C++：具有动态大小的指针浮点型数组

Question

Is this Correct?

Will stereoBuffer be an array of the pointer float type with size mixQty (ie 2);

// C++ in Header File

float **stereoBuffer;

// in cpp file inside a function of init

mixQty = 2; // this will be passed in function

stereoBuffer = new float*[mixQty];

for (int i = 0; i < mixQty; ++i) {
    stereoBuffer[i] = (float *)malloc(samplerate * 2 * sizeof(float) + 32768);
}

Help and Detail answer will be rewarded.

Answer 1

Is this Correct?

No . Mixing new and malloc() is not a good idea.

If you must use dynamic memory allocation, then read this: How do I declare a 2d array in C++ using new?

Otherwise, use an std::vector .

Answer 2

Will stereoBuffer be an array of the pointer float type

It will be (a pointer to the first element of) an array of type pointer-to-float.

Each element of this array will be a pointer to the first element of an array of float.

As gsamaras notes, mixing new and malloc like this is terrible practice. It's needlessly hard to correctly deallocate and there's no error checking. You could at least use std::vector<std::unique_ptr<float[]>> and let it take care of deallocation correctly for you.

using StereoBuffer = std::vector<std::unique_ptr<float[]>>;

StereoBuffer allocateStereoBuffer(size_t mixQty, size_t samplerate)
{
  StereoBuffer buf(mixQty);

  for (size_t i = 0; i < mixQty; ++i) {
    buf[i] = make_unique<float[]>(samplerate * 2 * 32768); // ?
  }
  return buf;
}