[GR-11887] Specs and fix for rb_str_export_to_enc.

PullRequest: truffleruby/756

Author: aardvark179

lib/truffle/truffle/cext.rb

@@ -931,7 +931,9 @@ def rb_str_conv_enc_opts(str, from, to, ecflags, ecopts)
 
     ec = Encoding::Converter.new(from, to, ecopts || ecflags)
     dest = ''
-    status = ec.primitive_convert str, dest, nil, nil, ec.options
+    # This C API will (unlike primitive convert) not alter the source
+    # string, so we need to duplicate it.
+    status = ec.primitive_convert str.dup, dest, nil, nil, ec.options
     status == :finished ? dest : str
   end
 

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

@@ -176,6 +176,10 @@ VALUE string_spec_rb_str_encode(VALUE self, VALUE str, VALUE enc, VALUE flags, V
   return rb_str_encode(str, enc, FIX2INT(flags), opts);
 }
 
+VALUE string_spec_rb_str_export_to_enc(VALUE self, VALUE str, VALUE enc) {
+  return rb_str_export_to_enc(str, rb_to_encoding(enc));
+}
+
 VALUE string_spec_rb_str_new_cstr(VALUE self, VALUE str) {
   if(NIL_P(str)) {
     return rb_str_new_cstr("");
@@ -435,6 +439,7 @@ void Init_string_spec(void) {
   rb_define_method(cls, "rb_str_new_offset", string_spec_rb_str_new_offset, 3);
   rb_define_method(cls, "rb_str_new2", string_spec_rb_str_new2, 1);
   rb_define_method(cls, "rb_str_encode", string_spec_rb_str_encode, 4);
+  rb_define_method(cls, "rb_str_export_to_enc", string_spec_rb_str_export_to_enc, 2);
   rb_define_method(cls, "rb_str_new_cstr", string_spec_rb_str_new_cstr, 1);
   rb_define_method(cls, "rb_external_str_new", string_spec_rb_external_str_new, 1);
   rb_define_method(cls, "rb_external_str_new_cstr", string_spec_rb_external_str_new_cstr, 1);

spec/ruby/optional/capi/string_spec.rb

@@ -877,6 +877,27 @@ def inspect
     end
   end
 
+  describe "rb_str_export_to_enc" do
+    it "returns a copy of an ascii string converted to the new encoding" do
+      source = "A simple string".encode(Encoding::US_ASCII)
+      result = @s.rb_str_export_to_enc(source, Encoding::UTF_8)
+      result.should == source.encode(Encoding::UTF_8)
+      result.encoding.should == Encoding::UTF_8
+    end
+
+    it "returns the source string if it can not be converted" do
+      source = ["00ff"].pack("H*");
+      result = @s.rb_str_export_to_enc(source, Encoding::UTF_8)
+      result.should equal(source)
+    end
+
+    it "does not alter the source string if it can not be converted" do
+      source = ["00ff"].pack("H*");
+      result = @s.rb_str_export_to_enc(source, Encoding::UTF_8)
+      source.bytes.should == [0, 255]
+    end
+end
+  
   describe "rb_sprintf" do
     it "replaces the parts like sprintf" do
       @s.rb_sprintf1("Awesome %s is replaced", "string").should == "Awesome string is replaced"