JSON: Templatize the JSON serialization code

This makes it possible to use something other than a StringBuilder for
serialization (and to produce something other than a String.) :^)

AK/JsonArray.cpp

@@ -3,22 +3,4 @@
 
 namespace AK {
 
-void JsonArray::serialize(StringBuilder& builder) const
-{
-    builder.append('[');
-    for (int i = 0; i < m_values.size(); ++i) {
-        m_values[i].serialize(builder);
-        if (i != size() - 1)
-            builder.append(',');
-    }
-    builder.append(']');
-}
-
-String JsonArray::serialized() const
-{
-    StringBuilder builder;
-    serialize(builder);
-    return builder.to_string();
-}
-
 }

AK/JsonArray.h

@@ -44,8 +44,13 @@ public:
     void append(const JsonValue& value) { m_values.append(value); }
     void append(JsonValue&& value) { m_values.append(move(value)); }
 
-    String serialized() const;
+    template<typename Builder>
-    void serialize(StringBuilder&) const;
+    typename Builder::OutputType serialized() const;
+
+    template<typename Builder>
+    void serialize(Builder&) const;
+
+    String to_string() const { return serialized<StringBuilder>(); }
 
     template<typename Callback>
     void for_each(Callback callback) const
@@ -60,6 +65,26 @@ private:
     Vector<JsonValue> m_values;
 };
 
+template<typename Builder>
+inline void JsonArray::serialize(Builder& builder) const
+{
+    builder.append('[');
+    for (int i = 0; i < m_values.size(); ++i) {
+        m_values[i].serialize(builder);
+        if (i != size() - 1)
+            builder.append(',');
+    }
+    builder.append(']');
+}
+
+template<typename Builder>
+inline typename Builder::OutputType JsonArray::serialized() const
+{
+    Builder builder;
+    serialize(builder);
+    return builder.build();
+}
+
 }
 
 using AK::JsonArray;

AK/JsonObject.cpp

@@ -3,28 +3,4 @@
 
 namespace AK {
 
-void JsonObject::serialize(StringBuilder& builder) const
-{
-    int index = 0;
-    builder.append('{');
-    for_each_member([&] (auto& key, auto& value) {
-        builder.append('"');
-        builder.append(key);
-        builder.append('"');
-        builder.append(':');
-        value.serialize(builder);
-        if (index != size() - 1)
-            builder.append(',');
-        ++index;
-    });
-    builder.append('}');
-}
-
-String JsonObject::serialized() const
-{
-    StringBuilder builder;
-    serialize(builder);
-    return builder.to_string();
-}
-
 }

AK/JsonObject.h

@@ -2,13 +2,14 @@
 
 #include <AK/AKString.h>
 #include <AK/HashMap.h>
+#include <AK/JsonArray.h>
 #include <AK/JsonValue.h>
 
 namespace AK {
 
 class JsonObject {
 public:
-    JsonObject() { }
+    JsonObject() {}
     ~JsonObject() {}
 
     JsonObject(const JsonObject& other)
@@ -63,13 +64,90 @@ public:
             callback(it.key, it.value);
     }
 
-    String serialized() const;
+    template<typename Builder>
-    void serialize(StringBuilder&) const;
+    typename Builder::OutputType serialized() const;
+
+    template<typename Builder>
+    void serialize(Builder&) const;
+
+    String to_string() const { return serialized<StringBuilder>(); }
 
 private:
     HashMap<String, JsonValue> m_members;
 };
 
+template<typename Builder>
+inline void JsonObject::serialize(Builder& builder) const
+{
+    int index = 0;
+    builder.append('{');
+    for_each_member([&](auto& key, auto& value) {
+        builder.append('"');
+        builder.append(key);
+        builder.append('"');
+        builder.append(':');
+        value.serialize(builder);
+        if (index != size() - 1)
+            builder.append(',');
+        ++index;
+    });
+    builder.append('}');
+}
+
+template<typename Builder>
+inline typename Builder::OutputType JsonObject::serialized() const
+{
+    Builder builder;
+    serialize(builder);
+    return builder.build();
+}
+
+template<typename Builder>
+void JsonValue::serialize(Builder& builder) const
+{
+    switch (m_type) {
+    case Type::String:
+        builder.appendf("\"%s\"", m_value.as_string->characters());
+        break;
+    case Type::Array:
+        m_value.as_array->serialize(builder);
+        break;
+    case Type::Object:
+        m_value.as_object->serialize(builder);
+        break;
+    case Type::Bool:
+        builder.append(m_value.as_bool ? "true" : "false");
+        break;
+#ifndef KERNEL
+    case Type::Double:
+        builder.appendf("%g", m_value.as_double);
+        break;
+#endif
+    case Type::Int:
+        builder.appendf("%d", m_value.as_int);
+        break;
+    case Type::UnsignedInt:
+        builder.appendf("%u", m_value.as_uint);
+        break;
+    case Type::Undefined:
+        builder.append("undefined");
+        break;
+    case Type::Null:
+        builder.append("null");
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+    }
+}
+
+template<typename Builder>
+typename Builder::OutputType JsonValue::serialized() const
+{
+    Builder builder;
+    serialize(builder);
+    return builder.build();
+}
+
 }
 
 using AK::JsonObject;

