提升原始 C 数组的序列化、反序列化 [英] boost serialization, deserialization of raw C arrays

问题描述

我正在尝试使用下面的示例序列化和反序列化原始 C 指针及其数据.它似乎序列化得很好，但我不确定如何使其反序列化 - 当我反序列化它时，它只会因内存访问冲突异常而崩溃.我想这是因为它不知道如何反序列化它，但我在哪里指定?

I'm trying to serialize and deserialize raw C pointers and their data, with the example below. It seems to serialize just fine, but I am unsure how to make it deserialize - it just crashes with a memory access violation exception when I deserialize it. I suppose it is because it dosn't know how to deserialize it, but where do I specify that?

使用向量不是一种选择，在非常大的原始数据量中它非常慢

Using a vector is not an option, in very large primitive data amounts it is painfully slow

#include <stdint.h>
#include <string>
#include <iostream>
#include <fstream>
#pragma warning (push) 
#pragma warning( disable : 4244 ) 
#include <boost/serialization/serialization.hpp>
#include <boost/serialization/vector.hpp>
#include <boost/serialization/string.hpp>
#include <boost/serialization/array.hpp>
#include <boost/archive/binary_oarchive.hpp>
#include <boost/archive/binary_iarchive.hpp>
#pragma warning (pop) 

struct Monkey
{
    uint32_t num;
    float* arr;

};


namespace boost
{
    namespace serialization
    {
        template<class Archive>
        void serialize(Archive & ar, Monkey& m, const unsigned int version)
        {
            ar & m.num;
            ar & make_array<float>(m.arr, m.num);
        }
    }
}


int _tmain(int argc, _TCHAR* argv[])
{
    const char* name = "monkey.txt";

    {
        Monkey m;
        m.num = 10;
        m.arr = new float[m.num];
        for (uint32_t index = 0; index < m.num; index++)
            m.arr[index] = (float)index;

        std::ofstream outStream(name, std::ios::out | std::ios::binary | std::ios::trunc);
        boost::archive::binary_oarchive oar(outStream);
        oar << (m);
    }

    Monkey m;
    std::ifstream inStream(name, std::ios::in | std::ios::binary);     
    boost::archive::binary_iarchive iar(inStream);
    iar >> (m);

    return 0;
}

推荐答案

我衷心推荐你在这里使用 std::array 或 std::vector，因为... 你搞砸了 :)

I heartily recommend you use std::array or std::vector here, because... you messed this up :)

对于初学者来说，Monkey 不会初始化其成员.因此，加载最终会对 m.arr 碰巧拥有的任何指针值执行 load_binary 操作.您如何期望反序列化知道"您需要为此分配内存?你需要告诉它:

For starters, Monkey doesn't initialize its members. So, loading ends up doing a load_binary to whatever pointer value m.arr happened to have. How would you expect the deserialization to "know" that you needed to allocate memory for that? You need to tell it:

    template<class Archive>
    void serialize(Archive & ar, Monkey& m, const unsigned int version)
    {
        ar & m.num;
        if (Archive::is_loading::value)
        {
            assert(m.arr == nullptr);
            m.arr = new float[m.num];
        }
        ar & make_array<float>(m.arr, m.num);
    }

现在，让我们让 Monkey 不那么不安全(通过添加初始化和销毁​​，也许最重要的是，禁止复制语义):

Now, let's make Monkey a bit less unsafe (by adding initialization and destruction, and, perhaps most importantly, prohibiting copy semantics):

struct Monkey
{
    uint32_t num;
    float* arr;

    Monkey() : num(0u), arr(nullptr) {}

    Monkey(Monkey const&) = delete;
    Monkey& operator=(Monkey const&) = delete;
    ~Monkey() { delete[] arr; }
};

现在，您可以看到它起作用了:

Now, you can see it work:

#include <iostream>
#include <fstream>
#pragma warning(disable: 4244)
#include <boost/serialization/serialization.hpp>
#include <boost/archive/binary_oarchive.hpp>
#include <boost/archive/binary_iarchive.hpp>

struct Monkey
{
    uint32_t num;
    float* arr;

    Monkey() : num(0u), arr(nullptr) {}

    Monkey(Monkey const&) = delete;
    Monkey& operator=(Monkey const&) = delete;
    ~Monkey() { delete[] arr; }
};

namespace boost
{
    namespace serialization
    {
        template<class Archive>
        void serialize(Archive & ar, Monkey& m, const unsigned int version)
        {
            ar & m.num;
            if (Archive::is_loading::value)
            {
                assert(m.arr == nullptr);
                m.arr = new float[m.num];
            }
            ar & make_array<float>(m.arr, m.num);
        }
    }
}

int main(int argc, char* argv[])
{
    const char* name = "monkey.txt";
    {
        Monkey m;
        m.num = 10;
        m.arr = new float[m.num];
        for (uint32_t index = 0; index < m.num; index++)
            m.arr[index] = (float)index;

        std::ofstream outStream(name, std::ios::out | std::ios::binary | std::ios::trunc);
        boost::archive::binary_oarchive oar(outStream);
        oar << (m);
    }

    Monkey m;
    std::ifstream inStream(name, std::ios::in | std::ios::binary);
    boost::archive::binary_iarchive iar(inStream);
    iar >> (m);

    std::copy(m.arr, m.arr + m.num, std::ostream_iterator<float>(std::cout, ";"));
}

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