The Tor Browser: mfbt/ArrayUtils.h@97036ab72558

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.

     1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

     2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */

     3 /* This Source Code Form is subject to the terms of the Mozilla Public

     4  * License, v. 2.0. If a copy of the MPL was not distributed with this

     5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     7 /*

     8  * Implements various helper functions related to arrays.

     9  */

    11 #ifndef mozilla_ArrayUtils_h

    12 #define mozilla_ArrayUtils_h

    14 #include "mozilla/Assertions.h"

    15 #include "mozilla/Attributes.h"

    17 #include <stddef.h>

    19 #ifdef __cplusplus

    21 #include "mozilla/Array.h"

    23 namespace mozilla {

    25 /*

    26  * Safely subtract two pointers when it is known that end >= begin.  This avoids

    27  * the common compiler bug that if (size_t(end) - size_t(begin)) has the MSB

    28  * set, the unsigned subtraction followed by right shift will produce -1, or

    29  * size_t(-1), instead of the real difference.

    30  */

    31 template<class T>

    32 MOZ_ALWAYS_INLINE size_t

    33 PointerRangeSize(T* begin, T* end)

    34 {

    35   MOZ_ASSERT(end >= begin);

    36   return (size_t(end) - size_t(begin)) / sizeof(T);

    37 }

    39 /*

    40  * Compute the length of an array with constant length.  (Use of this method

    41  * with a non-array pointer will not compile.)

    42  *

    43  * Beware of the implicit trailing '\0' when using this with string constants.

    44  */

    45 template<typename T, size_t N>

    46 MOZ_CONSTEXPR size_t

    47 ArrayLength(T (&arr)[N])

    48 {

    49   return N;

    50 }

    52 template<typename T, size_t N>

    53 MOZ_CONSTEXPR size_t

    54 ArrayLength(const Array<T, N>& arr)

    55 {

    56   return N;

    57 }

    59 /*

    60  * Compute the address one past the last element of a constant-length array.

    61  *

    62  * Beware of the implicit trailing '\0' when using this with string constants.

    63  */

    64 template<typename T, size_t N>

    65 MOZ_CONSTEXPR T*

    66 ArrayEnd(T (&arr)[N])

    67 {

    68   return arr + ArrayLength(arr);

    69 }

    71 template<typename T, size_t N>

    72 MOZ_CONSTEXPR T*

    73 ArrayEnd(Array<T, N>& arr)

    74 {

    75   return &arr[0] + ArrayLength(arr);

    76 }

    78 template<typename T, size_t N>

    79 MOZ_CONSTEXPR const T*

    80 ArrayEnd(const Array<T, N>& arr)

    81 {

    82   return &arr[0] + ArrayLength(arr);

    83 }

    85 namespace detail {

    87 /*

    88  * Helper for the MOZ_ARRAY_LENGTH() macro to make the length a typesafe

    89  * compile-time constant even on compilers lacking constexpr support.

    90  */

    91 template <typename T, size_t N>

    92 char (&ArrayLengthHelper(T (&array)[N]))[N];

    94 } /* namespace detail */

    96 } /* namespace mozilla */

    98 #endif /* __cplusplus */

   100 /*

   101  * MOZ_ARRAY_LENGTH() is an alternative to mozilla::ArrayLength() for C files

   102  * that can't use C++ template functions and for static_assert() calls that

   103  * can't call ArrayLength() when it is not a C++11 constexpr function.

   104  */

   105 #ifdef __cplusplus

   106 #  define MOZ_ARRAY_LENGTH(array)   sizeof(mozilla::detail::ArrayLengthHelper(array))

   107 #else

   108 #  define MOZ_ARRAY_LENGTH(array)   (sizeof(array)/sizeof((array)[0]))

   109 #endif

   111 #endif /* mozilla_ArrayUtils_h */

The Tor Browser / file revision

mfbt/ArrayUtils.h@97036ab72558

mfbt/ArrayUtils.h