memory/build/mozmemory_utils.h

   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/. */
   6
   7 #ifndef mozjemalloc_utils_h
   8 #define mozjemalloc_utils_h
   9
  10 #include <optional>
  11 #include <type_traits>
  12
  13 #if defined(MOZ_MEMORY) && defined(XP_WIN)
  14 #  include <wtypes.h>
  15 #  include "mozmemory_wrap.h"
  16 #endif
  17
  18 namespace mozilla {
  19
  20 namespace detail {
  21 // Helper for StallAndRetry error messages.
  22 template <typename T>
  23 constexpr bool is_std_optional = false;
  24 template <typename T>
  25 constexpr bool is_std_optional<std::optional<T>> = true;
  26 }  // namespace detail
  27
  28 struct StallSpecs {
  29   // Maximum number of retry-attempts before giving up.
  30   size_t maxAttempts;
  31   // Delay time between successive events.
  32   size_t delayMs;
  33
  34   // Retry a fallible operation until it succeeds or until we've run out of
  35   // retries.
  36   //
  37   // Note that this invokes `aDelayFunc` immediately upon being called! It's
  38   // intended for use in the unhappy path, after an initial attempt has failed.
  39   //
  40   // The function type here may be read:
  41   // ```
  42   // fn StallAndRetry<R>(
  43   //     delay_func: impl Fn(usize) -> (),
  44   //     operation: impl Fn() -> Option<R>,
  45   // ) -> Option<R>;
  46   // ```
  47   //
  48   template <typename DelayFunc, typename OpFunc>
  49   auto StallAndRetry(DelayFunc&& aDelayFunc,
  50                      OpFunc&& aOperation) const -> decltype(aOperation()) {
  51     {
  52       // Explicit typecheck for OpFunc, to provide an explicit error message.
  53       using detail::is_std_optional;
  54       static_assert(is_std_optional<decltype(aOperation())>,
  55                     "aOperation() must return std::optional");
  56
  57       // (clang's existing error messages suffice for aDelayFunc.)
  58     }
  59
  60     for (size_t i = 0; i < maxAttempts; ++i) {
  61       aDelayFunc(delayMs);
  62       if (const auto opt = aOperation()) {
  63         return opt;
  64       }
  65     }
  66     return std::nullopt;
  67   }
  68 };
  69
  70 #if defined(MOZ_MEMORY) && defined(XP_WIN)
  71 MOZ_JEMALLOC_API StallSpecs GetAllocatorStallSpecs();
  72 MOZ_JEMALLOC_API_NODISCARD void* MozVirtualAlloc(LPVOID lpAddress,
  73                                                  SIZE_T dwSize,
  74                                                  DWORD flAllocationType,
  75                                                  DWORD flProtect);
  76 #endif
  77
  78 }  // namespace mozilla
  79
  80 #endif  // mozjemalloc_utils_h