Implement in terms of public C API methods

Author: eregon

lib/cext/ABI_check.txt

@@ -1 +1 @@
-12
+13

src/main/c/cext/string.c

@@ -160,7 +160,7 @@ VALUE rb_str_to_str(VALUE string) {
 }
 
 VALUE rb_fstring(VALUE str) {
-  return RUBY_INVOKE(str, "-@");
+  return rb_str_to_interned_str(str);
 }
 
 VALUE rb_str_buf_new(long capacity) {
@@ -440,9 +440,9 @@ long rb_str_coderange_scan_restartable(const char *s, const char *e, rb_encoding
 
 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);
+  return rb_str_to_interned_str(str);
 }
 
 VALUE rb_str_to_interned_str(VALUE str) {
-  return rb_fstring(str);
+  return RUBY_INVOKE(str, "-@");
 }

src/main/java/org/truffleruby/cext/CExtNodes.java

@@ -796,6 +796,8 @@ RubyString rbStrNewNul(int byteLength,
 
     }
 
+    /** Alternative to rb_str_new*() which does not copy the bytes from native memory, to use when the copy is
+     * unnecessary. */
     @CoreMethod(names = "rb_tr_temporary_native_string", onSingleton = true, required = 3, lowerFixnum = 2)
     public abstract static class TemporaryNativeStringNode extends CoreMethodArrayArgumentsNode {