Add C API rb_enc_interned_str_cstr function

Co-authored-by: Thomas Marshall <thomas.marshall@shopify.com>

CHANGELOG.md

@@ -44,6 +44,7 @@ Compatibility:
 * Do not autosplat a proc that accepts a single positional argument and keywords (#3039, @andrykonchin).
 * Support passing anonymous * and ** parameters as method call arguments (#3039, @andrykonchin).
 * Handle either positional or keywords arguments by default in `Struct.new` (#3039, @rwstauner).
+* Add `rb_enc_interned_str_cstr` function (#3408, @goyox86, @thomasmarshall).
 
 Performance:
 

lib/cext/ABI_check.txt

@@ -1 +1 @@
-10
+11

spec/ruby/optional/capi/ext/string_spec.c

@@ -584,6 +584,11 @@ static VALUE string_spec_rb_str_unlocktmp(VALUE self, VALUE str) {
   return rb_str_unlocktmp(str);
 }
 
+static VALUE string_spec_rb_enc_interned_str_cstr(VALUE self, VALUE str, VALUE enc) {
+  rb_encoding *e = rb_to_encoding(enc);
+  return rb_enc_interned_str_cstr(RSTRING_PTR(str), e);
+}
+
 void Init_string_spec(void) {
   VALUE cls = rb_define_class("CApiStringSpecs", rb_cObject);
   rb_define_method(cls, "rb_cstr2inum", string_spec_rb_cstr2inum, 2);
@@ -685,6 +690,7 @@ void Init_string_spec(void) {
   rb_define_method(cls, "rb_str_catf", string_spec_rb_str_catf, 1);
   rb_define_method(cls, "rb_str_locktmp", string_spec_rb_str_locktmp, 1);
   rb_define_method(cls, "rb_str_unlocktmp", string_spec_rb_str_unlocktmp, 1);
+  rb_define_method(cls, "rb_enc_interned_str_cstr", string_spec_rb_enc_interned_str_cstr, 2);
 }
 
 #ifdef __cplusplus

spec/ruby/optional/capi/string_spec.rb

@@ -1227,4 +1227,29 @@ def inspect
       -> { @s.rb_str_unlocktmp("test") }.should raise_error(RuntimeError, 'temporal unlocking already unlocked string')
     end
   end
+
+  describe "rb_enc_interned_str_cstr" do
+    it "returns a frozen string" do
+      str = "hello"
+      val = @s.rb_enc_interned_str_cstr(str, Encoding::US_ASCII)
+
+      val.should.is_a?(String)
+      val.encoding.should == Encoding::US_ASCII
+      val.should.frozen?
+    end
+
+    it "returns the same frozen string" do
+      str = "hello"
+      result1 = @s.rb_enc_interned_str_cstr(str, Encoding::US_ASCII)
+      result2 = @s.rb_enc_interned_str_cstr(str, Encoding::US_ASCII)
+      result1.should.equal?(result2)
+    end
+
+    it "returns different frozen strings for different encodings" do
+      str = "hello"
+      result1 = @s.rb_enc_interned_str_cstr(str, Encoding::US_ASCII)
+      result2 = @s.rb_enc_interned_str_cstr(str, Encoding::UTF_8)
+      result1.should_not.equal?(result2)
+    end
+  end
 end

src/main/c/cext/string.c

@@ -437,3 +437,8 @@ long rb_str_coderange_scan_restartable(const char *s, const char *e, rb_encoding
   *cr = ENC_CODERANGE_VALID;
   return e - s;
 }
+
+VALUE rb_enc_interned_str_cstr(const char *ptr, rb_encoding *enc) {
+  VALUE str = rb_enc_str_new_cstr(ptr, enc);
+  return rb_fstring(str);
+}