direct map-like serialization

Author: grisumbras

include/boost/json/detail/writer.hpp

@@ -50,7 +50,6 @@ struct writer
 
 // template<bool StackEmpty> bool write_true   (detail::writer&, stream& ss);
 // template<bool StackEmpty> bool write_false  (detail::writer&, stream& ss);
-// template<bool StackEmpty> bool write_string (detail::writer&, stream& ss);
 // template<bool StackEmpty> bool write_array  (detail::writer&, stream& ss);
 // template<bool StackEmpty> bool write_object (detail::writer&, stream& ss);
 
@@ -68,6 +67,20 @@ BOOST_JSON_DECL
 bool
 write_value<false>(writer& w, stream& ss);
 
+template<bool StackEmpty>
+bool
+write_string(writer&, stream& ss);
+
+extern template
+BOOST_JSON_DECL
+bool
+write_string<true>(writer&, stream& ss);
+
+extern template
+BOOST_JSON_DECL
+bool
+write_string<false>(writer&, stream& ss);
+
 bool
 BOOST_JSON_DECL
 write_int64(detail::writer&, stream& ss);

include/boost/json/impl/serializer.hpp

@@ -12,6 +12,7 @@
 
 #include <boost/core/addressof.hpp>
 #include <boost/json/conversion.hpp>
+#include <boost/core/addressof.hpp>
 
 #ifdef _MSC_VER
 #pragma warning(push)
@@ -149,6 +150,113 @@ serialize_write(writer& w, stream& ss0, floating_point_conversion_tag )
     return resume_buffer(w, ss0);
 }
 
+template<bool StackEmpty, class T>
+bool
+serialize_write(writer& w, stream& ss0, map_like_conversion_tag )
+{
+    using std::get;
+    using ConstIterator = iterator_type<T const>;
+    using Mapped = remove_cvref< mapped_type<T> >;
+
+    T const* pt;
+    local_stream ss(ss0);
+    ConstIterator it;
+    ConstIterator end;
+    if( StackEmpty )
+    {
+        BOOST_ASSERT( w.st_.empty() );
+        BOOST_ASSERT( w.p_ );
+        pt = reinterpret_cast<T const*>(w.p_);
+        it = pt->begin();
+        end = pt->end();
+    }
+    else
+    {
+        BOOST_ASSERT( !w.st_.empty() );
+        writer::state st;
+        w.st_.pop(st);
+        w.st_.pop(it);
+        w.st_.pop(pt);
+        end = pt->end();
+        switch(st)
+        {
+        default:
+        case writer::state::obj1: goto do_obj1;
+        case writer::state::obj2: goto do_obj2;
+        case writer::state::obj3: goto do_obj3;
+        case writer::state::obj4: goto do_obj4;
+        case writer::state::obj5: goto do_obj5;
+        case writer::state::obj6: goto do_obj6;
+            break;
+        }
+    }
+do_obj1:
+    if(BOOST_JSON_LIKELY(ss))
+        ss.append('{');
+    else
+        return w.suspend(
+            writer::state::obj1, it, pt);
+    if(BOOST_JSON_UNLIKELY(
+        it == end))
+        goto do_obj6;
+    for(;;)
+    {
+        {
+            string_view key = get<0>(*it);
+            w.cs0_ = { key.data(), key.size() };
+        }
+        if( true )
+        {
+            if(BOOST_JSON_UNLIKELY( !write_string<true>(w, ss) ))
+                return w.suspend(writer::state::obj2, it, pt);
+        }
+        else
+        {
+do_obj2:
+            if(BOOST_JSON_UNLIKELY( !write_string<false>(w, ss) ))
+                return w.suspend(writer::state::obj2, it, pt);
+        }
+do_obj3:
+        if(BOOST_JSON_LIKELY(ss))
+            ss.append(':');
+        else
+            return w.suspend(
+                writer::state::obj3, it, pt);
+        {
+            Mapped const& ref = get<1>(*it);
+            w.p_ = boost::addressof(ref);
+        }
+        if( true )
+        {
+            if(BOOST_JSON_UNLIKELY( !(serialize_write<true, Mapped>(w, ss)) ))
+                return w.suspend(writer::state::obj4, it, pt);
+        }
+        else
+        {
+do_obj4:
+            if(BOOST_JSON_UNLIKELY( !(serialize_write<false, Mapped>(w, ss)) ))
+                return w.suspend(writer::state::obj4, it, pt);
+        }
+        ++it;
+        if(BOOST_JSON_UNLIKELY(it == end))
+            break;
+do_obj5:
+        if(BOOST_JSON_LIKELY(ss))
+            ss.append(',');
+        else
+            return w.suspend(
+                writer::state::obj5, it, pt);
+    }
+do_obj6:
+    if(BOOST_JSON_LIKELY(ss))
+    {
+        ss.append('}');
+        return true;
+    }
+    return w.suspend(
+        writer::state::obj6, it, pt);
+}
+
 template<bool StackEmpty, class T>
 bool
 serialize_write(writer& w, stream& ss0, sequence_conversion_tag )

