CopyMemory Non-POD

Question

我有结构和矢量看起来像：

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;

我需要将这些复制到内存中，以便我可以从另一个程序重建它们。 我已经映射了内存，但后来我意识到我不能在其中任何一个上使用CopyMemory或MemCpy。

我该如何复制？

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结构中的结构。

您的ListOfItems向量可以非常容易地展平，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包含另一个vector ，因此ListOfModels向量将更难以展平，但同样的概念通常适用：

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 += ...;
}

我通常为这样的事情做的是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);