AK/JsonValue.cpp

@@ -158,50 +158,6 @@ void JsonValue::clear()
     m_value.as_string = nullptr;
 }
 
-void JsonValue::serialize(StringBuilder& builder) const
-{
-    switch (m_type) {
-    case Type::String:
-        builder.appendf("\"%s\"", m_value.as_string->characters());
-        break;
-    case Type::Array:
-        m_value.as_array->serialize(builder);
-        break;
-    case Type::Object:
-        m_value.as_object->serialize(builder);
-        break;
-    case Type::Bool:
-        builder.append(m_value.as_bool ? "true" : "false");
-        break;
-#ifndef KERNEL
-    case Type::Double:
-        builder.appendf("%g", m_value.as_double);
-        break;
-#endif
-    case Type::Int:
-        builder.appendf("%d", m_value.as_int);
-        break;
-    case Type::UnsignedInt:
-        builder.appendf("%u", m_value.as_uint);
-        break;
-    case Type::Undefined:
-        builder.append("undefined");
-        break;
-    case Type::Null:
-        builder.append("null");
-        break;
-    default:
-        ASSERT_NOT_REACHED();
-    }
-}
-
-String JsonValue::serialized() const
-{
-    StringBuilder builder;
-    serialize(builder);
-    return builder.to_string();
-}
-
 JsonValue JsonValue::from_string(const StringView& input)
 {
     return JsonParser(input).parse();

AK/JsonValue.h

@@ -3,6 +3,7 @@
 #include <AK/AKString.h>
 #include <AK/IPv4Address.h>
 #include <AK/Optional.h>
+#include <AK/StringBuilder.h>
 
 namespace AK {
 
@@ -57,14 +58,16 @@ public:
     JsonValue& operator=(JsonArray&&) = delete;
     JsonValue& operator=(JsonObject&&) = delete;
 
-    String serialized() const;
+    template<typename Builder>
-    void serialize(StringBuilder&) const;
+    typename Builder::OutputType serialized() const;
+    template<typename Builder>
+    void serialize(Builder&) const;
 
-    String to_string(const String& default_value = {}) const
+    String to_string() const
     {
         if (is_string())
             return as_string();
-        return default_value;
+        return serialized<StringBuilder>();
     }
 
     Optional<IPv4Address> to_ipv4_address() const
@@ -151,7 +154,10 @@ public:
     }
 #endif
 
-    Type type() const { return m_type; }
+    Type type() const
+    {
+        return m_type;
+    }
 
     bool is_null() const { return m_type == Type::Null; }
     bool is_undefined() const { return m_type == Type::Undefined; }
@@ -160,9 +166,15 @@ public:
     bool is_int() const { return m_type == Type::Int; }
     bool is_uint() const { return m_type == Type::UnsignedInt; }
 #ifndef KERNEL
-    bool is_double() const { return m_type == Type::Double; }
+    bool is_double() const
+    {
+        return m_type == Type::Double;
+    }
 #endif
-    bool is_array() const { return m_type == Type::Array; }
+    bool is_array() const
+    {
+        return m_type == Type::Array;
+    }
     bool is_object() const { return m_type == Type::Object; }
     bool is_number() const
     {

AK/StringBuilder.h

@@ -8,6 +8,8 @@ namespace AK {
 
 class StringBuilder {
 public:
+    using OutputType = String;
+
     explicit StringBuilder(int initial_capacity = 16);
     ~StringBuilder() {}
 
@@ -17,6 +19,8 @@ public:
     void appendf(const char*, ...);
     void appendvf(const char*, va_list);
 
+    String build() { return to_string(); }
+
     String to_string();
     ByteBuffer to_byte_buffer();
 

DevTools/FormCompiler/main.cpp

@@ -2,6 +2,7 @@
 #include <AK/JsonObject.h>
 #include <AK/JsonValue.h>
 #include <AK/LogStream.h>
+#include <AK/StringBuilder.h>
 #include <LibCore/CFile.h>
 #include <stdio.h>
 
@@ -70,7 +71,7 @@ int main(int argc, char** argv)
         auto class_name = widget_object.get("class").to_string();
         dbg() << "    " << name << " = new " << class_name << "(main_widget);";
 
