是否良好的做法是使用std :: vector作为一个简单的缓冲区？ [英] Is it good practice to used std::vector as a simple buffer?

问题描述

我有一个应用程序正在对一些图像执行一些处理。

I have an application that is performing some processing on some images.

由于我知道宽度/高度/格式等（我这样做）只是定义一个缓冲区来存储像素数据：

Given that I know the width/height/format etc. (I do), and thinking just about defining a buffer to store the pixel data:

然后，而不是使用 new 和<$ c $在 unsigned char * 上保留一个单独的缓冲区大小的注意事项，我想要简化的事情， std :: vector 。

Then, rather than using new and delete [] on an unsigned char* and keeping a separate note of the buffer size, I'm thinking of simplifying things by using a std::vector.

所以我要声明我的类如下：

So I would declare my class something like this:

#include <vector>

class MyClass
{
    // ... etc. ...

public:
    virtual void OnImageReceived(unsigned char *pPixels, 
        unsigned int uPixelCount);

private:
    std::vector<unsigned char> m_pImageBuffer;    // buffer for 8-bit pixels

    // ... etc. ...
};

然后，当我收到一个新的图片详细信息），我可以调整向量（如果需要）和复制像素：

Then, when I received a new image (of some variable size - but don't worry about those details here), I can just resize the vector (if necessary) and copy the pixels:

void MyClass::OnImageReceived(unsigned char *pPixels, unsigned int uPixelCount)
{
    // called when a new image is available
    if (m_pImageBuffer.size() != uPixelCount)
    {
        // resize image buffer
        m_pImageBuffer.reserve(uPixelCount);
        m_pImageBuffer.resize(uPixelCount, 0);
    }

    // copy frame to local buffer
    memcpy_s(&m_pImageBuffer[0], m_pImageBuffer.size(), pPixels, uPixelCount);

    // ... process image etc. ...
}

$ b b

这对我来说似乎很好，我喜欢这个事实，我不必担心内存管理，但它提出了一些问题：

This seems fine to me, and I like that fact that I don't have to worry about the memory management, but it raises some questions:

1. 这是 std :: vector 的有效申请吗？还是有更合适的容器吗？


2. 通过调用 reserve 和 resize ？


3. 总是是底层内存是连续的，所以我可以使用 memcpy_s 如图所示？

1. Is this a valid application of std::vector or is there a more suitable container?
2. Am I doing the right thing performance-wise by calling reserve and resize?
3. Will it always be the case that the underlying memory is consecutive so I can use memcpy_s as shown?

任何其他意见，批评或建议都是非常欢迎的。

Any additional comment, criticism or advice would be very welcome.

推荐答案

1. 当然，这会正常工作。你需要担心的一件事是确保缓冲区正确对齐，如果你的类依赖于一个特定的对齐方式;在这种情况下，您可能想使用数据类型本身的向量（如 float ）。


2. 不， ;调整大小会根据需要自动增加容量。


3. 在C ++ 03之前，技术上不是（但实际上是）。从C ++ 03开始，是的。

1. Sure, this'll work fine. The one thing you need to worry about is ensuring that the buffer is correctly aligned, if your class relies on a particular alignment; in this case you may want to use a vector of the datatype itself (like float).
2. No, reserve is not necessary here; resize will automatically grow the capacity as necessary, in exactly the same way.
3. Before C++03, technically not (but in practice yes). Since C++03, yes.

顺便提一下， memcpy_s isn这里的惯用方法。请改用 std :: copy 。请记住，指针是一个迭代器。

Incidentally, though, memcpy_s isn't the idiomatic approach here. Use std::copy instead. Keep in mind that a pointer is an iterator.

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