From 4271d987cdd8d515bb824ec6649e321d55872b88 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Mon, 18 Feb 2013 08:38:18 -0700
Subject: [PATCH] ffi/unsafe: fix a bug in conversion to UTF-16

Characters outside of the BMP were translated incorrectly.
---
 collects/tests/racket/foreign-test.rktl | 3 +++
 collects/tests/racket/unicode.rktl      | 8 ++++++++
 src/racket/src/string.c                 | 1 +
 3 files changed, 12 insertions(+)

diff --git a/collects/tests/racket/foreign-test.rktl b/collects/tests/racket/foreign-test.rktl
index 4beb061338..e0345d8a5b 100644
--- a/collects/tests/racket/foreign-test.rktl
+++ b/collects/tests/racket/foreign-test.rktl
@@ -494,6 +494,9 @@
   (test 4.4t0 extflvector-ref v 2)
   (test 2.2t0 ptr-ref (ptr-add (extflvector->cpointer v) (ctype-sizeof _longdouble)) _longdouble))
 
+;; Check a corner of UTF-16 conversion:
+(test "\U171D3" cast (cast "\U171D3" _string/utf-16 _pointer) _pointer _string/utf-16)
+
 (report-errs)
 
 #| --- ignore everything below ---
diff --git a/collects/tests/racket/unicode.rktl b/collects/tests/racket/unicode.rktl
index 874feda7c9..6a3314304f 100644
--- a/collects/tests/racket/unicode.rktl
+++ b/collects/tests/racket/unicode.rktl
@@ -988,6 +988,14 @@
 		     (bytes-convert c
 				    (bytes-append (integer->integer-bytes #xDC00 2 #f) 
 						  (integer->integer-bytes #x1000 2 #f))))))))
+
+;; Check a corner of UTF-16 conversion:
+(let ([c (bytes-open-converter "platform-UTF-8" "platform-UTF-16")])
+  (let-values ([(s n status) (bytes-convert c (string->bytes/utf-8 "\U171D3"))])
+    (let ([c2 (bytes-open-converter "platform-UTF-16" "platform-UTF-8")])
+      (let-values ([(s2 n2 status2) (bytes-convert c2 s)])
+        (bytes->string/utf-8 s2)))))
+
 (when (eq? (system-type) 'windows)
   (let ([c (bytes-open-converter "platform-UTF-8-permissive" "platform-UTF-16")])
     ;; Check that we use all 6 bytes of #"\355\240\200\355\260\200" or none
diff --git a/src/racket/src/string.c b/src/racket/src/string.c
index 5e909388bc..f8e10ed32a 100644
--- a/src/racket/src/string.c
+++ b/src/racket/src/string.c
@@ -5389,6 +5389,7 @@ unsigned short *scheme_ucs4_to_utf16(const mzchar *text, intptr_t start, intptr_
   for (i = start, j = 0; i < end; i++) {
     v = text[i];
     if (v > 0xFFFF) {
+      v -= 0x10000;
       utf16[j++] = 0xD800 | ((v >> 10) & 0x3FF);
       utf16[j++] = 0xDC00 | (v & 0x3FF);
     } else