Imported from /home/lorry/working-area/delta_mozilla_mozjs24/mozjs-24.2.0.tar.bz2.HEADmozjs-24.2.0master

1 files changed, 56 insertions, 0 deletions

diff --git a/mfbt/Char16.h b/mfbt/Char16.h
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+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Implements a UTF-16 character type. */
+
+#ifndef mozilla_Char16_h_
+#define mozilla_Char16_h_
+
+#include "mozilla/Assertions.h"
+
+/*
+ * C11 and C++11 introduce a char16_t type and support for UTF-16 string and
+ * character literals. C++11's char16_t is a distinct builtin type. C11's
+ * char16_t is a typedef for uint_least16_t. Technically, char16_t is a 16-bit
+ * code unit of a Unicode code point, not a "character".
+ *
+ * For now, Char16.h only supports C++ because we don't want mix different C
+ * and C++ definitions of char16_t in the same code base.
+ */
+
+#ifdef _MSC_VER
+   /*
+    * C++11 says char16_t is a distinct builtin type, but Windows's yvals.h
+    * typedefs char16_t as an unsigned short. We would like to alias char16_t
+    * to Windows's 16-bit wchar_t so we can declare UTF-16 literals as constant
+    * expressions (and pass char16_t pointers to Windows APIs). We #define our
+    * char16_t as a macro to override yval.h's typedef of the same name.
+    */
+#  define MOZ_UTF16_HELPER(s) L##s
+#  include <yvals.h>
+#  define char16_t wchar_t
+#elif defined(__cplusplus) && \
+      (__cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__))
+   /* C++11 has a builtin char16_t type. */
+#  define MOZ_UTF16_HELPER(s) u##s
+#else
+#  error "Char16.h requires C++11 (or something like it) for UTF-16 support."
+#endif
+
+/*
+ * Macro arguments used in concatenation or stringification won't be expanded.
+ * Therefore, in order for |MOZ_UTF16(FOO)| to work as expected (which is to
+ * expand |FOO| before doing whatever |MOZ_UTF16| needs to do to it) a helper
+ * macro, |MOZ_UTF16_HELPER| needs to be inserted in between to allow the macro
+ * argument to expand. See "3.10.6 Separate Expansion of Macro Arguments" of the
+ * CPP manual for a more accurate and precise explanation.
+ */
+#define MOZ_UTF16(s) MOZ_UTF16_HELPER(s)
+
+MOZ_STATIC_ASSERT(sizeof(char16_t) == 2, "Is char16_t type 16 bits?");
+MOZ_STATIC_ASSERT(sizeof(MOZ_UTF16('A')) == 2, "Is char literal 16 bits?");
+MOZ_STATIC_ASSERT(sizeof(MOZ_UTF16("")[0]) == 2, "Is string char 16 bits?");
+
+#endif /* mozilla_Char16_h_ */