Fix decoding of "\uDBFF\uDFFF" surrogate pair.

c_src/utf8.c

@@ -207,7 +207,7 @@ unicode_to_utf8(int c, unsigned char* buf)
         } else {
             return -1;
         }
-    } else if(c < 0x10FFFF) {
+    } else if(c <= 0x10FFFF) {
         buf[0] = (unsigned char) 0xF0 + (c >> 18);
         buf[1] = (unsigned char) 0x80 + ((c >> 12) & 0x3F);
         buf[2] = (unsigned char) 0x80 + ((c >> 6) & 0x3F);

test/jiffy_04_string_tests.erl

@@ -108,6 +108,10 @@ cases(uescaped) ->
         {
             <<"\"\\uD83D\\uDE0A\"">>,
             <<240, 159, 152, 138>>
+        },
+        {
+            <<"\"\\uDBFF\\uDFFF\"">>,
+            <<244, 143, 191, 191>>
         }
     ];