folly/folly/memory/MallctlHelper.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// Some helper functions for mallctl.

#pragma once

#include <folly/memory/Malloc.h>

#include <stdexcept>
#include <type_traits>

namespace folly {

namespace detail {

[[noreturn]] void handleMallctlError(const char* fn, const char* cmd, int err);

template <typename T>
void mallctlHelper(const char* cmd, T* out, T* in) { … }

} // namespace detail

template <typename T>
void mallctlRead(const char* cmd, T* out) { … }

template <typename T>
void mallctlWrite(const char* cmd, T in) { … }

template <typename T>
void mallctlReadWrite(const char* cmd, T* out, T in) { … }

inline void mallctlCall(const char* cmd) { … }

/*
 * The following implements a caching utility for usage cases where:
 * - the same mallctl command is called many times, and
 * - performance is important.
 */

namespace detail {

class MallctlMibCache { … };

} // namespace detail

class MallctlMibCallCache : private detail::MallctlMibCache { … };

template <typename ReadType>
class MallctlMibReadCache : private detail::MallctlMibCache { … };

template <typename WriteType>
class MallctlMibWriteCache : private detail::MallctlMibCache { … };

template <typename ReadType, typename WriteType>
class MallctlMibReadWriteCache : private detail::MallctlMibCache { … };

MallctlMibExchangeCache;

} // namespace folly