include/boost/json/impl/serializer.ipp

@@ -209,6 +209,14 @@ do_utf5:
     goto do_str3;
 }
 
+template
+bool
+write_string<true>(writer& w, stream& ss);
+
+template
+bool
+write_string<false>(writer& w, stream& ss);
+
 inline
 bool
 write_buffer(writer& w, stream& ss0)
@@ -305,99 +313,8 @@ template<bool StackEmpty>
 bool
 write_object(writer& w, stream& ss0)
 {
-    object const* po;
-    local_stream ss(ss0);
-    object::const_iterator it;
-    object::const_iterator end;
-    if( StackEmpty )
-    {
-        BOOST_ASSERT( w.st_.empty() );
-        BOOST_ASSERT( w.p_ );
-        po = reinterpret_cast<object const*>(w.p_);
-        it = po->begin();
-        end = po->end();
-    }
-    else
-    {
-        BOOST_ASSERT( !w.st_.empty() );
-        writer::state st;
-        w.st_.pop(st);
-        w.st_.pop(it);
-        w.st_.pop(po);
-        end = po->end();
-        switch(st)
-        {
-        default:
-        case writer::state::obj1: goto do_obj1;
-        case writer::state::obj2: goto do_obj2;
-        case writer::state::obj3: goto do_obj3;
-        case writer::state::obj4: goto do_obj4;
-        case writer::state::obj5: goto do_obj5;
-        case writer::state::obj6: goto do_obj6;
-            break;
-        }
-    }
-do_obj1:
-    if(BOOST_JSON_LIKELY(ss))
-        ss.append('{');
-    else
-        return w.suspend(
-            writer::state::obj1, it, po);
-    if(BOOST_JSON_UNLIKELY(
-        it == end))
-        goto do_obj6;
-    for(;;)
-    {
-        w.cs0_ = {
-            it->key().data(),
-            it->key().size() };
-        if( true )
-        {
-            if(BOOST_JSON_UNLIKELY( !write_string<true>(w, ss) ))
-                return w.suspend(writer::state::obj2, it, po);
-        }
-        else
-        {
-do_obj2:
-            if(BOOST_JSON_UNLIKELY( !write_string<false>(w, ss) ))
-                return w.suspend(writer::state::obj2, it, po);
-        }
-do_obj3:
-        if(BOOST_JSON_LIKELY(ss))
-            ss.append(':');
-        else
-            return w.suspend(
-                writer::state::obj3, it, po);
-        w.p_ = &it->value();
-        if( true )
-        {
-            if(BOOST_JSON_UNLIKELY( !write_value<true>(w, ss) ))
-                return w.suspend(writer::state::obj4, it, po);
-        }
-        else
-        {
-do_obj4:
-            if(BOOST_JSON_UNLIKELY( !write_value<false>(w, ss) ))
-                return w.suspend(writer::state::obj4, it, po);
-        }
-        ++it;
-        if(BOOST_JSON_UNLIKELY(it == end))
-            break;
-do_obj5:
-        if(BOOST_JSON_LIKELY(ss))
-            ss.append(',');
-        else
-            return w.suspend(
-                writer::state::obj5, it, po);
-    }
-do_obj6:
-    if(BOOST_JSON_LIKELY(ss))
-    {
-        ss.append('}');
-        return true;
-    }
-    return w.suspend(
-        writer::state::obj6, it, po);
+    return serialize_write<StackEmpty, object>(
+        w, ss0, map_like_conversion_tag() );
 }
 
 template<bool StackEmpty>

test/serializer.cpp

@@ -15,6 +15,8 @@
 #include <boost/json/null_resource.hpp>
 #include <boost/json/parse.hpp>
 #include <iostream>
+#include <map>
+#include <vector>
 
 #include "parse-vectors.hpp"
 #include "test.hpp"
@@ -697,6 +699,19 @@ class serializer_test
             char buf[32];
             BOOST_TEST( sr.read(buf) == "[3.5E0,-1.4E1,7.7111E3]" );
         }
+        {
+            std::map<std::string, int> m{
+                {"one", 1}, {"two", 2}, {"three", 3} };
+
+            serializer sr;
+            sr.reset(&m);
+
+            char buf[32];
+            string_view output = sr.read(buf);
+            BOOST_TEST((
+                parse(output) ==
+                value{ {"one", 1}, {"two", 2}, {"three", 3} } ));
+        }
     }
 
     void