-        widget_object.for_each_member([&](auto& property_name, auto& property_value) {
+        widget_object.for_each_member([&](auto& property_name, const JsonValue& property_value) {
             if (property_name == "class")
                 return;
 
@@ -79,7 +80,7 @@ int main(int argc, char** argv)
             if (property_value.is_null())
                 value = "{}";
             else
-                value = property_value.serialized();
+                value = property_value.to_string();
 
             dbg() << "    " << name << "->set_" << property_name << "(" << value << ");";
         });

DevTools/VisualBuilder/VBForm.cpp

@@ -4,6 +4,7 @@
 #include "VBWidgetRegistry.h"
 #include <AK/JsonArray.h>
 #include <AK/JsonObject.h>
+#include <AK/StringBuilder.h>
 #include <LibCore/CFile.h>
 #include <LibGUI/GAction.h>
 #include <LibGUI/GMenu.h>
@@ -318,7 +319,7 @@ void VBForm::load_from_file(const String& path)
             (void)property_name;
             (void)property_value;
             VBProperty& property = vbwidget->property(property_name);
-            dbgprintf("Set property %s.%s to '%s'\n", widget_class.characters(), property_name.characters(), property_value.serialized().characters());
+            dbgprintf("Set property %s.%s to '%s'\n", widget_class.characters(), property_name.characters(), property_value.to_string().characters());
             property.set_value(property_value);
         });
         m_widgets.append(vbwidget);
@@ -349,7 +350,7 @@ void VBForm::write_to_file(const String& path)
         widget_array.append(widget_object);
     }
     form_object.set("widgets", widget_array);
-    file.write(form_object.serialized());
+    file.write(form_object.to_string());
 }
 
 void VBForm::dump()

Kernel/FileSystem/ProcFS.cpp

@@ -208,7 +208,7 @@ Optional<KBuffer> procfs$pid_fds(InodeIdentifier identifier)
         description_object.set("offset", description->offset());
         array.append(move(description_object));
     }
-    return array.serialized().to_byte_buffer();
+    return array.to_string().to_byte_buffer();
 }
 
 Optional<KBuffer> procfs$pid_fd_entry(InodeIdentifier identifier)
@@ -241,7 +241,7 @@ Optional<KBuffer> procfs$pid_vm(InodeIdentifier identifier)
         region_object.set("name", region.name());
         array.append(move(region_object));
     }
-    return array.serialized().to_byte_buffer();
+    return array.to_string().to_byte_buffer();
 }
 
 Optional<KBuffer> procfs$pci(InodeIdentifier)
@@ -294,7 +294,7 @@ Optional<KBuffer> procfs$net_tcp(InodeIdentifier)
         obj.set("sequence_number", socket->sequence_number());
         json.append(obj);
     });
-    return json.serialized().to_byte_buffer();
+    return json.to_string().to_byte_buffer();
 }
 
 Optional<KBuffer> procfs$pid_vmo(InodeIdentifier identifier)
@@ -449,7 +449,7 @@ Optional<KBuffer> procfs$df(InodeIdentifier)
         fs_object.set("mount_point", mount.absolute_path());
         json.append(fs_object);
     });
-    return json.serialized().to_byte_buffer();
+    return json.to_string().to_byte_buffer();
 }
 
 Optional<KBuffer> procfs$cpuinfo(InodeIdentifier)
@@ -541,7 +541,7 @@ Optional<KBuffer> procfs$memstat(InodeIdentifier)
     json.set("super_physical_available", MM.super_physical_pages());
     json.set("kmalloc_call_count", g_kmalloc_call_count);
     json.set("kfree_call_count", g_kfree_call_count);
-    return json.serialized().to_byte_buffer();
+    return json.to_string().to_byte_buffer();
 }
 
 Optional<KBuffer> procfs$all(InodeIdentifier)
@@ -577,7 +577,7 @@ Optional<KBuffer> procfs$all(InodeIdentifier)
     build_process(*Scheduler::colonel());
     for (auto* process : processes)
         build_process(*process);
-    return array.serialized().to_byte_buffer();
+    return array.to_string().to_byte_buffer();
 }
 
 Optional<KBuffer> procfs$inodes(InodeIdentifier)

Userland/jp.cpp

@@ -1,6 +1,7 @@
 #include <AK/JsonArray.h>
 #include <AK/JsonObject.h>
 #include <AK/JsonValue.h>
+#include <AK/StringBuilder.h>
 #include <LibCore/CFile.h>
 #include <stdio.h>
 
@@ -65,6 +66,6 @@ void print(const JsonValue& value, int indent)
         printf("\033[32;1m");
     else if (value.is_null() || value.is_undefined())
         printf("\033[34;1m");
-    printf("%s", value.serialized().characters());
+    printf("%s", value.to_string().characters());
     printf("\033[0m");
 }