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【ObjC】精简的实现一个内存池

作者:RootAlways / 发布于2015/11/12/ 948


	#ifndef _ARENA_H_
	#define _ARENA_H_
	
	#include <iostream>
	#include <stdint.h>
	#include <vector>
	
	namespace mlib {
	
	struct StatusRet {
	 // true if sucess and default true.
	 bool bRet;
	 // the point we alloc and default NULL.
	 char* ptr;
	 //
	 StatusRet():bRet(true),ptr(NULL) { }
	};
	
	class Arena {
	public:
	 Arena():alloc_bytes_remain_(0),alloc_ptr_(NULL),memory_used_(0) { }
	 ~Arena();
	
	 // allocate bytes memory and return true when new sucess.
	 StatusRet Allocate(size_t bytes);
	 // return size of memory used
	 size_t MemoryUsed();
	private:
	 // allocate new memory
	 StatusRet AllocateNewMem(size_t bytes);
	 // strategy about allocate
	 StatusRet AllocateStrategy(size_t bytes);
	
	 // remain size of block
	 uint32_t alloc_bytes_remain_;
	 // itor point of memory
	 char* alloc_ptr_;
	 uint32_t memory_used_;
	
	 std::vector<char*> blocks_;
	 // no copying allowed
	 Arena(const Arena&);
	 void operator=(const Arena&);
	};
	
	} // namespace mlib
	
	#endif // _ARENA_H_

	

	

	// arena.cc
	
	#include "arena.h"
	
	namespace mlib {
	
	// size of block
	static const int kBlockSize = 4096;
	
	Arena::~Arena() {
	 for(int i = 0; i < blocks_.size(); i++) {
	 delete[] blocks_[i];
	 }
	}
	
	StatusRet Arena::Allocate(size_t bytes) {
	 if(bytes <= alloc_bytes_remain_) {
	 StatusRet result;
	 result.ptr = alloc_ptr_;
	 alloc_ptr_ += bytes;
	 alloc_bytes_remain_ -= bytes;
	 return result;
	 }
	
	 return AllocateStrategy(bytes);
	}
	
	size_t Arena::MemoryUsed() {
	 return memory_used_ + blocks_.capacity() * sizeof(char*) + alloc_bytes_remain_;
	}
	
	StatusRet Arena::AllocateNewMem(size_t bytes) {
	 StatusRet result;
	 result.ptr = new char[bytes];
	 blocks_.push_back(result.ptr);
	 memory_used_ += bytes;
	 return result;
	}
	
	StatusRet Arena::AllocateStrategy(size_t bytes) {
	 // if bytes greater than 1M
	 if(bytes > kBlockSize / 4) {
	 StatusRet result;
	 result = AllocateNewMem(bytes);
	 return result;
	 }
	
	 StatusRet result;
	 result = AllocateNewMem(kBlockSize);
	 alloc_ptr_ = result.ptr;
	 alloc_bytes_remain_ = kBlockSize;
	
	 alloc_ptr_ += bytes;
	 alloc_bytes_remain_ -= bytes;
	 return result;
	}
	
	} // namespace mlib

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