在反C的memcpy [英] C memcpy in reverse

问题描述

我与音频数据的工作。我想在相反的方向播放样本文件。数据存储为无符号整数，包装好和紧张。有没有一种方法来调用的memcpy 将在相反的顺序复制。也就是说，如果我有存储在一个数组1,2,3,4，我可以打电话给的memcpy 和神奇的逆转他们，所以我得到4,3 ，2,1。

I am working with audio data. I'd like to play the sample file in reverse. The data is stored as unsigned ints and packed nice and tight. Is there a way to call memcpy that will copy in reverse order. i.e. if I had 1,2,3,4 stored in an array, could I call memcpy and magically reverse them so I get 4,3,2,1.

推荐答案

这适用于复制 INT S IN相反：

This works for copying ints in reverse:

void reverse_intcpy(int *restrict dst, const int *restrict src, size_t n)
{
    size_t i;

    for (i=0; i < n; ++i)
        dst[n-1-i] = src[i];

}

就像的memcpy（），各地区指出，由 DST 和 SRC 不得重叠。

Just like memcpy(), the regions pointed-to by dst and src must not overlap.

如果你想扭转就地：

void reverse_ints(int *data, size_t n)
{
    size_t i;

    for (i=0; i < n/2; ++i) {
        int tmp = data[i];
        data[i] = data[n - 1 - i];
        data[n - 1 - i] = tmp;
    }
}

上述

两者的功能是便携式的。您可能能够使用特定硬件的code，使他们更快。

Both the functions above are portable. You might be able to make them faster by using hardware-specific code.

（我没有测试code的正确性。）

(I haven't tested the code for correctness.)

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