object_pool.h 4.08 KB
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// bthread - A M:N threading library to make applications more concurrent.
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// Copyright (c) 2014 Baidu, Inc.
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// 
// 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.
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// Author: Ge,Jun (gejun@baidu.com)
// Date: Sun Jul 13 15:04:18 CST 2014

#ifndef BTHREAD_BASE_OBJECT_POOL_H
#define BTHREAD_BASE_OBJECT_POOL_H

#include <cstddef>                       // size_t

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// ObjectPool is a derivative class of ResourcePool to allocate and
// reuse fixed-size objects without identifiers.
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namespace butil {
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// Specialize following classes to override default parameters for type T.
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//   namespace butil {
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//     template <> struct ObjectPoolBlockMaxSize<Foo> {
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//       static const size_t value = 1024;
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//     };
//   }
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// Memory is allocated in blocks, memory size of a block will not exceed:
//   min(ObjectPoolBlockMaxSize<T>::value,
//       ObjectPoolBlockMaxItem<T>::value * sizeof(T))
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template <typename T> struct ObjectPoolBlockMaxSize {
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    static const size_t value = 64 * 1024; // bytes
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};
template <typename T> struct ObjectPoolBlockMaxItem {
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    static const size_t value = 256;
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};

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// Free objects of each thread are grouped into a chunk before they are merged
// to the global list. Memory size of objects in one free chunk will not exceed:
//   min(ObjectPoolFreeChunkMaxItem<T>::value(),
//       ObjectPoolBlockMaxSize<T>::value,
//       ObjectPoolBlockMaxItem<T>::value * sizeof(T))
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template <typename T> struct ObjectPoolFreeChunkMaxItem {
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    static size_t value() { return 256; }
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};

// ObjectPool calls this function on newly constructed objects. If this
// function returns false, the object is destructed immediately and
// get_object() shall return NULL. This is useful when the constructor
// failed internally(namely ENOMEM).
template <typename T> struct ObjectPoolValidator {
    static bool validate(const T*) { return true; }
};

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}  // namespace butil
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#include "butil/object_pool_inl.h"
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namespace butil {
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// Get an object typed |T|. The object should be cleared before usage.
// NOTE: T must be default-constructible.
template <typename T> inline T* get_object() {
    return ObjectPool<T>::singleton()->get_object();
}

// Get an object whose constructor is T(arg1)
template <typename T, typename A1>
inline T* get_object(const A1& arg1) {
    return ObjectPool<T>::singleton()->get_object(arg1);
}

// Get an object whose constructor is T(arg1, arg2)
template <typename T, typename A1, typename A2>
inline T* get_object(const A1& arg1, const A2& arg2) {
    return ObjectPool<T>::singleton()->get_object(arg1, arg2);
}

// Return the object |ptr| back. The object is NOT destructed and will be
// returned by later get_object<T>. Similar with free/delete, validity of
// the object is not checked, user shall not return a not-yet-allocated or
// already-returned object otherwise behavior is undefined.
// Returns 0 when successful, -1 otherwise.
template <typename T> inline int return_object(T* ptr) {
    return ObjectPool<T>::singleton()->return_object(ptr);
}

// Reclaim all allocated objects typed T if caller is the last thread called
// this function, otherwise do nothing. You rarely need to call this function
// manually because it's called automatically when each thread quits.
template <typename T> inline void clear_objects() {
    ObjectPool<T>::singleton()->clear_objects();
}

// Get description of objects typed T.
// This function is possibly slow because it iterates internal structures.
// Don't use it frequently like a "getter" function.
template <typename T> ObjectPoolInfo describe_objects() {
    return ObjectPool<T>::singleton()->describe_objects();
}

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}  // namespace butil
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#endif  // BTHREAD_BASE_OBJECT_POOL_H