CopyMemory非POD

Question

我有看起来像这样的结构和向量：

typedef struct
{
    int SX, SY;
    int X, Y, Z;
    std::vector<Vector3D> Vertices;
    const void* VBOPointer;
} Model;

typedef struct
{
    int X, Y;
    struct
    {
        int VX[4], VY[4];
        int TX[4], VY[4];
    } Quad;
} Item;

std::vector<Item> ListOfItems;
std::vector<Model> ListOfModels;

我需要将它们复制到内存中，这样我才能从另一个程序中重建它们。我已经映射了内存，但是后来我意识到我不能对它们中的任何一个使用CopyMemory或MemCpy。

我怎么复制它呢？

我如何复制标准数据类型/结构的示例：

struct
{
    int X;
    int Y;
} POD;

//pData is a void pointer to mapped memory given to be by MapFileView..

POD Foo = {100, 50};
long double* Data = static_cast<long double*>(pData);
//Check if Data[1] contains a request command then copy.

CopyMemory(&Data[0], &Foo, sizeof(Foo));

Answer 1

由于您必须处理非POD数据，因此您需要将结构数据展平为序列化格式，然后其他应用程序可以将其解析回其一端的结构。

您的ListOfItems矢量可以很容易地展平，因为它的元素是POD数据。将vector大小存储为整数，将其复制到缓冲区中，然后复制每个Item (假设缓冲区足够大，可以容纳展平的数据)：

long double* Data = static_cast<long double*>(pData);  
//Check if Data[1] contains a request command then copy.  

unsigned char *Work = static_cast<unsigned char *>(pData);

int number = ListOfItems.size();
CopyMemory(Work, &number, sizeof(int)); 
Work += sizeof(int);

for (int i = 0; i < number; ++i)
{
    CopyMemory(Work, &ListOfItems[i], sizeof(Item)); 
    Work += sizeof(Item);
}

由于Model中包含另一个vector，因此您的ListOfModels向量将更难扁平化，但相同的概念通常也适用：

long double* Data = static_cast<long double*>(pData);  
//Check if Data[1] contains a request command then copy.  

unsigned char *Work = static_cast<unsigned char *>(pData);

int number = ListOfModels.size();
CopyMemory(Work, &number, sizeof(int)); 
Work += sizeof(int);

for (int i = 0; i < number; ++i)
{
    Model &m = ListOfModels[i];

    CopyMemory(Work, &(m.SX), sizeof(int) * 5);
    Work += (sizeof(int) * 5);

    int num = m.Vertices.size();
    CopyMemory(Work, &num, sizeof(int));
    Work += sizeof(int);

    for (int j = 0; j < num; ++j)
    {
        Vector3D &v = m.Vertices[j];
        // copy v as needed...
        Work += ...;
    }

    // copy m.VBOPointer as needed ...
    Work += ...;
}

对于这样的事情，我通常使用模板来帮助简化逻辑并使其更容易阅读：

template<typename T>
void Copy(unsignd char* &Work, const T &value)
{
    CopyMemory(Work, &value, sizeof(T));
}

template<template T>
void Copy(unsigned char* &Work, const std::vector<T> &vec)
{
    int number = vec.size();
    Copy(Work, number);
    for (int i = 0; i < number; ++i)
        Copy(Work, vec[i]);
}

。

long double* Data = static_cast<long double*>(pData);  
//Check if Data[1] contains a request command then copy.  

unsigned char *Work = static_cast<unsigned char *>(pData);
Copy(Work, ListOfItems);

。

template<>
void Copy<Vector3D>(unsigned char* &Work, const Vector3D &vec)
{
    // copy vec as needed...
    Work += ...;
}

template<>
void Copy<Model>(unsigned char* &Work, const Model &m)
{
    Copy(Work, m.SX);
    Copy(Work, m.SY);
    Copy(Work, m.X);
    Copy(Work, m.Y);
    Copy(Work, m.Z);
    Copy(Work, m.Vertices);

    // copy m.VBOPointer as needed ...
    Work += ...;
}

long double* Data = static_cast<long double*>(pData);  
//Check if Data[1] contains a request command then copy.  

unsigned char *Work = static_cast<unsigned char *>(pData);
Copy(Work, ListOfModels);