Reduce allocations in parse and load argument handling

Avoid needless hash allocations and such that degrade performance
significantly on micro-benchmarks.

ext/json/lib/json/common.rb

@@ -221,8 +221,12 @@ module JSON
   #   # Raises JSON::ParserError (783: unexpected token at ''):
   #   JSON.parse('')
   #
-  def parse(source, opts = {})
-    Parser.new(source, **(opts||{})).parse
+  def parse(source, opts = nil)
+    if opts.nil?
+      Parser.new(source).parse
+    else
+      Parser.new(source, opts).parse
+    end
   end
 
   # :call-seq:
@@ -543,15 +547,23 @@ module JSON
   #      #<Admin:0x00000000064c41f8
   #      @attributes={"type"=>"Admin", "password"=>"0wn3d"}>}
   #
-  def load(source, proc = nil, options = {})
-    opts = load_default_options.merge options
-    if source.respond_to? :to_str
-      source = source.to_str
-    elsif source.respond_to? :to_io
-      source = source.to_io.read
-    elsif source.respond_to?(:read)
-      source = source.read
+  def load(source, proc = nil, options = nil)
+    opts = if options.nil?
+      load_default_options
+    else
+      load_default_options.merge(options)
     end
+
+    unless source.is_a?(String)
+      if source.respond_to? :to_str
+        source = source.to_str
+      elsif source.respond_to? :to_io
+        source = source.to_io.read
+      elsif source.respond_to?(:read)
+        source = source.read
+      end
+    end
+
     if opts[:allow_blank] && (source.nil? || source.empty?)
       source = 'null'
     end

ext/json/parser/parser.c

@@ -1824,7 +1824,15 @@ static VALUE cParser_initialize(int argc, VALUE *argv, VALUE self)
     if (json->Vsource) {
         rb_raise(rb_eTypeError, "already initialized instance");
     }
-    rb_scan_args(argc, argv, "1:", &source, &opts);
+
+    rb_check_arity(argc, 1, 2);
+    source = argv[0];
+    opts = Qnil;
+    if (argc == 2) {
+        opts = argv[1];
+        Check_Type(opts, T_HASH);
+    }
+
     if (!NIL_P(opts)) {
 	VALUE tmp = ID2SYM(i_max_nesting);
 	if (option_given_p(opts, tmp)) {
@@ -1916,7 +1924,7 @@ static VALUE cParser_initialize(int argc, VALUE *argv, VALUE self)
 }
 
 
-#line 1920 "parser.c"
+#line 1928 "parser.c"
 enum {JSON_start = 1};
 enum {JSON_first_final = 10};
 enum {JSON_error = 0};
@@ -1924,7 +1932,7 @@ enum {JSON_error = 0};
 enum {JSON_en_main = 1};
 
 
-#line 828 "parser.rl"
+#line 836 "parser.rl"
 
 
 /*
@@ -1942,16 +1950,16 @@ static VALUE cParser_parse(VALUE self)
   GET_PARSER;
 
 
-#line 1946 "parser.c"
+#line 1954 "parser.c"
 	{
 	cs = JSON_start;
 	}
 
-#line 845 "parser.rl"
+#line 853 "parser.rl"
   p = json->source;
   pe = p + json->len;
 
-#line 1955 "parser.c"
+#line 1963 "parser.c"
 	{
 	if ( p == pe )
 		goto _test_eof;
@@ -1985,7 +1993,7 @@ st0:
 cs = 0;
 	goto _out;
 tr2:
-#line 820 "parser.rl"
+#line 828 "parser.rl"
 	{
         char *np = JSON_parse_value(json, p, pe, &result, 0);
         if (np == NULL) { p--; {p++; cs = 10; goto _out;} } else {p = (( np))-1;}
@@ -1995,7 +2003,7 @@ st10:
 	if ( ++p == pe )
 		goto _test_eof10;
 case 10:
-#line 1999 "parser.c"
+#line 2007 "parser.c"
 	switch( (*p) ) {
 		case 13: goto st10;
 		case 32: goto st10;
@@ -2084,7 +2092,7 @@ case 9:
 	_out: {}
 	}
 
-#line 848 "parser.rl"
+#line 856 "parser.rl"
 
   if (cs >= JSON_first_final && p == pe) {
     return result;

ext/json/parser/parser.rl

@@ -719,7 +719,15 @@ static VALUE cParser_initialize(int argc, VALUE *argv, VALUE self)
     if (json->Vsource) {
         rb_raise(rb_eTypeError, "already initialized instance");
     }
-    rb_scan_args(argc, argv, "1:", &source, &opts);
+
+    rb_check_arity(argc, 1, 2);
+    source = argv[0];
+    opts = Qnil;
+    if (argc == 2) {
+        opts = argv[1];
+        Check_Type(opts, T_HASH);
+    }
+
     if (!NIL_P(opts)) {
 	VALUE tmp = ID2SYM(i_max_nesting);
 	if (option_given_p(opts, tmp)) {