From e3f198e52cb35caf1feed6c7abe334c84554083b Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Sun, 19 Sep 2021 15:37:49 +0300
Subject: [PATCH] Add error_condition::to_string

---
 include/boost/system/detail/append_int.hpp    | 32 +++++++++++++++++++
 include/boost/system/detail/error_code.hpp    | 15 +++++----
 .../boost/system/detail/error_condition.hpp   | 16 +++++++---
 test/error_condition_test3.cpp                | 10 ++++++
 4 files changed, 62 insertions(+), 11 deletions(-)
 create mode 100644 include/boost/system/detail/append_int.hpp

diff --git a/include/boost/system/detail/append_int.hpp b/include/boost/system/detail/append_int.hpp
new file mode 100644
index 0000000..d927376
--- /dev/null
+++ b/include/boost/system/detail/append_int.hpp
@@ -0,0 +1,32 @@
+#ifndef BOOST_SYSTEM_DETAIL_APPEND_INT_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_APPEND_INT_HPP_INCLUDED
+
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/system/detail/snprintf.hpp>
+#include <string>
+
+//
+
+namespace boost
+{
+namespace system
+{
+namespace detail
+{
+
+inline void append_int( std::string& s, int v )
+{
+    char buffer[ 32 ];
+    detail::snprintf( buffer, sizeof( buffer ), ":%d", v );
+
+    s += buffer;
+}
+
+} // namespace detail
+} // namespace system
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_DETAIL_APPEND_INT_HPP_INCLUDED
diff --git a/include/boost/system/detail/error_code.hpp b/include/boost/system/detail/error_code.hpp
index 0984be7..6f4adef 100644
--- a/include/boost/system/detail/error_code.hpp
+++ b/include/boost/system/detail/error_code.hpp
@@ -18,6 +18,7 @@
 #include <boost/system/detail/interop_category.hpp>
 #include <boost/system/detail/enable_if.hpp>
 #include <boost/system/detail/is_same.hpp>
+#include <boost/system/detail/append_int.hpp>
 #include <boost/system/detail/snprintf.hpp>
 #include <boost/system/detail/config.hpp>
 #include <boost/assert/source_location.hpp>
@@ -549,18 +550,18 @@ public:
         {
             std::error_code const& e2 = *reinterpret_cast<std::error_code const*>( d2_ );
 
-            char buffer[ 32 ];
-            detail::snprintf( buffer, sizeof( buffer ), "%d", e2.value() );
+            std::string r( "std:" );
+            r += e2.category().name();
+            detail::append_int( r, e2.value() );
 
-            return std::string( "std:" ) + e2.category().name() + ":" + buffer;
+            return r;
         }
         else
 #endif
         {
-            char buffer[ 32 ];
-            detail::snprintf( buffer, sizeof( buffer ), "%d", value() );
-
-            return std::string( category().name() ) + ":" + buffer;
+            std::string r = category().name();
+            detail::append_int( r, value() );
+            return r;
         }
     }
 
diff --git a/include/boost/system/detail/error_condition.hpp b/include/boost/system/detail/error_condition.hpp
index c52d495..a16ce57 100644
--- a/include/boost/system/detail/error_condition.hpp
+++ b/include/boost/system/detail/error_condition.hpp
@@ -15,6 +15,7 @@
 #include <boost/system/detail/enable_if.hpp>
 #include <boost/system/detail/is_same.hpp>
 #include <boost/system/detail/errc.hpp>
+#include <boost/system/detail/append_int.hpp>
 #include <boost/system/is_error_condition_enum.hpp>
 #include <boost/system/detail/config.hpp>
 #include <boost/config.hpp>
@@ -246,14 +247,21 @@ public:
 
 #endif
 
+    std::string to_string() const
+    {
+        std::string r( "cond:" );
+
+        r += category().name();
+        detail::append_int( r, value() );
+
+        return r;
+    }
+
     template<class Ch, class Tr>
         inline friend std::basic_ostream<Ch, Tr>&
         operator<< (std::basic_ostream<Ch, Tr>& os, error_condition const & en)
     {
-        {
-            os << "cond:" << en.category().name() << ':' << en.value();
-        }
-
+        os << en.to_string();
         return os;
     }
 };
diff --git a/test/error_condition_test3.cpp b/test/error_condition_test3.cpp
index 4d3c58d..567ac8f 100644
--- a/test/error_condition_test3.cpp
+++ b/test/error_condition_test3.cpp
@@ -22,6 +22,8 @@ int main()
     BOOST_TEST( !en.failed() );
     BOOST_TEST( !en );
 
+    BOOST_TEST_EQ( en.to_string(), std::string( "cond:generic:0" ) );
+
     {
         sys::error_condition en2( en );
 
@@ -34,6 +36,8 @@ int main()
 
         BOOST_TEST_EQ( en, en2 );
         BOOST_TEST_NOT( en != en2 );
+
+        BOOST_TEST_EQ( en2.to_string(), std::string( "cond:generic:0" ) );
     }
 
     {
@@ -48,6 +52,8 @@ int main()
 
         BOOST_TEST_EQ( en, en2 );
         BOOST_TEST_NOT( en != en2 );
+
+        BOOST_TEST_EQ( en2.to_string(), std::string( "cond:generic:0" ) );
     }
 
     {
@@ -63,6 +69,8 @@ int main()
 
         BOOST_TEST_NE( en, en2 );
         BOOST_TEST( en != en2 );
+
+        BOOST_TEST_EQ( en2.to_string(), std::string( "cond:generic:5" ) );
     }
 
     {
@@ -78,6 +86,8 @@ int main()
 
         BOOST_TEST_NE( en, en2 );
         BOOST_TEST( en != en2 );
+
+        BOOST_TEST_EQ( en2.to_string(), std::string( "cond:system:5" ) );
     }
 
     return boost::report_errors();