Only define String.json_create & al when json/add is required

All the `json/add` related methods for string were
always defined unconditionally from the generators.

It's preferable to only define them if `json/add` is actually used.

ext/json/generator/generator.c

@@ -31,7 +31,7 @@ typedef struct JSON_Generator_StateStruct {
 #define RB_UNLIKELY(cond) (cond)
 #endif
 
-static VALUE mJSON, cState, cFragment, mString_Extend, eGeneratorError, eNestingError, Encoding_UTF_8;
+static VALUE mJSON, cState, cFragment, eGeneratorError, eNestingError, Encoding_UTF_8;
 
 static ID i_to_s, i_to_json, i_new, i_pack, i_unpack, i_create_id, i_extend, i_encode;
 static VALUE sym_indent, sym_space, sym_space_before, sym_object_nl, sym_array_nl, sym_max_nesting, sym_allow_nan,
@@ -835,18 +835,6 @@ static VALUE mFloat_to_json(int argc, VALUE *argv, VALUE self)
     return cState_partial_generate(Vstate, self, generate_json_float, Qfalse);
 }
 
-/*
- * call-seq: String.included(modul)
- *
- * Extends _modul_ with the String::Extend module.
- */
-static VALUE mString_included_s(VALUE self, VALUE modul)
-{
-    VALUE result = rb_funcall(modul, i_extend, 1, mString_Extend);
-    rb_call_super(1, &modul);
-    return result;
-}
-
 /*
  * call-seq: to_json(*)
  *
@@ -861,51 +849,6 @@ static VALUE mString_to_json(int argc, VALUE *argv, VALUE self)
     return cState_partial_generate(Vstate, self, generate_json_string, Qfalse);
 }
 
-/*
- * call-seq: to_json_raw_object()
- *
- * This method creates a raw object hash, that can be nested into
- * other data structures and will be generated as a raw string. This
- * method should be used, if you want to convert raw strings to JSON
- * instead of UTF-8 strings, e. g. binary data.
- */
-static VALUE mString_to_json_raw_object(VALUE self)
-{
-    VALUE ary;
-    VALUE result = rb_hash_new();
-    rb_hash_aset(result, rb_funcall(mJSON, i_create_id, 0), rb_class_name(rb_obj_class(self)));
-    ary = rb_funcall(self, i_unpack, 1, rb_str_new2("C*"));
-    rb_hash_aset(result, rb_utf8_str_new_lit("raw"), ary);
-    return result;
-}
-
-/*
- * call-seq: to_json_raw(*args)
- *
- * This method creates a JSON text from the result of a call to
- * to_json_raw_object of this String.
- */
-static VALUE mString_to_json_raw(int argc, VALUE *argv, VALUE self)
-{
-    VALUE obj = mString_to_json_raw_object(self);
-    Check_Type(obj, T_HASH);
-    return mHash_to_json(argc, argv, obj);
-}
-
-/*
- * call-seq: json_create(o)
- *
- * Raw Strings are JSON Objects (the raw bytes are stored in an array for the
- * key "raw"). The Ruby String can be created by this module method.
- */
-static VALUE mString_Extend_json_create(VALUE self, VALUE o)
-{
-    VALUE ary;
-    Check_Type(o, T_HASH);
-    ary = rb_hash_aref(o, rb_str_new2("raw"));
-    return rb_funcall(ary, i_pack, 1, rb_str_new2("C*"));
-}
-
 /*
  * call-seq: to_json(*)
  *
@@ -2091,13 +2034,7 @@ void Init_generator(void)
     rb_define_method(mFloat, "to_json", mFloat_to_json, -1);
 
     VALUE mString = rb_define_module_under(mGeneratorMethods, "String");
-    rb_define_singleton_method(mString, "included", mString_included_s, 1);
     rb_define_method(mString, "to_json", mString_to_json, -1);
-    rb_define_method(mString, "to_json_raw", mString_to_json_raw, -1);
-    rb_define_method(mString, "to_json_raw_object", mString_to_json_raw_object, 0);
-
-    mString_Extend = rb_define_module_under(mString, "Extend");
-    rb_define_method(mString_Extend, "json_create", mString_Extend_json_create, 1);
 
     VALUE mTrueClass = rb_define_module_under(mGeneratorMethods, "TrueClass");
     rb_define_method(mTrueClass, "to_json", mTrueClass_to_json, -1);

ext/json/lib/json/add/core.rb

@@ -7,6 +7,7 @@ require 'json/add/date_time'
 require 'json/add/exception'
 require 'json/add/range'
 require 'json/add/regexp'
+require 'json/add/string'
 require 'json/add/struct'
 require 'json/add/symbol'
 require 'json/add/time'

ext/json/lib/json/add/string.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+unless defined?(::JSON::JSON_LOADED) and ::JSON::JSON_LOADED
+  require 'json'
+end
+
+class String
+  # call-seq: json_create(o)
+  # 
+  # Raw Strings are JSON Objects (the raw bytes are stored in an array for the
+  # key "raw"). The Ruby String can be created by this class method.
+  def self.json_create(object)
+    object["raw"].pack("C*")
+  end
+
+  # call-seq: to_json_raw_object()
+  # 
+  # This method creates a raw object hash, that can be nested into
+  # other data structures and will be generated as a raw string. This
+  # method should be used, if you want to convert raw strings to JSON
+  # instead of UTF-8 strings, e. g. binary data.
+  def to_json_raw_object
+    {
+      JSON.create_id => self.class.name,
+      "raw" => unpack("C*"),
+    }
+  end
+
+  # call-seq: to_json_raw(*args)
+  # 
+  # This method creates a JSON text from the result of a call to
+  # to_json_raw_object of this String.
+  def to_json_raw(...)
+    to_json_raw_object.to_json(...)
+  end
+end