #include "transaction_id.hpp"
 #include "id.hpp"
 #include "buffer.hpp"
+#include "xid.hpp"
 
 namespace wsrep
 {
@@ -64,7 +65,7 @@ namespace wsrep
                                     wsrep::transaction_id client_id,
                                     int flags,
                                     const wsrep::const_buffer& data,
-                                    const std::string& xid) = 0;
+                                    const wsrep::xid& xid) = 0;
 
         /**
          * Update fragment meta data after certification process.

include/wsrep/transaction.hpp

@@ -29,6 +29,7 @@
 #include "sr_key_set.hpp"
 #include "buffer.hpp"
 #include "client_service.hpp"
+#include "xid.hpp"
 
 #include <cassert>
 #include <vector>
@@ -127,21 +128,21 @@ namespace wsrep
             return !xid_.empty();
         }
 
-        void assign_xid(const std::string& xid)
+        void assign_xid(const wsrep::xid& xid)
         {
             assert(active());
             assert(xid_.empty());
             xid_ = xid;
         }
 
-        const std::string xid() const
+        const wsrep::xid xid() const
         {
             return xid_;
         }
 
-        int restore_to_prepared_state(const std::string& xid);
+        int restore_to_prepared_state(const wsrep::xid& xid);
 
-        int commit_or_rollback_by_xid(const std::string& xid, bool commit);
+        int commit_or_rollback_by_xid(const wsrep::xid& xid, bool commit);
 
         bool pa_unsafe() const { return pa_unsafe_; }
         void pa_unsafe(bool pa_unsafe) { pa_unsafe_ = pa_unsafe; }
@@ -273,7 +274,7 @@ namespace wsrep
         wsrep::streaming_context streaming_context_;
         wsrep::sr_key_set sr_keys_;
         wsrep::mutable_buffer apply_error_buf_;
-        std::string xid_;
+        wsrep::xid xid_;
     };
 
     static inline const char* to_c_string(enum wsrep::transaction::state state)

include/wsrep/xid.hpp

@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2019 Codership Oy <info@codership.com>
+ *
+ * This file is part of wsrep-lib.
+ *
+ * Wsrep-lib 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Wsrep-lib 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 wsrep-lib.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef WSREP_XID_HPP
+#define WSREP_XID_HPP
+
+#include <iosfwd>
+#include <string>
+
+namespace wsrep
+{
+    class xid
+    {
+    public:
+        xid() : xid_() { }
+        xid(const std::string& str) : xid_(str) { }
+        xid(const char* s) : xid_(s) { }
+        bool empty() const { return xid_.empty(); }
+        void clear() { xid_.clear(); }
+        bool operator==(const xid& other) const { return xid_ == other.xid_; }
+        friend std::string to_string(const wsrep::xid& xid);
+        friend std::ostream& operator<<(std::ostream& os, const wsrep::xid& xid);
+    private:
+        std::string xid_;
+    };
+
+    std::string to_string(const wsrep::xid& xid);
+    std::ostream& operator<<(std::ostream& os, const wsrep::xid& xid);
+}
+
+#endif // WSREP_XID_HPP