连续的内存块的动态分配（malloc的） [英] Dynamic allocation (malloc) of contiguous block of memory

问题描述

有关的转让，我不得不分配一个连续的内存块的结构，但我第一次尝试使用整数第一的二维数组做到这一点，看看我是否理解正确。我们在这对指针阵列（行）产生的存储器的块，然后初始化cols和指向指针给他们的书的例子。这个例子是：

For an assignment, I have to allocate a contiguous block of memory for a struct, but I'm first trying to do it with a 2D array of ints first and see if I understand it correctly. We had an example in the book that creates a block of memory for the pointer array (rows), and then initializes the cols and points the pointer to them. This example was:

int **CreateInt2D(size_t rows, size_t cols)
{
    int **p, **p1, **end;
    p = (int **)SafeMalloc(rows * sizeof(int *));
    cols *= sizeof(int);
    for (end = p + rows, p1 = p; p1 < end; ++p1)
        *p1 = (int *)SafeMalloc(cols);
    return(p);
}

void *SafeMalloc(size_t size)
{
    void *vp;

    if ((vp = malloc(size)) == NULL) {
        fputs("Out of mem", stderr);
        exit(EXIT_FAILURE);
    }
    return(vp);
}

基本上，我需要做上述code确实只是让一个内存连续块的东西。约束是我只允许一次调用malloc，然后我不得不使用指针数学知道的指针初始化。所以，我想我会初始化内存不够用是这样的：

I basically need to do what the above code does except make it one contiguous block of memory. The constraint is I'm only allowed to call malloc once, and then I have to use pointer math to know what to initialize the pointers to. So I thought I would initialize enough memory with something like:

int *createInt2D(size_t rows, size_t cols) 
{
    malloc(rows * sizeof(int *) + (row + cols) * sizeof(int));
}

但是，这似乎并不完全正确，因为我想我将不得不类型转换的void *从malloc返回，但它是int和int的组合*。所以，我不太肯定我是否在正确的轨道上。思考？

But that doesn't seem quite right since I would think I would have to typecast the void * returned from malloc, but it's a combination of int and int*. So I'm not quite sure if I'm on the right track. Thoughts?

推荐答案

如果你想有一个连续的数组，你应该的malloc（行* COLS *的sizeof（INT））

If you want a contiguous array, you should malloc(rows * cols * sizeof(int)).

然后你访问改编[X，Y] 这样的：

arr[x * cols + y]

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