The Tor Browser: mfbt/Char16.h@97036ab72558 (annotated)

mfbt/Char16.h@97036ab72558 (annotated)

mfbt/Char16.h

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* -*- 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 _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
     * _CHAR16T here in order to prevent yvals.h from overriding our char16_t
     * typedefs, which we set to wchar_t for C++ code.
     *
     * In addition, #defining _CHAR16T will prevent yvals.h from defining a
     * char32_t type, so we have to undo that damage here and provide our own,
     * which is identical to the yvals.h type.
     */
 #  define MOZ_UTF16_HELPER(s) L##s
 #  define _CHAR16T
    typedef wchar_t char16_t;
    typedef unsigned int char32_t;
 #else
    /* C++11 has a builtin char16_t type. */
 #  define MOZ_UTF16_HELPER(s) u##s
    /**
     * This macro is used to distinguish when char16_t would be a distinct
     * typedef from wchar_t.
     */
 #  define MOZ_CHAR16_IS_NOT_WCHAR
 #  ifdef WIN32
 #    define MOZ_USE_CHAR16_WRAPPER
 #  endif
 #endif
 #ifdef MOZ_USE_CHAR16_WRAPPER
 # include <string>
   /**
    * 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, but GCC
    * follows 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* ptr;
     static_assert(sizeof(char16_t) == sizeof(wchar_t), "char16_t and wchar_t sizes differ");
   public:
     char16ptr_t(const char16_t* p) : ptr(p) {}
     char16ptr_t(const wchar_t* p) : ptr(reinterpret_cast<const char16_t*>(p)) {}
     /* Without this, nullptr assignment would be ambiguous. */
     constexpr char16ptr_t(decltype(nullptr)) : ptr(nullptr) {}
     operator const char16_t*() const {
       return ptr;
     }
     operator const wchar_t*() const {
       return reinterpret_cast<const wchar_t*>(ptr);
     }
     operator const void*() const {
       return ptr;
     }
     operator bool() const {
       return ptr != nullptr;
     }
     operator std::wstring() const {
       return std::wstring(static_cast<const wchar_t*>(*this));
     }
     /* Explicit cast operators to allow things like (char16_t*)str. */
     explicit operator char16_t*() const {
       return const_cast<char16_t*>(ptr);
     }
     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>(ptr);
     }
     explicit operator unsigned int() const {
       return reinterpret_cast<uintptr_t>(ptr);
     }
     explicit operator long() const {
       return reinterpret_cast<intptr_t>(ptr);
     }
     explicit operator unsigned long() const {
       return reinterpret_cast<uintptr_t>(ptr);
     }
     explicit operator long long() const {
       return reinterpret_cast<intptr_t>(ptr);
     }
     explicit operator unsigned long long() const {
       return reinterpret_cast<uintptr_t>(ptr);
     }
     /**
      * 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*>(ptr);
     }
     explicit operator const unsigned char*() const {
       return reinterpret_cast<const unsigned char*>(ptr);
     }
     explicit operator unsigned char*() const {
       return const_cast<unsigned char*>(reinterpret_cast<const unsigned char*>(ptr));
     }
     explicit operator void*() const {
       return const_cast<char16_t*>(ptr);
     }
     /* Some operators used on pointers. */
     char16_t operator[](size_t i) const {
       return ptr[i];
     }
     bool operator==(const char16ptr_t &x) const {
       return ptr == x.ptr;
     }
     bool operator==(decltype(nullptr)) const {
       return ptr == nullptr;
     }
     bool operator!=(const char16ptr_t &x) const {
       return ptr != x.ptr;
     }
     bool operator!=(decltype(nullptr)) const {
       return ptr != nullptr;
     }
     char16ptr_t operator+(int aValue) const {
       return char16ptr_t(ptr + aValue);
     }
     char16ptr_t operator+(unsigned int aValue) const {
       return char16ptr_t(ptr + aValue);
     }
     char16ptr_t operator+(long aValue) const {
       return char16ptr_t(ptr + aValue);
     }
     char16ptr_t operator+(unsigned long aValue) const {
       return char16ptr_t(ptr + aValue);
     }
     char16ptr_t operator+(long long aValue) const {
       return char16ptr_t(ptr + aValue);
     }
     char16ptr_t operator+(unsigned long long aValue) const {
       return char16ptr_t(ptr + aValue);
     }
     ptrdiff_t operator-(const char16ptr_t &other) const {
       return ptr - other.ptr;
     }
 };
 inline decltype((char*)0-(char*)0)
 operator-(const char16_t* x, const char16ptr_t y) {
   return x - static_cast<const char16_t*>(y);
 }
 #else
 typedef const char16_t* char16ptr_t;
 #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)
 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(MOZ_UTF16('A')) == 2, "Is char literal 16 bits?");
 static_assert(sizeof(MOZ_UTF16("")[0]) == 2, "Is string char 16 bits?");
 #endif
 #endif /* mozilla_Char16_h */

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mfbt/Char16.h@97036ab72558 (annotated)

mfbt/Char16.h