1 files changed, 149 insertions, 0 deletions
diff --git a/mfbt/Char16.h b/mfbt/Char16.h
new file mode 100644
index 0000000000..b0ba40d0e0
--- /dev/null
+++ b/mfbt/Char16.h
@@ -0,0 +1,149 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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
+
+#ifdef __cplusplus
+
+/*
+ * C++11 introduces a char16_t type and support for UTF-16 string and character
+ * literals. C++11's char16_t is a distinct builtin type. Technically, char16_t
+ * is a 16-bit code unit of a Unicode code point, not a "character".
+ */
+
+#  ifdef WIN32
+#    define MOZ_USE_CHAR16_WRAPPER
+#    include <cstdint>
+#    include "mozilla/Attributes.h"
+/**
+ * Win32 API extensively uses wchar_t, which is represented by a separated
+ * builtin type than char16_t per spec. It's not the case for MSVC prior to
+ * MSVC 2015, but other compilers follow the spec. We want to mix wchar_t and
+ * char16_t on Windows builds. This class is supposed to make it easier. It
+ * stores char16_t const pointer, but provides implicit casts for wchar_t as
+ * well. On other platforms, we simply use
+ * |typedef const char16_t* char16ptr_t|. Here, we want to make the class as
+ * similar to this typedef, including providing some casts that are allowed
+ * by the typedef.
+ */
+class char16ptr_t {
+ private:
+  const char16_t* mPtr;
+  static_assert(sizeof(char16_t) == sizeof(wchar_t),
+                "char16_t and wchar_t sizes differ");
+
+ public:
+  constexpr MOZ_IMPLICIT char16ptr_t(const char16_t* aPtr) : mPtr(aPtr) {}
+  MOZ_IMPLICIT char16ptr_t(const wchar_t* aPtr)
+      : mPtr(reinterpret_cast<const char16_t*>(aPtr)) {}
+
+  /* Without this, nullptr assignment would be ambiguous. */
+  constexpr MOZ_IMPLICIT char16ptr_t(decltype(nullptr)) : mPtr(nullptr) {}
+
+  constexpr operator const char16_t*() const { return mPtr; }
+  operator const wchar_t*() const {
+    return reinterpret_cast<const wchar_t*>(mPtr);
+  }
+
+  operator wchar_t*() {
+    return const_cast<wchar_t*>(reinterpret_cast<const wchar_t*>(mPtr));
+  }
+
+  constexpr operator const void*() const { return mPtr; }
+  constexpr explicit operator bool() const { return mPtr != nullptr; }
+
+  /* Explicit cast operators to allow things like (char16_t*)str. */
+  constexpr explicit operator char16_t*() const {
+    return const_cast<char16_t*>(mPtr);
+  }
+  explicit operator wchar_t*() const {
+    return const_cast<wchar_t*>(static_cast<const wchar_t*>(*this));
+  }
+  explicit operator int() const { return reinterpret_cast<intptr_t>(mPtr); }
+  explicit operator unsigned int() const {
+    return reinterpret_cast<uintptr_t>(mPtr);
+  }
+  explicit operator long() const { return reinterpret_cast<intptr_t>(mPtr); }
+  explicit operator unsigned long() const {
+    return reinterpret_cast<uintptr_t>(mPtr);
+  }
+  explicit operator long long() const {
+    return reinterpret_cast<intptr_t>(mPtr);
+  }
+  explicit operator unsigned long long() const {
+    return reinterpret_cast<uintptr_t>(mPtr);
+  }
+
+  /**
+   * Some Windows API calls accept BYTE* but require that data actually be
+   * WCHAR*.  Supporting this requires explicit operators to support the
+   * requisite explicit casts.
+   */
+  explicit operator const char*() const {
+    return reinterpret_cast<const char*>(mPtr);
+  }
+  explicit operator const unsigned char*() const {
+    return reinterpret_cast<const unsigned char*>(mPtr);
+  }
+  explicit operator unsigned char*() const {
+    return const_cast<unsigned char*>(
+        reinterpret_cast<const unsigned char*>(mPtr));
+  }
+  explicit operator void*() const { return const_cast<char16_t*>(mPtr); }
+
+  /* Some operators used on pointers. */
+  char16_t operator[](size_t aIndex) const { return mPtr[aIndex]; }
+  bool operator==(const char16ptr_t& aOther) const {
+    return mPtr == aOther.mPtr;
+  }
+  bool operator==(decltype(nullptr)) const { return mPtr == nullptr; }
+  bool operator!=(const char16ptr_t& aOther) const {
+    return mPtr != aOther.mPtr;
+  }
+  bool operator!=(decltype(nullptr)) const { return mPtr != nullptr; }
+  char16ptr_t operator+(int aValue) const { return char16ptr_t(mPtr + aValue); }
+  char16ptr_t operator+(unsigned int aValue) const {
+    return char16ptr_t(mPtr + aValue);
+  }
+  char16ptr_t operator+(long aValue) const {
+    return char16ptr_t(mPtr + aValue);
+  }
+  char16ptr_t operator+(unsigned long aValue) const {
+    return char16ptr_t(mPtr + aValue);
+  }
+  char16ptr_t operator+(long long aValue) const {
+    return char16ptr_t(mPtr + aValue);
+  }
+  char16ptr_t operator+(unsigned long long aValue) const {
+    return char16ptr_t(mPtr + aValue);
+  }
+  ptrdiff_t operator-(const char16ptr_t& aOther) const {
+    return mPtr - aOther.mPtr;
+  }
+};
+
+inline decltype((char*)0 - (char*)0) operator-(const char16_t* aX,
+                                               const char16ptr_t aY) {
+  return aX - static_cast<const char16_t*>(aY);
+}
+
+#  else
+
+typedef const char16_t* char16ptr_t;
+
+#  endif
+
+static_assert(sizeof(char16_t) == 2, "Is char16_t type 16 bits?");
+static_assert(char16_t(-1) > char16_t(0), "Is char16_t type unsigned?");
+static_assert(sizeof(u'A') == 2, "Is unicode char literal 16 bits?");
+static_assert(sizeof(u""[0]) == 2, "Is unicode string char 16 bits?");
+
+#endif
+
+#endif /* mozilla_Char16_h */