Use official JSON encoding for stream

runtime/platform/text_buffer.cc

Index: runtime/platform/text_buffer.cc
diff --git a/runtime/platform/text_buffer.cc b/runtime/platform/text_buffer.cc
index 1536dac13b3adb2f7a329e1eb3b30a4abe86b2cb..24dfb018f0bc3c2a4b8c9de81d788f68aa975ce1 100644
--- a/runtime/platform/text_buffer.cc
+++ b/runtime/platform/text_buffer.cc
@@ -8,6 +8,7 @@
 #include "platform/globals.h"
 #include "platform/utils.h"
 #include "vm/os.h"
+#include "vm/unicode.h"
 
 namespace dart {
 
@@ -78,9 +79,8 @@ intptr_t TextBuffer::Printf(const char* format, ...) {
   return len;
 }
 
-
-// Write a UTF-16 code unit so it can be read by a JSON parser in a string
-// literal. Use escape sequences for characters other than printable ASCII.
+// Write a UTF-32 code unit so it can be read by a JSON parser in a string
+// literal. Use official encoding from JSON specification. http://json.org/
 void TextBuffer::EscapeAndAddCodeUnit(uint32_t codeunit) {

[rmacnak, 2016/06/21 16:56:56]

Perhaps this should be split into EscapeAndAddUTF16CodeUnit (with the old
behavior, for encoding Dart strings) and EscapeAndAddCodePoint (with your new
behavior), see below.

[cbernaschina, 2016/06/21 21:24:43]

Done.

   switch (codeunit) {
     case '"':
@@ -108,27 +108,10 @@ void TextBuffer::EscapeAndAddCodeUnit(uint32_t codeunit) {
       Printf("%s", "\\t");
       break;
     default:
-      if (codeunit < 0x20) {
-        // Encode character as \u00HH.
-        uint32_t digit2 = (codeunit >> 4) & 0xf;
-        uint32_t digit3 = (codeunit & 0xf);
-        Printf("\\u00%c%c",
-               digit2 > 9 ? 'A' + (digit2 - 10) : '0' + digit2,
-               digit3 > 9 ? 'A' + (digit3 - 10) : '0' + digit3);
-      } else if (codeunit > 127) {
-        // Encode character as \uHHHH.
-        uint32_t digit0 = (codeunit >> 12) & 0xf;
-        uint32_t digit1 = (codeunit >> 8) & 0xf;
-        uint32_t digit2 = (codeunit >> 4) & 0xf;
-        uint32_t digit3 = (codeunit & 0xf);
-        Printf("\\u%c%c%c%c",
-               digit0 > 9 ? 'A' + (digit0 - 10) : '0' + digit0,
-               digit1 > 9 ? 'A' + (digit1 - 10) : '0' + digit1,
-               digit2 > 9 ? 'A' + (digit2 - 10) : '0' + digit2,
-               digit3 > 9 ? 'A' + (digit3 - 10) : '0' + digit3);
-      } else {
-        AddChar(codeunit);
-      }
+      char encoded[6];
+      intptr_t length = Utf8::Length(codeunit);
+      Utf8::Encode(codeunit, encoded);
+      AddRaw(reinterpret_cast<uint8_t*>(encoded), length);
   }
 }